How many stars?

10/23/2016. Last night I could actually see the Milky Way running through Cygnus and Cassiopeia. That that is noteworthy says plenty about the skies overhead and about the effectiveness of signal processing.

First, M39 and the Cocoon Nebula. The bright cluster and the faint nebula are almost connected by a dark ribbon of gas and dust. Visually, I mean, apparently. The two are not physically related. The cluster is about 800 light years away, the nebula about 4,000. But they are close together on the sky and when viewed under truly dark, clear skies, the arrangement of dark clouds in the area sure makes them seem connected. The view in binoculars --whether 7x50 or 14x70-- and in widefield telescopes invites a voyage along that dark river.

 

M39 and IC 5146
56x180s (2h 48m)
Canon 6D @ ISO 1600
TMB92SS @ F4.4
Click the pic!

 

The photo shows why it's so difficult to get all the way from the nebula in the lower left to the cluster in the upper right. The river doesn't go. Not quite. If you think you can trace that dark course all the way between these two skymarks (and it's tempting to think you have), you're wrong!

The larger version of that picture begins to suggest the myriad stars in the distance. Take a good look at the photo above, click for the big one, and take a guess at how many stars are in the frame. Go on. A pretty fair estimate is down below.

I slewed to M33 and watched as it cleared the branches of Bird Feeder Tree. High cirrus moved in with moonlight after a couple of hours, but I think I got enough to be worth working up:

 

M33
44x180s (2h 12m)
Canon 6D @ ISO 1600 (cropped)
TMB92SS @ F4.4
Click the pic!

 

...which also says to me that I need a better way of making flats. There's way too much cropping and local correction going on the way I'm doing it now. Still, it works.

So if you're counting red blood cells under a microscope, you use a slide with a ruled square 1 mm on a side. I opened the full-resolution image, defined three squares 100 pixels on a side, counted the stars in each (126, 104, and 160), took the mean (130), and multiplied it out (10,000 pixels counted, 15,100,000 in the photo) to estimate the number of stars in the picture.

Remember your guess? Here's the answer: 196,000 stars.

 

 

 

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.

 

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