- Continue my attempts to see an eclipse for two binary stars that I'm observing with a student. We started in October with 4 binary stars with completely unknown orbital periods. For two of the stars we've seen multiple eclipses and have been able to calculate orbital periods. But for the other two we've only seen one eclipse each, which isn't enough to determine orbit time. So tonight I'll grab one brightness measurement per hour over the whole night on each of the other two stars and see if an eclipse occurs.
- Test a new piece of software that does dynamic subexposure planning. It uses each image that I take to build a better and better understanding of the sources of image noise that night: light pollution, read noise in the camera, shot noise from the target, and pixel-level dark noise. It also measures atmospheric transparency and overall telescope/camera performance. It then predicts performance, and uses that to pick good image exposure plans.
- Get as many "normal" variable star measurements as I can while doing the first two.
Nothing. Nada: (But even non-eclipse data can be useful, since it might help resolve ambiguous orbital period calculations later on.)
Dynamic Exposure Planning Software
This actually worked fairly well. Ran into one software coding bug that ended the observing session a few minutes early. But it was easily fixed and would have been really disruptive if I hadn't stumbled across it.
Performance was pretty good. This thing estimates the brightnesses of all the stars I care about in any given image (at each wavelength I care about), then uses what it's learned earlier in the evening about sky brightness, image noise, and transparency to calculate a set of exposure options. For example, here's some extracts from what it came up with for imaging the variable star X Draco:
This was the first night I've allowed the new exposure planner to actually control the exposure times, and it did a good job. My motivation for writing this software is somewhat convoluted, but is fallout from my camera upgrade planning, where I realized that I can pick up a good additional 4-5 hours/night of imaging time if I can make my exposure planning more precise than what I was doing previously. (But that's a whole other story.)12/3/2020 5:40:48 Extracted V mag for X-Dra is 14.0
12/3/2020 5:40:48 Predicted mag for V(green) is 14.0
12/3/2020 5:40:48 Predicted mag for R(red) is 11.9
12/3/2020 5:40:48 Predicted mag for B(blue) is 15.5
12/3/2020 5:40:48 Predicted mag for I(infrared) is 9.4
At subexposure time of 30 seconds with Red filter:
readnoise = 107.411
darknoise = 30.5615
skyglownoise = 132.583
target_shotnoise = 201.876
total flux = 40754
Subexposure choices for Red:
120 secs: 1 exposures.
60 secs: 1 exposures.
30 secs: 1 exposures.
10 secs: 2 exposures.
6 secs: 4 exposures.
I was able to make 71 observations on a total of 19 different stars, all sent in to the AAVSO. Didn't have to throw anything away due to satellite trails (unusual good luck). Seeing was generally poor and the moon very bright, and both combined to affect my limiting faintest magnitude (faintest report was mag 16.660 (green) for the star U Cnc; was unreportable in blue: too faint to see. This star is just beginning to brighten up after its minimum last month. It will rise in brightness by 7+ magnitudes over the next 4 months -- an increase of 1,000x). Brightest measurement was mag 6.471 in infrared (the star S Lyn, which is approaching max brightness during the next few weeks).
All in all, a good observing session.
- Mark M