Louis D

You may have trouble locating "Making every photon count" in the US.  I see Amazon has a used copy for $120.  You could cross import a new edition from FLO in the UK for much less than that.

In the US, The Deep-Sky Imaging Primer by Charles Bracken might be a good alternative as well.

If the OP already has a 2" diagonal, all he needs to add is a Mak to SCT thread adapter and a 2" visual back to use it with his 127 Mak, and then he can use 2" eyepieces with it.

I've found the vignetting to be minimal to the eye as I discussed in the following thread:

Repeating myself from this thread:

The equation for Barlow magnification is M = 1 - L / fb where L is the distance from the Barlow lens to the eyepiece's field stop and fb is the Barlow focal length (always a negative number for magnifying Barlows).

Regardless of the Barlow focal length, which is never reported by any Barlow makers to my knowledge, it is clear that increasing the working distance between the Barlow lens and the eyepiece is going to increase the magnification.  That's why using Barlow elements in front of a binoviewer generally yields more magnification than when the Barlow is used as designed.  This assumes that the Barlow had a shorter working distance as designed than the optical path length of the binoviewer.  There are vintage long Barlows for which this might not be the case, but they didn't generally have removable lens cells.

BTW, I find most Barlows yield around 3x to 4x when used with binoviewers.

I find I prefer eyepieces in the 16mm to 25mm range because they can be wider in field (than 32mm Plossls) and still not vignette when used with 22mm clear aperture binoviewers like the one I own while maintaining good eye relief and ease of merging.  I can then go from widest field at 25mm up to a slightly higher power at 16mm with an eyepiece swap, or I can change Barlows for a higher magnification range if the seeing permits.  Zooms can also be particularly well suited to binoviewers as well.  They're just narrower at the lower powers.

2 hours ago, aeneas said:

having an observatory dome installed on top of our flat roof

Unless your flat roof is covered in sod, heat from the day radiating off of it during the night will ruin your seeing conditions.  Most folks build their observatories well away from buildings for this and other reasons.

You don't state the f-ratio of your scope.  Multiply 7 by your f-ratio to determine the typically longest focal length eyepiece you would want to use with your scope.  This is because you don't want to go much above a 7mm exit pupil because that about the biggest your eye's iris will dilate during dark adaptation.  That, and the skies get really washed out making it difficult to pick out DSOs.

Let's say you have an f/6 scope, 7*6=42mm would be the longest you'd probably want to go.  For an f/10 SCT, theoretically, you could go to 7*10=70mm, but the view would be like looking through a straw due to the limits of a 2" visual back.  For an f/4 Dob, it would only be 7*4=28mm, thus the popularity of the 21mm Ethos or 25mm ES-100.

32 minutes ago, NGC 1502 said:

Agreed, Panoptics do have edge of field pincushion.  When David Nagler was at Astrofest in London I was able to speak to him about eyepiece design.  He said it’s a trade off to get better sharpness towards edge of field. He further explained that  there’s no way round this  idea of trade off, for instance if we want wide field and long eyerelief we generally have to accept a larger more expensive design. If we sacrifice eyerelief we can get a smaller more compact wide field eyepiece- the T6 Naglers are an example of this.....etc.

David is very approachable and happy to discuss, just like his dad.

 

And yet the original NT2 eyepieces and their NT5/NT6 equivalents have similar eye reliefs around 10mm to 12mm despite the NT2s being much larger than their NT5/NT6 nearest equivalents.  Sometimes it is possible to reduce size and weight while maintaining eye relief through improved designs.

As the scope gets faster (lower f-ratio), the Panoptic line pulls away from the ES-68 line.  If your scope is f/8 or slower, the difference would be minimal.  Around f/5 to f/6 differences start to appear, and by f/4.5 or faster, Panoptics generally have a significant edge.  The downside to this improved edge performance is increased pincushion distortion.  The moon gets stretched into an egg shape and stars appear to move across a globe during panning.  This also happens in the ES-68 line, but not to the same degree.

2 hours ago, Connor brad said:

Would the 27mm panoptics work well on a 200pds skywatcher explorer? 

It should be fine at f/5.  I've used my 1990s vintage 27mm Panoptic in my 15" f/5 Dob to good effect.

@Connor brad Why didn't you start a new thread instead of resurrecting this 7 year old thread?

On 03/09/2020 at 13:47, Louis D said:

Look for an older, long Barlow.  They usually require a fair amount of out focus rather than in focus.  My favorite very long Barlow is the 1.25" Orion Fully Baffled 2x made in Japan in the 90s.  Side by side testing on the Trapezium showed it is slightly sharper than my Tele Vue 1.25" 2x and Meade 140 2x, both of which are phenomenally sharp and mid-length Barlows.  The Orion is about 6 inches long and focuses about 2 inches out, IIRC.  I just don't insert it all the way into the focuser rather than crank the focuser that far out.

I was out last night with my Dob and binoviewer.  I was able to verify that using a Meade 140 Barlow nosepiece as the reference distance that a Celestron Ultima type shorty barlow required about another 1/2" of in-focus while the above Orion long barlow required about 1" of additional out-focus.  This was also true with just an eyepiece.  The shorty Barlow required in-focus while the long Barlow required about double that out-focus.

I had this issue with my 127 Maks, so I swapped sides on my DSV-1 and DSV-2B alt-az mounts, rotating everything including the handle 180 degrees.  I don't know if the AZ-5 mount is as flexible to allow this.

The OP might want to try the new Svbony 8-24mm SV171 zoom available on ebay, amazon, aliexpress, and Svbony's website.  It's been getting quite a bit of good chatter by early adopters on Cloudy Nights.

The 27mm Panoptic is a fine eyepiece, but only has 14mm of usable eye relief.  I've scratched at least one eyeglass lens on the exposed eye lens retaining ring by trying to push in enough to see the entire field.

It took nearly 20 years, but I've finally found a worthy replacement that is easy and safe to use with eyeglasses, the 30mm APM UFF.

2 hours ago, Don Pensack said:

I should have said "all", or 4.5mm through 17.5mm.  The 4.5mm and 6.5mm are "tight" with glasses on, but the other focal lengths are easy.

Curious that the same thing happens to the 4.5mm and 6.5mm Meade HD-60s.  They are a few millimeters tighter on eye relief than the 9mm and above, but still usable with eyeglasses.  The shorter FL Pentax XLs and XWs don't do this. 
@Don PensackWhat about the shorter FL Delos and Delites?  I've only got the 10mm Delos, so no experience there.

On 19/09/2020 at 18:56, Alan64 said:

The telescope will also be good for low-power, wide-field views of the dimmer, deep-sky objects; if you get a star-diagonal for it in future.  The Moon may look alright through it, too; but for the planets, not as well as they would otherwise. 

Enjoy, and best of luck.

Oh, by the by, I have this 70mm f/4.3 achromat...

It's even shorter.  I plan on making a finder-scope out of it for my Maksutov.  It's going to need it.

Did something similar with a $25 ebay 70-300.  I had to remove a 35mm aperture stop behind the objective, remove the focuser, remove the objective lens cell, paint the interior of the tube flat black, put the lens cell back on, fashion a 2" drawtube focuser out of PVC plumbing parts and thumb screws I had lying around from other projects, paint its interior flat black as well, attach it to where the focuser used to be, put a 6" vixen dovetail on it I had lying around, and then put a 2" diagonal in it with a TSFLAT2 on its nose piece along with a widest field 30mm to 40mm eyepiece.  Once I put about $500 of quality equipment around it and several hours of work, that 70mm achromat gives pretty nice wide field views for a $25 ebay special. 😆

51 minutes ago, badhex said:

What I find most interesting overall is that it seems like there's little to nothing else in the same price and quality range that is mostly praised. It seems like the next step up is most likely the Vixen, but at nearly 3x the cost. Others at the same price point seem to have varying degrees of praise. 

Thomas M. Back did a really good job designing the 40mm TMB Paragon, and then it was sold under other brands without permission.  The same thing happened to his TMB Planetary series.  He designed each to be as good as possible at a particular price point.  Apparently, he also designed the 30mm TMB Paragon.  However, it is unknown who did the 35mm version's design.  Did TMB design it but never release it under his TMB Paragon brand?  Did someone else extrapolate the design based on the 30mm and 40mm versions?

You also have to watch out for "rust"/soft coating failure in some of the older Lumicon OIIIs:

To Don's list, I would add

Meade 5000 HD-60 4.5-25mm : discontinued, but still some new-old-stock out there and lots of used, very good at 6.5mm and 9mm in particular with the 25mm a strong contender

BST Starguider 25mm : Only one of the line usable with eyeglasses, but still not that well corrected

Pentax XF 8.5-12mm : Field curvature can be bothersome for some

Astro Tech AF70, also known as the Celestron Ultima LX, Olivon 70, Omegon Redline SW, Skywatcher SWA-70, etc.) 3.5mm to 22mm : VG at 22mm getting worse at shorter focal lengths

Pentax XL 5.2-40mm :  long since discontinued in favor of the XWs, but still pop up second-hand and still very worthy

Meade 4000 UWA smoothie 14mm :  An old favorite from the late 80s/early 90s

Wide Scan III 80° 30mm clones : Surprisingly good in slower scopes at the edges, super sharp inner 40° in most scopes

Meade MWA 26mm : Can get 78° with eyeglasses, but there's a lot of SAEP to deal with

Baader Scopos Extreme/Orion Stratus 35mm : Baader recently sold out of NOS (I think I got the last one), but comes up used once in a while.  Well corrected, great eye relief, super heavy.

Meade 5000 Plossl 40mm : Most likely same optics as ES-62 40mm, but much cheaper on the secondary market.  Super sharp in the inner 50% of the field.

Vixen LV, NLV, and LVW : All discontinued, but all fine performers, and all show up regularly on the secondary market

Celestron Regal 8-24mm Zoom : Hard to find, also sold with some Olivon spotting scopes (has a rubber grip instead of metal ribbing).  Easily usable with eyeglasses once the twist-up eye cup is screwed all the way off (just keep twisting the cup down).

4 hours ago, Stardaze said:

What's your go-to filter for Orion please? Be interested to know. 

Generally none, but my 1990s Lumicon OIII will show the faint outer edges that blend into the sky-glow.

3 hours ago, Don Pensack said:

Oof.  That is poor edge performance even at f/10.  His measurements are in arc-minutes.  The predominant aberration is astigmatism.

These are not well-designed eyepieces, IMO.

The 40mm Aero ED is well designed for it's price point.  It would be unrealistic to expect Panoptic 41mm correction for 20% of the price.

The 40mm Aero ED performs about as well as the 40mm Pentax XL, a bit worse than the ES-68 40mm offerings, way better than the GSO Super View, slightly better at the edge than the Vixen LVW 42mm, and better than the WO SWAN 40mm.  The Panoptic 41mm is indeed in a class by itself correction wise, though.  When you factor in weight, the Aero ED is a big winner for smaller scopes that are easily unbalanced.

The 24mm APM UFF would be a good widest 1.25" field eyepiece with good eye relief for eyeglass wearers.

38 minutes ago, vlaiv said:

Very interesting methodology for testing out eyepieces. This gives me all sorts of ideas.

Maybe MTF graphs could be used, or at least artificial star images?

I think he uses a microscope of sorts with a reticle eyepiece to precisely examine the aerial image of the eyepiece.  This allows for fairly accurate measurements of blur spots.  The problem comes in with irregularly shaped blur spots.  I get the impression that they're sometimes really diffuse or asymmetrical.  He uses an artificial star to the best of my knowledge.  He also tries to use them under the stars in actual telescopes as well to give his impressions of real world usage.

2 hours ago, badhex said:

Good to know. Can I safely assume that the 35mm will be the same though? I'd love to see a direct comparison of the 40mm and 35mm.

According to Ernest in Russia who tests many eyepieces on his optical test bench, the 35mm falls somewhere between the 40mm and 30mm.  You can look on his summary page for United Optics, ED toward the bottom of the table.  I've tried to repeat it below.  The numbers reflect the size of the blur spot of an artificial star at center/70%/98% to the field stop using an F4 and an F10 lens.  He moves the eyepiece to center the area of interest over the center of the lens image to eliminate lens aberrations influencing the results.  The actual full report page is here.  Try using Chrome browser to translate them.

2 hours ago, badhex said:

Good to know. Can I safely assume that the 35mm will be the same though? I'd love to see a direct comparison of the 40mm and 35mm.

One other question springs to mind - why did they discontinue the 40mm? Is it just lack of interest in those long focal lengths or some other reason?

I'm guessing the manufacturer is just waiting for someone to pony up enough money for another full production run.  These Chinese factories that supply the rebranding market don't generally start a production run unless they have a paying customer ordering a large enough quantity to make it worth their while.  I've heard you have to order 300 to have you brand printed on them, but I don't know how many to actually restart a sold-out production run.  I'm guessing well over 1000.

15 minutes ago, badhex said:

It looks to me that apart from some softening around the edges, I'd be getting a pretty good deal going with the Aero ED 35mm - and from what know the softening should be much less obvious at F7.5 as you've mentioned.

At 71° AFOV, if you concentrate on the center, the fuzzy parts are mostly in your peripheral vision where they are harder to perceive.

I forgot to add my ~30mm line-up which includes the 30mm ES-82, 30mm APM UFF, and 30mm 80° WideScan clone.  None of which will show as much sky (TFOV) as the Aero ED 35mm, though.

The WideScan clone suffers mostly from massive field curvature which the cell phone camera suppresses with its depth of focus, so be aware it actually looks worse to the human eye which has less depth of focus.  Make no mistake, it also has edge astigmatism, but it improves quite a bit by refocusing for the edge.  If the design had a field flattening element or two ahead of the field stop, it would have a massively improved reputation.

55 minutes ago, badhex said:

Thanks - although I'm a bit confused  - this link *is* for the Aero ED, or are your referncing the 35mm version? Or are there two version of the 40mm, like an older one as you mention? I was looking at exactly this EP but sadly, the 40mm is no longer available from FLO (or anywhere else that I can see) and the 35mm is not a huge difference from my existing 30mm in terms of power.

The 35mm version has a 71° AFOV (and a 73° effective AFOV due to distortion) and a 44.4mm field stop by my measurements, so it comes pretty close to maxing out the field of view possible in a 2" format (46mm field stop).  It should perform well enough at f/7.5 for your needs.

The 40mm Maxvision/Meade 5000 SWA has the same optics as the 40mm ES-68, so if you can find one used, it's an excellent choice.  It is much better corrected in faster scopes, but also much heavier (30.8 ounces vs. 12.3 ounces for the Aero ED).

Below is comparison image of my widest field eyepieces taken through a field flattened f/6, 72ED refractor.  It should give you some idea of the relative edge correction characteristics of various eyepieces.  The 40mm Meade 5000 Plossl is basically the same as the new 40mm ES-62.  The Baader Scopos is discontinued.