From: "Tim" <tjp314@pacbell.net>

Date: June 25, 2007 8:29:04 AM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Got my Cass "running"

A tad off topic, but I was so excited that I had to post...

Friday, I bought a lasermax holographic collimator on astromart.  I

took it home, read the directions, and within about an hour (most of

which I spent figuring out the geometries involved) I had my 12.5"

f/23 Cassegrain pretty close to collimated.  

Since you start with the focuser, then the secondary, and finally the

primary, the only tweaking I needed to do on the sky was of the

primary.  This is a good thing, because from the NJP mount, the top

end of the tube is about 7 feet off the ground when pointed even into

the lower sky.  

In spite of the long focal length, I was quickly able to center

Jupiter in a 28mm RKE.  The N limb was pretty soft, so I tweaked the

primary mirror adjustment screws on the back of the cell and

recentered with the hand control, until the limb and moons were "flare

free".

I used the flea2 to grab a few videos, but the seeing wasn't up to

snuff for posting any results.  The flea2 offers a terrific image

scale without a barlow.

Only remaining drawback to the Cass is that it's pretty scary putting

it on and removing it from the saddle plate, as it is about head

height.  The only solutions I can think of are permanently mounting it

inside an observatory or putting the NJP mount on something like a

pier-tech tri-pier, and either option is going to cost a few $K.

So for the time being, I'll probably continue to favor my C-8 and C-9.25.

-Tim.