For a few months, I had been searching for an ultra-short focal length telescope with a fairly fast focal ratio to go with it. Unfortunately, a QSI 660wsg-8 CCD camera has a backfocus of 50.4mm, which exceeds the maximum backfocus distance supported by standard Canon or Nikon DSLR lenses. I sent an e-mail off to Ted Ishikawa of Borg telescopes and as usual, he replied in mere minutes with information - the Borg 45EDII. As per Ted's recommendation, this is Borg's smallest diameter telescope meant for astrophotography in terms of fast focal ratio, coma-free imaging and good CCD sensor illumination.
The Borg 45EDII is paired with Borg's 7870 focal reducer, which in turn produces a focal length of just 228mm at f/5. This produces a field of view with my CCD camera of 3.113 x 2.491 degrees, which is an area of sky roughly 2.676x the area of sky visible through my Borg 77EDII. The small aperture is not actually a problem for sensor illumination, as the Sony ICX694 is a small sensor and add to it the fact that both the 77EDII and 45EDII are meant to cover a full-frame 35mm sensor.
Ted e-mailed me the above image to show me what a Borg 45EDII with a FeatherTouch focuser looks like. The odd configuration of tubes is present purely to allow the use of regular Borg tube bands for clamping on to a dovetail bar. I wanted the FeatherTouch focuser as I am particularly keen these focusers, and ordered a third Lakeside Motorised Focuser motor to attach to it for autofocusing. Good news is that I was able to save money by not ordering the Borg 7870 focal reducer, since I already own one for my Borg 77EDII.
Above is a demonstration of how much more area of sky is captured by the 45EDII compared to the 77EDII. Essentially the same target captured with two mosaic segments as opposed to six. This will no doubt be my constellation hunter.