4x Powermate, 2x Barlow, f/6.3 Reducer Comparison of M2
Again with data from June 26th 2010, I diligently put some effort into determining exactly what the impact of barlowing would be on M2. Sort of like the M13 comparison, I thought this would be an interesting way to really see the difference.
In this comparison, the constants were a big, bright full moon, haze, the CPC 1100, Orion StarShoot Pro v2.0, and the f/6.3 reducer. Processing was done in MaximDL and I left the reducer on even with the barlows – generally a weird thing to do – simply for the flatness effect. In retrospect, this probably was a bad idea since I would have cropped things down so much anyway. Then I scaled each image to be approximately the same size, simply so the overall effects would be visible. I also tried to scale exposure times to be a bit more in line equally. I also used the Orion SkyGlow Imaging filter, just to help weed out any extra light – with the bright moon, I could use all the help I could get!
The upper left image is with a 4x Televue Powermate. The camera was set in monochrome mode using 2×2 binning and the result is built from 12x 30s exposures. This mostly looks like a b/w image and the center, while not very clear, does show some contrast – just not very much.
The lower left image is with a 2x “BIG” Barlow, 12x 15s exposures. The 2x Powermate is supposedly nearly parfocal with the 4x, so it’s a bit sad that I had to go through refocusing here, but nonetheless, this is clearly the worst overall. Partly because it’s moldy green looking (poor processing) and partly because the subs were “cloud challenged”. However, I felt it was important to include it alongside the others.
Lastly, the one which I’d have to say looks best, the upper right image is just the f/6.3 reducer – no barlows – and 12x 10s exposures. Arguably this is a little bit more exposure time than the others, but this image is much more vibrant. The “fuzz factor” looms wonderfully around the core. The obvious take away from this is that the reducer is certainly nice on DSOs, and the focal length increasers probably should be left to the planets on the CPC.