Sub length vs Sub count?

[wxsatuser]

are you letting DSS make your master dark during stacking or do you make a master prior to using DSS and then use that?

I used to just throw everything in DSS and let it do it's stuff, although I have made master darks in Imagesplus.

For the limited amout of data I have collect in imaging runs, this has been just fine.

What I am doing now is gathering darks and bias at various temps and using Auto Dark matching in Imagesplus.

From what I gather this scales the master dark for each light and is not directly temperature related.

It is possible just to have a set of darks at every 10 degrees F and pick the nearest to the temperature of the lights.

The only thing is imaging runs have been very few and far between here, did'nt realise how cloudy it could be.

[Pete Presland]

I used to just throw everything in DSS and let it do it's stuff, although I have made master darks in Imagesplus.

For the limited amout of data I have collect in imaging runs, this has been just fine.

What I am doing now is gathering darks and bias at various temps and using Auto Dark matching in Imagesplus.

From what I gather this scales the master dark for each light and is not directly temperature related.

It is possible just to have a set of darks at every 10 degrees F and pick the nearest to the temperature of the lights.

The only thing is imaging runs have been very few and far between here, did'nt realise how cloudy it could be.

Thanks Mike for taking the time to explain.

[Christopher Davenport]

I use DSS to create master darks, bias and flats.

I use this library for noise reduction. I have not splashed out yet on astro specific software (imagesplus vs pixinsight)

My (incomplete) Dark library is 5C,10C,15C exif temp buckets and in timing buckets (3,5,7 min). Quiet painful to pull all this together. (270 pics @ 22.5 Hrs)

My Bias library is 5C,10C,15C exif temp buckets.

My Flat library is 5C, less the 5C bias.

I have created a Master for each of these combinations. (Am missing some darks master combinations.)

I tried to do this for a 10min run, but my 10min darks increase the noise significantly, to the point where DSS cannot match the stars.

Not sure if the library was built poorly, but a 10min 15c is nosier than the neighbours son on his drums.

[sharkmelley]

Apparently Deep Sky Stacker will match the dark frame to light frames when "Dark Optimisation" is switched on.  It calculates a multiplier (in the range 0 to 1) for the dark frame using "Entropy-based Dark Frame Subtraction". Further details and a link to a techincal article are found here:

http://deepskystacker.free.fr/english/technical.htm

Mark

[Christopher Davenport]

Apparently Deep Sky Stacker will match the dark frame to light frames when "Dark Optimisation" is switched on.  It calculates a multiplier (in the range 0 to 1) for the dark frame using "Entropy-based Dark Frame Subtraction". Further details and a link to a techincal article are found here:

http://deepskystacker.free.fr/english/technical.htm

Mark

Aaah, so it is best not to create a master, but to include the whole stack each time. Nice to know.

I was wondering why I got better results when I used the entire stack vs a single master.

[sharkmelley]

No, the way I understand it is that a master dark would be created from the stack of dark frames anyway and then a different multiplier is used  when applying the master dark to the each light frame.

Mark

[Davey-T]

If it's based on the square root I'd have thought the returns would be diminishing long before 64.
 

Dave

[glowingturnip]

In each case the rear LCD was switched off because this generates significant extra heat which is very noticeable on the exposures. 

mine only comes on once, for a couple of seconds at the end of each exposure, showing the pic just taken, am I still better turning it off ?

[glowingturnip]

I regularly get amp-glow problems with my noisy old DSLR, especially in the corners, like these calibrated stacks:

lights running hotter than darks

darks running hotter than lights

Very hard to balance them properly, I'm getting quite good at unconventional techniques for dealing with my corners now !

[sharkmelley]

mine only comes on once, for a couple of seconds at the end of each exposure, showing the pic just taken, am I still better turning it off ?

That should be fine - I often leave it to do a few second preview.  As long as it is off during exposures.

Mark

[Christopher Davenport]

mine only comes on once, for a couple of seconds at the end of each exposure, showing the pic just taken, am I still better turning it off ?

Magic lantern allows you to use the set button to turn your screen on and off.

I leave mine off as I run everything through APT.

Edit - come to think of it that heat may be from your battery. Have you considered permanent power solution for your camera?

[glowingturnip]

actually you know what, you may very well have a point there, i'll definitely look into it, thanks !

edit:  just ordered a power supply from amazon 

[wxsatuser]

With my 60Da I leave swivel screen out and off, power is via the Canon psu.

[Russe]

Re darks.....

I am in the process of making darks at various subs and temps, doing this on cloudy nights.

If a master dark is made then you really want at least 64 darks or may be 100 at the most.

64 frames will only add 1/8 of the noise that a single dark adds and 1/10 for 100 frames.

So your master dark really wants to be a good quality one.

Very interesting! I shall use more subs from now on! Great advice!