Hello all,
I purchased an ATIK 383L+ mono recently, but have only started using it in earnest in the last couple of weeks. The camera was bought new and I have it located in my remote observatory. I use Prism and SGPro (rarely) to take images, including calibration images. For now, my challenges are limited to calibration frames. Darks are fine, however, Bias frames are definitely an issue. I also have issues with Flats, but that maybe me, more so than anything else - but I will like help on that as well.
About the Bias frames -
I initially started taking Bias frames using the minimum suggested exposure time of 200ms. What I am noticing is that there is distinct light leak on to the camera sensor and as a result, the ADU is around 6000 (which is too high, ADU for darks is less than 10). I have always had CCD cameras in the past where the shutter would actually remain closed while taking Bias frames, so the assumption was that once I selected "Bias" frames in the image capture program (especially SGPro), the ASCOM driver would interpret that to mean the shutter needed to remain shut. That obviously does not happen given the high ADU value. As a result of that, I took 0s exposures both in Prism and SGPro - I was still seeing the same issue. (All this while, the Darks seem to be perfect - the point being, if I tell SGPro to take Darks, it seems to keep the shutter shut, not letting any light to leak on to the sensor, but that is not happening with Bias frames). Last night, I did take Bias frames using the Artemis software (again 0s exposures - I am not sure if there is a way to take "calibration frames" using Artemis - if there is, do please let me know how) - the result was much better with the ADU near 350. However, I would expect ADU for the Bias frames to be in the same range as the Dark frames - around 10. I tried calibrating one of my light frames with a SuperBias frame (created using PixInsight from about 25 Bias subs), but that did not seem to work. My only other option at this point is to use SGPro and trick the ASCOM driver by telling SGPro to collect a 0s "Dark" frame. I am not sure if that will work, but I am hoping it does. As a result, there are a few questions that I have -
1) The obvious one is - what am I doing wrong? Why can't I get the ADU values of the Bias frames to match (within a threshold if need be) with the Dark frames? (or more importantly, what is the best way to take Bias frames with this particular camera)?
2) Is there a way to take calibration frames (especially Bias and Dark frames) using Artemis software?
3) Does anyone believe there could be an issue related to the ASCOM driver itself - so that when I select BIAS in SGPro, it does not open the shutter? If so, is there a fix for that?
About the Flats -
I have an Alnitak Flip-flat that I use to collect flats. I usually keep brightness level around 50 on the Flip-flat. This results in an exposure time of 0.38s to achieve 24000 ADU level for my luminance filter (for all other filters, the exposure times are greater than 2s to achieve the same ADU level). I have read in other forums that with this particular camera, I need to take at least 2s flats, otherwise I will notice a shadow of the shutter on the flats (which I am pretty sure exists for luminance flats - I don't see that on RGB flats). So, I guess the question is - should I try reducing the brightness of the Flip-flat for luminance filter and ensure I take about 2-3s flats thereby eliminating any issues with shutter shadow? If so, shouldn't the advertised minimum exposure time be 2s and not 200ms? What am I missing?
If anyone wants a link to the calibration frames that I've taken, I will be more than happy to share those with on this forum.
Thanks for your help.
Dhaval
Topic: Struggling with Bias frames (and also Flats)..Help needed, please! (Read 8490 times)