Which 2" Eyepiece?

[prova]

Looking to purchase a low power 2" eyepiece for nice wide field views of star clusters, globs (guessing 30-45mm?)

I'm not really familiar with 2" as all my current eyepiece's are 1.25"

After a "good quality" ep that will last me a long time, but don't want to spend several hundred's if I can avoid it ..

Any recommendations would be appreciated...

[Solanum]

First of all, how high a focal length you can deal with depends on your scope (I forget the formula), with my 1200mm, 10" F5 Dob, any eyepiece above about 32 mm will apparently be vignetted. So don't go for an eyepiece with a longer focal length than you can use.

Secondly, I (and I think most people) don't end up using such low magnifications very often, so unless you are very sure you will, I wouldn't break the bank to get the best. On the other hand I find a wide-angle 2" eyepiece does give great "my head is in the stars" type views.

So I have the MyAstroShop 30 mm 80 degree Ultra Wide 2" eyepiece (currently at $129). This same eyepiece is sold at various places under different names and at different prices, so look around! The build quality is good, it's a nice solid eyepiece. Weighs quite a bit though.

In my F5 scope there is a lot of visible coma with this eyepiece, I'd say about the outer 30% (in terms of radius - so quite a lot in terms of field of view) suffers from coma. With the outer 10% looking very smeared. If your scope is slower it won't be as bad, but that is what you get at this sort of price. If you want sharp stars over 70-80 degrees AFOV in a fast scope I think you'll have to pay a fair bit more.

I still quite like the eyepiece, it does give those big views with it's very large eye lens and is great as a finder eyepiece for deep sky objects that can't been seen in my standard finder.

[prova]

thanks for the reply.

my 8" has a focal length of 1000mm, the coma your talking about sounds
a little worrying .. would I still get the same effect with a 1.25" Ultra-wide eyepiece opposed to 2" ?

[koputai (Jason)]

The theoretical longest eyepiece is fl=(scope_f x 7mm).
So, in your f5 Newt it is 5 x 7mm = 35mm.
I use a 35mm in my f5 with no problems.

Cheers,
Jason.

[dannat (Daniel)]

Prova - you will still get coma from a 1.25" eyepiece, it relats more the the fast scope (f5) & the quality of the eyepiece. Ep's that are sharp right out to the edge are quite expensive, Alternatively you could get an eyepiece with a smaller field of view (instead of 70-80 degree ) you might look at 55-60. It is a compromise no matter which way you look at it , unless you pay for the premium ep's with big fov & are sharp to the edge

[Solanum]

Originally Posted by koputai

The theoretical longest eyepiece is fl=(scope_f x 7mm).
So, in your f5 Newt it is 5 x 7mm = 35mm.
I use a 35mm in my f5 with no problems.

Cheers,
Jason.

That is assuming your pupil reaches 7 mm right? So if you eye only gets to 6 or so, them you'd be limited to 30 mm in an F5 scope? (Dunno where I got my 32 mm from as my scope is F5 as well! Must have remembered it wrong)

As for the coma, I think it would be the AFOV that governs that rather than the diameter of the eyepiece. Presumably the field stop / size of objective lens in the 1.25 would limit the AFOV??

You can probably tell that this isn't really my area of expertise....

My understanding is that with a fast (F5) scope you basically can't have a wide AFOV without corrective lenses in the eyepiece. The better the correction (e.g. Nagler/Ethos etc.) the higher the price.

Away from the very edge I wouldn't say that the coma in my MAS Ultra-Wide is really distracting, but it is there.

[Jeff]

Hi Mark,

Agree with the comments below.

Also, I think it depends a bit on your eyes. A couple of months back I purchased an Panoptic 35mm for use in my f/5 dob reflector, but my ageing 43 year old eyes could not cope with the 7mm exit pupil (my eye had to be alighned in exactly the right spot to see the image). The best I can comfortably cope with is an exit pupil of 6mm (30mm EP in my scope).

The 30mm GSO SuperView (68deg) and 26mm Meade QX (70deg) 2 inch eyepieces suffered from heaps of coma used with my scope .... okay for locating things in the scope but unfortunately spoiling large nebulas and open clusters.

Long focal length 1.25 inch EPs generally have a narrower AFOF (eg. 45 or 50 deg).

Hope this helps.

Cheers, Jeff

[fraunhofer]

I'd like to suggest the MEADE 40mm SWA.

[koputai (Jason)]

Yes, the 7mm in the formula is your max pupil dilation, which is accepted as 7mm for a young adult, decreasing with age.

Originally Posted by Jeff

A couple of months back I purchased an Panoptic 35mm for use in my f/5 dob reflector, but my ageing 43 year old eyes could not cope with the 7mm exit pupil

Major bummer! I'm just about 40, with very imperfect eyes (thankfully no astigmatism), and don't have a problem with 7mm exit pupils yet. Does this mean I'll be selling my Pan35 in a couple of years? I hope not, I love it!!

The 30mm GSO SuperView (68deg) and 26mm Meade QX (70deg) 2 inch eyepieces suffered from heaps of coma used with my scope

I agree, they're both ordinary at f5, but at f6 the QX is actually not too bad.
I've been on a quest for widest field for a little while, tried all the easily available cheaper ones, but alas none of them was worth having. The Pan35 is the go if you can stretch to it. I did get a 40mm Konig last week for the f6, but haven't had a chance to try it yet.

Cheers,
Jason.

[koputai (Jason)]

Originally Posted by fraunhofer

I'd like to suggest the MEADE 40mm SWA.

I do hope you're joking.
40mm in Prova's f5 scope will be way too big an exit pupil, and, for the same price as the Meade you could buy the Panoptic 35 or another TRUE premium eyepiece.

Cheers,
Jason.

[prova]

Originally Posted by koputai

I do hope you're joking.
40mm in Prova's f5 scope will be way too big an exit pupil, and, for the same price as the Meade you could buy the Panoptic 35 or another TRUE premium eyepiece.

Cheers,
Jason.

After a bit of further research, I went for a Vixen LVW 22mm 1.25"
I have the Vixen LV 5mm and I think they are a great quality eyepiece and the price of the Televue Panoptic was simply too far out of my budget (another $150+ over and above the LVW 22mm)

I also talked to Steve re: the MAS 2" 30mm Superview and he did advise that it would really suit my scope.

Hope I made the right choice!

Comments welcome ..

[dannat (Daniel)]

By all reports the LVW's are great ep's, you should be confident you will be happy with it for a long time

[JimmyH155]

I strongly recommend the Meade 26 mm QX wide angle. It is reasonable price, and I use it all the time on my 12" LB. It is really great and on clusters and all that stuff in Carina, it is mindblowing

[Tilt (Michael)]

Just on the topic of 2" EPs, does anyone know if a TV Nagler 22mm T4 will come into focus on a 10" GSO Dob? Reason I ask is I couldn't get a 22mm LVW into focus until I used the 1.25" adapter in the focuser. I'd be a bit peeved if I bought the Nagler only to find out it wouldn't reach focus

[acropolite (Phil)]

For something in between the GSO and Nagler proce ranges you could try the Baader Hyperion 31 or 35mm, they have 72 degree FOV and are available for around $190 US.