The AT 8" RC scope has arrived!

OK, the scope came in today. I unpacked it, mounted the Feathertouch focuser, made a top plate for my guide scope, it is set up for my NP101 and I did not want to have to change things every time I changed scopes. So, I have a plate with pairs of mounting holes spaced 1" apart for the guide scope plate. Now I can adjust the balance using the guide scope for a counter weight, this scope and camera setup is quite tail heavy. 8O

I also made a red dot finder mounting bracket from aluminum, so that I could use the WO RDF that I have sitting around. It fits the shoe of the finder bracket that came with the AT8RC. I made it pretty tall so that I can get my head behind it without touching the scope. I had problems with that during alignment.

Best thing, the case I made for the VC200L fits the scope quite nicely! So, I have a nice custom case for it with good foam saddles and padding. There was room for the extra focuser extensions and the finder too.

The scope looks very nice. The focuser plate has tilt screws to allow you to align the focuser. The primary mirror is fixed, so you only collimate the secondary, which worked great using my LaserMax laser, the holographic pattern is perfect for centering the secondary. The artificial star looked good, but I need to look at it on a real star as the amount of out focus required to achieve focus is really long with an EP. So I will dial it in with the camera on Polaris.

The Carbon Fiber tube is very pretty. It has a nice finish, smooth and shiny. The build looks very good, no real cheap parts that I can see. The only plastic is the front OTA cover which is still nice and fits well.

First impressions are favorable. I look forward to trying it out soon.

I thought I would post a few pics to show what the scope looks like on the mount, balanced and ready to find where the focal point is located.

Attached Image:

Did you not like the Vixen 8" cat, or are you just looking for shorter focal length?

Realistically what do you expect this scope to do for you compared with all the others that you have tried?

If you evaluate it in terms of having a perfect figure with the large c.o. of this RC design, you will get the light grasp of approximately a 6" to 6.5" clear unobstructed aperture. You can expect the resolution under normal atmospheric (i.e. good seeing but not super great) to be the equivalent of a 4" clear aperture.

Although the 8" aperture has a theoretical resolution of 0.57 arc sec, I would expect the star FWHM sizes to fall between 2.5 and 3.5 arc sec at best. It will be interesting to see what your results are.

I see RCs as being of value in the 12" and larger sizes. Reason is that the large central obstructions needed for flat fields and ease of construction significantly reduce their ability to produce tight stars due to atmospheric blurring of the first diffraction ring. Above 12" the size of the Airy disc with first diffraction ring approaches the minimum achievable on earth in our atmosphere for deep sky exposures (around 1 arc sec). So for these sizes, it matters little how large the obstruction becomes, and some fast scopes have over 60% obstruction by diameter. For smaller aperture you are not as limited by the atmosphere, but you are always fighting sharpness. This is where an unobstructed scope, or one with very small obstruction will produce the best results.

Here is an example of 10" RC scope with 50% obstruction. Resolution 3.7 arc sec: http://astrosurf.com/papilain/posts/M%2027%20au%20RC%20,%20juin%202009.3.jpg