Quote:
Originally Posted by Paul Haese
Stuart,
the focusor on this would not screw onto an SCT or vice versa. The thread is 90x1mm pitch.
The scope is on the an EM400 mount, so I got the good mount covered. I just need to get pempro onto the polar alignment which was done with my wide field scope. I did not have any guiding because I am waiting on guide rings for the vixen plate.
Forgive me, but the ACF is not an alternative for several reasons. Corrector plates don't make for long imaging runs (dew builds up and using a dew heater cancels out the chance of ultra sharp images, which is afterall the object of an RC scope; an ACF is not an RC), cool down time is longer in a closed tube and often cannot be controlled without active measures being taken and both tubes require better focusors to maintain optical alignment.
Besides I have never been a real fan of fork mounts. When I owned my LX200 I found that flexure was a major problem and using those wedges was just a total pain for precision polar alignment.
I think these RC scopes have the potential for great images. The scopes work straight of the box but need refining like any telescope one buys.
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90mm is pretty close to the rear thread on the OTA of mine, when you take off the SCT threaded bit, I'd ask Astro-physics if they're planning on making an adapter to the AP2.7" threaded stuff, that way you'll definitely get a nice focusser.
A decent dewshield fixes the dewing problems on a small SCT, similar to the RC actually, you've got a dewshield essentially the length of the main tube, should work pretty well. I don't understand the comment about the corrector temperature and image sharpness, can you explain further, off-line if you want.
I don't have too many problems with cooldown, the thing is permanently bolted to the pier in the observatory. I'll turn the fans on before I observe or image to help with the day/night transition, but it's not as bad as taking from a warm house to a cold outside. Watch out for that big primary mirror you've got there, it's got a large thermal mass and will also take quite a while to cool down properly. If you can clean the mirror, I'd be installing fans to help things along.
Yeah, fork mounts aren't the best for imaging, but that's why I was comparing the scope to the OTA versions of the ACF scopes. I'll get a decent GEM one day...
Cheers
Stuart