Q: focus problem - collimation or other causes?

My first effort at collimating a Newt produced unexpected
symptoms. They might be unrelated to collimation. I've
tried to do my homework, but I don't think I've found a
description of the same thing I'm seeing.

This is a club scope (meaning my eyes are the fanciest
collimation accessories I've got). It's an Orion Skyview,
6" f5. Before collimating, I saw asymmetrical comas.
So in the daytime I followed the procedure in Orion's user manual.
When I was finished everything looked as the manual says it should
by eye.

Then in use at night, well cooled, with good seeing,
I get very good focus at 20x, stars look slightly defocused
at 30x, and at 60x the best focus I can achieve is fuzzy
disks. The disks are nice symmetrical circles. I'm looking
at stars in the center of the field of view.

I don't think I had this symptom before collimating,
though the coma artifacts might have hidden a focus problem.
The eyepieces are decent quality from a variety of
manufacturers. The same eyepieces give great focus in a
different (but 8" aperture) telescope.

I plan to check that I get the same results on a different
night, but it looks like clouds for some nights to come.
What should I read to make progress? Thanks.

--
Glenn Holliday

Visit this site:

www.etnaastros.com Under "Of Interest" there is the reknown article on
collimation without tools. Yes, this sounds like a collimation issue.

Doink


"Glenn Holliday" wrote in message
...
My first effort at collimating a Newt produced unexpected
symptoms. They might be unrelated to collimation. I've
tried to do my homework, but I don't think I've found a
description of the same thing I'm seeing.

This is a club scope (meaning my eyes are the fanciest
collimation accessories I've got). It's an Orion Skyview,
6" f5. Before collimating, I saw asymmetrical comas.
So in the daytime I followed the procedure in Orion's user manual.
When I was finished everything looked as the manual says it should
by eye.

Then in use at night, well cooled, with good seeing,
I get very good focus at 20x, stars look slightly defocused
at 30x, and at 60x the best focus I can achieve is fuzzy
disks. The disks are nice symmetrical circles. I'm looking
at stars in the center of the field of view.

I don't think I had this symptom before collimating,
though the coma artifacts might have hidden a focus problem.
The eyepieces are decent quality from a variety of
manufacturers. The same eyepieces give great focus in a
different (but 8" aperture) telescope.

I plan to check that I get the same results on a different
night, but it looks like clouds for some nights to come.
What should I read to make progress? Thanks.

--
Glenn Holliday

Doink wrote:

"Glenn Holliday" wrote in message
...
My first effort at collimating a Newt produced unexpected
symptoms. They might be unrelated to collimation. I've
tried to do my homework, but I don't think I've found a
description of the same thing I'm seeing.

Visit this site:

www.etnaastros.com Under "Of Interest" there is the reknown article on
collimation without tools. Yes, this sounds like a collimation issue.

Thanks. I found that article. I guess I'll do another couple of
iterations of the procedure.

--
Glenn Holliday

You can make a real simple tool for alinment, just get a kodak 35mm film can
( plastic ) and drill a small hole in the dead center of the top, then cut
out the bottem, dot the main mirror and you've got a cheap tool for checking
the alinement.


--

The Lone Sidewalk Astronomer of Rosamond
Telescope Buyers FAQ
http://home.inreach.com/starlord
Astronomy Net Online Gift Shop
http://www.cafepress.com/astronomy_net
In Garden Online Gift Shop
http://www.cafepress.com/ingarden
Blast Off Online Gift Shop
http://www.cafepress.com/starlords




"Glenn Holliday" wrote in message
...
Doink wrote:

"Glenn Holliday" wrote in message
...
My first effort at collimating a Newt produced unexpected
symptoms. They might be unrelated to collimation. I've
tried to do my homework, but I don't think I've found a
description of the same thing I'm seeing.

Visit this site:

www.etnaastros.com Under "Of Interest" there is the reknown article
on
collimation without tools. Yes, this sounds like a collimation issue.

Thanks. I found that article. I guess I'll do another couple of
iterations of the procedure.

--
Glenn Holliday