M20 - Trifid Nebula

[CoolhandJo]

This is the second image taken with my 8 inch Newt and EQ6 pro with canon 350D (mod)

Its 8 x 10min, darks, flats applied at ISO 400

High Res version here http://i594.photobucket.com/albums/tt21/coolhandjo/Trifid-Nebula-sgl.jpg

Comments welcomed :)

[DavidU]

Nice colours Paul, a MPCC or such would tidy the edges.
Good work !

[renormalised]

Nice shot...background looks OK but you seems to have a bit of coma, were you using your mpcc. What might also be causing it is a slightly misaligned camera...you seem to have more pronounced distortion in the lower left hand side of the image. Other than that, the neb looks quite good, nice colours:)

[gregbradley]

Overall a nice image especially for 2nd light. The blue reflection nebula looks slightly violet/purplish on my monitor rather than a delicate blue.

As mentioned stars are showing some bad effect from coma or misalignment or collimation. The same thing perhaps has affected the neb itself which seems slightly out of focus but I imagine your focus was quite accurate as star sizes are small and it is something else.

Greg.

[bloodhound31]

G'day Jo, focus and tracking look good, but for 8 x 10 min, I suspect your black point is EXTREMELY clipped. Both the reflection and the emission nebulae of this object extend well beyond where you have stopped.

At the cost of a bit of noise and colour, see if you can extract more out of it, I'm sure it's there. You spent 80 minutes capturing those elusive photons, why not show them?

Baz.

[CoolhandJo]

Wow! what a difference 12 hours makes! I can now see its clipped (thanks Baz).

I thnk that Greg is correct. I think its actually th tracking that caused the star curvature / elongation. I wasn't happy with the tracking from the start of the session really. I had to use star rounder to round them out - hence the slightly out of focus nebula.

The guide star was off centre too and I think thats why ther is curvature in disproportionate areas on the image rather than everywhere.

I put it down to my canon power pack swaying around a bit so next run I am going to make sure that everything is tied down so I don't get that much movement. I am also going to ensure I pick a star closer to the centre and slighlty brighter than the one I used on this image.

I am going to do a repo based on the comments here (including fixing the blue colour)

Thanks for the comments and what a hobby we have!

[gregbradley]

The star rounder plugin uses the darken blend mode of layers to block out the unwanted elongation sections. It will reduce resolution of nebulas as well as it stretches and shifts the image.

Best to use a lasso tool and limit what area the star rounder plugin affects so it doesn't affect the neb areas. Then use the smudge tool to push from the outside to round out any elongated stars in the neb area.

Greg.

[CoolhandJo]

Ahhh! that would expain the clipping! Thanks for tip - I will post the outcome (I will ensure I stretch the background to compensate for the clipping also)

[CoolhandJo]

After taking the advice from the comments made I re processed from the ground up. The biggest change was saving in 16bit Tiff as opposed to 8bitt (somehow made the image smoother and less clipped).

Hope you find it better - I do :)

Higher res here: http://i594.photobucket.com/albums/tt21/coolhandjo/Trifid-16bit1024test.jpg