michael.h.f.wilkinson

Absolutely lovely images of an object I had never heard of. Might well try that at some time

I find open clusters are best viewed in a really wide field. You then see them in context, whereas if they fill most of the FOV you just feel you are looking at a bright star field.

I had a couple of LV EPs (7 and 9 mm) and they were superb on planets. I then moved to Pentax XWs (5, 7, and 10 mm) and they have a definite edge, and far wider FOV, but the LVs are great. If you can pick them up for that kind of money, go for them! I now have some SLVs (5, 9 and 15 mm) in a lightweight travel setup, and can't fault them. The only noticeable difference with the XWs is field of view. Build quality is fine too

Brilliant image! The only thing I might change is making the background a shade darker, but that might depend a lot on the monitor I am using

For really extreme portability, there's this, of course: 😉 Works well on lunar imaging, hope to test it on white light solar soon. Downside: only 62.5 mm aperture, but a decent FOV to capture the corona, should I be lucky with the weather on April 8

The C9.25 is around 9.4 kg, the mount will need a counterweight, but it should still fall well within the limits of the HEM15. I have seen plenty of sparkle in star clusters (especially globulars) with my C8. They are sensitive to collimation, but tend to hold collimation well. The MN190 mentioned earlier is 12.5 kg, or thereabouts, which is probably too much, especially when cameras or EPs are added.

That is a lovely image! Great detail

Really lovely set of images. Great processing too: very sharp, but not overcooked in any way.

Lovely images. The first looks a bit more natural on my laptop. Both are great, however

First quick stack I would call that quite a success, for only 62.5 mm aperture.

In the DSLR category there is this one of the Heart and Soul (modded Canon EOS 550D, Samyang 135mm L-eNhance filter, 12h total exposure over three nights) Or Comet NEOWISE from a few years back (unmodded EOS 80D, Sigma 50-100mm F/1.8 zoom, full aperture f=100mm, stack of 30 images)

Large clear patches between scudding clouds, so I quickly set up the HEM15 mount with the Carl Zeiss Mirotar and ASI183MC. Grabbed some SER files, and am curious to see how they turn out. The Mirotar is a cute little scope, isn't it?

The second is a lot better. I find Registax needs very gentle enhancement on the moon, and often prefer to use ImPPG.

Some tweaks of curves in Gimp added

Here is a stack of some 25 images made in Affinity Photo, sharpened in Registax 6. Not brilliant, but there is some promise here. I don't think I nailed focus (had to use the focus aid of the EOS M6 Mk-II rather than use a Bahtinov mask on the stars to get perfect focus). I hope I can test the lens on the HEM15 mount with ASI183MC soon

Total integration time is the main issue. More, shorter subs would mean a (marginal) increase in noise due to more read-out noise, but on modern cameras that is hardly noticeable. Going to a darker site would help much more. Faster optics also help (for a given FOV). Here's an integration of 12 h at F/2 using a Samyang 135 mm F/2 lens, Canon 550D (modded), and Optolong L-eNhance filter. The L-eNhance filter helps reduce background noise due to my Bortle 4-5 skies. The high speed of the optics help grab loads of light.

Theoretically, to double the signal to noise ratio (S/N), you need to quadruple integration time, so doubling the integration time should give a modest increase in S/N, in the order of 40% improvement. This means you can sharpen a bit more, without noise exploding, but not much. Mathematically S/N scales with the square root of integration time. This is one reason people may go for extremely long integration. Also note that the sky background (mathematically also just signal) also adds to the noise in the same way, so picking out a faint signal against a bright background can be very hard indeed, as the noise from the object of interest may be swamped by the noise from the sky background.

Had a quick test of the Carl Zeiss Mirotar I got some time ago as a compact telephoto for imaging the sun in white light during the upcoming eclipse in Texas. As the moon and Jupiter were peeping through the clouds, I quickly set the little telephoto on a tripod with the Canon EOS M6 Mk-II attached. I managed a couple of exposures with manual focus, before the clouds interfered. I will stack them tomorrow, but here is a crop of an unprocessed single frame. I hope to do a better test with the ASI183MM attached on a tracking mount, but that will have to wait for better weather.

Very nice work!

The first shows the dust very nicely, the second has more bling 😉, which distracts a bit from the dust, but the dust is definitely shown very well too.

Quite some years ago, I added an APM 80 mm F/6 triplet APO as wide-field visual scope and imaging scope to complement my Celestron C8. At only 2.5 kg it is wonderfully light, and can be taken abroad in cabin luggage easily. The wide-field views with the Nagler 31T5 and Vixen LVW 42 mm are just awesome. My best view of M33 was definitely with the Nagler 22T4. It also serves as my main solar imaging scope, and travelled with me to the USA for the 2017 eclipse, and got me the most memorable astrophoto ever. A scope like this is also different from a pair of big binoculars. I did a comparison a few years back They can pry this scope out of my cold dead hands.

The Maksutov design works brilliantly on planets and the moon, and is fine visually for all DSOs that fit into its smaller field of view. Using a 30 mm EP in the Skymax will give the same magnification as using a 12 mm in the StarTravel 120, both yielding 50x magnification at roughly the same aperture. The vast majority of DSOs fit, only a few larger ones don't. Only when imaging DSOs does the slow speed of the Maksutov become a drawback. When imaging planets or the moon, the Skymax is great. The StarTravel 120 is definitely better on wide-field objects, but it is going to suffer on planets. Ideally, you want both, of course, but if I had to choose just one it would be the Skymax.

Apparently the C8edgeHD is also better corrected in the centre, and that could mean quite bit for planetary. I have been considering a C9.25 for better planetary views as well, but then the weight of that scope is not that much lower than a C11, so I am tempted to go for that one (I also have an AM5 which could handle that). I will have a go with my HEM15 to see how well it carries the C8, should the weather clear at some point.

I have recently had the opportunity to use my HEM15 and use the iPolar electronic polar scope for polar alignment. Levelling the mount was easy: I plonked the tripod with mount attached onto a tiled garden path and the spirit level said all was fine. I then hooked up the iPolar to my laptop and fired up the iPolar app. It connected to the camera, and then lost connection... and connected again, and lost connection... and so on. Suspecting a poor cable (it wasn't the original), I replaced the cable (the original). That showed similar behaviour, but ultimately I got a long enough duration of connection to (a) get a dark image, and (b) get a first fix on the position of the pole, after plate solving by the app. I then tried to use the hand controller, which apparently did not like the cold, because the display was near impossible to read. I connected it up to the laptop, and fired up the iOptron Commander app to control the mount, and could duly rotate the RA axis some 90 degrees, get another fix on the pole, and perform the actual alignment. Although this was quite tedious, partly due to my inexperience with electronic polar scopes, partly due to poor connectivity (maybe due to the cold?), the polar alignment I got was absolutely spot on. I could easily do 180s subs with the Samyang 135mm F/2 without any trailing. As I had lost so much time I decided to go for imaging without guiding using 120s subs. I would go out into the garden from time to time to check progress, and perform some manual dithering if needed (usually the slight drift I get over time works out well enough). To my surprise, the tracking was extremely accurate, so I had to give the mount the odd nudge in RA and Dec for dithering. Even the next day (after leaving the mount covered overnight) it was still tracking beautifully. The result can be seen here:

I use Baader film on my SCT for WL. I also have an old Thousand Oaks glass filter I bought in 1999 for the eclipse, as the Mylar films used in those days were not as durable as the modern Baader film. Note that there are two different densities: 5.0 and 3.8. The former is perfect for visual, the latter for photography (although it can be used for visual if you use additional filters on the EP side). Here are two examples taken with my C8.