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Limiting Magnitude | ||
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I was interested to try and find the faintest object that I could cqapture from my light polluted roof terrace with the 216XT. With the alt-az setup, the longest good exposure seems to be 60 seconds. I have stolen a couple of pictures - M57 from Sky & Telescope and M104 from the Starlight Express website, which show the magnitude of stars. If either of these people have a problem with me using these pictures then please email me. With the MX7C being able to self guide, I have been able to record stars down to mag 19.5 and maybe fainter, see the image of M104 at the bottom.    From the above image I think everyone will agree that the mag 17.7 star is visible. Anything over that is dubious even with the origional fits file. The image has been heavily processed to try and bring out the faint details. This image is an average of 12 x 60s images which were dark and flat fielded, average combined in cadet, doubled in size and curves and levels to the extreme with a lot of unsharp masking and gaussian blurring applied in photoshop. Until I had taken this image I would not have thought my setup would go to mag 18 with a 60 second exposure (OK, noise has to be reduced with multiple exposures but the details are all recorded in 60 second exposures).   My image of M104 has not been processed in any special way to find the faintest object. Instead I have taken the jpg image from this site and immediately you can see a mag 16.5 star just above and to the right of the galaxy.  This image shows stars that are not on the comparison chart, which goes down to mag 19.5, so I think I have maybe cracked mag 20 with the MX7C. | ||