This week I received the Astronomy Technologies 8″ Ritchey-Chretien: the AT8RC. It is a pretty popular telescope and very liked by Astro Imagers. This telescope is produced by GSO (Taiwan) and carried by several popular brands. In the US both Astronomy Technologies and Orion sold these telescopes under their brand. I don’t think Orion carried the Carbon Fiber version that I am presenting here, though. And it seems that they are no longer carrying the Steel tube either – at this time they only have the 10″ Steel tube RC left.
The AT8RC comes with a 3″ focuser, a set of three extension tubes and two dovetail plates: one Vixen and one Losmandy D-plate. I got from ADM accessories a replacement plate for the Vixen so that I can use the hardware that I already have here to install a guide scope.
In order to check for and correct collimation, I decided to trust the instructions and only get a Cheshire eyepiece for now. According to these instructions, it is enough to align both secondary and primary mirrors. The instructions also say that it is usually not needed to make any correction to the primary mirror. However, I found a lot of people online claiming they had to readjust both mirrors. So far I’ve only checked collimation with the Cheshire but it is spot on. I have not checked collimation under actual stars yet but I plan on making sure the diffraction pattern is what it should be. I am either very lucky or maybe it is slightly off but not enough to detect it with the Cheshire.
As I said above, I replaced the Vixen dovetail by a D-plate dovetail from ADM accessories. I have some D-plate shows that I will install on my AT65EDQ that I will be using as a guide scope. I originally wanted to go directly to an off-axis guider but unless the AT65EDQ can’t pull it off I will wait until I start using a CCD so that I don’t have to buy a new off axis guider.
Other than that, I can say that it is an impressive OTA. It’s heavier than it looks. These telescopes have 90% of their weight at the back. The ADM plate will be used to secure the telescope on the mount. It’s slightly longer (about 1″) than the Astro-Tech D-plate and protrude slightly at the front and back. With some tweaking I should even be able to have it protrude 2″ at the back. This is probably a good idea to give a little more room for DEC balancing. But with the AT65EDQ installed on the top-front, I should be able to balance in DEC without trouble.
I installed an Astro-Tech Red Dot Finder (RDF) in the show that is already at the base of the tube. I wish I could use it on the AT65EDQ but it’s too small – with top and bottom D-plates there is no clearance for the RDF. I found it more efficient than an eyepiece to build a model. I didn’t like that I had to install the camera on the scope to balance the setup, then replace it by an eyepiece for the model and then replace it again to put the camera back in place.