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NGC 5907 - Luminance Only

Contains: NGC 5907, NGC 5906

Technical card

Resolution: 6521x4904

Dates: July 10, 2017

Frames: 40x600"

Integration: 6.7 hours

Avg. Moon age: 15.52 days

Avg. Moon phase: 99.36% job: 1653181

RA center: 228.972 degrees

DEC center: 56.329 degrees

Pixel scale: 0.281 arcsec/pixel

Orientation: 179.827 degrees

Field radius: 0.319 degrees

Locations: Ben's Backyard, Federal Way, WA, United States


This is an integration of several nights of benchmark shots of NGC 5907, the Splinter Galaxy or Knife Edge Galaxy in Draco. The knot in the middle of it is known as NGC 5906. From good old Wikipedia, I have gathered the following information: it is approximately 50 mly from us. It is unique in that it has low metallicity, has few giant stars, and instead has a higher fraction of dwarf stars. There is a tidal stream that others have imaged quite well, however that is not supported by my red zone location nor the relatively short amount of exposure.

In the Concise Catalog of Deep-Sky Objects, p 352, it is listed at 45 mly away, apparent size of 12.6' x 1.4'. Its optical diameter is 165,000 ly. It is part of the NGC 5866 (M102) galaxy group.

My main purpose for imaging this was to benchmark changes to my optics as I try to improve the symmetry and circularization of stars in my field of view. After having moved my corrector plate around within the plane of the aperture, which moved my secondary off-center in various ways, I was still unable to create a symmetric field of view. I now suspect that the focal reducer is the cause of the problems. I have a new one on order and will swap it out to see if the image is affected by the change. Meanwhile, this is an integration of 5 nights of imaging using two difference optical configurations that were mostly compatible with one another.

You may note non-circular stars throughout including the center, although I have minimized this quite a bit from where I was before. Stars above and to the right of center are the most circular, and there doesn't appear to be anything I can do with the corrector plate or secondary mirror to change that. I have even added a Gerd Neumann CTU just in front of the CCD, and it doesn't have any appreciable effect on the star shapes. This is a puzzle.

This is also my first published image using the Optec FastFocus Secondary Mirror Focusing System. Prior to this I attempted to autofocus using the RoboFocus system on the primary mirror, however this was problematic. Due to mirror shift, I was unable to incorporate continuous focusing with the FocusLock software. I am not in a position to do that, however I am presently concentrating on optimizing the optics. I will say that this is a very nice focusing system, and it has been working like a charm. It's so nice to be able to lock down the primary mirror and not see any significant focus shift.






Inverted Image


Annotated Image

Sky plot

Sky plot


NGC 5907 - Luminance Only, BenKolt

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