NGC 2841, also known as the Tiger Eye galaxy, is a 9th magnitude flocculent galaxy of type S_AB that lies in the constellation Ursa Major.  Measuring 8.1’ x 3.5’, NGC 2841 is relatively large and bright, yet imaging it poses a challenge due to the fine details in its densely packed spiral arms.  In addition, the faint, outer star bands are difficult to capture, though they came through in this image on the left side due to the deep luminance stack.  I did not think I would have any luck imaging the outer fringes from my Bortle 4+ backyard at f/5.5, but excellent transparency during this project helped a lot, as did the aggressive stretching.  I chose to apply minimal noise reduction, as I feel like smoothing out fine details in a galaxy image is a no-no when you’ve got a really good luminance stack on hand.  The Esprit 100ED did quite a good job resolving some of the flocculent structure, but it took some careful deconvolution, wavelet sharpening, and curves adjustment during post-processing.

This image is not going to break any records for resolution, but the wide field of view captured several distant companion galaxies that made for a unique image.  Perhaps the most interesting is the possible interacting pair PGC 26535 (MCG+08-17-087) and PGC 2372975 (LEDA 2372975), visible to the upper right of the orange double star.  I say “possible” because I was not able to find any information on them.  Please post something in the comments if you have some information.

Other galaxies in the image include several PGC entries in the 15th-17th magnitude range and many fainter objects.  Rather than list them all separately, I thought I’d post an annotated image generated in the fantastic, free program ASTAP (see B revision) using the HyperLEDA annotation feature.  I also love the limiting magnitude estimate in ASTAP, which indicates that this image captures objects down to mag. 21.9.   With images of >10 hours of luminance, it’s amazing how reliably the limiting magnitude ends up at 21.8 to 22.0 at my backyard location, regardless of whether the data were captured with the Esprit 100ED or the C11 EdgeHD.  I find it useful to have a quantitative measurement of how deep a given image goes compared to previous projects, as it pretty much tells me when I can stop collecting luminance on a given target.

I ended up throwing out about 4 hours of precious data that are not counted in the integration time, something I hate to do.  I shot 90 minutes of H-alpha last March, but the signal was so weak that I decided I didn't want to sink another 10 hours into it in order to get a few tiny, pink dots.  This galaxy does not have any really large H-alpha emissions.  Of interest to QHY268M users is an experiment I did to compare RGB data collected in two different camera modes.  The image shown is based upon 7 hours of RGB data shot in Mode 3 / Gain 14.  I also spent one evening in November shooting RGB in High Gain 2CMS-1 Mode, Gain 0.  Both sessions were 5-minute subs with the same Chroma filters.  I ended up not using the High Gain 2CMS-1 Mode subs at all.  Many more stars were overexposed due to shallow e- well depth (compared to Mode 3).  When I combined the data, some orange stars had blue centers, and there were pink fringes around some of the brighter stars.  Ugly.  It seems like I'd have to reduce sub length to ~2 minutes to use High Gain 2CMS-1 Mode effectively for RGB.