I look at first light with the Stella Lyra GSO telescope. I investigate a gain issue which ALL cameras which use a 294C sensor have.
Apologies for the lip sync on some clips, I have built a new computer as my other machine was 12 years old and finally needed to be upgraded. I am still getting it fully setup. My previous M Audio PCI soundcard won't fit in my new machine as PCI is superseded with PCIe, and I had to go with a Focusrite USB external one and it appears to have a 7 frame delay either on playback or record, which I need to address.
Flats information
Taking Flat and Dark Flat calibration frames 294C Sensor Cameras
I have been working hard on getting a procedure with my 294C camera (SV405CC) following many issues I have had with the data not calibrating.
The results have been infuriating as I could not get the images to calibrate. I have finally reached a workflow which works. I am 100% sure that there will be other workflows, which may be different. I know many will know this information and more, I just wished to help anyone to get your data to work.
294C Gain - avoid the 120 - 180 range. Go above 180 or below 119. Otherwise the pixels will not perform consistently. Altair cameras (therefore touptek) use a brightness multiplier factor from the CMOS sensor ADC, not dB. 1x gain is no gain (zero gain), 2x is 2x brighter etc. Therefore check where the HCG setting is for your camera 294C to ensure you are not in the problem gain area.
All calibration frames must have the same Temperature, Off set and Gain - ALL OF THEM. I know there is documentation which says that temperature is critical for Lights and Darks, but possibly not critical for Dark Flats and Flats. I have found that for this particular camera sensor, all frames, Lights, Darks, Flats and Dark Flats must have the same Temperature, Off Set and Gain in order to stack the data - identical.
The Flat frames and the Dark Flat frames must be over 3 seconds. I have read that below 3 seconds the IMX294 sensor does not perform consistently, in fact, it's data erratic. This issue is spoken about a lot on astro forums about the IMX294 sensors. Therefore I think it is sensible to continue with this to get consistent flats and dark flats, the IMX294 sensor becomes more stable at exposures beyond 2-3seconds where its performance in more consistent.
Making long flats is sensible because it also compensates for any flicker from your light source - LED panels can flicker and therefore longer flats can avoid issues caused by this.
Check your Bayer Pattern My 405CC camera Bayer pattern is GRBG (unlike other IMX294 camera which are RGGB - ZWO and Altair for example). It is important this is set - don't let the software chose.
Calibration frames required - Lights, Darks, Flats and Dark Flats. Bias needs to be checked to see if your camera needs it, I used 60 Dark Flat frames - I put 30 in the dark flat category and 30 in the Bias. It seem to work well.
Data is cleanest with Dithering and 4-7hrs plus data, more if you can get it.
Workflow for flats
Consistent light source - a tracing light panel on its lowest setting is ideal, or clear consistent morning sky.
Paper sheets/White T Shirt or a lighting diffuser between the light panel and the telescope. I used high quality drawing paper, for my scope, three sheets where required.
Use a flats wizard. The ADU value is calculated as being: half (2 to the power of 14{bit}) Therefore 2^14 = 16384. 16384x0.5=8192. An ADU of 8192 or just 8000 is fine. Put your minimum exposure time above 2sec and maximum around 30sec. Set the same Offset, Gain and Temperature as you Lights and Darks.
If your camera has upscaling to 16 bit (like my 405CC), redo the calculations above but for 16 bit.
My flats were around 7.25seconds. If you cannot reach a duration of above 3 seconds, increase the number of sheets of paper.
Use identical setting for the Dark Flats, be absolutely sure that there are no inconsistencies in the data. Ie, literally everything MUST be identical.
Hope this helps.
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