Not sure what eyepieces?

[itchytrigafinga]

Hi Guys,

Just signed up to the forum as I’m after a bit of advice, so hello!

I'm quite lucky where I live, as its very dark at night, and there is an observatory located on a hill only a couple of miles away, so I thought now is as good as ever to finally get a telescope and start seeing what’s out there, I have always loved looking up and thinking "If only I could see that closer" well now I can!

Anyway, back to my question, I’ve looked at the Sticky for eyepieces, and I think I’ve got the basic ones with my scope, what I’ve got so far is:

1.5x erecting eyepiece (which is ****, it’s so blurry, I may as well chuck it out)

2x Barlow lens

K10mm lens

K25mm lens

I must say, I only use the 25mm lens along with the 2x Barlow, the 10mm lens is just too small, and I’ve yet to come across something that I would think it would be better to use the 10mm instead of the 25mm? Maybe I am not using them correctly? I’m not sure what make these lenses are, I think I read what make before but can’t remember, and they said they were "ok" is this true?

To be honest I’ve kind of self fabricated this idea that I need a better Barlow lens (say, a 5x instead of 2x) and eyepiece about 45mm or bigger? Can anybody give me some advice, on what I should get, and what brands are good without being ridiculously expensive? The reason i think i need some wider eyepieces is becuase when i look at Jupiter, its quite small, i want to make it bigger?

Oh the focal length of my telescope is 900mm and the diameter is 114mm.

Thanks in advance!

[Craig20264]

If it's more magnification for planetary viewing you're after, you need an eyepiece with a smaller number.

A 5mm eyepiece in your scope will give you 180x magnification, 900/5 = 180. The 45mm eyepiece you mention will give you only 20x mag. (bigger the number, the less maginification)

Going any smaller than this, ie a 4mm will take you over 200 times which most experienced folk on here will tell you is probably your magnification limit due to seeing conditions.

[Catweazel]

Try barlowing the 10mm for planets.

[Capricorn]

Silly question: How long is the tube on your scope?

Better, the distance from mirror to secondary - not exact a reasonable approximation.

Make and model of the scope is an option to look up the dimensions, measurements are easier.

If 900 and 114 then f/7.9. An 8mm should be OK, 12mm for a bit less magnification and a bit wider view.

I suspect that the barlow and either eyepiece you have will not produce decent views.

The erecting prism will also be dubious.

I would suggest a few plossl's. They are fair middle of the road items and do a good job for the cost. The ones you have are Kellners.

If you try for greater magnification, short eyepieces, then the eye relief goes down.

[hemihaggis]

hi there the biggest eyepiece you can use is a 32mm for low power , tey googling bst explorers or sirrus plossls

[itchytrigafinga]

Ok, so I think I know what I need to do, as I’ve got the 10mm eyepiece, would it be a good idea to get, something like a 5x Barlow?

This may also be another daft question but, is there anyway, let’s say, to fill my 25mm eyepiece with Jupiter? It’s just 10mm is quite small, or is this unrealistic?

The length of the tube is 86cm and the length from the bottom mirror to the eyepiece mount is 76cm.

Capricorn, the erecting prism, is this the iron sight (The tube mounted on top the telescope) which you think might be dubious? I thought it was how I set it up, but no matter how much I try, when I align stuff up on the X it is NOT in the field of view, I have to line it up "roughly" in the middle of the top right quarter, a bit annoying.

Thanks again,

[hemihaggis]

hi, tell us what scope mount it is you have , think we need a little more info ,

where abouts in the country are you ?

think you need to do a little research , the smaller the number on you ep`s the more magnification you will get .

a x5 barlow is way to much

you said your scope is 114mm wide lens , this number is a good indicator as to how much usable magnification you can practically use , x 120 will be about your maximum mag ....

a focal lenght of 900mm means you will struggle to use any more mag than a 7mm ep, this will give you 128x mag .

focal lenght divided by ep in mm = magnification

a x5 barlow with a 10mm ep will give you a magnification of x450 well beyond the capability of just about any amatuer scope. you would need an 18" mirror to get anywhere near this number and perfect conditions

it is quite unrealistic to think you can fill your ep with jupiter , sorry .

but dont be dishartened , there is loads of great stuff to see ... do you have stellarium ?

[itchytrigafinga]

hi, tell us what scope mount it is you have , think we need a little more info ,

where abouts in the country are you ?

think you need to do a little research , the smaller the number on you ep`s the more magnification you will get .

a x5 barlow is way to much

you said your scope is 114mm wide lens , this number is a good indicator as to how much usable magnification you can practically use , x 120 will be about your maximum mag ....

a focal lenght of 900mm means you will struggle to use any more mag than a 7mm ep, this will give you 128x mag .

focal lenght divided by ep in mm = magnification

a x5 barlow with a 10mm ep will give you a magnification of x450 well beyond the capability of just about any amatuer scope. you would need an 18" mirror to get anywhere near this number and perfect conditions

it is quite unrealistic to think you can fill your ep with jupiter , sorry .

but dont be dishartened , there is loads of great stuff to see ... do you have stellarium ?

It’s a TS EQ3-1 equatorial mount according to Amazon, is that the type of mount?

I’m located in East Devon, right on the coast...

That’s ok, I’m a complete n00b so I just "assumed" incorrectly that the bigger magnification I would get, the bigger the image would be...

I don't want to waste money on some eyepieces that are not going to be much use, so I want to understand before I get any.

Not got Stellarium, but just Googled it, I will definitely have to get that as it looks like a fantastic piece of software! There is so much to see, and it being the UK it’s very not cloudy, I still haven’t properly explored it all....

Thanks,

[hemihaggis]

cool , just keep asking questions , dont go thinking you have to buy more kit , just use the stuff you have till you get used to to your kit , pick some targets for viewing .. m42 , m45, alberio ect .. try these next clear night .

[jfox61]

My take as newbie too, is this. It has worked for me so should be fine for you too. If the kit was new then I suggest ditching all the ep's the barlow and the erecting ep, you don't need it for astronomy anyway.

1x 30mm or 32m Plossl

1x 20 mm Plossl

1x 10mm Plossl

1x 6mm or 7mm

Eyepieces work back to front, so to speak, Higher the number lower the power and wider the field. Lower number is less field of vision but more magnification. Only get the 30 or 32 if you want really widefields of view and want to see nebulas and clusters etc. And only buy the 6 or 7mm if you want to look at the planets and moon. Try FLO their logo is at top of page, they are selling cheap Vixen ep's at the minute and are excellent value ep's.

Next, you want a decent, not cheapy, 1.5 or 2x Barlow, you don't need anything bigger for your scope. Get one with a coated lens and pay about £30-40 minimum for one. Don't use the Barlow with the 6mm or 7mm, waste of time and would make the ep's too powerful for you scope.

On to your scope. What you describe as a tube mounted on top of your scope is not the erecting prism. It sounds to me like it is the finderscope you describe. You say you have an erecting ep, that is what would get used to view things on earth the right way up.

The finderscope does indeed have a crosshair in it and it is used as you rightly think, for lining up your target in the main scope. However, you have to remember everything is upside down/back to front when using it.

On the finderscope mount you sould see some small screws, these move the line of sight of the finderscope by moving the tube slightly in its mount. Using the lowest power ep you have, and in daylight, at the minute yours is the 25mm, line up your scope roughly on a land object. Something like the tip of a tall tree or a Power pylon. Once you can see it iin the main telescope, try to get it dead centre by making small adjustments on your mount controls.

Once you have the pylon/tree tip in the centre move to your finderscope. Now, using the small screws in the finderscopes mount. This might take a bit of getting used to as some finderscopes show everything upside down and back to front others the right way.

Now change to your 10mm ep and do it all again, you are fine tuning your finderscope. Do this till you have the scope lined up dead centre in the scope and finderscope with your smallest most powerful ep, mine is a 6mm, yours a 10mm.

Onto viewing. I'll assume you have set it up facing north and aligned it to the Pole star. fairly easy to do, and hopefully you know how, if not just ask someone will walk you through it.

Take you lowest power ep, your 25mm. Look through the finderscope to find the object you want . when you see it and it is centred in the finderscope go to your ep an look through you should, if you aligned the finderscope correctly, see the object you want in the main view. Now once you have seen that you can either use the Barlow or a higher powered ep to get closer looks. Bear in mind more power means less field of view. So for instance use a lower powered ep for the moon so you can see it all, unless you want to look real close at a particular area.

Finally don't jump from a really low powered ep straight to a really high powered ep ie 30mm to 6mm. You will lose sight of the object you are looking at and lose interest very quickly. step up in power gradually and make small adjustments to the scope as you go. Oh and one final thing the more power you use , the faster they move out of you line of sight. This is more noticeable on the moon and planets, but it does affect the stars and other objects as well.

[Tribal-Wolf]

I think a better quality EP might help, the 10mm that came with my scope is a bit naff, I have just bought an 8mm BST which I'm hoping will be a better bet even with a barlow.

[Capricorn]

Thanks for the tube length.

Asked as there is a design called Bird-Jones, they (for example) will have a focal length of 1mtr and a tube length of 500cm.

They use a magnifier in the path to achieve this longer focal length. Also they tend to use a spherical mirror and the magnifing optics is supposed to take care of this as well.

Problem is they don't work in practise that well and the result is best described as garbage.

You have a tube length that means it is not this type.

Magnification = (Scope Focal Length) / (Eyepiece Focal Length).

in your case: 900/(Eyepiece Focal Length)

I wouldn't get a 5x barlow. Simply too damn much, the shortest eyepiece you could use it with is a 25mm eyepiece, if lucky. So your choice is 25mm or 32mm. All other eyepieces will simply be too much for the scope.

You really need a few reasonable eyepieces. Try the plossl's say 32mm, 15mm, 10mm. The scope may take a 6mm or 7mm but leave that for now, get used to the easy ones.

[itchytrigafinga]

Wow, thanks for all the replies! That’s so much useful information, I think I will bookmark this page and read it right before the sky is next clear.

Re: The finder scope, that’s what it’s called I couldn’t remember, I have tried adjusting it as much as possible with the screws, but it’s still miles out, I can get it on the cross, but I have to really push hard on the mount, almost to the point that it would damage the scope.

It’s a fairly cheap scope from amazon, so I think the bracket that mounts the finder scope to the main scope is bent, or not manufactured properly, it’s not too much of a problem now, because I have found out where the stars etc have to be lined up, for me to be able to see them through the eyepieces.

When I first got it I couldn’t work out why it wasn’t lining up, got so stressed and almost took the god damn finder scope off and trashed it. Luckily I just put it down and fiddled with it the next day!

The 2x Barlow I have at the moment seems ok, it’s a bit flimsy and cheap as its all made out of plastic, I think what I’ll do is practise with the Barlow and the 10mm and 25mm some more until I’ve got used to them properly and will then probably buy a new set with either a 32, 15, 10mm and a decent Barlow. I would love to spend out and buy a really good telescope and eyepieces, but I just don’t have the cash.

Thanks,

[Capricorn]

A barlow, say 2x, will double the magnification, the other way of looking at it is it halves the focal length of the eyepiece.

Your scope has an f number of 7.9, described/written as f/7.9, I would suggest not going much less then an 8mm, about the same as the f number.

The f number is the focal length divided by the diameter. It is a photographic term but has uses in the visual observing world.

Being f/8 you could probably get down to about 5mm, about 2/3 of the f number. I will say that this is very much the limit of what your scope can handle, and may not produce anything you call satisfactory, luck of the draw. If you stick to the f number, 8 in your case the magnification is the mirror diameter - nice easy way to work it out.

If you get a 2x barlow this equates to a 5mm eyepiece with the 10mm eyepiece you may get. 5mm is as said a boarderline size.

The 2x with the 32mm gives 16mm and with the 15mm makes 7.5mm.

So those 3 with a 2x barlow would make up a reasonable spread. In effect: 32, 15, 10, 16, 7.5, 5. Fairly decent.

Don't have a barlow, like eyepieces only, however people say the Tal barlow is one of the better ones for the cost, so perhaps one of them in the future.

Get used to the eyepieces you have, and the scope, before you do anything.

Check the UK Astro Buy and Sell site for used equipment, reasonable plossl's come up there fairly often.

Where are you?

Look for a club, possibly join. You may find members have bit for sale.

[Flaxinator]

The nearest Astro club for you if you are where i think you are, is at the Norman Lockyer Observatory, the astronomy club meet on Friday evenings starting at 7.30pm. They're a great group up there.

[jfox61]

Wow, thanks for all the replies! That’s so much useful information, I think I will bookmark this page and read it right before the sky is next clear.

Re: The finder scope, that’s what it’s called I couldn’t remember, I have tried adjusting it as much as possible with the screws, but it’s still miles out, I can get it on the cross, but I have to really push hard on the mount, almost to the point that it would damage the scope.

It’s a fairly cheap scope from amazon, so I think the bracket that mounts the finder scope to the main scope is bent, or not manufactured properly, it’s not too much of a problem now, because I have found out where the stars etc have to be lined up, for me to be able to see them through the eyepieces.

When I first got it I couldn’t work out why it wasn’t lining up, got so stressed and almost took the god damn finder scope off and trashed it. Luckily I just put it down and fiddled with it the next day!

The 2x Barlow I have at the moment seems ok, it’s a bit flimsy and cheap as its all made out of plastic, I think what I’ll do is practise with the Barlow and the 10mm and 25mm some more until I’ve got used to them properly and will then probably buy a new set with either a 32, 15, 10mm and a decent Barlow. I would love to spend out and buy a really good telescope and eyepieces, but I just don’t have the cash.

Thanks,

Try a Telrad instead of a finderscope you'll wonder why you never got one straight away. FLO are selling them for less than the cost of a decent finderscope

[itchytrigafinga]

The nearest Astro club for you if you are where i think you are, is at the Norman Lockyer Observatory, the astronomy club meet on Friday evenings starting at 7.30pm. They're a great group up there.

Without saying where i live.....I can see that observatory from my house, without even needing the scope, so i am fairly close, you could say?

[Flaxinator]

lol closer than me, I have a 35mile journey to get there