Deepskystacker Settings

Comment

Comment by Marc Basti on April 25, 2011 at 4:50pm

Russ is right, flats should be taken for each session. Flats reverse imperfections 1) in your optical light path (tunnel vision) and 2) dust shadows on your glass. Once the cam is moved these things are in different orientations. When you're starting out you shouldn't get too fired up about flats (that will come later). So for a 1/2 right way first read FAQ in DSS on how to take flats. Then decide on a imaging setup you are going to use say; 2" focuser,-lt poll filt,-2" nosepiece,-t ring,- camera-or whatever. Once you decide a good orientation for the camera stay w/it and mark it w/a piece of tape so that the camera always goes back pretty close to the same spot. This will get you close (not exact, this is also good if you shoot the same target over 2 nts). If you take a flat master w/this setup you can keep reusing it w/all your light frames (of the same setup) and it will at least clean up the tunnel vision. This will not remove the dust motes (can make them a little worse, PShp clone tool for that) and if you change your imaging train say an extension or FR, anything. you will need new flats. Again this is just a get in to it method that will help your pics for now. Disclaimer: the above written is Marc's opinion - ask 10 people about flats get 10 different answers. Known to cause much civil unrest amongst APers.

Comment by Russ Ruggles on April 25, 2011 at 1:35pm

Hey Al,
Making a library of Darks and Bias/DarkFlats is good but not for Flats. The optical problems change with each setup so you need to take fresh flats for every session - before moving the camera or changing the focus or anything.

Comment by Al McAdam on April 25, 2011 at 12:27pm

Great, that makes sense because you would end up spending the whole night doing everything but the lights. I kept getting confusing info while reading up on each, one would say you don't need to worry about temperature and the next article would say you have to keep them the same. Making a library of lens cap on and flats sounds great but what about moving the camera is it a minor problem?

Comment by Marc Basti on April 25, 2011 at 11:31am

They are (time, temp, iso, sensitive), but a 5mn 32* 1600 dark frame is going to be close enough to use w/a 5mn 36* 1600 light frame for calibration purposes. Most people I've seen use 10*F increments (some use 5*). Myself I used 10* incr. picked the lowest/closest temp for calibration. Then I would check the resulting pic close up and look for little black dots (holes) if they were there (most times not) I'd go back and adjust the multiplication factor (under dark frames) down to say .75 and stack again (a bit of trial and error). So a library can go as (lets assume all is iso1600 if 800 make an additional libr. for that)-
Dk 5mn 30*F master
Dk 5mn 40*F mas
Dk 6mn 40*F mas
Dk 6mn 50*F raws (might want to save these too if you switch stacking sftwre)
Dk 6mn 50*F mas
etc. Marc

Comment by Al McAdam on April 25, 2011 at 4:23am

Thanks I thought they were temperature sensitive?

Comment by Marc Basti on April 25, 2011 at 3:20am

Al, it's also a good to take the dark frames at another time so you can take full advantage of a clear sky. Marc PS save them and make a library (they're good for a year or 2+) and reuse them.

Comment by Al McAdam on April 24, 2011 at 7:13pm

I am using a DSLR and subtracting a dark frame from each light image I can do with the camera as I shoot but it takes an equal length of time for each shot. The one thing I realize is that I have to shoot more than one or two shots for the dark stuff but now I kind of understand why. I can actually just shoot with the ordinary lens and put a cap over the lens. Your are right that is a good site and I book marked it and I will try all of it if we ever have any good weather.

Comment by Sander Pool on April 24, 2011 at 11:39am

That looks interesting Al. Before I bought my first real CCD camera I bought and read HAIP (Handbook of Astronomical Image Processing) so I'd know what I was getting into before handing over my money. It explains signal to noise ratio and image calibration in great detail.

Comment by Al McAdam on April 24, 2011 at 11:37am

Sander Check out this site, now it is for CCDs but it is very interesting http://www.lefevre.darkhorizons.org/articles/proctutorialchap2.htm

Comment by Sander Pool on April 24, 2011 at 8:08am

A dark is an exposure with the same length and temperature (iso) as your lights except no light is allowed on the sensor. If your lights and flats have the same exposure length then the darks will be the same.

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