M13, by Markus Blauensteiner

A link to the full image is here: full resolution image. 

This M13, by Markus Blauensteiner, struck me as nicely captured and processed.  The image has depth. The sheer number of stars recorded here gives some idea of M13's grandeur.  It's a remarkably clear image at that depth for a focal length of only 500mm.  Markus said, “This was a night with extra good seeing conditions!”  Consistent with the depth and clarity is the detail in the galaxy at the upper left of the image, NGC 6207.  Of course, Markus has also caught IC 4617, in between NGC 6207 and M13.  That's a pretty dim target.  The image is stretched enough to show it clearly but the stretches were controlled so that neither noise nor lack of contrast play a role in the image. The middle of the globular is not overstretched and blown out, as is so easy to do either during capture or processing.  Just very nicely done.

The colors are vivid without being overdone, and the contrast between the blue, white, yellow, and orange stars is not only eye-catching but informative.  Notice the bright orange star left of the cluster?  Now notice the yellow one lower-left of it.  See the nice difference in color?  That's careful color processing.  Markus says he calibrates by B-V index, and it shows.

Exposure times were 20 x 3 minutes for luminance, 1x1 bin; and RGB 8 x 3 minutes, 2x2 bin.  The scope, described below, has a natural focal length of 500mm and an aperture of 150mm.  Capture occurred at the Gahberg in Upper Austria (which looks like a dark, rural place).  Markus generally images from a small, private observatory there.  I believe there is a picture on Markus's website.

The link is to Markus's website is here:

http://www.deeplook.astronomie.at/index.html

He's posted several other images.  Looking them over is good time spent.

I asked Markus about his scope, a  LICHTENKNECKER FLATFIELDKAMERA, and he reported:

The flat-field-camera (FFC) is a quite rare sort of telescope. It is derived from the so called “Schmidt-Camera”, which was used as a Richfield telescope in astrophotography. The problem with the Schmidt-Camera was that the film cassette was placed INSIDE the telescope. So, this wasn`t very practicable with SLRs and digital sensors.

So, in the 80s, a manufacturer named LICHTENKNECKER had the idea to put a secondary mirror in place of the film cassette. The company had the ambition to get a FLAT, fully corrected field for the APS-C format (25,1 mm × 16,7 mm) without the need of extra corrector systems.

The result was a system that looks like a Schmidt-cassegrain, but the secondary mirror is not fixed at the front lens, but about at the half of the tube.

The FFC has NO focuser, the camera and filter wheel are fixed directly on the telescope by a T2-thread.

For focusing, you have to open a little “door” in the tube, grab into the  tube and focus by twisting the secondary mirror.

So it is not possible to focus automatically, you always have to do it by hand.

You may adapt a focuser, but the quality of the picture is better the closer the chip is to the back of the scope. The optimal distance between the scopes back end and the camera chip is 55mm.

If the scope is once collimated (which is quite tricky), you have got a very quick system (f/3.5!!)  which makes beautiful stars up to the corners of DSLR-chips.

Here's a link to my equipment.  The second picture shows the FFC with the little "door" for focusing (right to the telrad):

http://www.deeplook.astronomie.at/Equipment/Ausruestung_Basis_Seite.html

Looks like a fast and precise set of glass.

Finally, I just wanted to note that Markus caught this image with an Atik 16HR, an older camera by today's standards and one that can be picked up quite inexpensively.

Thanks to Markus for the opportunity to blog this image and for the information about the camera, website, and history.