Darkness Testing 20th June 2020 – IMT3

20:00 – 23:48

Tonight GingerGeek came over for a bit of social distancing friendly astronomy along with a bottle of Malbec wine. The idea was to calibrate the AAG, specifically when it goes from Very Bright to Light to Dark and at those points what the SQM value is along with the Sun’s position below the horizon. The AAG needs to get to 2100 which is dark, light is 5 and very light is 0.

The first time we noticed the values starting to change on the AAG brightness when it moved from its continuous reading throughout the day was at 21:47 when the Sun was -3.45 degrees below the horizon and the SQM was 10.15.

Within seconds the AAG read 9 and was already on Light vs Very Light and the Sun was now -3.54 degrees below the horizon and the SQM read 10.28.

It took almost half an hour for the AAG to get to dark. At 22:16 the AAG finally reached 2100, the SQM was at 13.97 and Sun was at -6.52 degrees below the horizon.

GingerGeek had also developed a new server for IMT3 to visualise some of the data from the observatory. The Grafana dashboard charts below show the data along with the Sun altitude.

New IMT3 Grafana dashboard

Looking at the last 24 hours shows the effect of the light nights on the SQM. The raised values after 4am went the value should be reducing or zero is the effect of a cat or bird covering the sensor. Also worthy of note is the sky temperature which shows the effect of cloud as the SkyTemperature increases. A truly clear sky would yield a value of -18℃ or better.

Shows the entire night

We also took darks on the ASC and applied them since we had never bothered to do it before. The shot below shows the before and after effect of applying the dark/bad pixel map. The whole image looks a lot cleaner and darker, although there seems to be some negative representation going on with dark pixels.

Before and after applying darks

The setting that needed to be changed in the ASC software took GingerGeek a while to find.

ASC Setting to apply darks

During the daytime the ASC looked awful but remote the darkframe reference file and just applying the badpixel map seem to be better. Tonight’s set of images will show if this is better or not.

The only other odd thing that happened tonight was the dome closed without the safety setting it off. Not sure why yet ……