Louis D

1 hour ago, Ags said:

I thought the typical eyepiece curves opposite to the telescope, so surely a flat eyepiece is likely to be an improvement?

Maybe in that case (like the 14mm and 20mm Pentax XWs) it would be.  In my experience, the 10mm Delos, 9mm Morpheus, 30mm ES-82, both ES-92, and 9mm Vixen LV all appear flat to my eye.  The 27mm Panoptic might have a bit as do some of the Nagler T4s (17mm springs to mind).  The 14mm Morpheus has a bit as well, although Don P. doesn't see any in his copy.  The worst are the 80 degree, 30mm WideScan III clones.  They have several millimeters of curvature center to edge.

15 hours ago, Ags said:

I was thinking about the APM UFF 24mm as a widefield dark sky workhorse - does the "ultra flat field" mean the field curvature of my Zenithstar 66 will be less apparent?

No.  It just means it won't add or subtract any OTA field curvature.

Get a TSFLAT2 and put it ahead of your 2" diagonal if you want to flatten your Zenithstar 66's field.

2 hours ago, cwis said:

That sounds about right What  causing this effect?

I must have deep set eyes because I'm mashing my face into the eyecup to see the field stop... But if I fold it down then I get blackouts etc - too close.

You might be right after all that it could be a very mild case of exit pupil aberration.  It just doesn't manifest itself as kidney beaning (SAEP), though.

I see a much more severe version of it in the Meade MWA 26mm where the outer 2 degrees is completely black until you get close enough to see the field stop.  At that distance, kidney beans start dancing around the mid-distance part of the view.  At no point could I induce similar kidney bean shadows in the APM.

I'd try the Baader eye cup in your case.  It is 1mm shorter and quite flexible compared to the OEM eye cup.  It's not that expensive to experiment with.

It was generally accepted on astro forums back in the early 2010s that the Celestron Axiom LX, original Meade 5000 UWA, and original Explore Scientific 82 series with the mushroom top were all the same optically and differed only in cloak style and claimed focal lengths.  Perhaps this wasn't actually the case?

Okay, I dug out my 9mm Morpheus eye cup and its extension ring and tried them on the APM UFF 24.  Everything easily threads together.

The Baader eye cup alone is 1mm shorter than the APM's OEM eye cup.  Without eyeglasses, I preferred the view with the OEM eye cup, but I was just barely touching the eye cup, so stray light could be an issue, but jostling the scope would be minimized.  The Baader alone was just too short.

The Baader eye cup plus extension is 7mm taller than the OEM eye cup (8mm taller than the Baader eye cup alone).  I found I had to mash the eye cup into my eye socket to see the entire field without eyeglasses.  It's pliable enough that this works well.  It sealed pretty well around the perimeter, so stray light would likely not be an issue; however, scope jostling could be.

I did notice in daytime usage that just as the field stop comes into view, a shadow ring appears just inside it if you continue to look on axis.  If you pull back enough to get rid of the shadow, you lose the field stop.  If you look at the field stop and tilt your head properly, the shadow goes away.  Perhaps this is what the OP is seeing?

Here are the comparison images.  The Baader eye cup alone looks almost like the OEM one.  It's much less stiff, though.  I suppose the Baader could be unscrewed a bit to raise it up since the APM only has about 2 eye cup threads to grab onto anyway.

Left to right are the OEM, Baader, and Baader+extension eye cups:

3 hours ago, F15Rules said:

I just weighed the Axiom LX 31mm on my wife's electronic scales.

With all the parts including outer shell and both endcaps, it weighs in at 1483 grams (that's 1.483 kg or 3lbs 4 oz!).

Without the shell and endcaps it weighs 1082gms. So the decloaking has saved 401gms or 32.5% of the original weight.

Interesting that the Axiom is heavier than the ES-82 version.  1483g vs 1369g and 1082g vs 973g.  The Axiom cloak is only 5g heavier, while the main eyepiece body is 109g heavier.  I wonder what accounts for the ~10% difference in weight?

Growing up with both systems firmly entrenched here in the States, it doesn't bother me until I'm trying figure out what socket wrench will fit a particular nut or bolt head while working on a car or bike.  Then it can be quite infuriating.  It's typical that both units are used for different fittings based on tradition.  For instance, when changing a battery, the electrical posts are metric (10mm typically) while the hold-down bolt at the bottom is US Customary (USC) (1/2 inch typically).  I just shake my head each time I swap out a battery. 

In day to day parlance, I can't imagine what the SI equivalent would be for considering a person tall.  In the US, you're generally considered tall if you're 6 feet tall or taller.  That would be ~1.83 meters which seems a bit awkward to use in daily speech.  If a basketball player is 7 feet tall or taller, that person is considered extraordinarily tall.  That would be ~2.13 meters.  Again, awkward to use in daily speech.  I suppose you could round down to 2 meters, but now you're only talking about a ~6 foot 7 inch player which is fairly common in both college and pro basketball (and even for many high school teams).  My point is, USC units often align better with day to day, fuzzy measures than do SI units.  Thus, they happily live side by side most of the time.

In engineering, pretty much everything is expressed in SI units except for unwashed masses, customer facing descriptions, like the linear and cargo dimensions of a car.  They're always expressed in inches and cubic feet, respectively.  Liters have come to replace cubic inches for engine displacement, though, over the past 50 years.  That one still perplexes me how it was generally accepted when horsepower continues to be used for engine power. 

Why haven't time units gone decimal?

I have a GSO 2" diagonal with a TSFLAT2 field flattener attached to the front of the diagonal via an SCT to M48 thread adapter in place of the included diagonal nose.  This gives me a nice, field flattened view from edge to edge without changing the magnification.  Of course, you'd also need some nice eyepieces as well.

The only issue I've had with the early morning is that the temperature typically approaches the dew point and dew starts condensing on everything very easily.

You might look into converting a collapsible rubber lens hood into an oversized volcano style eyecup by inverting it and putting the wide end around the eyepiece and look through the lens attachment end.  You might have to visit a well stocked brick & mortar camera store to try out various ones until finding one the fits well.

A little off topic, but how do you mount another saddle on the other side so you don't need to utilize a counterweight by leaving the top mount empty?

I'm sure you'll enjoy it.  I have the TS Optics 90mm FPL-53 f/6.6 Triplet which is quite similar and like it a lot for visual observing.  Just be patient while waiting for it to acclimate.

2 hours ago, jock1958 said:

Hey Dave they look more sleek and expensive now, one thing what’s the purpose of those bits if they only add weight & bulk? 
 

Maybe they could etch Celestron Axiom on the barrels like the Halloween Plossls 🤔

I guess they thought it made them more distinctive to put gargantuan eye cups on them?  It was an early 2010s thing to go overboard on eyepiece cladding.

For instance, the Celestron Ultima-LX had bulbous rubber grips that were oversized:

They were the same optically as the Omegon Redline which I think are far more attractive and svelt:

5 hours ago, vagk said:

Has anyone compared any of these below :

Morpheus 9mm vs 10mm XW vs 10mm Delos

How close they are ?

 

 

 

 

 

 

 

I've compared my 9mm Morph to my 10mm Delos, and at f/6, they are almost indistinguishable except for field of view.  The Delos might be a hair sharper or contrastier, but it is a subtle difference if it exists.  I'm happy with both.

I took images through the APM UFF and ST80 combination with two different phone cameras (Galaxy S7 and LG G5 UWA).  The second one is the ultra wide angle one that really exposed any SAEP if it exists.  I can't see any shadows or beaning in either, just edge blurriness due to severe field curvature in the ST80:

I dug out my ST80 from ~2000 and put my APM UFF 24mm in it during the daytime and looked for kidney-beaning.  I couldn't see any at all.  I did notice that if I took my eyeglasses off, it is quite easy to get inside the exit pupil and watch the field of view shrink.  However, it was very well behaved in that it shrunk from the field stop inward.

I then screwed the Baader M43 eye cup extender onto the top of the APM UFF after peeling off the eye cup.  It threaded all the way down and looked OEM.  However, I could not get the APM eye cup to fit onto the extender because it expects a threaded lip with undercut below it, not a complete threaded cylinder.  Thus, you'd have to get the Baader Morpheus threaded foldable eye cup to fit onto the Baader extender.  With both, you would definitely avoid blackouts when not wearing eyeglasses.

Just now, johninderby said:

Better get your crystal ball polished up to see what’s going to happen to eyepiece prices. 😁

I'm no soothsayer, but I'd guess "go up" over the next 12 months.

In that case, it's cheaper to just buy them locally in the UK for £249.

I'm still seeing quite a few places selling Morphs over here for $259.

7 minutes ago, johninderby said:

In the ZuK

Mprpheous - £188.00

Pentax XW - £249 to £359.00

Sounds like cross importing the Pentax XWs from the US might save some serious money, although I think your prices include VAT which Don's do not.

3 hours ago, YogSothoth said:

what difference would I actually see between the two?

To refocus the thread back to your question, you'll see a 76 (or slightly more) degree apparent field of view (AFOV) in the Morpheus versus a 60 degree AFOV in the BST Starguider.  The usable eye relief of the Baader is about 18mm to 20mm while the BST has only about 12mm.  Thus, if you wear eyeglasses due to astigmatism, you'll see even less than 60 degrees in the BST, but should be able to see all 76+ degrees of the Morpheus.

The Morpheus will probably be sharper out the edge than the BST in faster scopes and may also have better contrast and stray light control preventing ghost images better.

The Morpheus is significantly larger and may pose a problem for binoviewing with a pair as compared to a BST pair.

Kind of high priced on your side of the pond.  They're $109.99 on ebay over here with free shipping.  Assuming 8.25% sales tax as I have to pay in my part of Texas, that would come out to $119.06.  £117 comes out to about $160 in the US.  That's 34% more expensive.

That's also not going to work for older lasers without a side port cutout like my AstroSystems one.

SVBONY is now marketing a whole range of astro products.  They seem to be curating their offerings more carefully than some of the predecessor Chinese/HK brands like Vite.  None of their offerings are junk, just low cost.

I have their solar finder and their 68° Ultra Wide Angle 20mm:

They've been repackaging some existing designs to make them more attractive, like the 68° Ultra Wide Angle line.  It's basically the same as the older 66° Ultra Wide Angle Expanse line, just more handsomely packaged.

Try to characterize the aberrations more by moving Jupiter around the field of view (edge to edge as a start) to see how they appear to change.  Also, try different eyepieces to see if the effects change.  Of course, repeat all this without the R/C.  You're likely seeing internal reflections from the baffle tubes, rear port, visual back, and/or the reducer or eyepiece.