michael.h.f.wilkinson

I used to work with the focal reducer for visual, but have since switched to a 2" visual back and diagonal. I only use the reducer for imaging. The moon is captured nicely in a crop sensor camera with the reducer in place

Nice work!

Really nice! If 2020 continues like this I will hit comet number 30 this year.

I think it also reduces coma

Not sure what the thin grey lines are. Could even be the edges of the lenses, which always show some scatter. I am not going to take them apart to find out. It does seem definite proof there are two different types of SLVs. I was apparently lucky enough to get three with blackened rings

Just compared the look of my EPs to the ones shown here. It looks like the light grey ring shown in the images above is black in mine (all three)

But then orthos have a narrower FOV (42 deg typically). I used to have an ortho or two (way back in 1979, when I built my first scope as a teenager). Both had 0.965" barrels. I absolutely loved the Circle-T 25 mm, which was so sharp in my 6" F/8 (small CO, good mirrors, a real planet scope, but also awesome on DSOs). Of course, the 25 mm had 20 mm eye relief, so that was fine. I also had a volcano-top 5 mm, and a symmetric achromat 9 mm. I found the latter just about usable, but the 5 mm ortho just didn't work for me. Eye relief was way too short at about 4 mm, even without glasses I tended to bang in to the EP, making the image shake terribly. The coatings of the EPs in those days were of course not as good as the ones you can get now, so the extra glass-air interfaces don't impact as much on image quality as they used to.

Planetary imaging would indeed be an option. An 8" scope will show lots of detail, especially when the planets are higher in the sky. Tracking doesn't have to be spot on, and there are modest-price cameras out there that really perform nicely. Yoiu will need aa Barlow or tele-centric lens to extend match the focal ratio of the scope to the pixel size of the camera. My former ASI224MC (since replaced by the ASI183MC) worked really nicely at F/16-F/20.

You can certainly image with an 8" Newtonian, but a flextube Dobson isn't the best choice for DSO imaging. It could probably be used for planetary imaging

The Flextube is really a visual scope, and you would need a focal reducer and very solid EQ mount to track or guide with that focal length. The only coma-corrector 0.73x reducer for Newtonians I know of is rather expensive (you can buy an SW 80ED and then some for just the price of a reducer. A short ED refractor is probably the best way to start, The SW 80 ED is one of the most used scopes in this field, by beginners and more advanced astrophotographers alike. There is also a 72 mm version. Both would probably need some focal-reducer/field flattener for use with a DSLR. I would certainly look out for second-hand scopes.

My first take on Bode's galaxy used rather more data (3 hours), a more powerful mount (Vixen GP-DX), and a smaller scope (still a 6" F/5, which is already quite a beast). Modding won't help much on galaxies, as a rule, unless they have many H-II (star forming) regions. You can get really nice results with a modded DSLR and small scope, like the 80 mm, but it does take a lot of time. M42 in a modded EOS 5550D looks like this, after 7h 10 minutes total exposure time. This was done over several nights with a simple, unguided EQ3-2 mount. I just stacked loads of 60s exposures, and it came out rather nicely

The Skymax is mainly suitable for planetary and lunar work. The ST102s are decent wide-field visual scopes, but not that useful in imaging, due to chromatic aberration. For long exposure DSO imaging an EQ mount is really way better than an alt-az mount. I have obtained some good results with a simple EQ3-2 mount and short refractor (APM 80mm F/6 with 0.8x reducer), but thse would be over budget. You could use a fast telephoto on an EQ mount as well to start off with. I have used a Canon 200mm F/2.8 and got decent results with that

Nice shot! The answer to your question depends on the scope, camera, and processing used. A stacked image using an ASI183MC camera behind an 80mm scope with 2x TeleXtender looks like this Whereas a big mosaic taken with planetary camera on a Celestron C8 looks like this: Click on image for full size version

Which particular infinity did you mean

It seems to have been solved a while ago, as I have had these for quite a while already. Maybe it's only earlier runs that suffered from this.

Got the APM 80 mm F/6 out, to take a quick shot of the moon. I inserted the Meade 2x TeleXtender to reach F/12 which is near optimal for the ASI183MC. Grabbed a few SER files of 2000 frames, but had difficulties with variations of sharpness across the field. I first blamed sag in the focuser, and tightened some grub screws to deal with it. After processing the lot, I now feel there might be some field curvature, as the centre seems sharper than the north and south parts. With saturation pushed a bit:

I know Don Pensack regularly mentions these reflections, and I do not doubt his report, but I see nothing of the kind. I can only explain this conflicting observations by differences between production runs.

After a quick lunar imaging stint with the APM 80 mm F/6 triplet, I had a quick look at the Moon with my 3 Vixen SLV eyepieces (5, 9 and 15 mm, for 96x, 53.3x and 32x). The views were really crisp, and very pleasing indeed. I then decided to move the scope around to see whether I could spot the reflections that some have seen in these EPs. Curiously, I couldn't spot these at all. I do not doubt the reports, but given my inability to replicate these observations, I wonder if there are different production runs of Vixen SLVs.

As said before the scope you are considering is pretty good for planetary work, but not so much for DSOs.

Certainly, binning helps.

I just use Gimp and AstroImagej. I write my own software in C at work, and want to develop a so called morphological connected filter for this task. It will be based on the MTObjects/Sourcerer code base. This is a replacement for SExtractor, used in astronomy for detection of objects. Our method is way more sensitive, and uses statistical tests to sift noise from real structure effectively. Should be fun to develop this idea into a tool that enhances only detected structure, and suppresses the noise.

Not really enough, but I think I am getting better at teasing out a bit more detail. Still need to control the colour noise in the background better

I have an ST80 as guide scope, and an APM 80 mm F/6 triplet. I use the latter for solar, and it works fine, showing loads of detail. The former should work, but the focuser is not great.

Had a bash at reducing the colour noise in the background, and fiddled with curves on my 5 hours of integration time. I basically reduce saturation in the areas of low luminance. I really want to do this more selectively, and write method to enhance saturation only in significant objects, and not in noisy areas. Might set up a student project for that. All data acquired with my Meade SN6 6" F/5 Schmidt-Newtonian and ASI183MC (not cooled) camera on Vixen GP-DX mount. Version one Version two, a bit lighter in the background: It seems to depend on the monitor which I like best. Next year, I plan to get a load more data to combine with this set.

Very nice indeed