Master Dark

Hi Douglas,

"I've just been creating Master files.  The Master Flat file and Master Bias files are one file but the Master Dark is split into four files, is this correct?."

That's most likely because you have fed APP darks of different exposure times ? Then APP will create different master darks.

"I'm also using a mortified DSLR and am trying to get away from using Darks by dithering, using a Master Bias as a dark file and Sigma Clipping can this be done with your software?.  If it can I take it I just add the Master Bias file where it says Darks or is there another way to do it."

Yes, this is perfectly possible.

What you will need to do is, first create a Bad Pixel Map (BPM) using a good set of darks (try to use darks with long exposures and more than 20) and flats (5-10 is enough):

https://www.astropixelprocessor.com/community/tutorials-workflows/creating-a-bad-pixel-map/

And a tutorial by Sara Wager as well:

https://www.astropixelprocessor.com/how-to-create-a-bad-pixel-map-bpm-by-sara-wager/

Then for calibration of your lights you can only calibrate them using a masterbias, masterflat and a BPM. The BPM will get rid of the hot pixels.

If you have dithered enough and your sensor hasn't very strong Fixed Pattern Noise in the dark current, then this should work really well.

Let me know if you can accomplish this 😉

Kind regards,

Mabula

Thanks for the reply, I'll give it a go once I get some clear skies.

Doug

You're welcome Doug 😉

Posted by: AstroOlly

So re starting this thread....

if I add Darks, Flats, Bias frames and tick the “create BPM” box, during my calibration routine,  and then it creates masters of all and a BPM so does it then calibrate the lights with the darks and BPM or just the BPM..??

as I was under the impression you just load the darks, flats and bias clicked create BPM and then let it do its thing, or at least that’s what I have been doing as Malabu showed in a tutorial with some data from the triffid Nebula...

or am I supposed to create masters of each plus BPM, then clear all and load just the master flat and bias and BPM and then calibrate and not use the master dark..?

its all so confusing.. 🤯🤯

Dear @astroolly,

if I add Darks, Flats, Bias frames and tick the “create BPM” box, during my calibration routine, and then it creates masters of all and a BPM so does it then calibrate the lights with the darks and BPM or just the BPM..??

If you load bias, darks, flats and enable create Bad Pixel Map, then you will end up with masters (bias, dark, flat) and a BPM created from the darks and flats. And all will be applied to your lights then 😉

Please realise that calibration with a masterdark and calibration with a Bad Pixel Map serve different purposes:

• Masterdark, needed to calibrate the dark current and possible amp-glow signals if any (in some cases a masterdark is not needed, in others it is really needed, depends on the sensor in your camera)
• Bad Pixel Map, needed to correct hot/cold pixels/columns on your sensor. (always usefull for all sensors)

A masterdark is optional I would say, but I would always use a Bad Pixel Map 😉 . If your camera has significant amp-glow for instance, I would create a masterdark and (always) a bad pixel map.

A Bad Pixel Map is not a substitute for a MasterDark and vice versa, they serve different data calibration goals.

Kind regards,

Mabula