Louis D

8 hours ago, Chandra said:

The Barlow operation is somewhat cryptic to me. I always hear that it is better to use a long Barlow tube than a short one, since these vignetting and also require a greater bending of the beams, with the aberration problems that this can entail. However, I also have the Q-Barlow and another 2" Svbony ED shorty (I think it's the same one that OSG builds and sells) and they both seem to do a good job with Baader Ortho and Plössl from the Q-Turret pack, and with the 28mm 2" SW LET and the 42mm 2" OSG SuperView. I don't know how much of a difference in visual quality there can be between short and long Barlows.

Shorty Barlows don't have to be bad.  The 1990s Japanese made Celestron Ultima, Orion Shorty Plus, Parks Gold Series 2x Barlow is a very good shorty Barlow.  It uses 3 elements and seems to work about as well as my TV 2x and Meade 140 2x.  On the other hand, I have a generic shorty Barlow from the early/mid 2000s that is so bad (adds fuzziness to image), a guy I permanently loaned it to insisted on giving it back to me after 6 months of use. 🤣

That US flag on the USD side above looks more like the Chilean flag which is often confused with the Texas flag:

Chile:

Texas:

At 60mm and f/15, it should be basically apochromatic:

I wonder if there was an equally long and skinny extension tube that originally came with it?  You can locate the focus point by lining it up on the moon as you did before and then hold a thin, white sheet of paper behind the focuser, noting the distance where the image is sharpest on the paper.

Since they're all made by KUO, they should all be optically identical.  There's an extensive thread on the Astro-Tech version of the 28mm on CN.

I've always assumed most of these commercial Dobs glue their secondaries onto the holder since there isn't a proper lipped holder as with the Astrosystems secondary holder:

I seriously doubt these commercial builders drill a threaded hole in the back of the mirror for a bolt to thread into.  That's the only other way I could conceive of attaching the secondary mirror without a lip or clips.

I hadn't thought about it, but I do use the arm rests on my plastic patio chair to steady myself while observing.  I would sorely miss it with a perch style chair.

I would lean toward either the GSO made StellaLyra 8" f/6 Dobsonian for features or the JOC made Bresser Messier 8" Dobsonian for its mechanics.  The latter's focuser can be upgraded later to dual speed if desired.  These two and the Synta made Sky-Watcher Classic 200P Dobsonian are all going to be similar optically.

Yes, the old R&P focusers slopped all over the place.  You can wedge plastic milk jug shims into them sometimes to reduce the slop by making them a bit more Crayford like.

14 minutes ago, JeremyS said:

 Not at all. In fact here it is in use the other day on the Mewlon 210

Looks ready for a night launch. 😉

The problem as I understand it with the Synta focuser is that it is not natively 2" without either tall adapter, so you can't use a stock, low profile 2" to 1.25" adapter.  It's a bit larger:

Does anyone make low profile versions of these Synta adapters?

The Lumicon Low Profile 2 Inch Prime Focus Adapter almost looks correct if you need a male T2 thread:

46 minutes ago, sorrimen said:

Being able to screw on the barlow directly would definitely help, but sadly mine doesn’t have the functionality. The stock SW adapter seems to extend ~50mm out from the top of the 2” top, so I’m hoping with a very low profile adapter I should gain enough to use the ADC. Just a cheap one on ebay seems to only extend 10mm above the 2” top, so I’ve got faith.

OMG, yes.  Those Synta eyepiece adapters are atrocious.  The whole point of having the focus point so far outside the tube is to facilitate astrophotography, but you can't take advantage of it with their focuser setup.

If they went with a low profile focuser from the factory and moved the focus position in closer to the tube to exclude AP, they could shrink the secondary size and improve visual contrast.  As it is, they've got the worst of both worlds with the current focuser.  Poorer visual contrast and lack of AP backfocus.

9 minutes ago, beka said:

So you can love astronomy and not love CATs???

CATs vs cats.  Nothing against the former (I've got a 127 Mak), and nothing against the latter as long as it's not living in my house or yard. 😉

I've got eyepieces that require over 20mm more infocus than I have even with a low profile Newt focuser.  My solution is to screw the optics section of my GSO coma corrector directly onto the end of the eyepiece and send it deep into the focuser that way.  The CC grabs the incoming light cone sort of like a relay lens and sends it up to the eyepiece where it can then reach focus.  The CC correction isn't perfect, but neither is the eyepiece I'm using it with.

Maybe you could do something similar with a GPC/Barlow element screwed directly to the bottom of the ADC?

1 hour ago, Don Pensack said:

If there were an eyepiece rental service, I bet they'd be busy and marks wouldn't matter at all.

OMG, rental photo equipment is often battered beyond belief by professional photographers.  I only buy used photo equipment from novices who have barely used their equipment and need quick cash.

@inFINNity Deck How did you get your Jupiter image looking so impressionistic?  Was that some sort of filter effect or just the atmosphere at work?  It's very cool looking.

Do you use any sort of OCA/OCS/GPC or Barlow element to reach focus?  Do you use the binoviewers in a slow SCT/Mak?  If so, you may be able to get away with cheaper wide fields as I do.  The Svbony 68° Ultra Wide Angle 20mm work great in my binoviewer setup at an effective f/18.

There's the Oberwerk 22mm eyepieces which are sold in pairs explicitly for binoviewer/binocular use.

They're $300 for the pair.

I wonder if wrapping the tube in an insulating blanket would help prevent dew formation on the tube as discussed in the below thead:

Here's an SCT entirely wrapped in insulation on CN:

I've never had dewing problems inside or out with the Sonotube exterior of my Dob.  It must be something about metal tubes.  We regularly have dew points just below 80 degrees F, so it's not like it's a desert here.

Why doesn't Europe (Russia excluded) have a manned space program?  Y'all are smack talking the US effort without offering up anything better.  Seriously, without huge military expenditures like the US has, y'all could have a top notch space program.

5 minutes ago, Mike Q said:

Just out of curiosity have you ever tried using the weak eye?  I have tried it and had to use an eyepatch to make it work.   

The difference in astigmatism is minor.  2.00 on the left, 1.75 on the right.  I'm left eye dominant, which has made using SLRs/DSLRs a pain over the years because they shift the viewfinder left assuming right eye dominance to make room for the nose.

To do a quick star test of the eyepiece, simply pick out a mag 1 or 2 star, bring it to best focus on axis, and move it from the center to the edge, observing any changes to the star's appearance.  Is it still a pinpoint everywhere in the field?  Does it change shape or spread out into a rainbow near the edge?  Does refocusing the star at the edge make it look sharper out there?  It's when you take the time to look for these sorts of changes that you can start to discern good eyepieces from terrific eyepieces.

21 hours ago, Mike Q said:

 Some people complain about the eye relief with glasses, for the wife and i its a non-issue, we take them off and focus the scope.  

If only I could simply turn a knob and "focus" out my strong eye astigmatism.  I have no desire to get LASIK, either.

IIRC, reports on the Luminos complained about excessive EOFB (Edge of Field Brightening) which makes the outer field appear brighter and cloudier than the inner area, and also excessive SAEP (Spherical Aberration of the Exit Pupil) or kidney beaning which makes holding the exit pupil tiring.  Some folks swear by them rather than at them, though, so YMMV.

As far as the Axiom LXs, they were the same optically as the Meade 5000 UWA and original ES-82 mushroom tops.  All were made by JOC.  I have the 30mm ES-82 decloaked, and it is just barely usable with eyeglasses.  While the 82 degree field is rewarding to look at, stars are a bit bloated across the field compared to others I have in this range, and especially near the edge as CAEP (Chromatic Aberration of the Exit Pupil) kicks in.  The moon turns orange in the outer field as a result, and planets split into red/blue slightly separated version of themselves.  Thus, for those of us with undriven scopes who enjoy observing objects drifting from edge to edge before nudging again, the 30m ES-82 doesn't really work for that use case.