Celestron CPC800 - First Light - Part 2

I have had the opportunity to take my new Celestron scope out a couple of times since my last blog. Once out to my local dark site and another last night in my back yard. The focus of both of these outings was to assess the optics of the scope.

The first task was to determine how well the scope was collminated.  This hast to be done before assessing the quality of the optics. This is pretty easy as you just find a bright star and focus on it. You then adjust the focus inside and then outside and see how the shape of the star changes. It should grow from a point into a perfect circle on both sides of the focus. If the shape is more elliptical and shifts on either side of focus then the scope is not collminated. I pleased to report that Calvin, as my daughter named the scope, is very well collminated.

Assessing the quality of the optics is done by performing a "Star Test."  I am the first to admit that I am not an expert at this technique, but it is pretty simple to perform. Here is a link to a pretty good description of how to perform this test.

Basically all you do is de-focus a star using a fairly high power lens, say 100-200x,  until you can see the diffraction rings appear. You make a mental picture of the rings and then de-focus the star on the other side of the focus. Ideally the ring pattern should be identical. The rings should all be perfect circles and well defined. The brightest rings should appear at the same spot in both the inside and outside of the focus tests. The star test for Calvin went extremely well. There were no signs of any astigmatisms or spherical aberrations.

I spent the remainder of the evening out at the dark site ripping off objects on my H400 list. I was able to log about 30 objects in the two hours I was out there.  Here are some highlights:

Arp 135 - mag 9.6 galaxy in Perseus. At 163x the galaxy appeares oriented in E-W direction, core appears non-stellar


Arp 225- mag 11.0 galaxy in Cam. At 127x it is a very faint smudge, no structure visible. Too low in the northern sky to make out anything to note.

NGC 40 - mag 10.7 planetary nebula in Cep. At 127x the central star appears to be visible. It really tends to pop out more with averted vision.

NGC 1342 - mag 7.2  open cluster in Per. At 127x there are about a dozen brighter stars, 2 dozen fainter ones, not well concentrated.

NGC 1502 - mag 4.1 open cluster in Cam.  At 127x the OC is dominated by a binary in center, it looks like two eyes staring back, 30 fainter stars, loose concentration.

NCG 6803 - mag 9.7 open cluster in Cyg. At 127x the OC forms a cross with 5 brighter stars in a line with fainter stars crossing at a right angle. Almost looks like a miniature Cygnus.

NGC 6885 - mag 5.7 open cluster in Vul. At 78x the OC is dominated by 1 britght star surrounded by 30 fainter stars. Slight mottled look on one side.

NGC 6910 - mag 7.3 open cluster close to the heart of Cygnus. At 127x the OC is dominated by 2 brighter stars, one of which is a nice gold color, about 10 fainter stars strung between the two brighter stars. Fairly well concentrated.

Well, the next blog will be after the new year and I will be taking an assessment of my observing activities of 2011, until then,

Clear skies,
rw