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Puffafish

How to choose a new eye piece

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I was on a thread the other day discussing having a look at Mars. The end result of the conversation was that I may want to get a new eye piece for a higher magnification, around the 6mm range (currently got the stock 10mm and 25mm, along with an aftermarket 2x Barlow). But I am not sure how to choose a good lens. I know the dictionary definition of the various specs used, but not 100% sure what that means in real life.

As I'm looking at this particular eye piece for planet watching, I don't think field of view is that important, but I could be wrong.

Eye relief is that bit easier; the larger the number the better. As you can hold your eye further away to get a good image.

Some EP don't seem to list these stats on the websites, which makes choosing it that bit harder.

Is there any advice people can give me?

(I have a 130mm diameter, 650mm focal length reflector, from Skywatcher)

Edited by Puffafish

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Yes, more magnification might help, but the limiting factor (along with the size of the 'scope) will be the weather.

My views of Mars have been fairly limited atm. and the best view the other night was at around 100x magnification.

Do you have a budget in mind, because it depends what you mean by 'good'!? :D

A lot of the middle of the road eyepieces are actually rather decent these days.

With the shorter focal length eyepieces, the eye relief can get a little tight.

I have the Williams Optics 6mm EP which is very decent with good eye relief.

I have the OVL Nirvana ES 82° 7mm EP and that also provides a wider field. The advantage of that is that it gives a longer drift time to observe, before the object disappears off the edge.

I've also used the 8mm BST which is very decent and very reasonably priced.

Had you considered a 2x Barlow? it effectively doubles the focal length of the 'scope and so doubles the magnification. It has the advantage that the eye relief is maintained.

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3 minutes ago, bingevader said:

Do you have a budget in mind, because it depends what you mean by 'good'!? :D

AHH yes, cost... The good limiting factor in all life decisions. I was wondering about the Baader Classic  range which is £49, or the Vixen NPL, which is £38, or the Orion Expanse which was £45. But it may be that I need to spend £100 to get an EP worth getting (in which case I'll wait for now) or I can get a good one for less (which I doubt)

3 minutes ago, bingevader said:

Yes, more magnification might help, but the limiting factor (along with the size of the 'scope) will be the weather.

The weather has not been good for visual observations recently that is true. Also had issues with trees being right between me and other interesting things! Mars has been quite low in the sky when I've been viewing it, so that won't have helped either.

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If you look at the plossl ranges on the various websites, you can see that the top glass element reduces in size as the focal length reduces.

I struggle below an 8mm in that sort of EP as the eye relief is too tight for me.

You may not have a problem though, and the Baader and Vixen plossls will give excellent views (no experience of the Orion). :)

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I got a 16mm Nirvana (82°) many years ago and use it to this day. It's the best budget eyepiece I ever bought. Well corrected down to f/5. There's also a 4 and a 7mm version.

Link.

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31 minutes ago, Ruud said:

I got a 16mm Nirvana (82°) many years ago

Indeed they do a 7 and 4mm version, but the 4 is apparently on 40 day lead time, which does seem to be quite a common thing at the moment. Has something happened to lens supply?

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12 minutes ago, Puffafish said:

Indeed they do a 7 and 4mm version, but the 4 is apparently on 40 day lead time, which does seem to be quite a common thing at the moment. Has something happened to lens supply?

This post from First Light Optics might explain:

This situation is facing all suppliers of astro equipment.

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You have a 130mm scope with a theoretical maximum magnification of 260, theoretical though.

To maintain a bright image and knowing what Uk conditions for viewing are usually like I would be thinking about a 7mm eyepiece and a 2x barlow. This gives x 93 and x 186 and would be great for planetary use, double stars, globular etc. 

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A 5mm BST Starguider will provide decent eye relief, a reasonable field of view of 60° and magnification of 130x

Not massive magnification, but realistic under poor UK seeing and considering your telescope focal length.

130x through a 130p will bag you Saturn and its rings, with a clear Cassini Division. Jupiter cloud bands plus the great red spot if it's on view and your seeing is good. Mars if you're quick will present albedo features. Uranus will be a tiny green disc and Neptune an even smaller blue dot.

Managing expectations is vital and pushing the scope too hard most nights will result in mush.

 

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2 hours ago, Puffafish said:

Indeed they do a 7 and 4mm version

I have both and there are very good in my 'scope if your budget will stretch that far. :)

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4 hours ago, John said:

This situation is facing all suppliers of astro equipment.

Ah right so it is covid related. I did wonder. I heard back in March that something like 70-80% of all screens worldwide are made within Wuhan district, so if you want a TV you may have to wait for a while! (Also had a major impact on my work getting circuit boards made, so I do understand the problem!)

2 hours ago, ScouseSpaceCadet said:

A 5mm BST Starguider will provide decent eye relief, a reasonable field of view of 60° and magnification of 130x

Yes I did think 5mm would be good, but I've got a 2x Barlow and a 10mm, so wanted to get something that would give a different sight.

 

3 hours ago, bomberbaz said:

You have a 130mm scope with a theoretical maximum magnification of 260, theoretical though.

Yes, I'd been told that before. I don't want to get a 3mm as that would then be right on the limit, so thought a 6mm would be good, as I can still get to 3mm with the Barlow but I still see an increase from the 10mm

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26 minutes ago, Puffafish said:

Yes, I'd been told that before. I don't want to get a 3mm as that would then be right on the limit, so thought a 6mm would be good, as I can still get to 3mm with the Barlow but I still see an increase from the 10mm

Go 7mm mate, it makes a lot of sense. 

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14 minutes ago, Puffafish said:

Yes I did think 5mm would be good, but I've got a 2x Barlow and a 10mm, so wanted to get something that would give a different sight.

The difference being, a decent mid range 5mm will blow out of the water the stock 10mm and a barlow. I've had the same set up as you. The difference in clarity and the extra detail gleaned is obvious immediately. The advice generally given is discard the 10mm as it's so bad.

However, if you're dead set on using your current set up, then consider an 8mm. On nights of good seeing you can then push the magnification a bit harder using the barlow.

Or buy a 15mm and barlow that for 7.5mm.

Or if you can afford it an 8mm & 15mm. Using the barlow, you will then have 25mm,15mm, 12.5mm, 10mm, 8mm, 7.5mm, 5mm and 4mm.

That covers a range of mags and objects you can view in their entirety.

There's loads of options, and no single right one really.

 

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I just got the Vixen NPL 6mm for my 150 skywatcher Explorer ( mainly due to it being  in stock ) the improvements over the 10 mm skywatcher stock is huge for £38 . Eye relief is low but manageable. 

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Or buy a decent zoom eyepiece until you get used to everything.

The OVL zoom will barlow for the highest powers but more over it really will complement the 25mm stock eyepiece which together will cover all your bases for now. Throw the 10mm in a drawer and forget about it.

https://www.firstlightoptics.com/ovl-eyepieces/hyperflex-72mm-215mm-eyepiece.html

I use a zoom in my frac and love it, very versatile and well worth the cash.

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What exactly is this stock 10mm eyepiece that everyone pans?  Is it a Ramsden or Huygens?  Kellners are generally not as bad as the descriptions of this 10mm.

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4 hours ago, Louis D said:

What exactly is this stock 10mm eyepiece that everyone pans?  Is it a Ramsden or Huygens?  Kellners are generally not as bad as the descriptions of this 10mm.

I'm pretty sure that it's a MA, as is the 25mm.

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4 hours ago, Louis D said:

What exactly is this stock 10mm eyepiece that everyone pans?  Is it a Ramsden or Huygens?  Kellners are generally not as bad as the descriptions of this 10mm.

think its a huygen louis, whatever it is it really is poor to use. 

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2 minutes ago, bomberbaz said:

think its a huygen louis, whatever it is it really is poor to use. 

Perhaps I misread the original post, but wasn't it a Sky-Watcher supplied set of EP's?

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2 minutes ago, merlin100 said:

Perhaps I misread the original post, but wasn't it a Sky-Watcher supplied set of EP's?

it is SW supplied but I seem to remember somebody stating they were huygen design.

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ahhh kelner and not huygen, my bad sorry. There you go @Louis D, they are a kelner type design.

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14 hours ago, bomberbaz said:

Or buy a decent zoom eyepiece until you get used to everything.

I have wondered about getting a zoom lens, but always thought you compromised on quality to get the zoom action.

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