Champagne imaging on a beer budget
By John O'Neill
Like me, many of you have struggled for years to take astro images that make others take notice. You get the "that's nice" comment or, worse no, response at all. Only astro imagers know the time and energy you have put into making that image and have experienced all the times you battled the elements and suffered through the technical problems that plague our hobby. How about all the hours you have put into working on setting up your imaging system, starring at your monitor hoping that your tracking is behaving and then the hours it takes to process just one image. Factor in the cost you have in your equipment and sometimes you wonder is all this worth it.
I have been imaging now for over 17 years. Started with film, then to small chip CCD's to my present camera, a trusted SBIG ST-10XME. Over the years I have had a plethora of scopes, looking for the perfect imaging scope, many came close but for the most part, no cigar.
Well I have some good news!
Recent advanced developments in the manufacturing of telescopes has made it possible to have quality Ritchey-Chretien optics in a Serrurier carbon fiber truss support system at an affordable cost. These scopes have put high quality imaging (the Champagne) in reach for all those on a limited budget (the Beer). I am talking about the new Astro Tech Ritchey-Chretien Truss scopes. There are many advantages this scope has to offer. First the RC mirrors are of top quality using low thermal expansion quartz substrata, the trusses are made of strong non-expandable carbon fiber and the overall construction uses CNC-machined stainless steel and aluminum components. The truss design is superior for imaging in that the primary and secondary mirrors are cooled down at the same time and cool much faster than closed tube scopes (more time to image). The carbon fiber is not affected by temperature variations making it a focus and forget system. The scope also has a fast focal ratio of f8, which means more data in less time. Besides that - the scope just looks cool. The Astro-Tech RC scopes provide a coma-free photographic field that large format CCD and DSLR astro photographers crave, but can't get from conventional reflectors and schmidt-cassegrains. Likewise, as a pure two-mirror system, the RC scopes have a wide spectral response and are totally free from the spurious color that affects the imaging of all but the most costly apochromatic refractors, and it does it with an aperture that dwarfs the light gathering of virtually every commercially-available APO refractor.
The supplied focuser is more than adequate for DSLR use but I recommend a Feathertouch; if using reducers, filter wheels and heavy CCD's. At present these Astro Tech scopes come in 5 configurations:, 10" 12" 14" 16" & 20"Ã‚Â. The 10, 12, and 16 sizes are available now, with the others on the way.
Now here is the really good news. You can buy an Astro Tech 10" RC truss telescope for $2,950. Compare this with other 10" RC scopes costing over $10,000 or more. If you are starting from scratch, with the $7,000 dollar savings, you can buy a nice mount, tripod and CCD camera and start imaging like the pros.
Now that we have a high quality scope we need to make some modifications to it to make it even better. The following is my recommendation but many of you may want to experiment. The scope already has a fast f8 focal ratio but I recommend using an Astro Physics .75X reducer (AP27TVPH). The reducer fits nicely into the barrel of the Feathertouch Focuser and converts your scope to an f6. You will also need to purchase the AP 2" adapter if you plan to use the 2 nosepiece on your CCD camera. A direct connect adapter is also available.
The next thing you will need is the collimating ring that connects directly to the back of the scope. RC's are not forgiving. If they are even slightly out of collimation, you will not get good results. The Collimating ring will center the focusing system (only use a Howie Glatter red or green 2" laser) Place the laser dot inside the circle on the secondary. Once that is accomplished using a good quality reflecting cheshire (Takahashi collimating telescope is best) collimate the secondary to make all the rings concentric. I have found from experience that different focusers will give you different results. The Collimating ring eliminates these variations.
Now that we have a good scope we need a good goto mount and tripod. Due to the variations available in this category and since many of you already have a good mount; I will only mention my setup. I presently have the 12" version of the Astro Tech truss scope. The 12" scope weighs 55lbs (70lbs with camera and guide scope) and requires a larger mount. Mine is the Takahashi EM400 M2. It has a carry capacity of 95lbs. The 10" scope is considerably lighter at 35lbs, so a Tak EM200 or equivalent would be more that adequate. Both of these mounts come with very sturdy tripods. What ever mount you choose, make sure that the capacity is twice the weight of the scope. There is absolutely no substitute for a strong sturdy mount with a quality gearing system.
As I mentioned earlier my camera is an ST-10XME but there are numerous camera's on the market both new and used that will get the job done. Another advantage of the Astro tech RC's design is that you have a large flat field to work with. Some of the newer cameras now have large chips that can take advantage of the RC's large imaging circle.
Attached is a shot I took of M101 in Chiefland, Florida, April 26th with the AT12RCT. As they say "the proof is in the pudding". Hope you like the shots.
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