Collecting  Photons

North is to the left  Roll over with the mouse to see the effects of the halo protection black magic   1600x1052  

Objects:             An overwhelming association of emission, reflection, dark nebulae with lots of dust added around.

Constellation:     Orion

Coordinates of field center: RA 5h 41m DEC +2° 31'

Notes: due to the awful weather I have been able to collect only a fraction of the integration time I desired, and that shows in the fainter peripheral extension. However, most of the object is so bright that it still shows up reasonably well.
 

Telescope and camera: ASA 10', f 3.6; SBIG STL 11000.

Exposure: Luminance 12x8'; R, B 8x10'; G 8x8'. H 13x16'. About 8.8 hrs total.

Date: 4 nights on 11, 19-11-09; 7, 8-02-10.

Software used: acquisition, CCDsoft. Calibration; registration and stacking: CCDstack, Registar; processing: PixInsight, Photoshop CS. 

The halo around Alnitak has been hell to process out: indeed, I had some light clouds during some of the luminance  acquisitions and it was so bad that I almost throw this image to the garbage bin. The control of the halo proceeded in different stages. Initially, at the time of the fusion of the RGB, Hα and Luminance data, the halo was attenuated by careful levels applications through appropriate luminance masks. At this stage I also applied an extremely useful trick: I modelled the halo by computing with PixInsight LE a background spline model with radial symmetry centred around the star. This model was then subtracted from the Luminance image, to produce a new Luminance file. At this point, back in Photoshop, I blended together the two luminance files through an appropriate highly feathered mask. If you roll over the image above you will see the result of the deactivation of all the procedures I described. The next image shows a screen capture of Photoshop with all the layers I used and the icons of the relative luminance masks.

The final image required additional tweaking. First the fused image was brought to Pix Insight LE for a moderate noise reduction of the low lights only and for a moderate passage through an erosion filter for the stars. Back in Photoshop I applied some unsharp masking (again through appropriate masks) and the final adjustments.

A two part mosaic of the region taken in 2008 with the modified DSRL. Notice the large relfections around stars. These were caused by the Astronomik 6nm filter I was using at the time. When I moved to the STL11000 I needed to get a new unmonted filter and I selected the Baader 7 nm. To my great delight the reflections are completely gone, now!

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Copyright © 2010 by Gimmi Ratto. (February 20, 2010)