Dark frames

[wigggyy]

Hi 

I hope this is not a silly question I have already got the light frames of M51 I use an Atik 383l and was going to get the dark frames later as I can set the temp and exp time as it was when taking the main images I am assuming I need to have the exact same size subframe and be on the same position on the sensor chip any easy way of making sure the dark subframe is in the correct part I am using artemis capture I have attached one of the images 300 sec exp SW Esprit 120 any help appreciated

[toilandtrouble123]

I thought you could just have a library of various darks to choose from in your stacking process?? Maybe I was wrong and it's more precise than that...

[kalasinman]

As there is no light in a dark frame, the entire chip is the same.. Are you not using the whole sensor for the lights? Stacking and calibration comes before any cropping or other processing.

[wigggyy]

Yes I am using the whole sensor just framing the object within the artemis software I have taken a set of darks without framing just leaving it as full screen when I attempt to register then in DSS it has a message that says the checked pictures are not compatible (width,height,number of colours,number of channels,only one master dark,offset and flat). any ideas what I am doing wrong

[lensman57]

Hi 

I hope this is not a silly question I have already got the light frames of M51 I use an Atik 383l and was going to get the dark frames later as I can set the temp and exp time as it was when taking the main images I am assuming I need to have the exact same size subframe and be on the same position on the sensor chip any easy way of making sure the dark subframe is in the correct part I am using artemis capture I have attached one of the images 300 sec exp SW Esprit 120 any help appreciated

m51 chc.jpg

If you were working @ -20C and lower @ 300s exposure   dark frames are not necessary. Just use about 100+ Bias  to calibrate with. I have not used darks with my 383 even @ 900s exposure.

A.G

[ollypenrice]

There is no framing of darks. Once you have covered up the chip it doesn't know where it's looking! (It isn't looking anywhere, really...) Just take the same sub length at the same temp in the same bin mode and you are good to go. However, when making your darks do so using the metal screw on cap supplied with the camera. This is seriously light proof. A lens cap is not, not by a long way in some cases.

I partly agree with AG but I think the best solution of all is to use a master bias as a dark and add a bad pixel map to pull out the hot pixels. You need a software stacking programme which supports this. I like AstroArt 5.0. It explains how to make a bad pixel map. Dead easy.

Olly

[wigggyy]

Many thanks for your help it is much appreciated

David

[kalasinman]

Agree with all of the above, but DSS is complaing as you seem to be cropping before stacking. Crop only after stacking.