Thursday, September 24, 2015

Processing Other People's Photos

Finding Inspiration

It's been a while since I did any astrophoto work.  I've been either distracted, time-limited, or otherwise unmotivated to get into any of the old data that I've had sitting around.

However, last week, I noticed a new photographer that was getting into the hobby over at the Pentaxforums.  IsaacT had some issues with what they could do with some data that was collected on M42 and was reaching out for some assistance.


He offered the source files from DSS and I did my usual process on them.

There was bad white balance on the original files but this was not the source of the problems.  In the end, the data was good, but thin.

He used a Pentax K5II camera with 200mm lens with the O-GPS Astrotracer to gather about 12 minutes worth of subs of 25 second duration.  I don't know what the ISO setting was or the F stop on the lens.



Steps:
Dynamic Background Extraction to eliminate some gradients
Masked Stretch
Color balance
Histogram Stretch to reset black point
Created luminance mask
Noise Reduction with mask
Masked Unsharp to bring back details on the high SNR areas
Masked Curves to drive the lower SNR areas towards black to minimize the grainy background glow

Plate solve results:
Projection origin.. [2459.416059 1629.742835]pix -> [RA:+05 35 11.59 Dec:-05 21 26.81]
Resolution ........ 2.558 arcsec/pix
Rotation .......... -58.067 deg
Focal ............. 403.19 mm
Pixel size ........ 5.00 um
Field of view ..... 3d 30' 5.5" x 2d 19' 9.1"
Image center ...... RA: 05 35 11.507  Dec: -05 21 39.81
Image bounds:
   top-left ....... RA: 05 34 57.516  Dec: -03 15 46.20
   top-right ...... RA: 05 27 30.589  Dec: -06 13 36.08
   bottom-left .... RA: 05 42 51.118  Dec: -04 29 22.04
   bottom-right ... RA: 05 35 25.596  Dec: -07 27 33.36


Here's a link to the full size jpg:
https://www.dropbox.com/s/san5fjybw8e5m57/20150923-M42Trial.jpg?dl=0
https://www.dropbox.com/s/r7ojwhkb4f89d83/20150923-M42Trial_Annotated.jpg?dl=0

Full size TIF:
https://www.dropbox.com/s/j6lar7fn76b91p7/M42Trial.tif?dl=0
https://www.dropbox.com/s/shkd5b2qlxumikz/M42Trial_Annotated.tif?dl=0


Here's the post where I replied with the images.

What I think could be improved would be:
Getting to a darker site.
Getting more subs.
Using a lower ISO to preserve the clipped stars.

In the long run, Isaac may find good results by modifying the camera to let more Ha data through.  Next steps would be either to shoot wide field with the astrotracer or getting a basic tracking mount.

On another note, I've been pleased with massaging his data and may return to my own datasets from earlier in the year.