Okay, a few more pictures, then it's back to business. Keep in mind that the purpose of this pictures is to first evaluate whether the 510 can be used as an affective imaging platform. Second, cameras can be the Great Equalizer; they provide an unbiased record of the overall field quality and they highlight each and every flaw and foible in a system. For example, I noted earlier that the field on the 510 in its original configuration showed a surprising amount of vignetting. This contrasted with my prior experience with the Unitron 155 which showed an excellent field with just a tiny amount of vignetting in the corners of a full frame camera field. I suspected that the baffles in the 510 might be restricting the field a bit, and when I looked inside the tube the primary baffles looked fine, but I found that there was an additional baffle inside the draw tube. This contrasted with the draw tube of the 155 which did not have this baffle. So, I decided to conduct a series of tests using the draw tube from the 155. I also wanted to evaluate the performance of the Baader Fringe Killer minus violet filter to reduce the small amount of residual violet halo around bright stars. I also happen to have a Baader Semi-Apo filter that does the same thing, but it also removes some additional regions of the color spectrum in an effort to preserve the overall color balance of the field. While this works fairly well for visual, it is not necessary for imaging as you can correct the color balance during processing. Using the Fringe Killer by itself eliminated the unnecessary light loss of the Semi-Apo filter. Also, I would note that neither filter is needed for visual. As I noted above the camera Sees All and the violet halos are really only visible in some images, and not visible (to me) visually with the image is precisely focused.
Any who... this is the first of 2 examples, the globular cluster M15. I will give a second example of M57, the Ring Nebula, in a later post. It should be noted that the conditions were pretty bad with thick haze and smoke set aglow by the light of the Sturgeon Moon. Still, the results are pretty impressive.
So, image #1...
M15 – Globular Cluster in Pegasus
Telescope: Unitron 510 5” f/16 refractor, Atlas EQ-G
Camera: Canon EOS Ra full frame DSLR
Filter: 2” Baader Fringe Killer (Minus Violet)
Guide scope: Williams Optics 50mm Guidescope, ASI290MM, PHD
Exposure: 32x60sec, ISO 1600, saved as RAW
Darks: Internal (Long Exposure Noise Reduction)
Flats: 32x1/125s tee shirt flats taken at dusk
Average Light Pollution: Bortle 8, very poor transparency, haze, smoke, full moon
Lensed Sky Quality Meter: 17.8 mag/arc-sec^2
Stacking: Mean with a 1-sigma clip
White Balance: Nebulosity Automatic
Software: Backyard EOS, Deepsky Stacker, Nebulosity, Photoshop