michael.h.f.wilkinson

I can well imagine. I have the 5 mm SLV, and is superb on planets. It is every bit as sharp as the Pentax XW 5 mm, all it lacks is the FOV of the XW (but then you pay for that). I use the SLVs (5, 9, and 15 mm) as my travel set, along with a 24mm 68 deg MaxVision. Works really nicely with the 80mm F/6 as travel scope.

I am not sure any of the refractors you mention could beat the views with your SkyMax 180, and in terms of imaging the 180 will win hands down. I have a Celestron C8, which has a planetary performance similar to the SkyMax 180, and to complement it I got myself a wide field refractor (APM 80mm F/6 triplet) for viewing larger DSOs, and DSO imaging in general. For planetary imaging, aperture is definitely king, and the lower contrast caused by the central obstruction of the SkyMax is really not such a big deal. The SkyMax is also much easier to set up than the bigger refractors (even though it is quite a hefty OTA). To get an idea what your SkyMax OTA could do on e.g. Jupiter under good conditions, here is one of my best shots of Jupiter I should note I have looked through a 4" F/10 achromat at Jupiter, with my C8 right beside it, and the view through the 4" scope didn't come anywhere near the level of detail seen through the C8

Very nice scope indeed!

I only have the LVW 42 which is great, and a 25 mm Ortho which is wonderful in solar H-alpha, and I used to have a 5mm circle T, which was very sharp indeed, but drove me nuts with its small eye relief. I will stick with SLVs or XWs for the shorter focal lengths

I had a bash in Astro Pixel Processor, just doing background calibration and automatic stretching, and got this: I tried gradient removal, but because these are 16 bits-per-channel data, already stretched massively I get all sorts of banding artefacts: If you could save your stack as floating point data in FITS (default in Astro Pixel Processor) or TIFF, it should be possible to get far more out of the image.

Amazing image!

Unlikely, the main optics are very different.

The classical Cassegrain is a reflector, not a catadioptric. My C8 can get 1.33 deg true FOV which is fine for most DSOs, after investing in a 2" visual back and is my main visual scope for moon, planets, and most DSOs (planetaries, galaxies, globulars, etc). The classical Cassegrain may however have issues off-axis, as (like the Newtonian) it is only perfectly corrected on axis. However, not all cats are based on the Cassegrain design. Mak-Newts and my own 6" F/5 Schmidt-Newtonian have a beautiful wide fields (3.3 deg at 24.5x), with considerably less coma than a regular Newtonian

I have a similar 7.5-22.5mm zoom to what I suppose must be the Hyperflex 9-27mm, and it performs very nicely in my solar scope, and the 180mm F/15 is pretty forgiving, so I guess it should perform reasonably. I have never looked through either the 9-27mm nor the 6.7 mm ES. The latter has such a small eye relief that it wouldn't work for me with my glasses. The Hyperflex has great eye relief at 18 mm (much the same as my 7.5-22.5 mm WO Zoom II

If you have the 9-27 and the 6.7mm you could simply test them side by side on the moon once the weather clears. The 6.7 mm in your F/15 scope yields roughly the same magnification as my XW 5 in my F/10 SCT, and I rarely use that in practice. I think it has only been useful on Mars and the Moon under exceptionally seeing conditions. I tend to use the XW 7 as maximum in my C8. The XW 5 is fine in both the Meade SN6 6" F/5 and the APM 80 mm F/6 triplet. If you have any slower scopes, the 6.7 would certainly come in handy.

Difficult to say. That image has been processed quite heavily, I would guess from the appearance of the stars that some star size reduction filter has been applied. I do seem to see a residual elongation that almost suggests field rotation, like my shot, which is more-or-less a stretched stack without any noise reduction or filtering

I have reverted back to my 0.8x reducer, which gives better results, both on ASI183MC and on the EOS 550D Clear skies are so rare at the moment I don't want to waste time experimenting with spacing. If the weather turns for the better I might experiment a bit. I might put the ASI183MC on the Meade 6" F/5, and once that is clicking away, set up the little APM 80mm with the 0.6x reducer and a bunch of spacing rings with the EOS 550D.

55 mm is the starting point. I will have to get spacers to see what improvements I can make. It would be nice if I could work at 288 mm F/3.6, on the ASI183MC at least.

Pure reflectors are completely free of CA, not almost. They may still suffer from monochromatic aberrations such as spherical aberration, coma and astigmatism. Catadioptric scopes like my Meade 6" F/5 Schmidt-Newton are practically free of CA, their corrector plates or meniscus lenses will correct for spherical aberration perfectly only at one wavelength, so a residual "sphero-chromaticity" may occur.

That is the one I have, and gave this result on the ASI183MC. There are some gradients due to problems with the flats, but the eggy stars ar clear to see in the corners. Spacing might be an issue, of course, but I had the sensor at the rated distance of 55 mm. Note that there was no issue with field rotation as polar alignment was pretty good

The ASI183MC has a considerably smaller sensor than the 1600 or 294, so I cannot guarantee anything

Reducers can be fine, I get good results on an APS-C sensor with my APM 80 mm F/6 triplet (FPL-53), with a Tele-Vue TRF2008 0.8x reducer, yielding a very useful 384 mm focal length at F/4.8. I have tried a 0.6x reducer, which seems OK on the smaller ASI183MC's sensor, but even there seems to give slightly eggy stars at the corners, so I haven't dared use it on an APS-C sensor

Regarding the MaxVision 24 mm 68 degree EPs, they work well down to F/5, but I tried one in an F/4.2 scope and that showed a lot of astigmatism. At F/4.7 this might also be an issue.

The really small galaxies require more than 1 m focal length, and even an EQ6 will start to struggle, I would guess. On my GP-DX I use a 762 mm focal length scope (Meade SN6), but with a smaller sensor and pixel size which gives reasonable results on the likes of M51 and M81. I sometimes struggle to get longer subs working reliably, I should add.

What I mean is I have at times stacked hundreds of 30s exposures (not so much on M42), and got good results. This is 3 hours worth (360 30s subs) of data, still a bit noisy, but I will return later to gather more. For the blown out core of M42, I have combined different subs in Astro Pixel Processor, combined with some unsharp masking to reduce the dynamic range, and that worked pretty well.

Very nice! Lovely detail

Very good first shot, especially from a Bortle 8 location, and certainly for such a relatively short exposure. What camera and scope did you use? Blowing out the core of M42 is a common problem, and combining the result with short exposures helps. I tend to combine loads of relatively short exposures anyway, and get decent results. The "correct" ISO value to use depends heavily on the camera. On my EOS 80D I think 200 is fine, but my EOS 550D works better around 800-1600, I find.

I have Helios LightQuest 16x80s which work well enough on a monopod with ball head and trigger grip, but 25x100 bins are considerably beefier, so I am not sure that they will hold that weight. My Falcon-Eyes pistol grip is listed as suitable for 4 kg load, whereas 25x100 bins can weight in at 4.7 kg.

I image from a suburban garden, which has quite some LP, but I still manage to image galaxies, with a CLS clip filter in my (modded) EOS 550D. Got some quite decent results on M31 and M33 with my 80mm F/6 triplet and 0.8x reducer This is a crop, and only represents about one hour of data. I also use a Meade SN6 6" F/5 Schmidt Newton, with ASI183MC and simple UV-IR block filter and get good results with many galaxies, especially by imaging near zenith whenever possible. The image below is 5h of data on the Leo Triplet

Welcome from the north of the Netherlands, Peter. I still have my good old C8, great scopes. Clear skies!