Simple but Eccentric ...

[David Fitz-Henr]

Having taken some images of M19 for some focusing tests, I decided to supplement them with more luminance and RGB data. M19 is the most eccentric (oblate) globular known and is immersed in a rich star field.
26min of luminance + 18mins each of R,G & B (all 2min subs).

Small version:
http://www.pbase.com/david_fitz_henry/image/125267597/large

Large version:
http://www.pbase.com/david_fitz_henry/image/125267597/original

[madwayne]

David

A very nice image of something we don't see alot of, well done. I particularly like the star colors you have captured - beautiful.

I did notice a vertical band of some sort on the original sized image. It starts just to the left of the bright star near the top right of the field. In fact there are two lines there very close together that look like a couple of hairs but they are perfectly vertical. I have no idea what it is but saw it and thought I would bring it to your attention so you can investigate it further.

Again well done and please keep them coming.

Wayne

[dugnsuz]

Beautiful, very widefield image David.
I like this one a lot - stars are very nice with natural colour and field is flat from edge to edge.
S-w-e-e-t!!!
Doug

[multiweb]

Beautiful. That field is rockin' now. Flat as a pancake. A pleasure to browse and so well resolved everywhere. There even seem to be a line of stars coming from the center of the cluster like a jet pointing at 4 o'clock. Very cool. Top shot. :thumbsup:

[strongmanmike]

I agree with Marc, great shot. A field of nice point like stars always rocks my socks ;) - excellent work.

The glob doesn't look that elongated though...? Omega seems more eccentric to me..?

Although it is a bit bigger and brighter M22 sits in a remarkably similar looking field:

http://www.pbase.com/strongmanmike2002/image/115623325/original

[David Fitz-Henr]

Thanks Wayne! And thanks for spotting that vertical streak! I've been busy investigating it. There are a number of dim vertical columns (read noise) that should be subtracted out by the dark frames. However, I have found that the brightness of one of these columns has decreased between the time I took the dark frames and the images. Thus when I subtracted the dark frame, this particular column was over-compensated for and ended up too dark. I'm not sure what the maximum time between dark frames and images should be - ideally on the same night but that's just not that practical. I'm about to process a stack of data I have taken over several nights for the Swan nebula, so this will save me some heartache! I'm redoing my darks (sure enough that particular column is looking dimmer in the new darks), and have experimented with some pixel math targeting the column (added a constant 100 adu to the column in a calibrated frame) which rendered it invisible.



Thanks Doug! I'm quite pleased with how flat I've been able to get the field using the Paracorr in cojunction with a simple Newtonian.


Thanks Marc! Yes I noticed that "jet" as well! I'm now chomping at the bit to get on with processing image data that I have taken for the Swan nebula - and try out your star processing tutorial technique!


Thanks Mike! Wikipedia lists it as the most oblate globular, and Universe Today calls it one of the most oblate globulars. I seem to recall that it is the closest to the centre of the Milky Way which acounts for this. I think the richness of the surrounding star field lessens the impact perhaps?
That's an absolutely beautiful image of M22 by the way ...