My AT8RC came with the stock Astronomy Technologies focuser. It is known to somewhat under-perform. Mine was no exception but I have to admit it was quite a bit better than what I was expecting (considering the bad comment I had read about it).
There is not a great choice when it comes to after market focusers (especially for this telescope). MoonLite has good reputation and a lot of 8″ RC (from GSO) owners have been satisfied with their MoonLite CS SCT Focusers. To be honnest at a base price of $345 I didn’t feel like I was taking any risk.
I went with: the Black Anodize finish, CS Flange with RC 8″ Thread, the 1.5″ Travel Brass Compression Ring Drawtube and the 1.5″ Dual Rate, Tri-Knob with Shaft Lock (+ $125). My focuser was assembled and shipped within 24 hours and it arrived 48 hours later.
Here are some of the difference I’ve noted (so far):
- Cosmetically, the product quality is just fantastic. It looks so much better than the stock focuser.
- Mechanically, it is perfect. All parts are well adjusted. Knobs spin perfectly and without tight spots. The low speed knob on the AT focuser is really difficult to use. As you start turning it, there is about 1/16 of a turn where nothing happens: the draw tube doesn’t move at all. It really made precision focusing difficult. While I haven’t tried focusing with the MoonLite yet, I already know the low speed knob is highly precise.
- Another nice feature on the MoonLite is the fact you can rotate the whole focuser assembly by just loosening one thumb screw. On the AT, you would have to loosen the whole focuser assembly from the rear cell of the telescope. Once loosened enough, you would rotate the focuser and retighten it in position. If you are doing this in your garage that’s OK but if your telescope is already installed on your mount, balanced, if you’ve done your polar alignment, modeling, well then there is chance you will have to do some of these things again as it’s not always easy to loosen this large compression ring without holding the rear cell really really tight to make sure it doesn’t move.
- The draw tube I chose for my MoonLite focuser has three adjusting screws and a brass compression ring. I’ve installed a few 2″ nose pieces in there: they fit slightly better than with the AT which already was a pretty decent fit; and the third adjusting screws do help holding the nose piece in place. This should prove even more beneficial when I install my imaging gear.
- Both focusers came with a 2″ to 1.5″ adapters. I rarely use them (other than for plugging the opening).
And now, I can’t wait to test it under the stars.