Just search "ONAG" and there are a lot of hits. The one long thread about it is here:
http://www.iceinspace.com.au/forum/s...highlight=onag
If you go to my page at pbase under equipment there is a picture of the ONAG on my TEC140. And, two of the images there were with the ONAG M83 and M16 FL=1740 mm.
I am using the ONAG with my TEC140 when I increase the focal length with a barlow. I've had pretty good success with it but it may be better suited to an SCT type scope with bigger aperture and plenty of back focus. The refractor has plenty of back focus but there are issues with IR passing through an APO. It works for sure but I've found guiding focus to be more fussy and difficult than I hoped for. I'm told it is fine with an SCT type, but even so the focusing is just by a draw tube. A helical focuser can be added but only if there is enough back focus and ability to move the imaging camera an equal distance away from the ONAG.
On the positive side finding a guide star is quite easy compared to using an OAG! And there are arguments presented on the ONAG website that guiding in the IR can offer benefits. One member here at IIS said he was going to try to prove or disprove those assertions by using an IR filter on an OAG. It would be an interesting experiment that has yet to be carried out. I'm told there are plans to motorize the stage for the guide camera. That will certainly improve the ONAG for remote usage. Another option rather than hunting for guide stars by moving the stage by hand might be to use a much larger chip in a guide camera. I must say I have been contemplating whether the new Skyris 274M with a chip size of 1600x1200 would be a solution? Expensive solution and not sure about drivers and sensitivity compared to the usual guide cameras. For sure with the ONAG one needs a very sensitive guide camera like the ST-1 or Lodestar.
What scope are you contemplating for the ONAG?
Peter
