Post Processing Problems

[kaymann]

I am using SC (lastest version -everytime) for one stop shopping my OSC setup. This means I take my Flats and Lights within SC and live stack in SC. I save all individual Light FITS including my individual Flat FITS. I then like to post process (align and stack) those individual files in ASTAP or Deep Sky Stacker or Siril. When ASTAP or DSS or Siril ask for Flats and Bias and Darks which of SC Flats-Dark or Flat-Bias files go where. I do not take darks and but your software combines Bias' with the Flats hence the confusion.

[admin]

Hi,

the individual frames get saved into folders as if you had set the target name to 'dark', 'flat', 'flat bias' or 'dark flat' - these will be saved within your normal SharpCap capture folders, perhaps inside a sub-folder with today's date as the name (depending on your filename settings). If you watch the green notification bar while capturing darks/flats/etc with the 'keep individual frames' option ticked, you will see the path name briefly and be able to click on the blue underlined folder name to open the folder.

For re-processing you should not need bias frames - those are only used in reprocessing in the case where the light frames and the dark frames have different exposure lengths. If the darks and lights have the same exposure length then bias frames are not useful.

cheers,

Robin

[kaymann]

Hi,
For re-processing you should not need bias frames - those are only used in reprocessing in the case where the light frames and the dark frames have different exposure lengths. If the darks and lights have the same exposure length then bias frames are not useful.

cheers,

Robin

I can easily find the individual and combined Flat files, flat bias files, flat dark files. I have no problem with that.

If I am hearing you correctly you are saying if I want to stack my individual (100 or so count) light files in say ASTAP stacking software then all I need are the plain vanilla flats files (60 count). Is it correct if I do not use dark files ever than I do not need Bias files. I remember Starizona telling me for HyperStar that when stacking I should use Flats and Bias files and darks are not necessary. If they are correct then I should create my own set of Bias files. If I can use the Flat Bias individual files do they go in the Flat section or Bias section of ASTAP (ASTAP does not have a combined flat-Bias folder.

To take this a little further if I understand you correctly, I take the 16bit master fit file I tell SC to output at the end of a session that should be every bit as good as ASTAP stacking the individual Fits I have SC output. In other words That SC Master Light Fits can go directly into Siril post process tweaking.

[EDIT] Yes I can take your SC stacked light fits and throw them into Siril and go to town post processing (what a time saver) they look great without any additional processing by ASTAP or DSS. [EDIT]

Thank you for your time and consideration given all my poor communication.

[admin]

Hi,

I expect that you will get slightly better images by post-stacking in Siril, DSS, etc than the ones created by SharpCap - SharpCap uses algorithms for processing that are designed for speed rather than getting the highest possible image quality. The difference may not be very large though.

As to which files you need, there are so many options that work well and lots of places to make mistakes. The basic setups that work are

1) Lights and Darks - providing they have the same exposure length and other settings then no need for bias frames (they will do nothing for the final image) - no flat correction in this case.

2) Lights, Darks, Flats and DarkFlats (optionally bias frames in place of darkflats if flats are short exposure). Again, if Lights and Darks are the same exposure then no need for bias frames in the dark processing side

3) Lights, Flats and Bias frames - no dark correction here. Bias frames are required to isolate the background level introduced by the camera from the brightness coming from the image in the lights/flats

For short exposures with modern cooled CMOS cameras, dark frames may well be unnecessary - they produce much less thermal noise than CCD cameras that is further reduced by moderate cooling to say 0C or -5C. The latest generations have eliminated the fixed pattern glow (amp glow) seen on the older cameras like the IMX183 etc.

cheers,

Robin

[kaymann]

Robin, thank you for the response greatly appreciated - very nice summary. However, the question of where do flats with biases combined go/get used: use them in the flats folder and leave the bias folder empty. I got that from this video: Manually Calibrate and Stack Astrophotography Images in Siril by Deep Space Astro (https://www.youtube.com/watch?v=jwBLVT3Ecas).

Thank you again for your time and consideration!