2" Eyepeices for a fast scope

[lawsio]

Hi folks.

So I've been dithering on a grab and go scope for a while but think I'm ready to order the F4.9 ST102 now. What im now pondering is eyepeices.

I have no 2" eyepeices so far (Even though my Dob takes them too) so I'm thinking of investing in one to maximise the FOV on the ST.

I know you can't mess about with cheap eyepeices on this scope but it's hard to tell what you can and can't do. So far I've had the StellaLyra 30mm UFF recommended following a chat in another thread but thought I'd ask in the area more people are to get any other feedback.

Looking for something as entry level as I can get away with at this point!

Thanks!

Edited September 26, 2023 by lawsio

[bosun21]

I think you mean the 30mm Stella Lyra UFF eyepiece as there is no 40mm. This is a great eyepiece with good correction across almost the entire FOV.  This to me is important with a wide field eyepiece otherwise the outer area will be suffering from aberrations and not pleasant to view.

[Zermelo]

You beat me to it.

The UFF performs very well, even in faster scopes.  I compared it (actually, it was the Altair badged version) with the cheaper Stellayra Superview, here.  The Superview did well enough in my Mak, but struggled at F/5.9.  The UFF was noticeably better.

Several recent mentions:

https://stargazerslounge.com/search/?q=Stellalyra UFF 30mm&quick=1&updated_after=any&sortby=newest&search_and_or=and

[globular]

Have you measured your dark adapted exit pupil?

The UFF30 will give an exit pupil of 6.1mm in your f/4.9 scope - might be a bit big?  Unless you are young or very lucky!

At f/4.9 I think I'd try the APM XWA 100° 20mm.  This will give 4.0° (verses 4.4° with the UFF30) but with more magnification and a more usable 4.1mm exit pupil.

It will only be an option if you don't wear glasses to observe - and at £279 it's not exactly entry level price.  (But then the UFF30 is £179 so you're already past entry level).

[lawsio]

1 hour ago, bosun21 said:

I think you mean the 30mm Stella Lyra UFF eyepiece as there is no 40mm. This is a great eyepiece with good correction across almost the entire FOV.  This to me is important with a wide field eyepiece otherwise the outer area will be suffering from aberrations and not pleasant to view.

Yes you're right, I've edited the post, thanks!

[lawsio]

1 hour ago, Zermelo said:

You beat me to it.

The UFF performs very well, even in faster scopes.  I compared it (actually, it was the Altair badged version) with the cheaper Stellayra Superview, here.  The Superview did well enough in my Mak, but struggled at F/5.9.  The UFF was noticeably better.

Several recent mentions:

https://stargazerslounge.com/search/?q=Stellalyra UFF 30mm&quick=1&updated_after=any&sortby=newest&search_and_or=and

Thanks for this. I notice a few comments refer to the weight of it. I plan to use this mostly on the AZ5 Deluxe mount that comes with the ST, and potentially on the AZGti I already have. Is this going to be OK?

[lawsio]

1 hour ago, globular said:

Have you measured your dark adapted exit pupil?

I'm not going to lie, I've not even considered it! Is there a method to this?

[Zermelo]

4 minutes ago, lawsio said:

I'm not going to lie, I've not even considered it! Is there a method to this?

The 30mm UFF will give a lighter background sky, and reduced contrast, compared with the 20mm XWA.  Targets like fuzzy DSOs will be affected most. This will be worse if you're already observing from a light-polluted location.

One crude way of measuring it is to go into a completely dark room, wait a few minutes, hold a ruler next to your face and take a flash selfie (but make sure the phone doesn't do a "pre-flash flash", or it won't work. Then compare the pupil size to the ruler in the resulting image.  A better way is to see if the optician will measure it for you when/if you visit.

Also, you might be interested in this

https://stargazerslounge.com/topic/375282-eyepiece-selection-based-on-exit-pupil/

 

[PeterC65]

I've been searching for a good, reasonably priced 2" eyepiece for the last year and after an abortive purchase of a Baader Aspheric 36mm I've recently purchased a StellaLyra UFF 30mm. It's great, with a much flatter field than any of my other eyepieces. It's only a little wider field than my 24mm but the flat view really makes a difference on widefield targets.

 

[lawsio]

So I've done a FOV comparison between a standard 32mm Plossl (This shows an Astro Essentials one - mine are Orion Sirius ones but for the purposes of this I'll assume they're about right) and the 30mm UFF EPs and the 2" obviously has a bigger view but it doesn't seem that much different. Does this comparison look right?

This will be my first widefield scope so for the experienced observers - is that extra view worth nearly £200 more?

 

[John]

That looks about right.

I have a 31mm Nagler and that compared with a 32mm plossl looks like this:

So a little bit more again. 

Is that extra view worth the investment ?

Well that is a question that is often asked but virtually impossible to answer. I suppose it depends on your observing preferences. If you like to see as much of the larger deep sky objects as possible or to see well known pairings / groups of objects in the same field of view then you will welcome the wider view. If you are happy to stay with a quite wide view, which, lets face it, most deep sky objects will fit easily into, then there are probably better ways to spend the money.

 

 

Edited September 27, 2023 by John

[Mr Spock]

The StellaLyra 30mm UFF has become my favourite low power eyepiece. I use it in preference to my 42mm LVW as it has fewer aberrations, almost none in fact. It works really well in my 12" f5 Dob. I've also had one view with it through my new 8" f4, which works at F4.4 with the coma corrector, and it's pin sharp in that too.

[lawsio]

Thanks all, think the feedback on this EP is pretty conclusive!

On more (quite fundamental!) question - I assume for the ST102 I'm going to need to upgrade the diagonal to take 2" EPs? Any advice here?

Ben

[PeterC65]

9 hours ago, lawsio said:

This will be my first widefield scope so for the experienced observers - is that extra view worth nearly £200 more?

This is what I've been wrestling with for the last several months. In my case the FoV of the UFF 30mm is only about 25% larger than my ES68 24mm eyepiece.

After much debate I decided that:

• The extra FoV did better frame many of the larger DSO objects (having checked on Stellarium).
• A really flat FoV, even if only a little wider, is much nicer visually than one with even a little aberration so the flatness alone is worth investment.
• The StellaLyra UFF 30mm is flatter than even the most expensive TeleVue and Pentax eyepieces (that I cannot afford) and I wanted that experience.

Personally, I really like a widefield view as well as the more zoomed in view of a specific DSO. Widefield lets you take in objects that are otherwise not observable with a narrower FoV such as Kemble's Cascade.

I purchased a Sky-Watcher 2" Deluxe Di-Electric Coated Star Diagonal second hand from @bosun21 which is perfect. I'd recommend any of the mid priced 2" diagonals (from StellaMira, Sky-Watcher, Askar, William Optics). The Askar 2" diagonal looks good and has the advantage of its optical path length being specified.

 

[Mr Spock]

2 hours ago, lawsio said:

I assume for the ST102 I'm going to need to upgrade the diagonal to take 2" EPs? Any advice here?

 Revelation Quartz Dielectric Diagonal 2". It has no negatives as far I can tell - the performance is similar to much more expensive diagonals. Unlike some it doesn't have a restricted aperture (there's thread on that here somewhere).

[bosun21]

2 hours ago, lawsio said:

I assume for the ST102 I'm going to need to upgrade the diagonal to take 2" EPs? Any advice here?

I have just purchased my second Williams Optics 2" diagonal for a new scope. I have owned several different manufacturers 2" diagonals and still find the Williams Optics to be the best value. The mirror is thicker than most others and is polished to 1/12th wave. The diagonal is also partially made of polished carbon fibre which saves weight and both sides can be removed to allow access to the mirror for cleaning. All in all great value for money.

[John]

The William Optics diagonals (and clones under other brandings) use quite a thick internal ring to attach the eyepiece holder to the diagonal body. This ring might slightly vignette the field of view of 2 inch eyepieces which max out the field stop diameter. I think this is the point that @Mr Spock makes in his earlier post ?

My own 2 inch diagonals are Tele Vue Everbright and Astro Physics but carry a substantial cost premium so I won't push those on you !

I have used the Revelation / GSO 2 inch diagonals in the past (and a number of others) and found the former pretty good performers. 

 

 

 

Edited September 27, 2023 by John

[bosun21]

16 minutes ago, John said:

This ring might slightly vignette the field of view of 2 inch eyepieces which max out the field stop diameter. I think this is the point that @Mr Spock makes in his earlier post ?

My own 2 inch diagonals are Tele Vue Everbright and Astro Physics but carry a substantial cost premium so I won't push those on you !

The ring is quite small in the WO diagonal and the open aperture is larger than the largest field stop in my WF eyepieces which is the SL 30mm UFF. This of course should be taken into consideration when buying a diagonal and making sure that it can accommodate all your eyepieces.

Edited September 27, 2023 by bosun21

[John]

19 minutes ago, bosun21 said:

The ring is quite small in the WO diagonal and the open aperture is larger than the largest field stop in my WF eyepieces which is the SL 30mm UFF. This of course should be taken into consideration when buying a diagonal and making sure that it can accommodate all your eyepieces.

The 30mm UFF field stop (which I believe is 36.9mm in diameter or thereabouts) does not max out the 2 inch barrel so no issue with that one 🙂

The Nagler 31 has a 42mm field stop so that might be an issue.

[bosun21]

11 minutes ago, John said:

The 30mm UFF field stop (which I believe is 36.9mm in diameter or thereabouts) does not max out the 2 inch barrel so no issue with that one 🙂

The Nagler 31 has a 42mm field stop so that might be an issue.

That's one large field stop!

[Mr Spock]

The 42mm LVW has a field stop of 47mm  I had a WO diagonal and it vignetted noticeably - I can't recommend that diagonal or its clones to anyone.

Here's the Revelation:

[johnturley]

14 hours ago, lawsio said:

Thanks for this. I notice a few comments refer to the weight of it. I plan to use this mostly on the AZ5 Deluxe mount that comes with the ST, and potentially on the AZGti I already have. Is this going to be OK?

Although the 30mm UFF is no lightweight at around 550g, it is considerably lighter that a lot of other equivalents, such as the 24mm ES 82 at around 800g, or the 31mm Nagler or the 30mm ES 82 at around 1.2kg.

John 

[John]

If you add the weight of a 2 inch diagonal to that of a low power / wide angle 2 inch eyepiece you have 2lbs plus hanging off the back of the scope so the focuser needs to be reasonably robust and scope balance might need to be adjusted.

 

Edited September 27, 2023 by John

[johnturley]

5 hours ago, Mr Spock said:

The 42mm LVW has a field stop of 47mm  I had a WO diagonal and it vignetted noticeably - I can't recommend that diagonal or its clones to anyone.

 

 

Mr Spock

Do you have a 42mm Vixen LVW, I was wondering what the edge performance would be like in my f7 Esprit, I assume that it would be superior to my Baader 36mm Aspheric.

I already have a StellaLyra 30mm UFF, which I use as my lowest power through my 14in Newtonian, hence was thinking of using in my Esprit (which is piggybacked on the Newtonian) at the same time, and selling my 36mm Aspheric, and possibly also my 56mm Plossl.

Not many suppliers currently list the 42mm LVW, so wondered whether it had been discontinued, in which case if I want one, I need to order it fairly soon.

John 

[Ricochet]

I was in a similar position. I had an 8” Dob, but wanted a small refractor for grab and go. I went for the 72ED, so a slightly shorter focal length (420 vs 500mm) and I have found that I don’t really use my 2” eyepieces and diagonal with the scope and instead take just a 1.25” diagonal and three 1.25” eyepieces for grab and go sessions. A 24mm 68º eyepiece gives a wide enough field for most nights. It is only if I specifically want to have the widest possible views that I would take a wider eyepiece. With this in mind you might find that you are better off buying just the scope for now and trying it with your existing 1.25” eyepieces to see if you feel the need to buy any 2” eyepieces to go with it. That would also allow you to assess the exit pupil and darkness of the background sky at various focal lengths before committing to a 2” eyepiece in that focal length.

Having said that, I don’t think that 1.25” eyepieces go wide enough for a finder eyepiece to use with your Dob, so you probably want a 2” eyepiece or two for that scope whether or not you use them with the grab and go scope.