michael.h.f.wilkinson

It is quite sunny here at the moment, so I had a short morning tea break (never drink coffee), and got the Coronado SolarMax-II 60 mm out for a quick look. Off band nothing could be seen in terms of sunspots, but on-band a large prom could be seen easily at the 2 o'clock position (roughly north-east, given I use a BF-15 diagonal). A smaller prom could be seen at the 4 o'clock position. The disc did not show a huge amount of activity, but south and just east of centre, a filament could be spotted, and the area between it and the limb seemed alive with smaller filaments and curling patches of plage. The south-eastern quadrant of the sun seems restless, as if a sunspot could appear there any minute. I am also curious to see whether any ARs emerge around the limb where the two proms are visible. The forecast is for sunny weather, so I should be able to follow this up.

The key trick is to stack many images, not to extend the single exposure time beyond what light pollution allows. From my Bortle 4-5 back yard, I typically go for 60s subs at ISO1600 on my modded Canon EOS 550D, and on the Horse Head nebula, using an 80mm F/6 triplet and 0.8x reducer (so 384mm focal length at F/4.8) I get this: After calibration with darks and flats, stacking, gradient removal, and some tweaks in Gimp, stacking some 45 minutes worth of data looks a lot better: Adding data gathered over several sessions, for a total of 7 hours 37 minutes of data is better still: Of course, moving to a darker site works wonders, but results like these can be obtained with camera lenses. Using my 200 mm F/2.8 I got this:

Even if the camera orientation is not the same, things will work, I find. Even from my own back garden, camera orientation can vary quite a bit, but that doesn't hurt the end result. There may of course be large differences in gradients caused by light pollution, so I generally stack each session in Astro Pixel Processor (APP), and let it compute a weight map as well. I then remove light pollution in APP as well, and later combine the different results, by importing the images with pollution correction and the weight maps in APP, and stacking those (generally very quick because you are combining just a few "subs".

2020 has been the year my DSO imaging took a very different turn with the arrival of a second-hand Meade SN-6 6" F/5 Schmidt-Newton (with upgraded focuser for just EUR 165). It has opened up a whole new range of targets. I used it exclusively with the (uncooled) ASI183MC I normally use for planetary imaging, and it got me way better images than before. 5 hours of data (not enough) on the Leo Triplet 13 hours on M27 (getting there), using an Optolong L-eNhance filter 8 hours and more on M106 (needs a lot more) 4 hours of M101 and of course my first supernova image (SN2020fqv)

Last night the skies cleared sufficiently for me to set up the APM 80 mm F/6 with Tele-Vue TRF-2008 0.8x reducer, and my modded Canon EOS 550D on my EQ3-2 mount. There was some haze in the sky reflecting city lights, so I included my Optolong L-eXtreme filter in the optical path. I managed to get 81 60s subs, before clouds cut the proceedings short. A quick stack in APP, using its gradient removal (hardly needed) and automatic stretch yielded this: Combining this with 60 minutes worth of data from January 30 and some subtle tweaks in Gimp yields this: Some of the fainter outlying bits are starting to come through. Hopefully I can add some more later this week

Got the little APM 80 mm F/6 triplet out, grabbing data on the Rosette Nebula once more

Brilliant image, especially from Bortle 7 skies. Great catching such a distant object.

Focus does look a bit off. I use a Bahtinov mask to achieve exact focus

Very nice images indeed

I don't use PIPP except for doing a pre-selection of lights. I do everything in AS!3. If I have dark/bias frames, I first load the appropriate SER or AVI, and stack that as a dark (using the image calibration pull down menu), then do the dark-flats, then load that as a dark reference in AS!3, then select the flats and create a flat reference with that (which will be corrected for dark current because the dark-flat reference has been loaded). I then unload the dark-flat reference, load the dark/bias reference (if I have one), and load the flat reference I have just created. Then I stack the lights. This is roughly my work flow for lunar and solar. Again, for planetary work, even flats are not always needed (as log as there are no dust bunnies over the planet), and the following images were obtained with an ASI224MC without calibration For DSOs I would not use PIPP or AS!3, but Astro Pixel Processor. Which got some nice results with the ASI178MM I have used, in combination with a filter wheel and just a monochrome M51

In my experience, flats are far more important than darks in planetary imaging, except in one or two older image sensors which showed clear pattern noise (ASI130MM, I am looking at you). Bias frames tend to be enough in most cases, and even those add relatively little. If the flats need longer exposures (as they do when I use a flat panel), then it makes sense to take dark flats at the same exposure time as the flats. I always use AS!3 to create both flats and dark flats for planetary imaging. The trick is to make the dark flats first, then load the resulting dark flat, to make dark-current-corrected flats. I then unload the dark flat, load the flat, load either the regular dark or bias frame as needed, and process the lights.

Very sorry to hear this.

Very nice result

Very nice result

I also have an L-eNhance (1.25" rather than 2") which clearly creates a brighter background and brighter stars. Note that the California Nebula was imaged with a 85% moon quite close by.

For that kind of money the EQM-35 Pro Go-To is probably the best option. It has a slightly higher rated payload than the EQ5, oddly, and is the newer mount.

I have taken images with my modded 550D and L-eXtreme filter. it is hard to spot the stars, but then with Alnitak in the FOV that is not a great problem. The background becomes so dark that you have to be more careful about walking noise. A slight noise pattern can be seen in the HH image. In the image of the California Nebula, it is less prevalent, despite being only half an hour of data from a Bortle 4-5 site. In the latter case I did more (manual) dithering I also did just 3 minutes on M42, but didn't like how the Running Man and other reflection components were all but completely removed.

With the short exposures, and Bortle 4-5 skies, amp glow is manageable, as long as you take darks at (approximately) the same temperature as the lights.

Very nice and crisp results

Interesting thread. I am looking for my first cooled astro camera, and the ASI294MM Pro is the main contender (although I did consider the ASI183MM Pro earlier on). I already have a ZWO filter wheel (7 position), so should be ready to go. I must say, the uncooled ASI183MC I have (originally bought for planetary and lunar) has been surprisingly good at DSO imaging, clearly more sensitive than the old EOS 550D (modded).

Very nice, especially for such a short exposure time

I have a mini-giro mount which is a handy little alt-az mount. I use it mainly for solar observing, however. For some reason I find star-hopping in RA and DEC easier, so at night I really always hook out one of my EQ mounts. Whatever floats your boat.

Did a slight tweak with curves to brighten the image.

The promised clear skies didn't fully materialise, but as I had set up the APM 80 mm F/6 with TRF-2008 0.8x reducer, Optolong L-eXtreme filter and Canon EOS 550D (modded), I might as well give it a go. Only manage 1 h of data between scudding starnds of hazy clouds, but I am not unhappy with the result. Noisy, but not too bad for just 1 h of data under a full moon and skies that could have been a lot more transparent

That is of course an issue. I store my C8 OTA in an unheated garage, and that ensures cooling time is relatively short. Not always possible, of course