M13 – Hercules Cluster

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I have a guilty pleasure: I like globular clusters. I should put more effort into more challenging classes of objects – diffuse nebulae and galaxies, but I’ve always loved GCs, even though they are easy to see. M13 is my favourite.

This was a test image last night, after a couple of days of maintenance, collimating the scope and then re-doing the mount polar alignment and pointing model.

Exposure Luminance: 60 minutes (20 x 3 minutes)
Colour: 15 minutes (5 x 1) of each of Red, Green, Blue
Camera QSI583wsg, with Astrodon LRGB filters, running at -15°C
Image scale 0.69 arceconds/pixel (luminance), 1.38 (colour)
Telescope AT8RC
Mount Paramount MX+
Guiding Autoguided with Starlight XPress Lodestar
Processing 32 dark frames per sequence
32 flat frames per filter
Sigma-clip mean combination on the darks and flats
Sum-combination on the light frames
Aligned, combined, and deconvolved with CCDStack2

Added Colour to NGC 4565

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Here is the first round of adding colour data to the previous NGC 4565 image. Colour doesn’t come through my light-polluted sky very well – I could use a lot more time on the colour channels, but will have to wait until next year because there isn’t much time now between darkness and the target setting.

Details:

Exposure Luminance: 90 minutes (18 x 5 minutes)
Colour: 20 minutes (10 x 2) of each of Red, Green, Blue
Camera QSI583wsg, with Astrodon LRGB filters, running at -15°C
Image scale 0.69 arceconds/pixel (luminance), 1.38 (colour)
Telescope AT8RC
Mount Paramount MX+
Guiding Autoguided with Starlight XPress Lodestar
Processing 32 dark frames per sequence
32 flat frames per filter
Sigma-clip mean combination on the darks and flats
Sum-combination on the light frames

 

NGC 4565

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Finally a couple of beautifully clear nights, not cold, and not busy with other things.  I started data gathering for NGC 4565.  This is 90 minutes of Luminance only (18 5-minute frames).  It’s still a bit noisy in my poor quality skies, so I plan to do another hour or so next clear night.  Haven’t gathered any colour yet.

NGC 4565

Replaced observatory computer

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My old observatory PC has started becoming unstable, with sudden unexplained restarts and failures.  Not bad – it’s had a good 5-year run, living permanently outdoors in the cold.  It was also time to do something about the demise of Windows 7, and I found I couldn’t upgrade it to Windows 10 easily (nor was I sure that would fix the failures problem).

So, I’ve replaced it with a new machine.  As before, I configured the machine for no moving parts – especially no rotating hard drives – to reduce the effect of cold weather. I found, a couple of PCs ago, that hard drives seize up in the cold. (In fact the new machine has one moving part – a fan – but, being thermostatically controlled, a computer fan is rarely a problem in the cold since it doesn’t try to come on anyway.) The new one is installed in the observatory now and seems to be fine, and stable.

I forgot a number of configuration things though.  It took a couple of weeks to get all the necessary software and drivers installed and working.  Then, last night, I tried a “real” observing run and instead generated a big to-do list of things I forgot to set up.  Things such as transferring the PEC and TPoint models for the mount.

I think I’ve done all the necessary things now, but we’re back in cloudy weather for several days, so next test is some time away.

Flat Frame Acquisition App

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A sibling to the Dark Frame app announced below, this application orchestrates the collection of Flat Frames. It is simpler, designed to be used at the end of an imaging session when the scope and camera are already running – so it does not contain delayed start and finish logic.

It’s available for download, in both Mac and PC binaries, here.  Use at your own risk and don’t build commercial dependencies on these tools – I’ll continue to work on them best-effort.

The program is written in python (v3.8) and is open-source.  View or modify here.

Dark Frame Acquisition app

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Weeks and weeks of cloudy nights.  To stay involved, I’ve refined that dark frame acquisition script, mentioned below, into a full application.  It’s available for download, in both Mac and PC binaries, here.  Use at your own risk and don’t build commercial dependencies on these tools – I’ll continue to work on them best-effort.

The program is written in python (v3.8) and is open-source.  View or modify here.

This program has many dependencies.  Most important, it communicates with TheSkyX Professional Edition, which must be running on the same computer or another one in the same LAN, and listening with its built-in “TCP Server” option.

   

Start M1 with Luminance

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Last night was not only clear, it was excellent.  Clear, moderate seeing, no moon, and temperature only about -3°C.  It’s late enough in the year now that the Orion area is now above my high horizon.  With the AT8 scope presently mounted, I started on M1.  Mount was performing very well – tracking very well on its own, and autoguiding to around 1 arcsecond (which is less than seeing jitter, and so just a guess).

Here is the start of M1, the Crab Nebula.  This is 2 hours of luminance as 24 5-minute subframes.  It’s going to be clouds for many days now, so I’ll add colour later if and when the sky permits.

Dark Frame Acquisition script for TheSkyX v2.2

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Over the last few cloudy nights, I finished an automation assistant script, and am making it available here.

This is a JavaScript script to run within TheSkyX to acquire a large number of dark frames.  It automates the following sequence:

  1. Delay until a specified start time (so you can start the script before the desired acquisition time then go out for dinner).  (Since TheSky’s scripting environment doesn’t include a good “delay” feature, it takes and discards long camera exposures to achieve this delay);
  2. At specified start time, turn on camera cooling and wait until the specified target temperature is reached;
  3. If the target temperature can’t be reached (i.e. the ambient temperature is higher than the camera’s cooler can handle), turn off cooling, wait a while, and retry;
  4. Once target temperature has stabilized, take sets of dark frames – you can specify multiple sets, giving number of frames, exposure length, and binning for each;
  5. Stop dark frame acquisition at a given later time (for me, dawn the following morning);
  6. Also stop acquisition if the CCD temperature rises – indicating rising ambient has overwhelmed the cooler.

The idea is:

  • Enter into the script all the dark frames I want for a given temperature.
  • Then run it overnight – where there isn’t enough time to capture them all.
  • Next day, comment-out or delete the lines for the sets that were successfully captured, and modify the frame-count in the set that was interrupted in-progress.
  • Repeat the next night.

This script is highly dependent on TheSkyX, and would require extensive modification to work in any other system.  It works on both the Mac and PC versions of TheSkyX.  I have no way to test it on the Linux version but would expect it to work there.  It requires a connected CCD with cooling, but does not require or assume any other connected gear.

Run it from within TheSkyX using the “Run Javascript” command in the Tools menu.  First edit some of the parameters near the top of the script to specify your desired time window, target temperature, etc.

Copyright ©2019 Richard McDonald.

You are free to use and modify this script, and to redistribute it freely.  Modified versions should be marked as such so they are not confused with the original.

Download here.   Then change the file name suffix from “.txt” to “.js”.  (I’m not storing it and downloading it as “.js” because that presents security vulnerabilities.)

Start NGC 891

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I started a new imaging portrait, with about 90 minutes of data capture before the almost-full moon rose and lit up the sky.  This is 16 300-second subframes of NGC 891, calibrated with darks and flats, luminance only, stacked and processed in CCDStack.

On the next few clear nights I’ll add more luminance data and colour.  This image is cropped – about the inner 75% of the full frame – to eliminate distortion I’m getting around the edges.

This was my first “real” use of the mount, as opposed to testing and calibration, since all the refurb work.  It’s performing quite well.  Despite the testing suggesting unguided imaging at 300 seconds would be fine, I used guiding – why not, and for practice.  Seeing was poor – about 2 arcseconds of jitter, so I took longish guide exposures (5 seconds) to average out the seeing and avoid having the guider chase it around.Guiding corrections were within +/- 1 pixel, which is 1.05 arcseconds on the guide camera, and usually within +/- 0.5 pixels, or .5 arcseconds – consistent with seeing scintillation of 2-3 arcseconds.  The large spikes in guiding are artificial – that’s the software deliberately throwing the guide position off by 3 pixels after each subframe, then letting the guider drag it back in line, to create subframe dithering.