NGC1365 - Backyard Observatory Sydney (North Curl Curl)
TEC140 + IDAS LP + Moravian G2-8300 at -20
LRGB: 150, 50, 50, 50 min all at 1x1 binning: 7 subs (3 x 10 min lum)
I'm feeling fairly happy to get what I did considering light pollution, but wishing I could get smoother looking results in the fainter areas. The luminance data looks quite nice but I probably could have done better collecting colour data at 2x2, or a lot more time at 1x1. Not sure to be honest.
Thanks for looking and comments much appreciated.
Peter
Last edited by PRejto; 10-01-2013 at 01:36 PM.
Reason: Uploaded improved version
Peter, you are possibly right, though I took care to lower the black point in the final step I tried hard not to clip any black. But, saying that, looking only at the jpeg posted, the green channel is slightly clipped...red/blue are not. But you are right, perhaps the sky is too dark! Thanks.
It looks a bit over processed to me with a lot of colour noise present but the detail is very nice. I think extra colour data would definitely fix this as 50 minutes at 1x1 is definitely not enough. Try 50 minutes at 2x2.
Very nice result for a 140mm scope in suburbia. Good detail and colours in the galaxy core and arms. When you lift the background levels you can see a few other small galaxies in the field.
Thank you alpal. Rick, John, Paul, and Graeme for your kind words. Much appreciated! Yes, the black is clipped. I will replace the image soon.
Steve, I totally agree with your comments. I normally have collected colour 2x2 but I think I lose detail and I don't get the tight stars I managed with all 1x1....but I've paid a price with not enough colour saturation. Perhaps I will try 2x2 for the galaxy and 1x1 for the stars. I have not ever tried this so I'm sure I can waste many hours! Is there a tutorial anywhere on how one might do this? I can think of two ways I might try...or, is this just a crazy idea?
Thank you alpal. Rick, John, Paul, and Graeme for your kind words. Much appreciated! Yes, the black is clipped. I will replace the image soon.
Steve, I totally agree with your comments. I normally have collected colour 2x2 but I think I lose detail and I don't get the tight stars I managed with all 1x1....but I've paid a price with not enough colour saturation. Perhaps I will try 2x2 for the galaxy and 1x1 for the stars. I have not ever tried this so I'm sure I can waste many hours! Is there a tutorial anywhere on how one might do this? I can think of two ways I might try...or, is this just a crazy idea?
Peter
You do theoretically lose a bit of resolution but with the LRGB process it matters less if the colour is binned as long as the luminance is unbinned. Of course just shooting more unbinned colour is another way. One advantage of shooting unbinned colour is that you can add the colour into the luminance to get a bigger signal to noise ratio. Your suggestion sounds most unconventional to me and I can't see how it would work. So I would try both methods and just see how they go. There should be plenty of stuff on the web. Just google LRGB.
You always wind up wasting many hours on this stuff.
Hi Peter,
That last trick is a clever one to deal with backgrounds.
Another trick but a bit time consuming:
Let's say you have a galaxy and a noisy background.
Make 2 stacks for each of the LRGB:
(1 set ) for the background with everything set to median.
(2nd set ) with everything set to Kappa sigma clipping for the bright areas of the galaxy.
You can then combine the 2 images in layers with Photoshop.
( Put the galaxy on a hide all layer mask & paint it through. )
You'll get a smoother background & sharper details in the brighter galaxy.
Hi Peter,
That last trick is a clever one to deal with backgrounds.
Another trick but a bit time consuming:
Let's say you have a galaxy and a noisy background.
Make 2 stacks for each of the LRGB:
(1 set ) for the background with everything set to median.
(2nd set ) with everything set to Kappa sigma clipping for the bright areas of the galaxy.
You can then combine the 2 images in layers with Photoshop.
( Put the galaxy on a hide all layer mask & paint it through. )
You'll get a smoother background & sharper details in the brighter galaxy.
Thanks Ross! I was very lucky the night I collected blue....skys were very clear and steady and I actually got the lowest fwhm values I have yet to see.
