Louis D

So, has anyone compared the APM SZ doubled with a Barlow to roughly 4mm to 8mm against the Svbony 3-8mm?  I have the latter and find it very nice except for the tight eye relief.  The doubled APM SZ might be a nice alternative, but it would rival my 5-8mm Speers-Waler for length.

7 hours ago, Franklin said:

My mum told me that to get rid of floaters you must flush the toilet harder!

9 hours ago, Alan White said:

I displaced a Panoptic 27 with the 30 UFF in APM clothing sometime ago.

Same here.  The Panoptic might have a hair's breadth tighter stars on axis, but that's about it to recommend it over the APM.

2 hours ago, PeterC65 said:

It gets rave reviews on SGL and according to the Ernest Eyepiece Review it is flatter (and considerably less expensive) than the equivalent Nagler and Panoptic, which are both flatter than the ES 82° 30mm.

I can't speak for the 31mm Nagler or 35mm Panoptic, but my 30mm ES-82 is flatter than my 27mm Panoptic.  I can't detect any defocus due to field curvature in the former, while there is a bit in the latter.  The 30mm APM UFF is flat of field as well.

My big issue with the 30mm ES-82 is severe chromatic aberration of the exit pupil (CAEP) at the edges.  The visual effect is to split Jupiter into slightly separated red and blue copies in the last 10% of the field.  The whole point to having an 82 degree eyepiece for me is to allow more drift time to observe an object in an undriven scope, and this optic aberration ruins the usefulness of the extra field over the 30mm APM UFF which has perfect spectral alignment at the edge.

If you look straight at the center and keep the edge in peripheral vision, you won't notice the CAEP in the 30mm ES-82, so it may not matter depending your viewing style.

You can see the CAEP manifesting itself as a rainbow circle in the AFOV image of the 30mm ES-82 below:

4 hours ago, Coco said:

I want to start using binoviewers but cannot find some that will work with a dob for reasonable money I’m contemplating a linear set but reviews are not encouraging me, I’m also sensitive to binocular collimation, and I’m not the sort to buy and try, I don’t like to mess people about. I hope to have a peep through a set one day, that'll make my mind up.

I use the nosepiece from a vintage 1990s Meade Series 4000 140 APO 2x Barlow to reach focus with my Arcturus BVs in my Dob.  It only has 25mm of in-travel from primary focus, so this solution would probably work for any Dob.  The Barlow element operates at 3x when screwed into the filter threads of the BV's nosepiece.  As long as you stay above 15mm on eyepieces, you shouldn't have any issues merging images.  Just watch out for eyepieces tipping in their holders when you tighten them down.  I push them hard into the holder while tightening to prevent tipping.  I'm too lazy to fill the undercuts.

I can get it back down to 1.0x magnification by putting a 0.5x focal reducer between the Barlow element and the BV with 45mm of spacer tube distance between the Barlow and FR.  Of course, there's severe field curvature due to the cheap FR, so TANSTAAFL.

The trick to getting decent night shots is to prevent the camera from trying to render black (or near black) as 18% gray (the logarithmic midpoint between white and black).  To do this, go into the exposure compensation settings of the phone and dial back the exposure into the negative side (under exposure).  Try several settings to see which works best for your camera and sky conditions.

3 hours ago, Basementboy said:

As for the C5, I have never used one – really have no idea. Focal length shorter than a Mak so maybe a better all-rounder? Will the sharpness be an issue now that I'm used to refractors? I suppose the only way to find out for sure is to try it

My only concern about traveling with any SCT is the probability of the thin corrector plate cracking during handling.  The thick meniscus corrector of a Mak has no such issues.

Click on the following posting showing lots of shattered SCT corrector plates:

By was of comparison, here's a damaged, but not shattered, Mak corrector:

Mask off that damaged area with tape, and you're good to go observing again.

The only concern I might have with photographic filters is when using them for solar observing.  Some photographic line filters strongly leak in the IR wavelengths.  This is not an issue photographically because they are usually paired with a UV/IR blocking filter when imaging in the visual spectrum because test images will clearly reveal this leakage.  However, the human eye can't perceive this leakage beyond a mild discomfort while viewing.  Thus, be careful and knowledgeable when using photographic filters for solar observing and take appropriate safety measures.

One problem I've had with Chinese made OIII filters in the past is that they tend to have poorer quality control.  I'm not saying that is the case any longer, but it really falls to the branding company to ensure the quality of what they offer under their name.

Note below how my decade old Zhumell OIII filter (Chinese made) is right shifted.  It actually made for a excellent comet filter on Comet ZTF to make it stand out better from my light polluted skies.  I'm actually quite happy with the $10 I paid for it now that I know it makes for a good comet filter.  By way of comparison, my Lumicon OIII filters basically masked it completely.

My new Svbony UHC is actually quite decent compared to my 25 year old Lumicon UHC, especially considering I paid $22 for it.  The slight blue-violet bleed isn't visually noticeable by my older eyes.  The view of the Orion Nebula looked remarkably similar through both.

I will say that while people are briefly interested in viewing imagers displaying DSOs being built-up on laptop screens at outreach events using high quality imaging rigs, they quickly lose interest and gravitate toward the visual-only scopes on the field despite having to wait in lines for a quick view.

Would it be easier and cheaper to simply swap the entire diagonal for monoviewing?  I do that with my rig.  I have a 1.25" WO dielectric diagonal for my Arcturus BV to limit in-travel requirements, and a 2" GSO dielectric diagonal for monoviewing.  It's pretty quick to loosen the 2" receiver on the scope to take out the adapter/1.25 diagonal/BV/eyepieces combo and swap in the 2" diagonal and eyepiece and then retighten the receiver.

Complete nonparfocality as in my Speers Waler 5-8mm zoom is a huge pain.  It's impossible to dial in the best magnification in real time because you have to zoom, focus, zoom, focus, etc.  I've tried zooming while focusing simultaneously without much success.  It would have been nice if Glenn had invested more effort in the mechanicals to include some cams to maintain focus while zooming as with camera zoom lenses.

Not that I've ever heard of.  You could try taking it to a local machinist to have the threads measured and have one made for you.

Alternatively, look for a vintage Meade series 4000 140 APO barlow.  Its optical nosepiece has standard filter threads.  It normally operates at 2.4x, not 2x as advertised.  In my Arcturus BV, it operates at 3x.  Optically, I've compared the Meade to my TV 2x Barlow, and I can't see any difference between them.  Both are Japanese made.  I've got 3 copies that I use for various purposes, and have never paid more than $50 for one.

As long as the bandpass(es) are within the range of human vision (photopic or scotopic, depending on the viewing conditions), photographic filters should work fine.  An example of one that would not work visually would be a Ca-K filter which operates at 393nm, or far violet, which is basically not perceivable by our eyes.

I use a Meade Green interference filter visually which was sold as part of a photographic set for LRGB photography.  It's probably my best green filter by far.  It has high transmission and very sharp cutoffs at the blue and red ends.

Note how tight, bright, and pure the Meade Green is compared to my other green filters:

The other two Meade interference color filters work well as blue and red filters as seen below:

I have the 3.5mm Pentax XW, and it is aberration free across the field as near as I can tell under close scrutiny.  It also has very good contrast and stray light control.  It might not be quite at TOE or HR levels, but it is very good for us eyeglass wearers.  It does not have any SAEP issues, so holding the exit pupil is a breeze.  However, I use it so rarely due to seeing conditions and floaters at that tiny exit pupil that I sometimes wonder why I bought one.  I highly recommend extending(?) some longer focal length eyepieces in your collection with your 2x ES Focal Extender first before buying a 3.5mm XW as recommended above.  You may find it to not be a very useful view.  I've found that observing with a larger aperture scope of longer focal length works much better for higher power views at larger exit pupils than trying to squeeze out the last bit of magnification at smaller apertures.

1 hour ago, Ratlet said:

When I first got mine I thought it was broken.  I'd accidently set the pulse time for the circle to incredibly slow so that the circle was almost never displayed.  That's what I get for not reading the manual.

When did Telrads start getting sold with built-in pulsers?  None of mine have one.  You generally have to install one of these kits yourself to get a pulsing function.  Are you referring to a Rigel QuikFinder instead?

That scope package has several optical knocks against it right out of the box.

• First, it uses a spherical mirror, so it will always have some level of spherical aberration leading to blurring of details.  Admittedly, at f/8, it's not as bad as at say at f/4 as with the Celestron FirstScope 76, but it is still there to some degree.
• Second, the three eyepieces are of ancient designs (Ramsden and Huygens) more suitable to f/12 or slower scopes.  While they will work at f/8, they will only be sharpest on axis.  I would primary use the H20 and H12.5 without the Barlow lens to learn your way around the sky.  See if those two produce sharper, more pleasing images with a cellphone camera held up to the eye lens (afocal projection).
• Third, the Barlows packaged with these scopes tend to be of dubious quality.  Many are singlets instead of doublets, so they introduce a lot of optical issues themselves.  A good Barlow will simply magnify the center of the image without degrading the image.  It may magnify the shortcomings of the scope's image not visible at lower magnifications, though.

The moon is a very good target to experiment on while learning what works well with a scope and what does not.

I've had issues with multiple Telrads over the years.  They all seem to revolve around the switch (a potentiometer with switch) failing.  I've had some that won't come on at all, some that won't light until at full output, some with limited brightness travel before full brightness.  I generally just buy another because I don't have the spare time to mess with repairs, but you could try swapping out the switched potentiometer to see if that fixes the problem.

1 hour ago, jetstream said:

I had Siebert make me a 50mm 1.25 EP, it is actually good but it didnt get along with the Quirk. It showed part of the Quarks internals along with Ha detail.

Dad joke ahead warning:

So, a Quirk of owning a Quark. 🤣

10 hours ago, Zermelo said:

I think we did that one in a thread last year.

The americans are correct, with "z".
Then they ruined it, by calling it "zee".

I had to look it up.  Y'all call it zed instead of zee.  It sounds cooler than zee and is less likely to be confused with other letters ending in ee.

I have heard it used, but I thought folks were using it trying to sound cool when spelling words.

It also makes me think of one of my favorite quotes from Pulp Fiction: Zed's dead, baby.  Zed's dead.

10 hours ago, John said:

Standardization or Standardisation ? 😁

I'll bite.  Does standardisation rhyme with condensation in the UK?  If so, then that would indeed be the correct spelling for y'all.

8 hours ago, markse68 said:

The starsense app was developed by SkySafari for Celestron I think so we can only hope that one day they will be allowed to incorporate it as a plug-in into full blown SS- would be really awesome then with the huge catalog and ability to make observing lists etc. right now I run Skysafari on my phone for the lists and Starsense on an older phone for the finding. So 🤞

That's exactly what I was going to suggest, running two phones with the two apps instead of waiting for them to be integrated together.

It's an ETX model.  Since you didn't take any photographs of the front of the optical tube with the cap off, that about all I can be sure of.  Take the cap off and take a photo of the writing around the front lens and post it here.

Based on its size, I'd say it's either their ETX-60 or ETX-70 model.  I don't think it's the ETX-80.

6 minutes ago, niallk said:

I had a filter wheel for my 10" dob and it was very handy.

How did you make that work?  Did you shorten your truss poles?  My Dobs have low profile focusers with about 25mm of in-focus from the primary focus point.  This was done to minimize secondary obstruction while maintaining decent illumination levels.

I tend to be very thoughtful about my eyepiece purchases, so I rarely feel a need to sell anything.  I did buy a Meade 5000 UWA 20mm for about $50 because the price seemed too good to pass up.  It is a decent eyepiece, but the eye relief is tight and SAEP is horrible.  I'll see if my daughter wants to use it sometime.  I doubt she will, though, because she also likes to view with eyeglasses on.  I may end up selling it someday without regrets at that point.