Saturn and Rhea, April 24 - 2009

Conditions: great high pressure weather, no wind, no clouds, normal haze, no moon, seeing was ok

Setup: Obsession 18" Dobsonian telescope with 5x Televue powermate (f/23), Lumenera Skynyx 2-2M camera with SBIG R,G,B filters. Here's a view of the imaging setup in my small garden.

Processing (MaxIm DL, Registax, Photoshop): Each R,G,B sequence consisted of 6400 frames. Each of these was first corrected for electronic noise, field rotation and first order alignment using MaxIm DL script processing. In Registax I selected and stacked best 500 frames for each R,G,B sequence, with a mild wavelet sharpening applied. Of these the R-channel appeared sharpest and from these 500 best images I manually selected the very best 100 frames to use as luminance data in a LRGB composite in Photoshop CS.

Note the dark appearance of the Saturn rings in this image. This is due to the fact that the rings are turning more nearly edge-on relative to the Sun than to Earth.

This was the first time I used monochromatic imaging through R,G,B filters to form the final image. Before my color data has come from a color camera and the sharpness here was significantly worse. The new features of Registax version 5 were essential for obtaining this image, most notably the ability work with very large files (each R,G,B sequence was 6.1GB in size). The resolution of my R-channel luminance data is 0.43 arcsec (see below), which is just 36% above the diffraction limited resolution of an 18" aperture.


Here's my main page where you can see more of the pictures I have taken so far.


Comments greatly appreciated! (mikael@leif.org)