Not M13, the galaxy cluster ABELL 2151. Unusual in that it is about 40% spiral galaxies while most clusters have very few spiral galaxies. I took this last September but unknown to me, the screw holding the filter wheel drive motor had fallen out and the screw pivot for the filter wheel itself was very tight. The result was the wheel never lined up a filter properly and often never even moved so was using the wrong filter. No way flats can work under such conditions. By now I could get up early in the morning and start a new series but what with nothing but clouds I spent the last few nights trying to salvage the mess from last fall. Color saturation is low to hide a lot of defects still in the color data, I spent most of my time working on the lum data. Pseudo flats got rid of the vignetting and large dust donuts but the smaller ones had to be dealt with individually on each frame. Then I had to sort out which color filter actually took the image. It often wasn't the one I thought did. Corners were cut off as filters never centered etc. I lost a lot of faint detail but with nothing else to do thanks to clouds I'm posting it anyway.
Full size image at:
14" LX200R, L=6x10' (out of 18 frames taken), RGB=3x10 minutes (out of 9 attempted in each color), STL-11000XM, Paramount ME.