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SirHarveyXXI

Something doesn't seem right...

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Hello all, my name is Harvey and I'm very new to astronomy. After countless hours of reading beforehand, I'd like to start off by saying I know I'm not expecting to see anything close to the pictures seen on the internet from telescopes like Hubble, but something doesn't seem to be right. I have a Celestron AstroMaster 76eq, this is quite a budget telescope due to the fact my budget is less than small. These are the specs:

  • 700mm Focal Length
  • 76mm Aperture
  • Focal Ratio of 9.21 
  • 2 lenses of focal length 10mm and 20mm

I'm quite young, and I've been super interested in any and all things space, so obviously getting into astronomy was a definite for me. This is hopefully going to be a life long hobby I'm gonna take up, so any tips for the future are well and truly appreciated (alongside any tips at all to help me get started). Please bare with me, I'm trying to condense this down as much as I can. 😂

I've done a lot of research into the telescope that I have, and I've read about many people being able to see deep space objects such as Andromeda's core. I have been able to see this (at least, I'm 99% sure) however, attempting to view other deep space objects (such as M1) proves to be difficult. I'm not entirely sure if this is due to me being unable to navigate the night sky effectively, if I'm doing something wrong or I'm expecting too much. I live in a fairly rural area in England with little light pollution, and when observing these deep space objects I make sure that I'm as far away from the light pollution as I can get. This leads on to my first question...

  • How much of a difference does the humidity make? England generally has VERY high levels of humidity, and I'm wondering if this is going to make a huge difference to what I can see? I've never really seen the humidity to be less than 75%, so if it makes a huge difference I presume that I won't be able to view any deep space objects?

That being said, should my telescope be able to see deep space object with this level of humidity amongst other viewing problems? I try my best to ensure (like I said earlier) that I can make the viewing conditions as optimal as possible where I can (i.e. not viewing objects in the direction of light pollution, making sure that I go out in low levels of cloud, making sure I observe objects as high up in the sky as I can etc). On the subject of the telescope itself... 

  • How much of a difference does collimation make? Will it be the difference between seeing an object or not if the collimation of my mirrors isn't very good?
  • Should a telescope of my calibre be able to make out the major details of planets? e.g. the ring of Saturn and the bands of Jupiter? Or am I expecting too much of my telescope? I have just ordered a 2x Barlow lens to bring me close up to the maximum magnification my telescope can realistically handle (140x), so I'm wondering if this will help me see these finer details or if Jupiter will still be merely a bright light?
  • How much of a difference do filters make at lower magnifications such as 70-140x on planets such as Jupiter, Saturn or Mars? Are they worth the investment this early on or are they more of an investment to make later on?
  • How important are high quality eyepieces? Are they worth the investment early on or later on? The problem with this is that eyepieces can get quite pricey and as I said before, I'm on a very low budget. 
  • That being said, is the level of astronomy I'm after even possible on my budget? Will I be able to see deep space objects like M1 and other nebulae? By seeing them, I mean as blurry blobs, not detailed objects. 

Terribly sorry for the masses of questions (of which I'm sure most of you will have seen a thousand times!), but I've been searching for a long time and haven't found many answers relevant to my situation. As I said, I'm very open to any suggestions, tips and recommendations! Thank you for reading! If there's any more information you need, ask me and I'll try my best to give you it! 

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Hi and welcome to SGL.

I'll try to address as many of your questions as I can, so let's start with humidity.

Humidity is important factor to consider in winter time. Two major difficulties it creates are poor local transparency and dew on optics. First one you can't do much about, but there is simple method to check conditions - "light sabre" method. Have torch with you - white light one that you will not be using when observing but is handy when setting up and packing. Use one with narrow beam of light. Before you start your dark adaptation - shine it towards the sky. If you see light leaving the torch and creating "light sabre" kind of effect (or "batman signal" for those not familiar with Jedi culture :D ) - transparency is poor and don't expect much on a given evening. You can still observe but less targets will be within your reach.

Second is dew on mirrors. This should not happen often since you have newtonian scope. Your primary mirror is not likely to dew up, but secondary might. Eyepieces are prone to this also. Keep eyepiece in your pockets rather then in the open when not in use so they don't get too cold. Even when there is no high humidity, eyepieces can dew up quickly if it is cold enough - your eye is moist and just bringing it close to eyepiece can form dew on eye lens. Sometimes you can see your secondary dewed up if you look thru focuser without eyepiece there - or look down the front of the scope and look at reflection of secondary from the primary. You can even sometimes notice dewing up while at eyepiece if stars develop halo around them and there is more scatter in the field than usual.

High humidity can be a problem sometimes - most often if there is no wind at all. If there is slight breeze - it will keep air moving and it will be harder for optics to dew up because it will not get colder than environment.

Collimation is important for both planetary views (more important here), but also for DSO. Poor collimation blurs the image. Fainter stars will be less bright and faintest ones will not be even seen which will make orienting difficult. Low contrast features will vanish, and while brighter patches will still be bright with even poor collimation - you will have trouble recognizing things because you will lack contrast - it will tend to blend into background more. Luckily collimation is easy to check - just observe star - in focus and a bit out of focus (both sides of focus). There is plenty resource on internet what star image should look like and what it might look like if collimation is poor. After some training it will take just a simple glance at bright star to see if you should adjust it or whether your collimation is good.

With 76mm scope you will certainly be able to see major features of planets. Four Galilean moons and major belts of Jupiter will be easy in decent seeing. With some patience and observing skill you will be able to recognize great red spot at some point. Saturn will certainly present nice image with very distinct rings. Venus will show features accessible in larger scopes - it is milky ball, so nothing on the surface, but phases will be easily seen. Moon will be nice also. With x2 barlow and 10mm eyepiece you will be at maximum of your scope capability, but have patience with such combination - at first things will look very blurry and it might feel like it is much worse than you expected, but with time you will see that it is mostly due to seeing, and some nights are better than others. It takes a lot of time to discover true high power performance of your scope when you are beginner. You can't know what the night of excellent seeing looks like until you experience one, and these are rare so it may take quite a while before it happens. So with time you will get used to recognize quality of seeing and you will have a patience to wait for moment of better seeing on particular night.

One general tip: Observing is a skill that you acquire by doing it. Later on you will see even more detail and deeper with this scope then in the beginning, so don't beat your self if you don't manage particular target on particular night. Just try it again another night. 

I think that you should stay away from filters for the time being. Filters remove some of the light and 76mm Newtonian is a small scope so using filters will probably make things too dim. First learn to observe planets without filters and later when you know how to observe and what features you want to enhance, you will be "ready" for filters and they will be much more meaningful for your observations than using them right away.

Same thing goes for eyepieces - spend some time with eyepieces that you already have. Learn about eyepiece types later on. You have a slow scope and odds are that eyepieces you have will work very well with it. If you are on a tight budget - wider FOV of more expensive eyepieces is not something that should be of much interest. At later date if you decide that you want to get something better (and yes, there will be difference, and it is hard to explain what difference you will see - the more observing experience you have - there will be more difference, but even from start there are some aspects that will feel improved - ultimately eyepieces are personal preference so things can vary from person to person), it will most likely be better high power eyepiece to replace 10mm. Depending on type and quality of eyepieces that you have - decent plossl of same focal length (or maybe better 12mm) should be step up.

From what I can tell - your expectations are not high and you should be able to achieve them with your budget and said scope. Just give your self time and enjoy the hobby. With experience you will be able to see more, things will be easier to find (until you find object for the first time it can be tricky - it is much easier to observe it again after - both easier to find and you will have idea of what you are looking for) and you will better know your way around the sky.

P.S.

I just checked eyepieces that come with AstroMaster 76EQ. You might want to replace both with decent plossls. Something like 20mm Skywatcher SP Plossl, and 12.5mm Skywatcher SP Plossl would be good combination (or 25mm and 10mm - if you have 20mm and 10mm and x2 barlow then 20mm and x2 barlow will double on 10mm eyepiece, it's better to spread them so that you get unique focal lengths). I usually would not recommend upgrading 20-25mm stock eyepiece, but AstroMaster 76EQ seems to come with 20mm erect image one, and I'm just doubting its quality. Hopefully someone else can shine some light on quality of these eyepieces.

Hope this helps a bit

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Hi Harvey,

Your 76mm Newtonian has a 700mm focal-length.  For your lowest power, a 32mm Plossl will help you find your way around the sky, along with your red-dot finder...  

700mm ÷ 32mm = 22x, and almost binocular-like, power-wise.  I would get one of those straight away...

https://www.365astronomy.com/32mm-GSO-Plossl-Eyepiece.html

The nice thing about getting eyepieces is that you will always have them, as long as you don't lose or break them.  Breaking one is actually extremely difficult to do.  They will be there for telescope after telescope after telescope in future.

The 20mm that came with your kit is an erecting eyepiece, and suitable only for daytime/terrestrial use; birds in trees, ships at sea, and other various and sundry land-targets during the day.  You can get a 20mm Plossl(35x) for use at night...

https://www.365astronomy.com/20mm-GSO-Plossl-Eyepiece.html 

Now, a 10mm eyepiece comes with your kit, but you might like a wider and improved view.  You can barlow the 20mm Plossl, and for a simulated 10mm(70x), with a 2x barlow...

https://www.365astronomy.com/GSO-2x-Barlow-2-Element-Achromatic-Barlow.html

For the higher powers, your telescope should be able to realise at least 125x, perhaps up to 150x if the collimation is bang-on, and for the Moon, the planets, and the double-stars.  Let's see what you'd need to reach 125x first...

700mm ÷ 125x = a 5.6mm eyepiece; well, that's an odd size.  You can get a 12mm Plossl(58x) from that same listing, combine it with the 2x barlow, and for a simulated 6mm(117x).  Now, let's see what 150x would require...

700mm ÷ 150x = a 4.7mm eyepiece; hmm, there's another odd size.  Let's round that off a bit.  With the 2x barlow, you can get a 9mm Plossl(78x), and for a simulated 4.5mm(156x).

With a 2x barlow, and three to four eyepieces, you can have six to eight different powers at your disposal.  It's like having six to eight individual eyepieces, but without the extra cost.

Eyepieces are fully one half of the telescopic experience.  A telescope and a set of eyepieces are as one, and inseparable.  You can't use one without the other, therefore eyepieces are just as important as the telescope.  Indeed, there are quite a few experienced amateurs who have spent more on their eyepieces...than they did on their telescopes.

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Hi, Harvey, and welcome to SGL.

The main restriction you will have is the size of the main mirror of your scope ... it is small, but useable.

Don't get too hung up on magnification ... the maximum useful magnification for a 76mm mirror is 2x76 = 152x ... and that is when conditions are perfect (when did you last get perfect conditions in the east midlands?😀).

Eyepiece-buying is a bit of a money-pit. I have a ton of eyepieces that rarely got used even before I moved to exclusively imaging. I would agree that a 32mm would be a good purchase for this scope ... exploring the star-vistas of the Milky Way with such a combination will put this scope in its best light. And I would also endorse a 2x barlow as a second purchase. This would give you (excluding your "erecting" eyepiece): 32mm(22x), 16mm(44x), 10mm(70x) and 5mm(140x). That should be plenty to get you started.

Enjoy the journey.

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Thank you all for your timely and detailed responses! I've certainly gained a lot of knowledge after reading all of your comments, so I will go through them one-by-one and reply to them all individually! So bare with me again... 
 

7 hours ago, vlaiv said:

Hi and welcome to SGL.

I'll try to address as many of your questions as I can, so let's start with humidity.

Humidity is important factor to consider in winter time. Two major difficulties it creates are poor local transparency and dew on optics. First one you can't do much about, but there is simple method to check conditions - "light sabre" method. Have torch with you - white light one that you will not be using when observing but is handy when setting up and packing. Use one with narrow beam of light. Before you start your dark adaptation - shine it towards the sky. If you see light leaving the torch and creating "light sabre" kind of effect (or "batman signal" for those not familiar with Jedi culture :D ) - transparency is poor and don't expect much on a given evening. You can still observe but less targets will be within your reach.

Second is dew on mirrors. This should not happen often since you have newtonian scope. Your primary mirror is not likely to dew up, but secondary might. Eyepieces are prone to this also. Keep eyepiece in your pockets rather then in the open when not in use so they don't get too cold. Even when there is no high humidity, eyepieces can dew up quickly if it is cold enough - your eye is moist and just bringing it close to eyepiece can form dew on eye lens. Sometimes you can see your secondary dewed up if you look thru focuser without eyepiece there - or look down the front of the scope and look at reflection of secondary from the primary. You can even sometimes notice dewing up while at eyepiece if stars develop halo around them and there is more scatter in the field than usual.

High humidity can be a problem sometimes - most often if there is no wind at all. If there is slight breeze - it will keep air moving and it will be harder for optics to dew up because it will not get colder than environment.

Collimation is important for both planetary views (more important here), but also for DSO. Poor collimation blurs the image. Fainter stars will be less bright and faintest ones will not be even seen which will make orienting difficult. Low contrast features will vanish, and while brighter patches will still be bright with even poor collimation - you will have trouble recognizing things because you will lack contrast - it will tend to blend into background more. Luckily collimation is easy to check - just observe star - in focus and a bit out of focus (both sides of focus). There is plenty resource on internet what star image should look like and what it might look like if collimation is poor. After some training it will take just a simple glance at bright star to see if you should adjust it or whether your collimation is good.

With 76mm scope you will certainly be able to see major features of planets. Four Galilean moons and major belts of Jupiter will be easy in decent seeing. With some patience and observing skill you will be able to recognize great red spot at some point. Saturn will certainly present nice image with very distinct rings. Venus will show features accessible in larger scopes - it is milky ball, so nothing on the surface, but phases will be easily seen. Moon will be nice also. With x2 barlow and 10mm eyepiece you will be at maximum of your scope capability, but have patience with such combination - at first things will look very blurry and it might feel like it is much worse than you expected, but with time you will see that it is mostly due to seeing, and some nights are better than others. It takes a lot of time to discover true high power performance of your scope when you are beginner. You can't know what the night of excellent seeing looks like until you experience one, and these are rare so it may take quite a while before it happens. So with time you will get used to recognize quality of seeing and you will have a patience to wait for moment of better seeing on particular night.

One general tip: Observing is a skill that you acquire by doing it. Later on you will see even more detail and deeper with this scope then in the beginning, so don't beat your self if you don't manage particular target on particular night. Just try it again another night. 

I think that you should stay away from filters for the time being. Filters remove some of the light and 76mm Newtonian is a small scope so using filters will probably make things too dim. First learn to observe planets without filters and later when you know how to observe and what features you want to enhance, you will be "ready" for filters and they will be much more meaningful for your observations than using them right away.

Same thing goes for eyepieces - spend some time with eyepieces that you already have. Learn about eyepiece types later on. You have a slow scope and odds are that eyepieces you have will work very well with it. If you are on a tight budget - wider FOV of more expensive eyepieces is not something that should be of much interest. At later date if you decide that you want to get something better (and yes, there will be difference, and it is hard to explain what difference you will see - the more observing experience you have - there will be more difference, but even from start there are some aspects that will feel improved - ultimately eyepieces are personal preference so things can vary from person to person), it will most likely be better high power eyepiece to replace 10mm. Depending on type and quality of eyepieces that you have - decent plossl of same focal length (or maybe better 12mm) should be step up.

From what I can tell - your expectations are not high and you should be able to achieve them with your budget and said scope. Just give your self time and enjoy the hobby. With experience you will be able to see more, things will be easier to find (until you find object for the first time it can be tricky - it is much easier to observe it again after - both easier to find and you will have idea of what you are looking for) and you will better know your way around the sky.

P.S.

I just checked eyepieces that come with AstroMaster 76EQ. You might want to replace both with decent plossls. Something like 20mm Skywatcher SP Plossl, and 12.5mm Skywatcher SP Plossl would be good combination (or 25mm and 10mm - if you have 20mm and 10mm and x2 barlow then 20mm and x2 barlow will double on 10mm eyepiece, it's better to spread them so that you get unique focal lengths). I usually would not recommend upgrading 20-25mm stock eyepiece, but AstroMaster 76EQ seems to come with 20mm erect image one, and I'm just doubting its quality. Hopefully someone else can shine some light on quality of these eyepieces.

Hope this helps a bit

Thank you! I'll certainly be trying that light sabre method to test my next trip out! I couldn't say I've had much problem with dew build up on my mirrors but definitely on the eyepieces, I have been keeping them in my pockets already to hopefully try and limit this problem. 

I'm almost certain that my collimation is a huge problem here, I could tell it wasn't well collimated from the box after some checking, so I'll have to hunt around for some collimating eyepieces until I'm more experienced. 

As for the 20mm eyepiece, as others have said now it isn't all that great, I was going to look into replacing both of them very soon, but I was going to try and make do for now. After the advice I've gotten, I will definitely look to upgrading them. I'll most likely go for the 25mm and 10mm combination as you said :)

6 hours ago, Alan64 said:

Hi Harvey,

Your 76mm Newtonian has a 700mm focal-length.  For your lowest power, a 32mm Plossl will help you find your way around the sky, along with your red-dot finder...  

700mm ÷ 32mm = 22x, and almost binocular-like, power-wise.  I would get one of those straight away...

https://www.365astronomy.com/32mm-GSO-Plossl-Eyepiece.html

The nice thing about getting eyepieces is that you will always have them, as long as you don't lose or break them.  Breaking one is actually extremely difficult to do.  They will be there for telescope after telescope after telescope in future.

The 20mm that came with your kit is an erecting eyepiece, and suitable only for daytime/terrestrial use; birds in trees, ships at sea, and other various and sundry land-targets during the day.  You can get a 20mm Plossl(35x) for use at night...

https://www.365astronomy.com/20mm-GSO-Plossl-Eyepiece.html 

Now, a 10mm eyepiece comes with your kit, but you might like a wider and improved view.  You can barlow the 20mm Plossl, and for a simulated 10mm(70x), with a 2x barlow...

https://www.365astronomy.com/GSO-2x-Barlow-2-Element-Achromatic-Barlow.html

For the higher powers, your telescope should be able to realise at least 125x, perhaps up to 150x if the collimation is bang-on, and for the Moon, the planets, and the double-stars.  Let's see what you'd need to reach 125x first...

700mm ÷ 125x = a 5.6mm eyepiece; well, that's an odd size.  You can get a 12mm Plossl(58x) from that same listing, combine it with the 2x barlow, and for a simulated 6mm(117x).  Now, let's see what 150x would require...

700mm ÷ 150x = a 4.7mm eyepiece; hmm, there's another odd size.  Let's round that off a bit.  With the 2x barlow, you can get a 9mm Plossl(78x), and for a simulated 4.5mm(156x).

With a 2x barlow, and three to four eyepieces, you can have six to eight different powers at your disposal.  It's like having six to eight individual eyepieces, but without the extra cost.

Eyepieces are fully one half of the telescopic experience.  A telescope and a set of eyepieces are as one, and inseparable.  You can't use one without the other, therefore eyepieces are just as important as the telescope.  Indeed, there are quite a few experienced amateurs who have spent more on their eyepieces...than they did on their telescopes.

Thank you for all the advice on different lenses! I had a look at both the 32mm and 20mm plossl eyepieces and I'm definitely looking towards them when I get to upgrade, along with the Barlow lens you linked! I think my arsenal of eyepieces will look like this:

  1. 10mm SkyWatcher Plossl  - https://www.harrisontelescopes.co.uk/acatalog/skywatcher-10mm-sp-eyepiece-1.25-20372.html
  2. GSO 2x Barlow - https://www.365astronomy.com/GSO-2x-Barlow-2-Element-Achromatic-Barlow.html
  3. 20mm GSO Plossl  - https://www.365astronomy.com/20mm-GSO-Plossl-Eyepiece.html
  4. 32mm GSO Plossl - https://www.365astronomy.com/32mm-GSO-Plossl-Eyepiece.html

Thoughts? Recommendations? This will probably be a big investment (for me, anyway) but it'll be worth it, right? It should be a step up from the stock eyepieces with aren't amazing quality. 

4 hours ago, Demonperformer said:

Hi, Harvey, and welcome to SGL.

The main restriction you will have is the size of the main mirror of your scope ... it is small, but useable.

Don't get too hung up on magnification ... the maximum useful magnification for a 76mm mirror is 2x76 = 152x ... and that is when conditions are perfect (when did you last get perfect conditions in the east midlands?😀).

Eyepiece-buying is a bit of a money-pit. I have a ton of eyepieces that rarely got used even before I moved to exclusively imaging. I would agree that a 32mm would be a good purchase for this scope ... exploring the star-vistas of the Milky Way with such a combination will put this scope in its best light. And I would also endorse a 2x barlow as a second purchase. This would give you (excluding your "erecting" eyepiece): 32mm(22x), 16mm(44x), 10mm(70x) and 5mm(140x). That should be plenty to get you started.

Enjoy the journey.

Thanks for the tips! Yeah, thankfully I learnt early that magnification isn't everything, and didn't learn the hard way but buying an eyepiece with a lens the size of a pin 😃. Unfortunately, I don't know "perfect" conditions size I don't think I've really experienced it 😂. So would you recommend the eyepieces I listed above? I tried to go for a wider range of lens sizes, would you recommend changing the list at all? I wasn't sure if I should go for lens that are 7mm and below, because I heard they put a lot of strain on your eyes and are difficult to use, so should I buy at least one smaller lens to try it?

Thank you all for your responses once again! And thanks for the warm welcomes! The pointers you've all given me are certainly helpful to get me started! 

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HI Harvey, welcome to the forum.
You've had some great advice already and I don't intend to add to the discussion on eyepieces.
As you're new to the hobby I know it is all confusing, remember we were all beginners once, but perseverance is worth the effort. Navigating the night sky is a skill that has to be learned , when I started out I was advised to get a copy of Turn Left at Orion. This is a book which covers over 100 night time objects, arranged by season, with directions on how to find them, sketches of what to expect to see and brief facts about each object. 
You mention you were trying to find M!, although the first object in Messier's famous list it is by no means the easiest to see. If I were you I would start with something easier, M42 in Orion, M36, M37, and M38 in Auriga for example. 
Good luck and keep asking questions.

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58 minutes ago, SirHarveyXXI said:

So would you recommend the eyepieces I listed above? I tried to go for a wider range of lens sizes, would you recommend changing the list at all? I wasn't sure if I should go for lens that are 7mm and below, because I heard they put a lot of strain on your eyes and are difficult to use, so should I buy at least one smaller lens to try it?

A 20mm eyepiece will give you a magnification of 35x and the barlow will just duplicate the 10mm eyepiece. I would be inclined to put that on the back-burner. As for something shorter, I would compare the 10mm with  10mm + barlow first. If the barlow gives better views (more detail) then think about a shorter eyepiece. In this case, a 7mm would fit in the above scheme quite well. If not, you could be purchasing something you will rarely use.

Edited by Demonperformer

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1 hour ago, Astro Imp said:

HI Harvey, welcome to the forum.
You've had some great advice already and I don't intend to add to the discussion on eyepieces.
As you're new to the hobby I know it is all confusing, remember we were all beginners once, but perseverance is worth the effort. Navigating the night sky is a skill that has to be learned , when I started out I was advised to get a copy of Turn Left at Orion. This is a book which covers over 100 night time objects, arranged by season, with directions on how to find them, sketches of what to expect to see and brief facts about each object. 
You mention you were trying to find M!, although the first object in Messier's famous list it is by no means the easiest to see. If I were you I would start with something easier, M42 in Orion, M36, M37, and M38 in Auriga for example. 
Good luck and keep asking questions.

Thanks for the recommendation! I've already added that book to my order list! It sounds like it could be really helpful since I have been having trouble finding some things, but that's something I know will go away with experience. 

I went for M1 because I had presumed it wouldn't be too difficult to find, but how wrong I was! Thanks for the guidance, I'll be sure to try my luck finding those objects. 

1 hour ago, Demonperformer said:

A 20mm eyepiece will give you a magnification of 35x and the barlow will just duplicate the 10mm eyepiece. I would be inclined to put that on the back-burner. As for something shorter, I would compare the 10mm with  10mm + barlow first. If the barlow gives better views (more detail) then think about a shorter eyepiece. In this case, a 7mm would fit in the above scheme quite well. If not, you could be purchasing something you will rarely use.

So, I should try the 10mm with a barlow lens and if that's quite good then I should go for the 7mm? And scrap the 20mm in favour of a larger lens such as the 32mm? Thanks!

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6 minutes ago, SirHarveyXXI said:

I went for M1 because I had presumed it wouldn't be too difficult to find, but how wrong I was! Thanks for the guidance, I'll be sure to try my luck finding those objects. 

There's a difference between finding something and seeing it 😀
 

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Regards magnification, all telescopes with an open focuser will allow the end user the ability to supply and  insert their own eyepieces, therefore varying the amount of  magnification by virtue of the fact that the telescopes focal length divided by the  focal length of the eyepiece in use, will dictate the value or power of the magnification.

Your F-700mm telescope and a 9mm eyepiece will provide 77x power or magnification, which is slightly more that the aperture of your scope in mm.

I always advise folk ( don't want to dash their dreams and/or expectations ) but sticking with the  main feature of the telescope, its aperture, then your scope is good for 76x power or magnification. Your scope was built for it, go higher with the magnification, and the image deteriorates, losing its brightness, sharpness and  overall, detail. Reduce the magnification and the image becomes sharper, more detailed but infinitely smaller?

Sticking with the details on the the  telescopes data plate, ensures you are well within the limitations of your telescopes ability. And no matter how well the setup is or what type of scope/eyepiece combination you use, the seeing conditions will always be the deciding factor as to how clear that final image will be.

In a statement above, it's acknowledged that twice the aperture is a 'useful maximum.
For me, that's just useful to know! but highly unlikely in the real world. My useful limit accordingly is 400x? I've used 375x on the moon with my 3.2mm EP but generally I use 200x or less because that's what works best on this scope, its within the capability of the scope. 

Sticking with your telescopes aperture in mm will provide an equivalent power and a reasonable  high power image, if using an eyepiece that closely matches the  focal ratio  of the scope. So, if you use a 9.86mm eyepiece, your scope would give you  70.99x power/magnification, nigh on, a perfect high power setup for your scope. 

I replaced my Skywatcher 10mm with a BST 8mm Starguider eyepiece and what a difference!
I wouldn't go much  lower than a 7mm on your scope, but unless you try, you won't know.

In relation to your GSO's, I have a set of Plössl's made by GSO, branded Revelation Astro, and their (from my experience) very good, and I had no issues with them, in-fact I favoured them over the more premium branded optics like Meade, Tele Vue.
I had always wanted to own a set of decent Plössl's. That requirement no longer exists ?

Edited by Charic
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2 hours ago, Charic said:

In a statement above, it's acknowledged that twice the aperture is a 'useful maximum.
For me, that's just useful to know! but highly unlikely in the real world. 

So using a 10mm lens with a 2x barlow to get 140x which is close to double my aperture is unlikely to give me a good image? Is it worth trying to find out for myself how good the conditions need to be so I can spot a night where I will be able to reach such a magnification?

2 hours ago, Charic said:

Sticking with your telescopes aperture in mm will provide an equivalent power and a reasonable  high power image, if using an eyepiece that closely matches the  focal ratio  of the scope. So, if you use a 9.86mm eyepiece, your scope would give you  70.99x power/magnification, nigh on, a perfect high power setup for your scope. 

I replaced my Skywatcher 10mm with a BST 8mm Starguider eyepiece and what a difference!
I wouldn't go much  lower than a 7mm on your scope, but unless you try, you won't know.

In relation to your GSO's, I have a set of Plössl's made by GSO, branded Revelation Astro, and their (from my experience) very good, and I had no issues with them, in-fact I favoured them over the more premium branded optics like Meade, Tele Vue.
I had always wanted to own a set of decent Plössl's. That requirement no longer exists ?

So is it worth buying a 9mm eyepiece AND a 10mm, or just one? How can I tell which one will be better, like you said with the 10mm eyepiece and 8mm eyepiece, the 8mm made a large difference, is there any way for me to guess how much of a difference it will make? As I said, my budget is low so I can't afford to go buying eyepieces that are substandard 😂

Thanks!

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Really depends on your budget.

How many eyepieces can you afford with barlow lens. Based on that we can work out good combination.

I also prefer GSO plossls by Skywatcher plossls are a bit cheaper. If you can afford get GSO. I don't think it is good idea to get eyepieces below 10mm, at least not Plossls. Eye relief will be tight on those so your observing comfort may suffer. While your scope can support down to about 5mm focal length for maximum magnification - I would not go as low as that. 12mm with barlow would get you to 6mm and that is decent magnification. If you go with 8 or 9mm eyepiece and try to use it with barlow, I think it will be too much magnification for enjoyable view. Using them on their own will have tight eye relief.

I like the idea of 32mm eyepiece, it is very good eyepiece for wide field, but I have some reservations on that one for your scope, and someone who used similar combination needs to step in and say if it works ok. With only 76mm aperture, I'm wondering what sort of secondary size your scope has. Since it is long focal length scope, I'm guessing 25% or less - that means around 20mm secondary. I'm simply not sure that you will be able to fully illuminate field of 32mm plossl eyepiece. You might get vignetting with this eyepiece. Most beginner scopes come with 25mm and 10mm eyepieces - which makes sense, add x2 barlow (if one is not included) and you get decent range of focal lengths: 25mm, 12.5mm, 10mm, 5mm. I wonder why Celestron opted to supply 20mm and 10mm with this scope - it might be precisely because small secondary, and even 25mm eyepiece vignettes a bit (again, someone needs to confirm this as I'm just guessing here).

Anyway, 12mm is eyepiece I think you should build your set around. With x2 barlow you will have 12mm and 6mm focal lengths. I have 12mm GSO plossl and it is decent eyepiece, nice on eye relief and sharp.

Now that we have those focal lengths covered, second thing to consider is what long focal length you want. 32mm is very good choice if your scope can handle it. 25mm is not very good choice as you will be duplicating focal length that you already have - 12mm (25/2 = 12.5). A good set would for example be:

32, 20, 12 + barlow, and that would give you following range: 32, 20, 16, 12, 10, 6, provided that 32mm works well.

Another set that you might consider is this:

20, 15, 12 + barlow. That one will give you following range: 20, 15, 12, 10, 7.5, 6.

In longer focal lengths you don't need to cover close values, but it ok to do that in shorter focal lengths. For example 20mm vs 15m will give you x35 vs x47 magnification. Compare that to 7.5mm and 6mm - x93 vs x116 - almost same increase in magnification for small shift in focal length.

 

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32 minutes ago, vlaiv said:

I like the idea of 32mm eyepiece, it is very good eyepiece for wide field, but I have some reservations on that one for your scope, and someone who used similar combination needs to step in and say if it works ok. With only 76mm aperture, I'm wondering what sort of secondary size your scope has. Since it is long focal length scope, I'm guessing 25% or less - that means around 20mm secondary. I'm simply not sure that you will be able to fully illuminate field of 32mm plossl eyepiece. You might get vignetting with this eyepiece. Most beginner scopes come with 25mm and 10mm eyepieces - which makes sense, add x2 barlow (if one is not included) and you get decent range of focal lengths: 25mm, 12.5mm, 10mm, 5mm. I wonder why Celestron opted to supply 20mm and 10mm with this scope - it might be precisely because small secondary, and even 25mm eyepiece vignettes a bit (again, someone needs to confirm this as I'm just guessing here).

I'll have to look around and see if anyone has tried this combination, but now you mention it I'm in doubt as to whether my scope could illuminate it.

34 minutes ago, vlaiv said:

Anyway, 12mm is eyepiece I think you should build your set around. With x2 barlow you will have 12mm and 6mm focal lengths. I have 12mm GSO plossl and it is decent eyepiece, nice on eye relief and sharp.

Another set that you might consider is this:

20, 15, 12 + barlow. That one will give you following range: 20, 15, 12, 10, 7.5, 6.

I think I'll definitely look into that set, it seems like my scope should be able to handle it and it should be good to get me started, the 12mm with the barlow lens will give me a decent magnification when I need it and the 20mm will be a definite upgrade from the 20mm supplied with the scope.

Thanks for the advice!

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2 hours ago, SirHarveyXXI said:

So using a 10mm lens with a 2x barlow to get 140x which is close to double my aperture is unlikely to give me a good image? Is it worth trying to find out for myself how good the conditions need to be so I can spot a night where I will be able to reach such a magnification?

5 hours ago, Charic said:

Absolutely worthwhile trying for your self, thats how you learn, what we offer is based on experience, our  own experience. 

You'll no doubt possibly get an image using the setup you describe, but the point I made earlier was that your scope is capable of producing decent images at 71x magnification, NOT at 140x twice the theoretical limit? You're  simply asking too much from that scope. If you need more power, and a decent image,  you'll probably  fare better or need another scope in order to achieve that,  but if you're  happy   with the result at 140x then keep at it.

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1 minute ago, Charic said:

Absolutely worthwhile trying for your self, thats how you learn, what we offer is based on experience, our  own experience. 

You'll no doubt possibly get an image using the setup you describe, but the point I made earlier was that your scope is capable of producing decent images at 71x magnification, NOT at 140x twice the theoretical limit? You're  simply asking too much from that scope. If you need more power, and a decent image,  you'll probably  fare better or need another scope in order to achieve that,  but if you're  happy   with the result at 140x then keep at it.

Maximum telescope magnification is not exactly defined since it also depends on visual acuity of observer.

Often quoted maximum magnification of x2 per mm of aperture, and in this case 76mm scope would give x152 is grounded in theory - most people have resolving power of 1' - one minute of arc. This value combined with Rayleigh criteria gives such value of x2 aperture in mm. For details check out this page:

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/Raylei.html

It discusses 5mm eye iris and resolving power - human resolving power is within x12 of Rayleigh criteria for 5mm aperture (according to above x2 per mm would give this ratio to be x10 so a bit off).

All of this is for perfect optics. For most telescopes this is really "top" constraint on useful magnification and in reality one should stay below that value.

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2 hours ago, SirHarveyXXI said:

So is it worth buying a 9mm eyepiece AND a 10mm, or just one? How can I tell which one will be better, like you said with the 10mm eyepiece and 8mm eyepiece, the 8mm made a large difference, is there any way for me to guess how much of a difference it will make? As I said, my budget is low so I can't afford to go buying eyepieces that are substandard 😂

 

The 8mm was better in my case due to the design of the eyepiece itself. The 8mm BST Starguider has a 60°afov (apparent field of view)  with comfortable eye-relief for me  ( how close my eye needs to be to the eye glass, and the overall size of that eye-glass ( I'm not looking through a pin-hole! ) just makes for a more comfortable eyepiece to use, on my scope.
Compared to the standard skywatcher 10mm eyepiece  the 8mm BST Starguider is a no brainer!

As for which  eyepiece will be better, based on your focal ratio,  I'd say a 12mm and 18mm would be a good start, as they would get more use than the 8 mm or shorter.  With a suitable 2x Barlow, you could achieve  the following powers, 18mm =38x  12mm= 58x   2xBarlow+18=77x  &  2xBarlow 12=116x.

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1 minute ago, vlaiv said:

Maximum telescope magnification is not exactly defined since it also depends on visual acuity of observer.

It is if we suggest using the size of the aperture!

But you're right, the limits of the scope will found by the end user, based on their visual acuity, skill,  their setup up, conditions,  I could add loads more, the list goes on and on, but there will be a limit.

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21 minutes ago, Charic said:

Absolutely worthwhile trying for your self, thats how you learn, what we offer is based on experience, our  own experience. 

You'll no doubt possibly get an image using the setup you describe, but the point I made earlier was that your scope is capable of producing decent images at 71x magnification, NOT at 140x twice the theoretical limit? You're  simply asking too much from that scope. If you need more power, and a decent image,  you'll probably  fare better or need another scope in order to achieve that,  but if you're  happy   with the result at 140x then keep at it.

Thanks! I'll have a play with it and see how it goes. If it isn't good enough then I'll buy a 15mm eyepiece and use the barlow to get just under 100x magnification or a 14mm and get just over, either should be good enough I hope. 

If I feel like I need more power I could always go for the 12mm you recommended. 

 

9 minutes ago, vlaiv said:

Maximum telescope magnification is not exactly defined since it also depends on visual acuity of observer.

Often quoted maximum magnification of x2 per mm of aperture, and in this case 76mm scope would give x152 is grounded in theory - most people have resolving power of 1' - one minute of arc. This value combined with Rayleigh criteria gives such value of x2 aperture in mm. For details check out this page:

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/Raylei.html

It discusses 5mm eye iris and resolving power - human resolving power is within x12 of Rayleigh criteria for 5mm aperture (according to above x2 per mm would give this ratio to be x10 so a bit off).

All of this is for perfect optics. For most telescopes this is really "top" constraint on useful magnification and in reality one should stay below that value.

I'll definitely read into that, thanks for the link! In that case, if I'm not happy with the 140x I get with my 10mm eyepiece, I'll buy a slightly bigger one (such as a 12mm) and go for just over 100x, which shouldn't be too bad I'm hoping. 

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4 minutes ago, Charic said:

It is if we suggest using the size of the aperture!

But you're right, the limits of the scope will found by the end user, based on their visual acuity, skill,  their setup up, conditions,  I could add loads more, the list goes on and on, but there will be a limit.

Yes, bad wording on my part - I was trying to point out that theoretical maximum resolution of telescope of a given aperture is around two times it's diameter in millimeters (not one time as you are suggesting), but this theoretical maximum power depends on quality of optics but also on visual acuity of observer. Not everyone has sharp enough vision to be able to exploit this maximum magnification.

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18 minutes ago, vlaiv said:

Yes, bad wording on my part - I was trying to point out that theoretical maximum resolution of telescope of a given aperture is around two times it's diameter in millimeters (not one time as you are suggesting),

Not at all vlaiv. 

I totally agree with the theory of twice the aperture.
My suggestion ( that's all it is ) is to assume that 1x aperture  ( equivalent to power ) is fully achievable,  and well  within the capability of the scope in use, any more is  often a bonus. 

So often, users are informed that their scope is capable of this or that, but in reality, not often achievable.

 

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8 minutes ago, Charic said:

Not at all vlaiv. 

I totally agree with the theory of twice the aperture.
My suggestion ( that's all it is ) is to assume that 1x aperture  ( equivalent to power ) is fully achievable,  and well  within the capability of the scope in use, any more is  often a bonus. 

So often, users are informed that their scope is capable of this or that, but in reality, not often achievable.

 

Let's agree to agree then :D

 

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A 32mm Plossl should stand alone, given its own physical length.  You'd have quite the tower jutting out of the focusser when combining a 32mm with a barlow...

1695325632_32mmbarlowed.jpg.1b169d313ecaa0e20cb2d4463db31833.jpg

...and I have no idea how far outward the combination would need to be racked to reach focus.  There on the right it's racked out about halfway; a "skyscraper" even, what?

That's the focusser of this Meade 114mm f/8 Newtonian that I have...

kit4b.jpg.9050bb379203a68d0257976faa054203.jpg

...and the configuration similar to your own.  Here, I have a 20mm Erfle combined...

598158110_20mmbarlowed.jpg.edf128e491be164836efb02c184f09c8.jpg

Better, but I rarely if ever barlow an eyepiece longer than 12mm.  However, for the economical aspect of a barlow, you can certainly combine a 20mm Plossl with one, and at a more practical limit.  You want to keep the combinations as short as possible, especially with a 76mm telescope.  I also have this "AstroMaster" 70mm long-focus refractor kit, and the refractive equivalent of your own...

kit3.jpg.34f3adc3b157025f8197de8308db34ad.jpg

I'd suggest a 32mm, a 20mm, a 12mm, all Plossls, and a 2x barlow.  In future, you can add a 9mm Plossl, or of another design, perhaps a wide-angle, then barlow that for a simulated 4.5mm(156x), when you're ready.  You might not use a power that high very often, but telescopes in the first place are for seeing faraway objects up close, and that would be about as close to practicality as you might realise with that kit.  The Moon, being so near to the Earth, takes a lot of magnification, so feel free to ramp up the power on it, maxing out the available aperture.  I've barlowed a 6mm before, for a simulated 3mm, and where "Wow!" and "Look at that!" exist.  You'll never know what you might see until you try.

Incidentally, with that wee 70mm refractor up there, I had it up to 225x on Polaris, albeit dank and dim, yet its first-diffraction ring was sharp to the point where it appeared as illuminated teeth of a whirling circular-saw blade.  Granted, that was after I had overhauled the telescope, fixing this and fixing that.

Now, you and I, both, have a Celestron "Deluxe" CG-2(EQ-1) equatorial mount.  It's a bit zippier, in appearance, than a dead-common CG-2 as found within the "PowerSeeker" series.  As shown above, I have one too, but I haven't tried one of these on it quite yet...

https://www.firstlightoptics.com/sky-watcher-mount-accessories/ra-economy-motor-drive-for-eq1.html

You shouldn't have to get the more costly "Celestron"-branded one, but here it is...

https://www.harrisontelescopes.co.uk/acatalog/celestron-astromaster-ra-drive-motor.html#tab-4

Here's my own Celestron drive...

7a.jpg.9f3184b2fdc5577c25b328481bb1c12c.jpg

The Celestron drive comes with two mounting brackets, one for the CG-2(EQ-1) like our own, and one for the CG-3(EQ-2).

With either 9V-battery motor-drive, you can track the objects you're observing, particularly at the higher powers where it's most needed, automatically and hands-free.  You can adjust the speed of the motor even, centering an object within an eyepiece to where it stands perfectly still, and for as long as you'd like.  You'll want to use a lithium-type 9V-battery for best performance, especially during the winter.  Now, it would be a basic, mechanical joining, the drive to the mount, and not the most precise of integrations.  You'd have to work with it to get it running smoothly, tinkering and puttering with it, but it's not that difficult really.  But before ever attaching it however, you must be able to turn the worm-shaft of the RA, or right-ascension, axis with your fingers somewhat easily, and without a telescope or counterweight(s) attached.  It is one of two critical areas of the mount where it may need your attention, and just as my own did in fact...

344670242_wormshaftgear.jpg.fb5e1ce8cf50164aa31e5b459585500e.jpg  

This is where you adjust the tension of the worm's shaft, and to enable it to turn more easily...

3f.jpg.3777e596e189872d06d345e895dde635.jpg

You must first loosen the set-screw, arrowed in green, with a 2mm hex-key I believe, but don't back it out to where it falls out, as it's quite tiny.  Then, you turn the tensioning-nut either inward or outward to adjust, arrowed in yellow.  Now, that nut is made of aluminum, and it can be damaged if you're not careful.  I used a pair of needle-nosed pliers to turn and adjust it.  There are two slots on the nut where you would insert the tips of the pliers.  You might lubricate where the nut is inserted into the block, if it's too tight, and with a dab of machine-oil or WD-40.  Once everything is adjusted, and to where you can twist the shaft with your fingers, with no binding of the worm or gear whatsoever, you then tighten down the set-screw, but do not torque it down.

The RA-worm must also engage the teeth of the RA-gear evenly and squarely; not too tightly, nor too loosely.  That can make the worm-shaft hard to turn as well.  Here, you can see where the worm meshes with the gear...

worm shaft & gear2

That meshing-together is adjusted by the bolts under the worm-block...

505006614_wormshaftgear3.jpg.16d77f40d02cc8422bdf59360b844f4f.jpg

You want the worm square and true to the gear.

The other critical area is at the rear of the RA-axis, the end of the RA-shaft and its lock-nut...

1966584039_RAlock-nut.jpg.834d519aeae0a61655c5447c3ebe977f.jpg

There is a thin, grey, textured, plastic cover that must be removed for access to the lock-nut.  The lock-nut may then be adjusted, either with a socket-wrench if one will fit into the cavity, or with a heavy-duty pair of needle-nosed pliers...

766281340_RAlock-nut2.jpg.85d18902a4dc46dedfa9e67595944a6a.jpg

You want the RA-axis to spin around freely and smoothly, and without slop.

A less critical and much easier adjustment is to the DEC, or declination, axis, and to its lock-nut.  The nut lies just under where the telescope is mounted and clamped.  It does not have a cover...

1947356913_DEClock-nut.jpg.b34c1d5016caa24fc51733f37a401d81.jpg 

In the end, you want both axes to rotate freely and smoothly, with no binding, no slop, and like a well-oiled gyroscope...

https://www.youtube.com/watch?v=p9zhP9Bnx-k

Do not think for one moment that these mounts leave the factory well-adjusted, for they do not, and as my own had revealed.  Once put in order, there will be little to no risk of damaging the mount or a motor-drive, or whether when using the manual, slow-motion controls that come with the kit.

Lastly, very few amateurs take these mounts seriously, but I do.  Many will say that it's "flimsy", "wonky", or belittle it in other ways.  The CG-2(EQ-1) is the smallest of equatorials, yet it is fully functional and usable, and best suited for a camera or a rather small telescope.  I have two or three such telescopes that will be mounted upon it, and after I disassemble and overhaul it.

Edited by Alan64

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It's sometimes possible to loose track with these threads of what the original posters scope is, in this case a 76mm newtonian.

Some of the eyepiece combinations suggested will cost a good chunk of the overall cost of something like a Heritage 130mm newtonian, bought on the used market.

I do wonder if getting used to using his current scope scope with whatever accessories are provided while saving to make the transition to a 130mm aperture might be a good and ultimately more satisfying alternative to investing £'s in eyepieces / barlows for the existing 76mm scope ?

Just a thought :smiley:

 

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What used, as the kit on hand is only £18 less than a brand-spanking new "Heritage" 130P...

...hint hint.  :D

Still, the 130P comes with the same modified-achromatic oculars, therefore the getting of the Plossls and a barlow is utterly independent of either kit, floating and hovering above them both, there in the aether.

 

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      First post on here looking for some telescope buying advise. I've searched and seen some similar topics which have been very useful but thought i'd summarise and see what the experts think.
      I'm looking at getting myself and my girlfriend a telescope as an anniversary gift. She's not scientifically minded at all but she really likes the aesthetic of the moon. The house is filled with 3D printed moon lamps, jewelry, cushion covers etc.. We're about to move into a new house in Forest Hill in SE London and the new house has a really large garden backing onto more gardens so quite sheltered from all street lights. We both said to eachother a telescope might be a nice thing to have in the new house and something we can enjoy together in the new garden. 
      I've got a budget of up to £200 but by no means want to spend that much if I'm paying for features we don't need or will use. 
      I've got some experience with a reflector scope that was my brothers. He got it years ago and we both obsessed over it for about a month and then once we'd seen the big planets and a few blurry distant clusters we got bored and it never got touched again. That was a 130mm DIA reflector (skywatcher I think). After the initial excitement, my overriding feeling towards it was it was not worth the faff! This was in dark Northumberland as well, not London. 
      I've tried to explain this to my girlfriend when we've talked about it and said if we don't want the faff we might have to invest in a Go to electric telescope. The logic being if its quicker and easier to see stuff, we'll use it more. I did get then quite excited reading reviews and trying to find second-hand goto scopes and it seems like something in my budget (or slightly pushed budget) is something like a Celestron SLT 127. (have seen second hand ones go for £250).
      However having then done a bit of reading on here I think i've worked out that those cheaper Go-to's are still not that quick and simple to use, ultimately i'm I'm still only going to see fairly blurry planets and smudges of deep space clusters. I honestly don't think the girlfriend will be impressed and I'll probably get bored after a while too.  
      So I think I've come to the conclusion that I want to get a much smaller refractor that would be much more accessible for viewing the moon and would allow us to see a smudgy Saturn and Jupiter on clear nights. A smartphone camera holder would be a bonus too as it adds a simple feature that would keep us entertained for longer. 
      Do you think that's a fair approach or am I being a little too pessimistic about what I'm going to see? If so then what scopes could anyone recommend? Stepping down to a slightly lower budget there are so many more options and it's a bit bewildering. 
      Thanks
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