I’m setting up my imaging system for capturing flats. I am using my TEC 140 with TEC field flattener and my QSI 683. Eventually I will also use an Astro-Physics Quad Telecompressor Corrector taking the focal length to 700mm, and even later my Celestron C8 SCT at f/10.
In the past I used an ELP for a flat light source with my DSLR. With a monochrome camera and filters the fixed brightness and the need to use Neutral density filters for LRG filters and extremely long integration times for narrow band filters with the ELP led me to purchase a Spike-A Flat USB flat panel. With the help of Andy Galasso (Andy, thanks again for the software and the personal help) and a friend who is an IT professional I have installed Andy’s Alnitak Emulator, gotten it configured, and have SGP controlling it.
I’m sure that the panel is connected to SGP and is functional as I have SGP up and running with a profile created for flats capture I can open the Flat Box tool and adjust the dimmer and see the brightness of the panel changing.
Now I’m at the point that I’m trying to develop a combination of panel brightness and exposure time to give me as near as possible to 33,000 ADU with as near as possible to 1 second exposure. I started with the panel at brightness 255 with a 1 second exposure just to verify that the panel was working. That worked fine, Image statistics showed that I was at 64,000 ADU as I hoped. Next I dropped the brightness to something like 100. I took another 1 second exposure and got an ADU of something along the lines of 256. I was surprised that the result was so low, but split the difference at around 190 and tried again. The result was again around 256 ADU. After a few more incremental changes with the same result I took the level back up to 255. The 256 ish ADU persisted.
At this point I removed the flat panel from the OTA and put on the dust cap, then set the flat panel on a shelf where I could see it and went on with testing.
I opened the Flat Box control and set the brightness to 250. I could see that the panel was lit brightly.
Then I opened the Equipment Profile Manager and selected correct sequence (140 980 683 flats). I opened the “Other” tab and, under Flat Box, selected “Adjust flat box settings per filter”. Under the Filter Name, Flats column on Lum row I clicked “Flats”. I set Flat Box Brightness to 5.00 and clicked Ok in Flats dialog box, then the Flats dialog box closed. I clicked OK in Filter Setup dialog box, then that dialog closed. Then I clicked “Save” in Equipment Profile Manager box, then Ok.
In the open sequence I clicked resume sequence with a single 1 second Lum flat frame set as event. The panel did not dim. As I was testing in daylight the panel light should not be visible at setting of 5.0 and it certainly was. The Flat Box control was open and showed brightness at 250 and Closed. The Command Prompt box showed panel light on, brightness 250.
I set the dimmer in The Flat Box control to 109. Repeated test without changing any other settings. Flat Box settings control returned to 250 and showed closed.
At that point I gave up. Clearly I’m doing something wrong and I don’t know what. So here I am posting this. What other steps do I need to take to get SGP to control the panel brightness per filter correctly?
I apologize for the length of this post, but I find that when asking advice it saves time for those advising if they know as many of the conditions involved as possible.
Thanks in advance for the help!