Daniel's Astronomy Site

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I do my imaging in suburban Sydney with a Meade 8" LX200R, DSI Pro II, Orion Starshoot Pro and an Orion ED80.

 

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Orion Starshoot Pro Images 

Playing With Time Scaled Darks

 

I've been having lots of problems with darks and noise since switching from the DSI III to the SSPRO. Lots of noise, streaks etc.

I started playing with some old data and thought that given the SSPRO was cooled, I could take darks at any time and reapply them.

 

Wrong - the SSPRO cools to 30C below ambient but can't be controlled so over the period of an imaging session there will still

be noise variations in the camera.

 

I started to think about how to treat this without having to make composite darks from different time periods and found a good

solution in CCDStack.

 

The two images below are both M20 (9x400sec) treated exactly the same way in CCDStack except the one on the left has had a

Dark master (stack of 3) subtracted with Time Scaling on and the one on the right using the same master with Time Scaling

turned off.

 

The result is pretty dramatic. I also found an improvement if you subtract flats after doing darks rather than using the batch

process provided in CCDStack.

 

 

It looks to me like I'll be having to use this type of technique going forward for all my darks with the SSPRO.

 

 

The difference can be seen in the following portions of the final full scale images processed in PS3

 

 

Yes there is some difference in hue but the big improvement is the need for less noise filtering in PS3

M20 Trifid Nebula

 

Taken with the ED80 - 9 RAW subs at 400 seconds each. This is a reprocess of the original above.

 

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 Full Scale          

 

NGC 253

Taken with the ED80 - 6 RAW subs at 300 seconds each.

 

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This one was more noisy - I believe due to a 13.7v power supply I was using. Using a 12v supply seems to fix the problem.

 

M17 Swan Nebula

Taken with the ED80 - 5 RAW subs at 300 seconds each.

      

 

Reduced Scale   Original Scale

 

 

 

M8 Lagoon Nebula

Taken with the ED80 - 5 RAW subs at 300 sec each

 

        

 

Reduced Scale   Original Scale

 

 

 

Processed in CCDStack with darks and some (not so good) flats. I've included reduced and full scale versions.

 

 

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 Last Updated on 02-Nov-2008

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