michael.h.f.wilkinson

Nice captures

Clear skies this morning, picked up the sunspot in Lunt SUNoculars, so set up the scope. Had a brief look with Lunt Herschel Wedge and Baader Solar Continuum filter, and attached the camera. Enter clouds. I managed to pull some WL data out, but gave up on Ca-K as more clouds were forming as I watched. Still, one more sunspot spotted: I think there might be a few pores in the region of faculae trailing the main spot

Don't have photoshop, and am no fan of software rental model, so it isn't likely this will change.

Managed to reduce the colour band in one of the stacks I made from last night's data (still there, might give it another shot later), and am reasonably pleased with what might be the last shot I have at NEOWISE The stars are a bit red, might want to look at that later. I also did a series (cut short by clouds) at a focal length of 50 mm, and found the culprit of the colour bands in the 100 mm stacks as well (someone with a fixation for shining light beams at the night sky). Not sure I can process that out. It does show the HUGE extent of the ion tail, however.

Very quick process, picked a series of 20 subs, 30 s each, and stacked them in APP The data looks promising, but the background noise needs to be tamed

I use 30 s subs at F/1.8, ISO 200. These are stacks if 9, 20, and 20 subs respectively, with darks, bias, dark flats and flats. A single, calibrated sub with gradients removed looks like this although not all had a meteor, or as much in the way of clouds

Couldn't resist putting together the three shots taken with the Sigma 50-100 mm F/1.8 zoom, at 100 mm F/1.8, ISO 200 in the last couple of days, showing the evolution of the comet. I tried to process all three identically, as near as possible. Quite pleased with the outcome.

The straight, blueish streak is the gas or ion tail, the more yellow-white tail is the dust tail. The heavier dust grains aren't blown away as fast as the light ions, so the dust tail lags along the orbit of the comet

Stacked 20 subs of 30s, taken with the Canon EOS 80D and Sigma 50-100 mm F/1.8 lens at 100 mm and F/1.8, ISO 200. Stacking, LP and gradient removal, and star colour calibration in APP, colour noise reduction in FITSwork, and final tweaks with curves in Gimp. Tried stacking all 50 subs in DSS in comet + stars mode, but the result was dismal. Will have to work on my own code later

I could see it with the naked eye, but the tail was only seen well in averted vision

At a length of about 12 degrees in the sky, and a distance of roughly 0.7 AU, the ion tail is about 22,000,000 km long, or 13,700,000 miles. The nucleus itself is probably just a few miles across. I would have to measure the coma to work that one out

Planetary and DSO imaging have almost diametrically opposed requirements, as for the former aperture is king, and slow scopes to match the pixel size of the camera to the Nyquist sampling frequency of the scope, whereas for the latter short, fast scope is the much preferred tool. The Stellarvue 4" F/7 would probably already require a focal reducer for best results on many targets. Likewise, the requirements for the mount are very different: planetary imaging requires far less in the way of accuracy in polar alignment and tracking or guiding than DSO imaging. Of course, a mount solid enough for DSO work is certainly going to be great for planetary stuff. For that reason, a minimum of two scopes, taking turns on a solid EQ mount would be best. I have a Celestron C8 on a Vixen Great Polaris mount, which is my main observing and planetary tool. With a 0.63x reducer it might be usable for smaller DSOs but getting that to track or guide with enough precision would be hard. For planets and the moon it is a killer: For DSO imaging and wide-field observing, I have an APM 80 mm F/6, which gets results like these: I have recently got a third scope, a Meade SN-6 6" F/5 Schmidt-Newtonian. This is great for smaller DSOs and should be a good planetary imaging and observing scope as well, as it has considerably more aperture than the little 80mm refractor. Here are some results on galaxies I haven't tried it on planets, but it works very nicely on the moon. The Schmidt-Newtonian and Maksutov-Newtonian designs are perhaps the closest thing to an alround performing scope. Meade Schmidt-Newtonians can sometimes be had for a song (mine cost just EUR 165 for the OTA). Mak-Newts are still made, but they are considerably more expensive. Both designs have better field correction than regular Newtonians, and lack the diffraction spikes cause by the support of the secondary. Both are also heavier and prone to dewing up of the corrector plate, so a dew shield and dew band are required.

Quick stack made last night. Canon EOS 80D with Sigma 50-100 mm F/1.8 zoom at 100 mm and full aperture. Stack of 10 30s subs, ISO 200, stacked in APP, post-processing in Gimp

I had to go to a slightly more light-polluted location, and what with NEOWISE getting fainter. Just got home, and couldn't resist having a quick bash at processing the data, just to see what's in there. I am not too disappointed Rather noisy, but stacking more might bring out more detail. I have something like 50 subs, so should be able to get out more than this quick and dirty result

I was part of the 1/5th. My parents allowed me to stay up WAY past my normal bedtime to watch it on our black-and-white TV

I just thought it would be interesting to post a comparison of the different shots of NEOWISE I have made, from the very earliest attempt, to the most recent, using different approaches, almost all images shot with my Canon EOS 80D, with a variety of lenses, and mounts. Here is my very first shot, on July 7, using the Canon 200mm F/2.8 on tripod, ISO 800 0.3 s F/2.8 exposure. I was quite chuffed at this result I took a series of these shots, and cropped and stacked 30 to achieve this: A few days later, on July 10, I went out once more, and also shot one wide field with the Canon 17-55 F/2.8, ISO 1600, 5 s at F/2.8, 20mm focal length Perhaps not brilliant, but it compares favourably with a smartphone image I took a few days later I also created a stack of 30 images taken with the 200mm F/2.8 at ISO 1600, F/2.8 and 1.3s exposure. This is just about the best I could do from a regular tripod. The next night I switched to the EQ3-2, and too far longer subs, at lower ISO. Below is a single sub, ISO 200, 30s, and ISO F/2.8 Stacking 10 of these produced a rather better result than anything I could achieve on a tripod, as can be seen below I did the same with the Sigma 50-100 mm F/1.8, stacking 9 exposures at ISO 200, 30s @F/1.8, and got a wider perspective Having more-or-less settled on my technique, I only used the Sigma zoom in the last attempt on July 15, but maybe I should set it wider. This last image is a stack of 20 30s exposures

Very nice collection

A telescope might be a bit much, I got data two nights ago, and at 100 mm on my Canon EOS 80D the tails didn't fit entirely in the FOV. On a crop-sensor camera, a 50 mm has a good chance of picking up the entire comet

Welcome back to SGL

The various 75-300 mm zooms Canon makes are not that good. They do not get very good reviews. I would much rather have a second-hand Canon 70-300mm zoom, than the 75-300. Yes the 70-300 is more expensive, but it is a lot better.

This was taken yesterday when clouds had swallowed up the comet. I used the non-modded Canon EOS 80D, rather than the modded Canon EOS 550D I have, just to see what a stack of 4 30 s exposures at ISO 200 with the lens wide open would do. Not displeased with the result. I wonder how the lens performs at F/2.0 or F/2.4. I would not be surprised the stars in the corners would improve a lot (they aren't too shabby as it is, unless you go pixel peeping. It might also do very well with the smaller field of t he ASI183MC. Must try this under darker skies with the other cameras.

Very nice collection

Slightly better process of the image, with darks and flats applied

I really love APP, it was a breath of fresh air after struggling with DSS. Really intuitive to use. All it misses is a comet stacking mode.

The skies are not that dark, as the sun doesn't go far enough below the northern horizon, but there isn't much in the way of artificial light around where I took these images. I don't use an LP filter but do use darks, flats, dark flats, and bias frames. I stacked in Astro Pixel Processor, removed much of the sky background with its light pollution reduction tool, and then tweak the image in GIMP (curves, and a slight saturation boost).