Saturday, September 21, 2013

IC 1396

IC 1396 by S Migol
IC 1396, a photo by S Migol on Flickr.
Via Flickr:
IC 1396 including the Elephant Trunk Nebula as seen from the back yard at the end of August into September.

This is the sum of a large stack of sub exposures - 66 frames at 1200 seconds at 100 ISO - for a total of 22 hours of integration.

Polar alignment could have been better for the session, but it was OK enough once stacked.

This target is much larger than the full field of view with the SV4 scope and the APSC sensor of the DSLR. A mosaic would be best to show the full detail. A mosaic would require at least 8 more frames to show the proper area. This may be a major effort lasting several seasons.

Standard setup:
Stellarvue SV4 scope
Modified and cooled Pentax K10D camera
SSF6 flattener
Baader UV/IR filter with IDAS LPS2
Stellarvue SV70ED Guidescope with SSAG
Losmandy G11 with Gemini 2

Major change to the previous hardware config was the use of the DSBS side by side platform. This lowered the center of gravity of the system. Also, I moved the counterweights as far up the shaft as possible, reducing the moment of inertia of the system. These helped to improve the tracking significantly. I also added a stiff dovetail bar that fully extended past the base of the DSLR, finally removing all flexure from the system.

Calibration was done in Maxim using sets for each night for flats. Stacking in DSS using Median Kappa Sigma stacking. In the past, I've used KS clipping and that has left a fair amount of noise. I will try the MKS and see how it goes.

Stretched in Pix Insight: DBE, Masked Stretch script, Histogram Stretch to reset black point, Masked TGVDenoise, and Curves to increase contrast.

Here's the platesolve result:
Referentiation Matrix (Gnomonic projection = Matrix * Coords[x,y]):
-1.56006e-006 +0.000529752 -0.692199
-0.000529579 -1.52832e-006 +1.05242
+0 +0 +1
Projection origin.. [1983.489450 1312.487627]pix -> [RA:+21 39 18.50 Dec:+57 27 57.47]
Resolution ........ 1.907 arcsec/pix
Rotation .......... -89.842 deg
Focal ............. 656.61 mm
Pixel size ........ 6.07 um
Field of view ..... 2d 6' 4.3" x 1d 23' 25.4"
Image center ...... RA: 21 39 18.505 Dec: +57 27 57.45
Image bounds:
top-left ....... RA: 21 34 00.498 Dec: +58 30 41.19
top-right ...... RA: 21 34 15.578 Dec: +56 24 40.51
bottom-left .... RA: 21 44 39.317 Dec: +58 30 26.31
bottom-right ... RA: 21 44 18.716 Dec: +56 24 26.48