Don Pensack

I owned this scope for several years.  It is actually a 121mm f/12.7 Maksutov with a 1540mm focal length.  It's been made by Synta since around 2000-2001 and maybe before in non-USA markets,

and sold under at least 10 different marks (like Orion, Celestron, SkyWatcher, etc.)

It's actually 121mm in clear aperture because Maks need an oversized mirror to field the entire corrector's light, and they did not use an oversized mirror.

The Sky & Telescope test many years ago confirmed that.

When I had mine, I used it primarily for Moon, Planets, double stars and smaller star clusters.

The maximum field with 1.25" eyepieces is 1.04°, using a Baader 24mm Hyperion eyepiece.

The APM Ultra Flat Field 24mm (also available as Stellalyra and Altair Astro UFF in the UK) yields a 1.03° field.

A 32mm Plössl as a low power will yield 1.00° field.

The visual back that holds the diagonal has 10mm of useless thread on its outer end.  If you machine this off, the focal length of the scope with a 1.25" diagonal drops to ~1510mm.

This gains you so little in true field that it's hardly worth it unless you have the machine tools to do it.

An eyepiece set that is usable in the scope could start with the 24mm Hyperion, but also could start with a 32mm Plössl if you want a larger exit pupil.

From 32mm, the logical steps are 32mm, 22-23mm, 16mm, 11-12mm, 8mm

From 24mm, the logical steps are 24mm, 17mm, 12-12.5mm, 8.5-9mm.

The scopes generally don't perform great above 200x, for many reasons, which is a 7.7mm eyepiece.

If you get fantastically good seeing, the scope can give decent images with 6-7mm eyepieces, but I think it's more cost-effective to use a Barlow to achieve magnifications above 190x or so.

You need a finder scope, for sure, and a dewshield on the front of the scope (this can be home-made), or your observing sessions will be cut short by dewing of the corrector.

You also need a nice steady mount.  Due to the long focal length, look for a mount that can handle a 5" refractor.  Even though the Mak is lighter and shorter, vibration in the mount is more visible

due to the long focal length and large image scale.

I do a fair amount of terrestrial observing with my 4" using a conventional 90° diagonal.

The image is upright, but reversed left to right.

Birds, trees, buildings, etc.  are still birds, trees, and buildings.

I really don't see what the big deal is.  I just remember to push the scope so the objective moves in the direction I want it to go.

It really doesn't take any brain power.

At night, it doesn't hurt in identifying craters on the Moon, or looking at celestial objects.

But the Amici prisms require too much in-focus, cost a lot, weigh more, and transmit less, with poorer image quality.

I really don't see the point unless it's in a finder scope attached to the main.

What scope?  What magnifications result from those focal lengths?  

Did you collimate the scope?  How are you collimating?

43 minutes ago, dweller25 said:

Would suggest eyepieces to give the following approximate magnifications…

Venus x120

Jupiter x180

Saturn x200

Mars/Uranus/Neptune x250

This depends on the scope and the orbital position of the planets, though.

With my 12.5", I typically look at the crescent phases of Venus, and 100x is plenty, so I'll concur with your recommendation.

For Jupiter, my lifetime best view was at 456X.  Otherwise, 200x is fine most of the time--close to your recommendation.  Details on the Moons require 400-500x+

Saturn needs magnification.  I typically use 304X and details are readily available.  My lifetime best view was at 1123X, however.  That was a once-in-a lifetime experience.  200x is fine in lesser seeing, so I'll go along with your figure.

Mars really needs 250-400x at opposition and even more away from opposition.  My lifetime best view was at ~500x, but 250x at opposition can give a pleasant view.  Surface details might take more, though.  Adding a Contras Booster filter helps a lot.

Uranus and Neptune really need 400-600x to see the discs well, and the fainter moons around Uranus (Triton at Neptune can be seen at 200x).  At 250x, the discs are too small to see much in the way of details, though you can tell they are discs.

Except for the 2 outermost planets, you recommendations are solid.  Especially given Patrick's scope is an 8".

6 hours ago, LondonNeil said:

Could someone tell me,  how much does exit pupil really matter?

My limited understanding so far is:

1. Your eye only dilates so far, and less as you age. So maybe 8mm for a child,  6 or maybe 5mm ish for someone like me about 50

2. If the exit pupil of light from the ep is smaller then the image isn't the brightest possible from the scope

3. If the exit pupil is larger than your eye pupil the image isn't brighter,  you can't get all the light in your eye

3. Equal pupils is 'just right'

4. Exit pupil size is EP FL/tube FR, so for example my f5 frac with a 10mm EP, the exit pupil is just 2mm. With a 5mm EP it's just 1mm.

Okaaaay, so I can see this helps you to understand the sweet spot for your scope and you.  If for example,  you know you will do alot of viewing of X target,  and want Y ish magnification,  you can chose the scope f ratio and EP to give you a good match on exit pupil and they sweetspot image should be good for you.   You can chose to go all in on the best scope a best EP for that one quality image role. 

But many of us are going to view a range of targets, using a range of magnifications, so it's a compromise.   How much of a compromise is it really?  

 

Hmm.....is this question really just 'why is a long FL tube/sloe scope, better for high magnification?'  It is isn't it?  It's as simple as that... maybe?

An exit pupil matching the pupil size of your eye is the brightest image you can get in the scope.  Lower magnifications will be equally bright, but you will lose resolution due to the smaller effective aperture.

And on a reflector scope, that can cause a problem with the secondary shadow becoming noticeable.  The largest exit pupil will also reveal the astigmatism in your own eye better than smaller exit pupils.

Exit pupils around 2-3mm usually have the highest visual acuity for more observers.  It's no accident this is also a common size for the pupil in the daytime.

Exit pupils of ~1mm is where the telescope achieves its maximum resolution because the Airy disc becomes visible.  Higher magnifications yield a larger image, but not an improved resolution.

Exit pupils smaller than 1mm starts getting into where out eyes have problems--floaters in the eye and corneal issues and developing cataracts can yield poor image quality.  Not to mention that small exit pupils mean high powers,

and the atmosphere Seeing starts interfering with image quality.

As I see it, Exit pupil choice is the realm between large pupil astigmatism and small pupil eye problems.

For me, that is 1-4mm exit pupils, though I have a range of eyepieces that yield 0.65-5.2mm exit pupils just to cover the objects that are best at those magnifications (example: Pleiades at one end, Neptune at the other).

In practice, I pay no attention whatsoever to exit pupil--I merely try to frame the object well and use the right magnification for the object to see it best.

Whatever exit pupil that results in is the exit pupil it happens to be.  I would never look at exit pupil to decide what eyepiece to use.  I wonder if anyone does.

I used the XL Zoom on nebulae and galaxies, and it rendered invisible many features I could see in the XW fixed focal lengths at the same focal lengths.

I didn't have the capability of measuring transmission, but I think the XL Zoom must have 15-20% or more less transmission than in the XWs.

I also used, a few years later, the same XL Zoom/XWs combination in a Pentax 80mm ED spotting scope, and the brightness difference at the same focal lengths was profound

in daylight use.  The XL Zoom was noticeably darker.  One of our testers commented that the XWs with sunglasses matched the XL Zoom without.  I saw that too.

16 hours ago, John said:

I'm glad that you have shared some experience with the Pentax Dave. That's a zoom that I have not had the pleasure of trying out 🙂

 

I tried the Pentax XF zoom and it was not sharp, had serious astigmatism at the edge, and was darker than fixed eyepieces of the same focal lengths.  That was at f/6.

So then I tried the Pentax XL and though it had slightly less astigmatism at the edge, and a trace wider field, it was even darker than the XF.

Comparing to Pentax XW eyepieces, the XL Zoom seemed to have a 25% neutral density filter added.

I do not recommend Pentax Zooms at all, though the XL might be OK as a Moon/planets observing eyepiece.

The Baader Hyperion Mk.IV was better in every way--wider, brighter, and sharper, and was the same price as the XL!

5 hours ago, Naughty Neal said:

As well as the SV215 3-8 zoom which many now own,  I bought the SV191 zoom 7.2 - 21.6 for a mere £23.99 on eBay some time before.

It now sells for around £75/ $100 and tbh it isn't too bad an ep for a cheapy and gives pretty good views, 42 - 65 degrees fov    as one zooms to higher power the fov becomes greater.

I haven't given it much time as an ep but the views I have had with it I can't complain, I need to spend more time with it and then give some impressions of it.

I believe the SV191 is an improved and better ep then the SV135 7 -21 zoom.

Measured apparent fields on the 7.2-21.6 zoom are 38° at 21mm and 59° at 7mm, so the fields aren't as wide as that, but that doesn't describe the quality of the image, just the width.

That is pretty narrow, though eye relief is good and there is no undercut on the lower barrel.

1 hour ago, quasar117 said:

Will the Morpheus provide less distortion?

No.  Distortion generally increases with apparent field, so a 78° eyepiece like the 14mm Morpheus will have more distortion at the edge than a narrower apparent field eyepiece.  If having the Moon appear undistorted at the edge of the field is critical,  then eyepieces narrower than the Morpheus will be better.

If you merely let the moon drift from 1/2way to the edge on one side to the same place on the other side, the Morpheus would be fine for an undistorted view.

Some good ones:

Leica 8.9-17.8mm

APM 7.7-15.4mm Super Zoom

Baader hyperion Mk.IV 8-24mm

Only if you find the 40x gap too large.

To decide on an eyepiece in between, figure out the halfway point in magnification, and divide the focal length of the scope by that magnification.  That will give you the eyepiece focal length to go for.

If your scope is 100mm or larger, I wouldn't think you would really need an in between magnification.

5 hours ago, quasar117 said:

Would the ES 24mm 68 degree be a better option than the 24mm UFF?

I think due to light pollution in my area the 24mm would be a better choice than 30mm for my low power eyepiece.

 

That depends.

If you wear glasses, the UFF. 27.6mm field stop.  The field stop is pushed a bit, so it may be out of focus for your eye, but that really doesn't matter if used on deep sky objects.

       It's probably too low a power for Moon and planet observing anyway.

If you want the sharpest star images in the outer field, the 24mm Panoptic.  27.0mm field stop.  No astigmatism at the edge.

If you want the widest field possible in a 1.25" eyepiece, the 24mm Hyperion (also glasses compatible). 28.0mm field stop.  Lots of astigmatism in the outer field, however.

If you want a sealed waterproof eyepiece, the 24mm 68° ES.  27.2mm field stop.

Personally, I wear glasses and the 24mm UFF was fine in that regard, with about 17-18mm effective eye relief from the rubber up to the exit pupil.

And I found it sharp enough in my 4" f/7 scope.  I used it with a set of Tele Vue Delites and it fit right into the sequence.

I also appreciated that it was the only one of the 4 24mm eyepieces that had no undercut on the 1.25" barrel.

That made it far easier to insert and remove.

Also, if you pan the scope, the distortion profile makes this one the easiest to pan across the sky with.

16 hours ago, quasar117 said:

Since I'm planning on buying a 2" diagonal, would the Stellarlyra 30mm UFF be superior to the 24mm UFF?

Or is it pointless getting a 2" diagonal if I can get excellent low power wide eyepieces in 1.25" format?

The 30mm UFF is a better eyepiece than the 24mm in some ways, and it will give you a true field 31.5% wider than the 24mm.

That wider field at lower power will:

--be more bothered by telescope field curvature--especially in a refractor

--have a much brighter sky background in the eyepiece if you are in a light polluted area

So it might not be a better eyepiece for you than the 24mm.  It depends on your circumstances.

17 minutes ago, quasar117 said:

Would something like the Stellarlyra 24mm UFF be a better option than the Vixen NPL 30mm? If so I think I could stretch the budget a bit.

Long term, would it be worth saving up for a 24mm Televue Panoptic to replace these for low power wide field?

Yes.  Longer eye relief and wider apparent and true fields in the UFF.

21 minutes ago, quasar117 said:

 

Thanks for all the suggestions so far.

I forgot to mention I will be using the Starfield on a manually controlled GEM mount. Only planning on plonking it down, pointing north with correct latitude for location and then tracking with RA and occasional adjustments to the DEC. 

Hopefully this should be sufficient for the smaller FOV orthos. 

I've seen FLO are selling two variants of orthos: BCO and Masyuama. The later being more expensive. Is there any difference in quality/ performance of the two?

The Masuyama eyepieces are classic Abbe Orthoscopic eyepieces, made in Japan.  AFOV about 42°.

The Baader eyepieces are also classic Abbe Orthoscopics, made in China.  AFOV about 50°.

The extra field width on the Baaders is not well-corrected, but might mean finding a target is a little easier.

In my limited experience, the Japanese-made orthos are a bit better, but recent production has included a LOT of eyepieces with dirt on internal lenses.  

The same maker, by the way, has made these same eyepieces since the '80s, when they were sold by University Optics.

Ernest Maratovich has tested a bunch of zoom eyepieces:

https://astro-talks.ru/forum/viewtopic.php?f=32&t=1483#p101290

Note which ones are highlighted blue (poor performance) and which are highlighted yellow (excellent performance).

23 hours ago, Louis D said:

Weird that Corning isn't mentioned.  I'm pretty sure they still supply a lot of optical glass for various space and DoD projects.

Yes, but no longer to the astronomy market.

5 hours ago, radiofm74 said:

After further deliberations (and finding very attractive offers on TV eyepieces with two Swiss dealers) it's now between

- UFF or ES 24 + Morpheus kit (14-9-4.5) or

- Pan 24 + Nagler T6 13, 9 (or 7), 5 (or 3.5) with the prospect of later completing the line. 

Both sets would be internally consistent (weight, eye relief) and work well with all my scopes I'm using or might use in the future. Based on what I read, they should be more or less equivalent in optical quality and FoV afforded. Comfort, hard to say…

- Pros of TV set: form factor (I am a traveller, light and small is my preference); I like the magnifications better, and as noted they're part of a line I can also expand (3.5, used 2.5… or Delites…); I cannot deny that their "classic" status appeals to me
- Pros of UFF/ES/Baader: the Morpheus might have an edge in comfort, usable FoV, and also maintenance (no eyelashes near the glass); the set costs less (I can have a great price on the TVs but I'll still have to sell something to stay in budget); I am used to and like very much Baader's little "eye-protecting wing". 
 
Tomorrow I'll go to a shop having both Naglers and Morphs in the house, and so I plan to see them side-by-side and if allowed to put my eye to them for a feel. 

Do you think that a daytime test could offer good indications as to their respective comfort and ease of use? I know that my pupils will be less dilated and thus react differently, but I'd still hope to get a rough idea… 

Your eye's pupil will be radically different in size in the daylight.

You will be able to get an idea of the field size, but not ergonomics of use.  That will take a dark-adapted pupil size.

If you don't wear glasses, both sets would be excellent.  Fields of view are nearly the same.  The 13mm Nagler is actually 79° and the 14mm Morpheus is 78°, and the 14mm (13.9) Morpheus has a true field about 4.5% wider than the 13mm Nagler.

3 hours ago, quasar117 said:

Looking at purchasing a few mid to high power eyepieces for planetary,  lunar and double stars for the soon to be arriving Starfield 102 F/7.

On a bit of a tight budget for eyepieces as I have splurged on the rest of the setup...

Would I best going for a set of Otho's such as the BCO or Masyuama Abbe ortho's or wider fields such as Starguiders and Nirvana's?

 

I'm aware of the short comings of Ortho's for FOV and eye relief,  but would that be a good sacrifice for better contrast and sharpness across the field?

 

 

That depends.  If the scope is on a tracking mount, then go for narrowfield planetary eyepieces.  You can use eyepieces down to 3mm with that scope, though if you have a lot of floaters in your eye,

then stick to 4mm and longer.

If, however, the scope is not on a tracking mount, you will want something wider in field so you get longer drift times before having to move the scope.

My 102mm f/7 is on a non-tracking mount, and I found 62° eyepieces to be about the narrowest I could tolerate when focal lengths were 5mm or shorter.

Today, used for Moon, planets and double stars, I use 4.8mm (78°), 4.7mm (110°), and 3.7mm (110°).

i know most people don't consider those to be 'planetary' eyepieces, but the star images in all three are tiny little pinpoints from center to edge, and I can watch a crater on the moon go from edge to edge in good focus.

Mine is a triplet, not a doublet, so might have a better corrected edge of field in terms of chromaticism, but you get the point--wider fields will be more rewarding in a non-tracking scope.

In my 102mm, I could tolerate 62° of field, but felt happier with 70°+.  And there are wider field eyepieces that will yield sharp fields with excellent contrast, and have better eye relief.

I'm not against orthos, but they are harder to use.

If you can tolerate ultra-tight eye relief and have a tracking scope, then go for the narrower eyepieces if you prefer.

Though, on the Moon, a wider field is better for context and to see the environment around the feature of study.

Here is an illustrated explanation of SAEP (spherical aberration of the exit pupil):

https://www.handprint.com/ASTRO/ae4.html#SAEP

On 01/03/2024 at 07:55, radiofm74 said:

I take your point. I might still want a 24mm for the nights when I'm out with my f/6.3 (reduced) C8 or C6 and the UFF is not available: the 24mm would effectively be my widest, lowest power eyepiece. 

I am intrigued however:

- What 22mm would you suggest? If I found a Vixen LVW 22mm I think I'd scoop it up in a heartbeat, but they're not on my market. And I haven't seen a 22 in the ES or UFF lineup.

- Between UFF and ES 68° 24mm, considering that I'd probably be comfortable with either in terms of eye relief, which one would you pick to complement the 14-9-4.5 Morphs? 

Thanks, and sorry for pestering you with my questions!

There are a few I'd recommend, but the Omegon Redline 22mm is glasses-friendly, and very well corrected at f/5, and a 70° field.

It's 2", though it's a fine eyepiece at an economical price (and available under other labels as well).

If we're limited to 1.25", however, and you prefer longer eye relief, and it is to be used in a scope under f/8, the APM UFF 24mm is the one.

It's a lot better than the 24mm Hyperion, the other glasses-compatible 24mm widefield.

It's available under other labels, too:

So you can shop price.

5 hours ago, Moonlit Night said:

My TV 102 was made in America, the objective was made in Japan. Not that’s exactly the same thing. I wonder which country the glass in your zoom was produced in? I am sure it must have been assembled in Portugal. 
 

Do you not have to buy from Russia to obtain glass produced on the European continent? 

Here is a list of 23 world optical glass manufacturers:

https://us.metoree.com/categories/5194/

The list includes many in Japan, US, Germany and elsewhere.

It does not include any Russian sources and is light on Chinese sources (I don't know why),

but there are many sources in the EU and UK.

2 hours ago, Moonlit Night said:

Dunno, maybe you’re right. Are they still making objectives for Skywatcher? They certainly don’t badge their scopes with Schott anymore. 

Sky Watcher is Chinese, including the glass.

8 minutes ago, radiofm74 said:

Plus – forgive the shallowness of the comment – UFFs look a lot like Morphs! The 30 UFF, 24 UFF and 14-9-4.5 Morphs will make for a nice set I think!

The 30mm to 17.5mm (17.2mm) jump in magnification is a reasonable jump in a lot of scopes.

For example, in a 1200mm focal length scope, it's 40x to 70x, not a large jump.

With longer focal length scopes, the 24mm in between makes some sense.

In a 2795mm focal length, that is 93x, 116x, and 163x.  A 22mm eyepiece would be closer to the in=between magnification, however.

The apparent field of the 24mm UFF doesn't feel like the others, alas, but it is quite comfortable to use.  It has an effective eye relief of 17-18mm, fine for glasses.

(it is one of the only glasses-friendly, widest-field, 1.25" eyepieces)

Measured apparent fields:

30mm UFF--70°

24mm UFF--64°

17.2mm (17.5mm) Morpheus--72°

13.9mm (14mm) Morpheus--78°

17 hours ago, Louis D said:

I find the well figured, ultra wide field, long eye relief 20mm to 26mm region to be rather skimpy at any price.  There's the 20mm SL/FM, 22mm NT4, and 26mm Meade MWA.  The MWA has excessive SAEP (and is discontinued), the NT4 has some SAEP, and I have no idea about the SL/FM and SAEP.  I'm holding out hope that ES expands the ES-92 line upward to 23mm or so.

The Stellalyra/Founder Optics (Long Perng) 80° eyepieces are reported as having no SAEP.  I can verify the 14mm had none.

If you don't need more than 12mm of effective eye relief(20mm from the glass), there are also the 23mm and 16.5mm Pentax XW 85°,  The 16.5mm is especially well-corrected in shorter f/ratios.

The 23mm had noticeable edge of field darkening, though whether that was inherent or due to its interface with a Paracorr, I can't say.

Neither of the Pentaxes had any SAEP I could detect, though I didn't take the photos you do.