By Dr Carl Tubbs - GRAS Member - USA
This fall brings dead leaves, raking, crisp evenings and more clear skies, and amongst the fall chores I was curious to see how my little home mount stacked up ( no pun intended) against the bigger guns at GRAS.
I therefore performed a very non-randomized high end non-funded pseudoscientific prospective trial to see how my M706 with ST-2000 and Losmandy G11 mount would compare to the GRAS G11, a 20 inch Planewave CDK with FLI camera in New Mexico.
Obviously, I could not blind myself as to processing the images, because they were certainly very different to begin with, and wearing a blindfold while processing just did not seem to work out very well either. But in the end I was pretty curious to see just what some of the differences were in using iTN as compared to my home system, and chose a dimmer than usual image as a stretch for the home equipment. IC 243, a spiral galaxy in Camelopardalis, seemed a reasonable target. It has a respectable size and internal detail with a surface brightness listed as 14.9 with a blue magnitude of 9.1, and is not something that one sees imaged routinely.
The home system has been tracking well after upgrading, and the Intes is a respectable flat field astrograph. With good balancing, alignment and guiding at home, I was able to collect a number of 900 and 600 second subs, and attempted to use days when we had the best skies, (which at this time of year are “average” at best) and catch the object at a low air mass.
Logging in to G11 can sometime be a challenge, because it is quite a popular scope for science and photographic work. For GRAS imaging, I decided to use what I felt was best as far as binning and image time, to balance cost of equipment use with outcome.
Below, you can see the two final images. They are at slightly different scales, but have been approximated as far as position, for easier comparison. Being only a moderately experienced processor, I did not bother to try to balance the color scale or brightness between the separate images, but did attempt to balance them in these sorts of ways as best I could, and used similar techniques to bring out contrast, sharpen, and to control noise.
Intes M706 and SBIG ST-2000 under suburban skies. 600 sec L and 900 sec RGB, Bin 2x2. LRGB 90:60:60:60 minutes. Fair central detail, good overall color, and some nice data in peripheral arms.
G-11. 600 Second subs, Bin 2x2. LRGB 140:90:90:90 minutes.
No Surprises. The initial things that struck me was the detail in the GRAS G11 image overall, with nice luminance detail in the low SN data in the periphery of the galaxy, and fairly strong color as well in those low SN areas. There even appears to be a soft arm of one spiral heading off into the lower left corner, almost touching a small galaxy at 7:00.
Processing the detail and sharpening in the higher SN ranges becomes much easier, and in this image, these could actually be toned down somewhat in order to better balance out the overall brightness- the core area is wonderfully bright.
It is interesting how well the human brain adapts to image quality and to colors- every time I look at the lower end resolution image, I am taken by how much I like the detail- unless
I again look at the G11 image in comparison. The star colors in the G11 image are also brighter and crisper, despite enhancing this in the Intes image. Obviously, the Intes should have collected more photos to make a more exact comparison as far as image timing, but the overall decrease in noise in further doubling the Intes exposure times would not amount to all that much help.
Well, GRAS is better, in this case, of course. If you can keep a secret, I was sort of expecting that to begin with. So why bother doing a comparison?
For me, such an exercise is motivational in attempting to tweak the home system to see if I can get a better image out of it next time.
I see things on my GRAS images that I want to go back and try to study in more detail with the smaller home system, and also use my home system to help select objects for high end quality images using GRAS.
It seems to be a nice marriage. And when I am too annoyed with the local weather or too tired to set up a home run, there’s usually GRAS sky that’s clear and ready to use.
Of course, if you don’t have a home telescope, you can remove yourself from those related uncertainties in data collection and get right to high end imaging!
Carl Tubbs - USA
See Also Carl’s guide to One Shot Color Imaging
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The GRAS Telescope Network ihas undergone some major changes and upgrades inline with our current Southern Observatory initiative and its place in international remote astronomy.
Several new telescopes are being prepared to be added to your network soon (G18 Spain and G21 New Mexico) along with more to be based in Australia once our new location is completed. (March of 2012). Telescope, Mounts & CCD hardware orders have already been placed.
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