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On 25th March I tried some live stacking with Sharpcap and a 102mm f5 Startravel achromat & ASI120MC camera. Mount was Celestron SLT on custom tripod. Image size: 1280x960. With this setup it is possible to dial in an object to the GoTo and be confident that it will appear on the laptop screen. These images may not look too exciting but they do mimic the FOV and general appearance as seen in a 203mm SCT with 25mm EP. Check the image for M87. When I checked the field in Stellarium I found that two faint non-star smudges matched with NGC4478 and NGC4476, which are 11th and 12th mag galaxies. I am gob-smacked that I managed to image these with such modest equipment from an urban site. There is no way I would be able to see these visually even with a C8 from here.
Hi folks, thought I'd post here as more people here seem to be using the Live Stacking feature of SharpCap now. SharpCap - if you haven't encountered it before - is a free Astro-focused capture application for Windows. SharpCap includes support for a wide range of cameras - including QHY, ZWO, Basler, QHY, Webcams, Frame Grabbers, ASCOM and others. Any camera that SharpCap supports can be used in live stacking mode, although to get decent results you will need to be able to set exposure lengths of about 1s or more. Live Stacking includes an alignment option (on by default) that will correct for drift and field rotation in each new frame as it is stacked. Alignment depends on being able to detect at least 3 stars in each frame. Additionally you can filter incoming frames based on a FWHM measurement of the stars detected, allowing frames with better seeing conditions to be stacked and worse frames discarded. There are simple functions allowing the histogram of the stacked image to be stretched for display and the stack can be saved either 'as seen' with the stretch applied in PNG format or in FITS format with no stretch applied for later post-processing. SharpCap also has an embedded scripting language which allows simple programs to be written that will automate a capture session - some users over on Cloudy Nights have been using this facility to automatically stack a target for say 30 minutes then move the mount to point at a new target and start stacking that. SharpCap 2.9 is currently in beta and will contain improvements to the live stacking features including an easier-to-use histogram stretch function, more star detection options for alignment and automatically remembering most stack related options. However, if you prefer to avoid beta software, feel free to use SharpCap 2.8 instead. Just as a taster, here is an M81 I produced in 30 minutes of 4s exposures with the ASI1600MM-Cool. This was really just a test stack - taken on first-light with the camera, testing a new version of SharpCap and with a whole bunch of other things in my setup changed - I'm sure it's possible to do better when hurrying a little less! I'd love to hear any feedback people have on how to improve the live stacking feature - and see any images you capture with it! cheers, Robin PS. For about the first 10 minutes of stacking I had left the mount accidentally on Lunar tracking rate having used the moon earlier to sort out focus and align the finder scope. The alignment feature took care of this quite happily and I didn't even notice until I spotted a little line of hot pixels building up due to the drift.
SHK 10 is the second most galaxy-rich of the 377 Shakhbazian compact groups (*), packing an astonishing 32 galaxies into a space of little over 6 minutes of declination. On the other hand it is rather faint: its brightest member shines at mag 17.7 from a distance of around 1.7 billion light years. SHK 10 can be found centred at [14 10' 56.1" +46 15' 54.7"] a degree or so from mag 4.2 lambda Bootis heading towards the border with Canes Venatici (chart BOO/5769 in the Pretty Deep Maps collection). Here's a screenshot showing the locations of the galaxies, numbered using Shakhbazian's scheme. For me, the challenge of the Shakhbazian groups is seeing how many members can be pulled out using near live viewing techniques -- literally seeing more and more of them appear on the screen as live stacking does its magic. To give a flavour of the live experience, I've prepared a cropped animated gif showing the progress as more subs come in: 1, 2, 4, 8, 16, 32 and 64 in total. This was also a test of fast stacking so the subs themselves are short, at 10s. Note that this is all live stacked in LodestarLive v0.12 and not post-processed in any way apart from rotation to match the chart. I retained the same brightness and contrast settings throughout, and used the ^0.25 compression mode. The group is in the central third of the shot.[Edit: animation appears not to work yet … here's a temporary dropbox link (0.5M)]Noise is greatly reduced by stacking, revealing the galaxies.Here's the last frame (64x10s stack) in full. Note the super-thin galaxy at top-right. This is mag 16.3 UGC 9066 at a distance of nearly 400 million LYs. Here I've blown up the central portion and labelled the constituents. There are a few obvious stars amongst this group and also some interlopers -- things that look like galaxies but are not listed by Shakhbazian. Checking the SDSS image using Aladin these are definitely galaxies. Whether all belong to the same physical cluster is another question. As recently as 2012 there were only 13 spectroscopically-confirmed members.The ones I've failed to split are 19/20 and 8/24, though the latter actually appears to be a single edge-on galaxy in the SDSS image.Details: SQM 20.2, windless, no moon, around 50 degrees up. Skywatcher Quattro 8" f/4, Lodestar mono X2, LodestarLive v0.12, no filters, AZ-EQ6 mount in alt-az mode. CheersMartin(*) The title goes to SHK 40 in Pisces, a relatively-bright 60-member group also known as Abell 193.