Posts Tagged ‘m42’

Barnard’s Loop

March 7, 2016 1 comment

When I was a kid, Barnard’s Loop was something that I saw on star charts, but it seemed so hopelessly dim, I never expected to actually see it.  And even when I started CCD imaging, it was still a somewhat elusive object: too large to capture unless you used a wide-angle lens, and even then you wouldn’t get decent resolution.  But the combination of a full-frame sensor and a very fast telephoto lens turns out to frame it nicely.

This image obviously has more in it than Barnard’s Loop.  M42/43, the Flame Nebula, the Horsehead Nebula, and M78 all sit nestled within the Loop.  But more interestingly for me, you can start to see the overall Orion Molecular Cloud complex in there: all the dim tendrils that connect each of these objects, some glowing, some blocking the view of the glow.  I regret stopping the lens down to f/2.8 now, as perhaps I would have captured more of the overall cloud that way.  I’d go back and retake the shot if I weren’t having so much fun with this new lens on other targets (and if I hadn’t spent five hours processing this one).  But I’ll consider this a success, as it’s another childhood dream accomplished.

Barnards_Loop_FINAL_50 percent

(This image is reduced to 25% of full size, as the 6D’s output is over 20 megapixels.)

Image data:

  • Exposures: 81×2 min at ISO800 – total exposure time:  2h 42m
  • Telescope: Samyang 135 mm f/2 lens at f/2.8 (reviewed here)
  • Camera: Canon 6D (modified) with Astronomik CLS clip-in filter
  • Mount: Takahashi EM200
  • Guiding: Orion Starshoot, guided using PHD2
  • Conditions:  fair transparency, calm winds
  • Processing: DeepSkyStacker -> PixInsight -> Photoshop
  • Date: Feb 28, 2016



Evaluating the full-frame performance of the William Optics Star71

January 23, 2016 1 comment

I’m excited to start imaging with my new Canon EOS 6D.  Having a full-frame chip will allow some very widefield shots that would require mosaics with a 4/3 sensor, like the KAF-8300 cameras I use most of the time.  Since conditions were less than ideal, I used the first couple of nights out to run some tests.  First up is a test of the 6D with the Star71.

The obvious target:  M42.  Below is a very brief exposure (17 min total, in 15s subexposures).

M42 17 min

That is a very wide field.  5.8 x 3.8 degrees.  I didn’t even intend to include the Horsehead Nebula when I pointed the mount at M42, but the field is so wide, I accidentally captured most of it.

Are the stars sharp out to the corners?  Yes.  The image below is a crop of 100 pixel squares from each corner of the above image.  No star reduction was done in any of these images. The performance is really good.  A little distortion on the right side, but quite tolerable.


What about vignetting?  I estimate less than 10% light falloff between the center and the corners from the flat frame analysis below (the image is highly stretched to reveal vignetting).  Note that there is a dark band across the bottom.  This was consistent across my images, and I’m not sure of the source, but I suspect something to do with dcraw (this image was imported into PixInsight, which calls dcraw for conversion).  DeepSkyStacker seemed to have trouble with some of the 6D’s images too.


The 6D and Star71 are a good pair, and it’s nice to have a DSLR again for simple one-shot color imaging, especially for wide fields.  Once I get some adapters, I look forward to running the same test with the Takahashi FSQ-106ED.

M42 Orion Nebula in Narrowband

February 5, 2012 1 comment

Some weeks, everything goes wrong.

To quench the never-ending thirst for more concentrated photons, I sold my previous scopes so I could trade up to two high-end, fast refractors:  a Borg 77EDII at f/4.3 and a TeleVue NP101 at f/5.3.  I seized rare opportunities to get both used and at great prices.  Only if a Tak FSQ came my way would I have room to improve in the short focal length department.  But with all new scopes come new problems.  The NP101 needed rings to sit on my mount, and an adapter for my stepper motor to control the focuser — $200 and two weeks.  The Borg needed precise spacers to fit my camera, and I’m still working out other kinks — $100 and at least two weeks.

Now I find out that my SBIG’s cooling is not functioning correctly, so basically every piece of imaging equipment I have is “in the shop,” in one way or another.  But sometimes even with adversity, something fun or beautiful slips through.  I took the NP101 out on a hazy, moonlit night because I really wanted to start working with narrowband data.  The obvious, reliable target sat just above my roof:  M42.

The world needs another image of M42 like a hole in the head, but I couldn’t resist.  Before it set, I grabbed two hours of narrowband exposures, and here is my very first narrowband image:

Stats:  SBIG ST8300M, Baader filters, TeleVue NP101 on a CGEM

6x300s H-alpha, 10x300s O-III, 12x300s S-II, 25 flats, NO darks

Stacked in DSS, process in Photoshop CS3.

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