M20

[peter_4059]

Last night there was a break in the clouds up here in Brissie and no moon - a rare occasion lately. I decided to make the most of it. Here's M20 taken with the 400D/paracorr/10" newt. This is a combination of 6x1.5, 6x2 and 2x4 min subs making a total exposure time of 29 minutes. ICNR/no flats. I've had to do quite a bit of re-sizing and compression to get under the 200kb limit.

I am seeing a horizontal band near the bottom of the image with this camera - not sure if it is coming from ICNR or some post processing artifact - any ideas?

Peter

[allan gould]

Nice shot Peter. Well captured for only 30 minutes of data and nicely framed. I really like the scale of the 10" with the paracorr, certainly worth every penny you told your wife you paid for it. ;)
A really good shot considering the light pollution present at your site and that you managed to bring out the faint nebulosity.

[jjjnettie]

Really nice work Peter.
Did you use DSS? The artefact could come from the stacking process.

[peter_4059]

Thanks Allan - it certainly was worth every penny I paid for it (that's my story anyway).

JJJ - yes I did use DSS - have you come across this artifact from DSS processing before?

[TrevorW]

Nice image Peter for limited data those clouds can be a pain

[jjjnettie]

I have. When I stack in Mosaic mode it sometimes happens.

[[1ponders]]

Very nice shot Peter. :thumbsup:

[troypiggo]

Great one mate. Really like the composition of this one. All ready for you to add more data to :)

[pmrid]

That's nice and crisp. Clean, sharp focus and no tracking artifacts.
Peter

[Hagar]

Very nice Peter, The band you talk about could be an overlay from the stacking process. Easy to crop this off and by doing so makes processing and histogram interpretation much easier.

This really is a lovely image. Good focus, good guiding and well captured. I hope you don't mind but I cut off the outer area and lifted the saturation a bit.
Definitely one for the pool room.

[peter_4059]

Thanks for all the comments and for the repro Doug. I would really like to find out if the band is coming from the stacking process or from something else. I found a similar issue with my M27 image which makes me think it's something in the optical system - perhaps some strange reflection although I'm not sure how you get a straight line like this if it is a reflection?

http://www.iceinspace.com.au/forum/showthread.php?t=46123

[Hagar]

Peter, I know it is a lot of work but if you process each image individually you will see pretty quickly if it is a stack issue or an individual image issue which would then require more investigation.

[peter_4059]

Good tip Doug - I processed one of the longer exposures and it is present in the single image so I guess it's either a camera artifact or an internal reflection. More testing coming up I guess....

[Hagar]

Check things like reflected light from laptop screens, near by street lights etc. even if not in the direct line of sight. You can always rule out the camera by Taking a half dark image with a lens on and see if it exists. Check for light coming in the bottom of the tube also.

[peter_4059]

I don't think it is from streetlights or lappy - but possibly my neighbors floodlighting :mad2::mad2: