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Annehouw

Sh2-155: First light of the imaging season

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Here in The Netherlands it only gets dark again around the first of August. Often the skies are clear at night. Only this year daytime temperature was almost 40 degrees and we had above 20 degrees at night. As a result, I could only cool my sensor to -10 degrees, but the results were OK.

A new image, a new processing goal. By design of my scope (combination of a mirror and lenses and lots of aperture), bright stars tend to be quite big. I spent a lot of time keeping them small. The method I chose was to partially stretch the image. From this image the stars were removed (Starnet in PI) and the starless image was then stretched and processed further.

This sounds straightforward, but in practice I had to experiment a lot and combine a lot of versions to get a pleasing effect.

A larger version of this image (with acquisition detals) here: https://www.astrobin.com/421021/

 

Sh2-155-final-small.jpg

Edited by Annehouw
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3 hours ago, Annehouw said:

I could only cool my sensor to -10 degrees, but the results were OK.

Nice image.

I've been using -10 as standard out here in Malta.

There's only a small difference between -10 and -15 and even less between -15 and -20.

John

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11 hours ago, Starwiz said:

Nice image.

I've been using -10 as standard out here in Malta.

There's only a small difference between -10 and -15 and even less between -15 and -20.

John

Definitively less mosquitoes at -20......

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1 hour ago, Annehouw said:

Definitively less mosquitoes at -20......

Ha ha ha.  You don't want to see the bites on my legs.  lol

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Hello John,

No 😉

But you are completely right there is not that much of a difference in noise between -10 and -15 or -20.  But since we are trying to separate tiny amounts of signal above the noise floor and my camera is specified for -35 below ambient and easily does -40 in practice I have standardized on -20 degrees below zero. Here in NL the summer is lousy for imaging anyway so this is fine for 90% of the imaging season. Malta is a bit warmer, even in winter. Lucky you!

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