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M51 (NGC 5194/5), The Whirlpool Galaxy,
in Canes Venatici — CCD Images
M51, with its small companion galaxy NGC5195 (left, North), is one of the most famous and certainly one of the most beautiful galaxy pairs in the northern sky. Although about the same size as the Milky Way and the Andromeda galaxy, it is about 37 million ly distant, and therefore quite small. Several knots of reddish hydrogen-rich star-forming regions can be seen in the spiral arms. (Note that much faint "nebulosity" around the smaller galaxy will only be visible on a monitor in a darkened room.) As suggested by the number of images on this page, M51 is a tricky target—it's easy to get an image of it but difficult to get (and process) a good image. North is to the left in these images. Note the two tiny additional galaxies (small smudges) below (about 7 o'clock) and to the left (about 8 o'clock) of the main pair.
| Date | 2003-05-31; 2003-06-01 |
| Scope |
RCOS Ritchey-Chretien 12.5 inch scope on an A-P 1200GTO mount with an A-P 0.75 x reducer for approximately f/6.8. Camera: SBIG ST-10XME with CFW-8A color wheel. MaxIm CCD camera control. Guiding was via the built-in guide chip. |
| Exposures |
L RGB: Luminance 16x10 min, 1x1 binning; red, green, and blue 6x5 min each, 2x2 binning. |
| Processing |
Frames were calibrated, hot pixels removed, combined, and gradients corrected in MaxIm DL. The RGB was then composed in MaxIm and a soft DDP run on it. The luminance frame was subjected to DDP in MaxIm and then 2 iterations of Richardson-Lucy deconvolution in CCDSharp. The RGB and luminance frames were then registered and cropped in RegiStar and brought nto Photoshop v 7. In Photoshop, the L and RGB were combined, stretched with levels and curves, and sharpened. Saturation of the RGB layer was increased and the layers were then flattened. |
As you can see from the three images below from 2002, this has been a work in progress. These were among my first partially successful CCD images, and replaced a low resolution film image taken in 2000. Processing CCD images is, I find, a much more subjective process than processing film images. The first image below was generated from CCD images captured on 2002-04-13 and was composed using AIP4WIN to enhance the luminance image, MaxIm to combine the RGB, and Photoshop to add a single luminance layer. Though the image is somewhat overprocessed, the duration of the luminance images was greater and the resulting image is sharper. The middle image (LLRGB), was constructed using Rob Gendler's method. The problem of preventing a burned-out core while bringing up the fainter arms is well-illustrated by this series and—from the above image—is still not completely under control.
LRGB Image:
| Exposures |
LRGB: Luminance 15x5 min; red 2x5 min; green 2x5 min; blue 2x5 min. |
LLRGB Image:
| Date | 2002-04-13; 2002-Feb-09 |
| Scope |
Astro-Physics 130 f6 on A-P 1200GTO mount, with ST-4 guider on a separate guidescope Camera: Meade 416 XTE with 616 color wheel. MaxIm CCD camera control. |
| Exposures |
L RGB: Luminance 5x5 min; red 5x5 min; green 5x5 min; blue 5x7.5 min. |
| Processing |
Images were combined, background-equalized, and converted to RGB in MaxIm DL. Imported into Photoshop, L and RGB combined, stretched with levels and curves, and sharpened. For the top image, a flattened LRGB (treated slightly differently from the bottom image) was then combined with a copy of the L image. Both images were then blurred slightly in NeatImage. |
LRGB Image
