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Member Junky
Posts: 11
Location: 33° 46' 17" N 84° 16' 2" W | Hi all. This is probably the best place to put this question, but I suppose could go into some other categories.
I have an Orion 10" XTI and am having a Tom Osypowski Equatorial platform built for it (and a future 14" Starmaster, assuming the economy turns around :-). The original purpose for the platform was for visual purposes, but I've inevitably gone down the path of "now if I could only get my Canon onto this thing...".
That said, the Orion 10" is obviously not an astrograph. The DSLR won't come into focus at prime focus with the stock focuser. In doing some experimenting though, I've found the ideal draw tube height to bring it into focus (2 1/16") - that's measuring form the outside of the scope to the flange of the T adapter attached to the camera. That height does appear to be achievable with a Moonlight focuser, but just barely.
Now, (and this get's me to the point) am I to understand correctly that the MPCC will extend the focus out approx 10mm? And, using the actual numbers, if, from the outside of my Dob tube to the top of the a draw tube, I need 2 1/16" in order to achieve focus, with a MPCC I'll be able to back the draw tube out to approximately 2.45" (2 1/16" + 10mm)?
I believe the MPCC may be a good choice for the scope for it's primary purpose (coma correction), but I believe this increase in "out-travel" may also be very helpful.
Hopefully that makes sense.
Thanks in advance.
Edited by mfulmer 3/21/2012 1:00 AM
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Member Junky
Posts: 11
Location: 33° 46' 17" N 84° 16' 2" W | Re-reading this post after almost a year, it's a kinda confusing post. So, I thought I would answer it myself.
In short, yes, the MPCC does extend the focal length (and therefore the back focus requirements) around 10mm, allowing my DSLR to come into focus on my 10" Dob, as long as I also changed the stock focuser to a (sweet) Moonlight focuser. Though I do have to use extension tubes for visual observing (not a big deal), because I also went with a 1.5" travel focuser since I didn't want so much of the tube sticking into the OTA.
And the MPCC does a nice job removing the coma.
And, with a autoguiding, I am just beginning to get a decent photo out of it. Attached image of M13 (not quite enough signal, but I got tired...)
I think I'll add a post recounting my "imaging on the dob" experience. I've learned alot and probably wouldn't go about it the same way if I had to do it all over again, but who knows.
Attachments
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 M13.jpg (41KB - 3 downloads)
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Admin
Posts: 5287
  
Location: Marysville,Wa 48.07N-122.21W | Cool stuff!! 
Just curious, what were the specs and camera used for your pic? |
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Member Junky
Posts: 11
Location: 33° 46' 17" N 84° 16' 2" W | Thanks.
This about a 50% crop of the final file (so it really doesn't show all of the benefits of the MPCC).
Original was 12x60s at 400iso, 20 darks, 20 bias stacked with DSS, levels, contrast, brightness adjusted in Photoshop along with a touch of usharp on the cropped image.
Camera is an unmodded Canon 50d with a light pollution filter clipped in (I have lousy light pollution near Atlanta). Subs were shot at full 15 Mpixels.
Edited by mfulmer 3/21/2012 1:00 AM
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New Junky
Posts: 2
Location: Poplarville, MS, USA | Very good. And you found a way to autoguide an equatorial platform? impressive!
Anyway, I'm new here and was going to answer your question, but I see you found out in the year since you posted!. I also observed about a half inch prime focus relocation outward. The MPCC did a good job on coma too with my 8 inch F5 newt. I have some before and after pics somewhere. I also used it with my 8 inch F4 schmidt-newt. Strangely enough, it fixed coma there too. Didn't measure focal position on tht one, though. |
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Expert Junky
Posts: 1947
 
Location: Deming, NM | Wow, 2400+ views and only 4 replies...I think there are a lot of DSLR owners on this forum! |
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Member Junky
Posts: 11
Location: 33° 46' 17" N 84° 16' 2" W | So it would seem. Every time I come back to look at this post, I feel like I find some bit of knowledge was missing when I wrote the original. I think it is more accurate to say the MPCC extends the focal plane back about 10mm. Per the literature, it doesn't extend the focal length - in other words, no change in field of view. As far as the imaging with a DSLR and a dob, let's just say I've moved onto other challenges. It's not the easiest thing to accomplish and having a 16 month old boy seems to reduce the spare time for fiddling. Now it's either the Atlas with a AT8IN (still using the MPCC) or the Astrotrac - enough fiddling can be found in those endeavors. The DSLR part is still there though - imaging with a modded Canon T3i now - much better than the 50D for these purposes (no banding in particular). |
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Elite Junky
Posts: 821
Location: Cincinnati, OH | Have you tried telesopeadapters.com? I recently bought a 40mm lens from them that will hook to the dslr (t2i, t3i) body with a t ring adapter. Hope this helps. Here is the link to the actual site.
http://www.telescopeadapters.com/
BTW I havent tried this with a dslr, but it worked on my video camera. |
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Expert Junky
Posts: 1947
Location: Deming, NM | It is amazing how kids change your hobbies and the time spent on them! The AT8IN is a great scope. My only issue (that I solved by putting the camera and focuser straight down when it is pointed to the north pole) was balancing a really heavy camera! The images are good but focus is quite critical and hard to reach. Still I would recommend it especially for a DSLR. I also like my Sirius mount and an Atlas is just a bit heavier duty! |
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MPCC with my DSLR
