Category Archives: Computing

Replaced observatory computer

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

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

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.


Dark Frame Acquisition script for TheSkyX v2.2

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.)

Pier Top Panorama

I have the new pier-top adaptor fixed up and ready to mount, so today I remounted the top plate.

Since the new mount hasn’t arrived yet, I thought I would take this opportunity to carefully take a panoramic photo from the telescope’s perspective, with the goal of installing a custom panorama into TheSkyX, to help plan and preview observing against a realistic simulation of what my very cluttered horizon looks like.

_DSD8221So, I temporarily mounted a tripod column on the pier top plate, with a ball head on top of that.  This places a camera at the same height where the telescope would normally sit, and the “pan-rotation” direction of the ball-head allowed me to take a bunch of carefully-aimed pictures.

I took a series of pictures (trying different focal lengths with a wide-angle zoom lens), being careful that they overlapped by about 30%. Here’s a sample (but many more were needed to get 360-degree coverage):

Then I used Lightroom and Photoshop to merge them into 360-degree panoramas. Since I took several different sets of input photos with different focal lengths, and with some with the camera oriented horizontally and others with the camera oriented vertically, I ended up with several panoramas of different quality (different kinds of distortion etc).

Taking the least-distorted, I adjusted it to be exactly 360-degrees, trimmed it to the size required by TheSkyX (which requires that both dimensions be multiples of 512), and set the sky area to transparent. The result looks like this:

EWHO-Pan-Port-24-05-transparencyI was able to load this panorama into TheSkyX so it shows up as the horizon on the star chart. This is a great feature of TheSkyX – I get the calculated sky chart overlaid on my actual horizon, so I can accurately see what is visible above the hedge, between the trees, etc.



PC Cabinet Interior Heater Installed

As mentioned in a previous blog entry, I’ve been trying to arrange that the observatory PC can remain outdoors in our frigid winter temperatures and still start reliably when I need it. The problem has been the hard drive – at sub-zero temperatures it won’t start, and the PC fails to boot. I tried replacing the mechnical hard drive with a solid-state unit and, while this solved the temperature problem, it created other problems, and I returned to a mechanical drive.

Before-Heater-ChartHeating just the interior of the observatory with a heater designed to keep things just above freezing wasn’t a solution. When the ambient temperature dropped below about -15°, the heater couldn’t keep up and the pocket of air in the bay where the computer sits was still about -5°, too cold for the computer.

The deep dip on this graph was an observing run with the interior heater switched off (once the PC is running, its internal heat keeps it healthy). But you can see that the temperature was sitting at -5 to -8, even with a “no freeze” space heater running in the observatory. (Outdoor temperature was about -20 at the time.)

So, I decided to try installing a small, low-power heater inside the cabinet of the PC, with a thermostat to keep the cabinet interior just above freezing. Continue reading

Sunday, March 7, 2010

Journal page, March 7

Clear all day and clear evening, and a wonderful warm spell has been going on about a week. Temp 8 degrees today. Did some pre-setup in the dome during the day, reloading drivers etc after having to re-image the observatory PC.

Out for imaging about 7:00 PM. Strange pointing problems continued with the mount, but I found a problem that I think might be the problem: the mount and software didn’t agree on epoch; software using J2000 and mount using JNow. I reset everything to J2000. That improved things a bit, but didn’t solve everything – right-clicking on plate-solved images is still not driving correct goto operations; must check the calibration of plate solving, image scale, etc.

Re-did autofocus calibration, about 5 V-curve runs. Did a test image on M45, trying to catch the reflection nebulosity. About 1 hour of images, LRGB. Guiding worked very well, +/1 1 pixel error. Rough guiding earlier in the year may have been related to cold temperatures making things run less smoothly? I gathered data until it sank below the hedge.

Quick look at the data indoors at end of session – seems to be some kind of smearing in the Green, resulting in a green gradient. I wonder if it was filter wheel problems registering wrong colours, will check that. In fact, I wonder if I have the Green and Blue filters swapped in the wheel. Once I get around to doing some G2V calibration I can firm this up; but will check the right filters are in place just to satisfy myself.

Saturday, February 13, 2010

Journal Page: February 13

I reinstalled the CCD camera and filter wheel today, after having cleaned the camera’s CCD window.

Installed a permanent observatory PC. Specs on this machine:

  • an older Dell computer running XP, so all the drivers should work well;
  • main C: drive replaced with a solid-state drive, so there are no moving parts except the fan. I’m hoping this will mean it can run in cold temperatures with no problems.
  • Wireless link back to the house for access to network-based storage

It took a while to get all the drivers configured, serial ports properly lined up, etc., but everything seems to be working. Now it’s forecast to be cloudy for at least a week, so it will be a while before testing this new setup.

Initial Design for Outdoor PC

My first thoughts on a PC that can work outdoors:

  • I’m hoping the mere fact that it gets cold and then later warms up is not a problem.  Laptops get cold in aircraft holds and survive. Starting while cold will be a challenge.
  • I think moving parts may be a problem when cold.
  • I’m especially concerned about the rotating hard drive.
    • First, a cold component will have tighter fit and may bind, drag, or burn out.
    • Second, I am especially concerned about condensation or frost forming inside the drive mechanism, which I think would almost certainly destroy the drive.

Continue reading