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2.5mm EP or x3 Barlow?


Yamez
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My telescope is the Skywatcher Explorer 130P GoTo

Is it worth getting a 2.5mm EP for my telescope or a x3 Barlow lens.

I'm asking because i would love to see mars and Saturn closer up for finer detail.

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In your scope (having a focal length of 650mm) a 2.5mm EP would give you 260x magnification, far too much mag for this country.

Remember, you are not just magnifying what you are looking at but all the atmosphere and dust particles in-between, generally, 260x mag is too much for our moisten laden air, try to keep it below 200x mag if you can, sometimes that can be even too much.

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For the 10mm no, a barlowing a 10mm will make it a 3.3mm ep.

Barlowing the 25mm will give you a 8.3mm ep.

The 3.3mm will give you 196x mag, I know that is below what I said (200x mag) but it is still pushing it.

The 8.3mm (barlowed 25mm) will give you 78x magnification.

Word of warning though on barlows, cheap ones are naff, dim the image you are trying to view and generally produce a bad view.

If you go down the barlow route, try to get a good one, like a Tal for example.

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1 minute ago, Daz Type-R said:

For the 10mm no, a barlowing a 10mm will make it a 3.3mm ep.

Barlowing the 25mm will give you a 8.3mm ep.

The 3.3mm will give you 196x mag, I know that is below what I said (200x mag) but it is still pushing it.

The 8.3mm (barlowed 25mm) will give you 78x magnification.

Word of warning though on barlows, cheap ones are naff, dim the image you are trying to view and generally produce a bad view.

If you go down the barlow route, try to get a good one, like a Tal for example.

Ive used a 4mm with a x2 Barlow and have still seen details on Jupiter although it has to be a still and calm night and is quite hard to focus. Could you suggest me a good x3 Barlow?

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There are several good 3x Barlows (the Bresser SA 3x Barlow is one), but I seriously doubt that would give great views. Your scope is F/5, so a 4 or 5mm EP tends to give optimal views. A 3.5 might still work quite well. Anything much shorter makes things bigger, but will typically not reveal much more detail. In my F/10 scope I do not go shorter than 7mm (equivalent to a 3.5mm in an F/5 scope), and only use that on very, very steady nights on Jupiter. I think investing in a good 4 or 5mm EP might bring more benefits than going for ultra high magnification.

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i am sure you know the theoretical max mag for your scope Yamez, it's approx 2x the aperture in mm..260x...so 200x should be ok.  The revelation barlow gets a pretty good write up, search it on here.   

One question to Daz... don't you class your 2" 2x powermate as a barlow then?

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24 minutes ago, Daz Type-R said:

+1 for the above.

Never owned a barlow so cant really comment but I would have a fixed length ep over a barlowed ep any day.

Remember though a good 2x Barlow will also double the amount of options that you can view the sky with. So with your 25mm & 10mm EP's, you would in effect have two new EP focul lengths to view things with, which with the 2x Barlow would also give you a 12.5mm & a 5mm EP, so four for the price of one. One other benefit sometimes also with using a Barlow with an EP is it is also easier to look through the eyepiece and view things. This is especially true when talking about plossl EP's, as higher magnification EP's (4mm for example) have a much more restricted view to peer through, so your eye has to be pressed real close to the EP to view through it. It is a quick way early on until you can expand your EP range to get more magnification options available. 

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4 minutes ago, mikeyj1 said:

i am sure you know the theoretical max mag for your scope Yamez, it's approx 2x the aperture in mm..260x...so 200x should be ok.  The revelation barlow gets a pretty good write up, search it on here.   

One question to Daz... don't you class your 2" 2x powermate as a barlow then?

Hi, no, Barlows and Power Mates are a different beast. While they do the same job, a Barlow (in my opinion) is no where near as good.

Im sure that will start a Barlow vs Power Mate debate :p 

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1 minute ago, Daz Type-R said:

Hi, no, Barlows and Power Mates are a different beast. While they do the same job, a Barlow (in my opinion) is no where near as good.

Im sure that will start a Barlow vs Power Mate debate :p 

haha i've never heard of a power mate :D

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I think its worth trying to keep on track for more relevant options for the OP. I know you didn't raise the topic Daz :)

One suggestion might be a good 7 or 8mm eyepiece, plus a x2 barlow of decent quality. This would give a medium and high power option and likely a better result than trying to x3 barlow a cheap eyepiece. BST Explorers get good reviews, and as has been suggested, Revelation barlows seem good value and good quality.

As for the barlow/powermate discussion, there are barlows of equal or better quality to the PMs out there, but they don't figure in this discussion because I would upgrade the scope before spending that type of money on accessories, far more of an improvement to be had.

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6 minutes ago, Stu said:

I think its worth trying to keep on track for more relevant options for the OP. I know you didn't raise the topic Daz :)

One suggestion might be a good 7 or 8mm eyepiece, plus a x2 barlow of decent quality. This would give a medium and high power option and likely a better result than trying to x3 barlow a cheap eyepiece. BST Explorers get good reviews, and as has been suggested, Revelation barlows seem good value and good quality.

As for the barlow/powermate discussion, there are barlows of equal or better quality to the PMs out there, but they don't figure in this discussion because I would upgrage the scope before spending that type of money on accessories, far more of an improvement to be had.

After reading these i was thinking maybe a 7 or 6 ive seen a 7.5 but is there a 6.5mm?

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+1 for the 7-8mm + barlow 2x . Don't forget to get a collimator too. If not collimated, a telescope won't perform well, particularly on planets and whatever requires high power.  

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1 minute ago, Piero said:

+1 for the 7-8mm + barlow 2x . Don't forget to get a collimator too. If not collimated, a telescope won't perform well, particularly on planets and whatever requires high power.  

Im still new to astronomy got my first scope at Christmas so what is a collimator and could you link me to one?

 

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In my opinion more is less. In my f6 scope I use three highish power EPs: 12mm, 8mm and 5mm. Even on a night of perfect seeing, I still prefer the view of Jupiter through the 12mm EP. And that's not me being strange, it's because I genuinely see more detail in the 12mm - the 5mm shows the same as what the 12mm does, just half a turn out of focus and a little bigger. In fact, even my 20mm EP shows more structure than the 5mm on almost any night! That 'twice your aperture' limit, in England should actually be more like 1-1.3* your aperture, in my opinion.

DEFINITELY DON'T go for anything lower than an effective 3.5/4mm, but ideally no less than 5mm as your highest power.

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17 minutes ago, Yamez said:

Im still new to astronomy got my first scope at Christmas so what is a collimator and could you link me to one?

Hi Yamez :) 

Collimation is the process of aligning the optics in a telescope. Your newton telescope needs to be collimated in order to work well. It is made of a primary and a secondary mirror. The former is the one you will need to check quite often, the latter sometimes. As you can see, there are three screws or hex screws for each of these mirrors. These serve to collimate it. The best thing is to just play on two of them, while leaving untouched the third one. 

Here is a guide I used for learning the process: http://www.skyandtelescope.com/astronomy-resources/how-to-align-your-newtonian-reflector-telescope/ 

and here is the collimator I have for my Newton: https://www.firstlightoptics.com/other-collimation-tools/cheshire-collimating-eyepiece.html 

At the beginning, you might find collimation a bit of a pain, but it is not really. It just takes a bit of practice and within a little you will collimate your telescope within few minutes. :) 

 

EDIT: in the Sky & Telescope guide, they also tell you how to add a circle on your primary mirror. If your telescope does not have a circle, don't add it. At this stage, you might damage the mirror. Anyway, you can also collimate it without that circle placed theoretically at the centre. 

Here is also another guide: http://garyseronik.com/a-beginners-guide-to-collimation/ 

Edited by Piero
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I can get 270x with my 130M Explorer with a TV 3x Barlow and a 10mm EP. I'd argue that 260-70x isn't possible in the UK with a 5.1" aperture. Of course, it depends where you are observing from and what the target is. I live in the greenbelt.

LuminosTV3x.jpg

I can get 270x on the Moon, but the transparency has to be good. I can get an 0.47 exit pupil for 270x. It is pushing it though and conditions have to be good.

Edited by Mak the Night
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I would suggest to increase magnification gradually depending on the seeing conditions. Although it is possible to use powers of +250x here in the UK, it is more likely that 200x is about the limit. Many don't like magnifications with exist  pupil below 0.5mm due to more visible floaters. 

My 2 cents,

Piero

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Yes, it's best to start with a low magnification and gradually increase it to see how far you can go on any particular night. I believe you should be able to see most planetary detail around the 150x mark. But I think it's worth seeing how far a 130mm scope can go. My 5.1" Newtonian has occasionally surprised me.

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27 minutes ago, Mak the Night said:

Yes, it's best to start with a low magnification and gradually increase it to see how far you can go on any particular night. I believe you should be able to see most planetary detail around the 150x mark. But I think it's worth seeing how far a 130mm scope can go. My 5.1" Newtonian has occasionally surprised me.

Indeed my Newt has surprised me as i pushed way up 362x mag with the 4mm and a 2x Barlow to see what would happen and surprisingly i saw the 2 bands on jupiter and the GRS just. That night was very calm though so i usaly stick to just the 4mm. From reading these replies i've changed my mind from a 2.5 and the x3 barlow and instead i am now intrested in the 6mm for medium to high power. https://www.firstlightoptics.com/celestron-eyepieces/celestron-omni-plossl-eyepiece.html This EP is still small enough to fit inside of my extension tube when imaging with a dslr unlike my huge planetary 4mm.

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1 hour ago, Yamez said:

Indeed my Newt has surprised me as i pushed way up 362x mag with the 4mm and a 2x Barlow to see what would happen and surprisingly i saw the 2 bands on jupiter and the GRS just. That night was very calm though so i usaly stick to just the 4mm. From reading these replies i've changed my mind from a 2.5 and the x3 barlow and instead i am now intrested in the 6mm for medium to high power. https://www.firstlightoptics.com/celestron-eyepieces/celestron-omni-plossl-eyepiece.html This EP is still small enough to fit inside of my extension tube when imaging with a dslr unlike my huge planetary 4mm.

It all really depends on conditions, but occasionally you can get high magnifications. It's nice to know you can reach them occasionally lol. The real problem is approaching the exit pupil limit for the particular scope. The human eye can't really process anything less than 0.5mm. I can get 0.47mm for 270x on my 130M.

I have three 6mm EP's, two of them are Celestron Plossls and the third is an Astro Hutech orthoscopic which rivals TeleVue for clarity and actually outdoes Plossls for contrast with planetary targets.

6mm 1.jpg

The Omni series, like most Celestron/Orion/Revelation Plossls are Guan Sheng Optical (GSO) and are perfectly decent Plossls, I still use some of mine.

6mm 2.jpg

The two Celestron 6mm are from Celestron kits, I'm pretty sure the one on the left is GSO, but the one on the right is heavier as it has a chromed brass draw tube. It also doesn't appear to be like a standard GSO Plossl in many other respects. The decal/writing is painted rather than silk screened and I think it gives a brighter, clearer image. I used it often on my 130mm scope. I'm fairly sure it is Synta-made. In fact, I liked this Plossl so much I acquired a 6mm Hutech ortho' to get 166x with my portable 90mm Mak. If you can deal with the tight eye relief of a 6mm Plossl and the corresponding smaller FOV they can produce some good results.

Edited by Mak the Night
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3 minutes ago, Mak the Night said:

It all really depends on conditions, but occasionally you can get high magnifications. It's nice to know you can reach them occasionally lol. The real problem is approaching the exit pupil limit for the particular scope. The human eye can't really process anything less than 0.5mm. I can get 0.47mm for 270x on my 130M.

I have three 6mm EP's, two of them are Celestron Plossls and the third is an Astro Hutech orthoscopic which rivals TeleVue for clarity and actually out does Plossls for contrast with planetary targets.

6mm 1.jpg

The Omni series, like most Celestron/Orion/Revelation Plossls are Guan Sheng Optical (GSO) and are perfectly decent Plossls, I still use some of mine.

6mm 2.jpg

The two Celestron 6mm are from Celestron kits, I'm pretty sure the one on the left is GSO, but the one on the right is heavier as it has a chromed brass draw tube. It also doesn't appear to be like a standard GSO Plossl in many other respects. The decal/writing is painted rather than silk screened and I think it gives a brighter, clearer image. I used it often on my 130mm scope. I'm fairly sure it is Synta-made. In fact, I liked this Plossl so much I acquired a 6mm Hutech ortho' to get 166x with my portable 90mm Mak. If you can deal with the tight eye relief of a 6mm Plossl and the corresponding smaller FOV they can produce some good results.

Hey Mak,

These EP's do sound quite good but due to the viewing hole being quite small is it still possible to use a DSLR to image through one of these EP's?

Thanks Yamez.

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1 minute ago, Yamez said:

Hey Mak,

These EP's do sound quite good but due to the viewing hole being quite small is it still possible to use a DSLR to image through one of these EP's?

Thanks Yamez.

Sorry, I have no idea. I don't see why they shouldn't work like any other EP though.

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