Originally, I used a ST7E camera with a CFW8 filter wheel and an AO7 guider. However, if you want to use a f/6.3 focal reduced with this combo you'll get severe abberations due to the long optical pathlength introduced by the AO7 and the CFW8. To solve this problem I developed a special means of mounting a filter inside the AO7, very close the entrance of the camera. This solution permits a proper spacing of the focal reducer and reduces the size and weight of the imaging assembly.
The filter adapter is square and has four holes for screws that go through the AO7 camera bracket and into the threaded holes on the camera front plate.
The adapter has a 1.25 inch threaded hole in a central depression for mounting the filter so that it is positioned as close as possible to the CCD chip and away from the AO7 mirror:
After mounting a filter the AO7 head is attatched in the usual way:
Here's how the complete imaging assembly looks when used with a f/6.3 focal reducer on my 8" SCT (the aluminum adapter on the side of the camera is used for wide-field imaging, i.e. not related to this discussion):
The main drawback of this method is that one looses the ability to easily change filters during a single night. However, this drawback can be compensated for simply by imaging several objects with the chosen filter during one night and then using another filter next time to gradually get all the color channels. I'm the patient type of person, so this doesn't bother me so much; if you want a color image from a single nights work then this method is not advisable.
Note, from the picture above, that the imaging assembly is attached to the SCT via a Finger Lakes DF-2 focusser. Doing this also
required a special set of adapters which are described here.
Here's my mechanical mating page where you can see more examples of custom made adapters.
Comments greatly appreciated! (mikael@leif.org)
