NGC 6888 Crescent Nebula

[Fay]

Was not going to post this, but interesting to compare with Chris's whose image was taken at a dark site.

Also 6x600, no flats or darks. WOZS66, 0.8 fr, Ha. Planning on adding to it. Taken from Chislehurst, 23/6, 23.47.

[Fay]

I think Chris's image is a lot tighter, crisper than mine.

[JohnP]

Chris's might be sharper but that's a lovely large FOV - love all the surrounding wispy bits...

[Fay]

Thanks John, kind

[Rocket Pooch]

And fay the FR hase given a nice flat field well done, ok not I'm going to get the check book out and get a dedicated FR for that bloody scope.

If anyone is interested I have a 23% field curvature with the ZS66 out of the box.

[MarkS]

I agree with John - all those wispy bits look really good.

I wonder why the image isn't that sharp though.

Mark

[MarkS]

If anyone is interested I have a 23% field curvature with the ZS66 out of the box.

Is the field curvature any different when it's in the box?

[Fay]

Mark, I am going to have another look at this, as it may be my processing

[Fay]

Think this may be a bit of an improvement

[JohnP]

Fay - I can't really see much difference...

To be honest I have always found the crescent difficult to do... I have had several attempts & they always seem to come out soft'ish..... even the one I took at Les Granges last year doesn't look pin sharp... Check out my webpage - there is also one I took in 2008 in Bromley.. (again soft) - Interestly these were all taken with ZS66... maybe there is something strange with this scope...??????

Nice image though - John

[Fay]

Thanks, John. It may be all the nebulosity everywhere, giving it a fuzzy look. Also, sky not that dark. I thought this version looked a bit sharper, we are never satisfied!

[mickw]

Second one looks sharper, but first one looks more gaseous.

Then again, I know bugger all about imaging 

[Ian]

looking at Chris's image there's lots of Ha going on around that region. I did wonder if it was his processing at first.

That'll go quite a way to reducing contrast in the area...

[RobertM]

Fay,  All the sky in that image has nebulosity so there isn't really a black level, just a minimum grey.  Also 6 x 600s will expose quite a bit of backgroud noise due to stretching because of the brighter background.  Chris could get away with less subs because of the dark sky, allowing his camera to record fainter detail.  All being said, I don't think you could expect much better from that exposure length.  When I did mine last year it was 20 x 300s so I would think another 6 x 600s would go a long way to meeting your expectations.

Great image by the way!!!

[Fay]

Thanks for that Robert