The Starry Night, 189

:: home ::


              <<  172  173  174   175  176  177  178  179  180  181  182  183  184  185  186  187  188  189  190  191  192  193 
                  194  195  196  197  198  199  200  201  202  203  204  205  206  207  208  209  210  211  212  213  >>    SRCH



11/22/2016. How about a field of galaxies with members both seasonal and local? Here's a bright galaxy in Pegasus that Charles Messier overlooked and two small clusters with different kinds of fame.

NGC 7331

NGC 7331, The Deerlick Group, and Stephan's Quintet
23x300s L + 4x300s RGB (2h 55m)


NGC 7331 is big and bright in a reasonably empty patch of space. You'd think Charles Messier or Pierre Méchain would have catalogued it, but no. Immediately to the left of NGC 7331 is "the Deerlick Group" named by amateur astronomer and writer Tomm Lorenzin after an observing site (Deer Lick Gap) on the Blue Ridge Parkway. You know the name has caught on, 'cause it's in both the caption of a NASA APOD and in Wikipedia. The little guys (aka "the fleas") are not satellites of NGC 7331. They lie 280 - 300 million light-years away, 250 million or so behind NGC 7331.

Down in the lower right is Stephan's Quintet, four distant, interacting galaxies and a nearer one (the nearer one is blue) which are featured in "It's a Wonderful Life" when the celestial powers talk about Jimmy Stewart and his apprentice angel. The four distant galaxies are also about 280 million light-years away, and the foreground galaxy is about as distant at NGC 7331. "The group was discovered by Édouard Stephan in 1877 at Marseille Observatory," says the big W. It was the first "compact galaxy group" ever catalogued. Before becoming director of Marseille Observatory, Édouard Stephan served Urbain Jean Joseph Le Verrier, who devined the existence and location of Uranus from residuals in the motions of the known planets.


From bright and small to huge and dim. I've only tried to photograph sprawling S-240 (Simeis 147) once a couple of years ago. I needed a wider field of view, something the TMB92 offers, especially with the TeleVue 0.8x compressor. This is a large supernova remnant that's mostly in Taurus but spills northward into Aurigae. It's not so far from IC 443, the remnant I shot during my previous overnight session. I parked the telescope on the brightest portion of the nebula, the southernmost bits in Taurus, and left it till dawn taking hydrogen-alpha images. I had it take a few O-iii images, too, and while they may have helped balance the star colors, doubly ionized oxygen plays practically no role in the nebulosity.



S-240 (Simeis 147)
12x900s H-a, 4x900s Oiii (4h00m


Tonight's Practical Lessons: pull the TeleVue compressor out a little when cinching it in the 2-inch accessory holder. The notch in its barrel can provide a pivot point for the brass compression ring, allowing the CCD to tilt. You want the compression ring to fit fully within the notch. And second, see if you can take up some of the weight so that the focuser doesn't have to be entirely responsible for holding the ST/CFW-10 combination motionless against gravity. Finally, if the tilt issue persists, remember that you did once put a counterweight on the ST2000XM for just that reason. You can do that again, more easily, using the Arca-Swift mounting hardware currently attached to it.


Those two images aren't even the real prizes of the night, but Ayers Rock doesn't look like much. Why yes, I am being cryptic. Wait till I get an "after" photo and maybe I can do some show and tell.



My deep-sky photos are made with a variety of sensors and optics. Deepest images usually come from a SBIG ST2000XM CCD behind a 10-inch Astro-Tech Ritchey-Chretien carried on an Astro-Physics Mach1GTO. The CCD is equipped with a CFW-10 loaded with Baader wide- and narrow-band filters. Camera control and guiding are handled by Maxim DL 5.12. A Canon 6D and a modded 50D find themselves mounted behind an Orion 10" F4 Newtonian or a 92mm Thomas Back refractor or a tiny but mighty AT65EDQ refractor, sometimes with Backyard EOS in control and PHD Guide keeping things on target. Really widefield photos are often made using the 6D and various camera lenses and an iOptron Skytracker mount. PixInsight does most of the heavy lifting in post-processing — alignment, stacking, gradient removal, noise-reduction, transfer function modification, color calibration, and deconvolution. Photoshop along with Focus Magic and a handful of other plugins get their licks in, too, especially when polishing for the web.


:: top ::



                   © 2016, David Cortner