Back to Home

ATM Forum Message

Forums: Atm · Astrophotography · Blackholes · Blackholes2 · CCD · Celestron · Domes · Education
Eyepieces · Meade · Misc. · God and Science · SETI · Software · UFO · XEphem
RSS Button

Home | Discussion Forums | Amateur Telescope Making | Post

Be the first pioneers to continue the Astronomy Discussions at our new Astronomy meeting place...
The Space and Astronomy Agora
Low-Profile Focusser Problem

Forum List | Follow Ups | Post Message | Back to Thread Topics
Posted by on July 16, 2000 18:04:00 UTC

Hi Everybody -

I`ve have enjoyed reading the
messages on this list. Some pretty knowledgeable folks out there. I`m fairly new at serious astronomy, though I`ve had a long-standing interest. I wonder if someone out
there could help me with a problem that I have.

A couple years ago I bought a Meade Starfinder Equatorial scope, 8-inch mirror, f/5.6. I found the plastic focuser did not provide very fine focussing, seemed kind of sticky when focussing, and so I bought a JMI low-profile focusser. After installing it, I found that I could not get
good images.

So I reset the focusser and spider not quite an inch forward (that`s all the space I had on the tube) and now with my 26-mm. eyepiece (46X) I
can get fairly good images (though there seems to be a touch of coma). But I have to use a one-inch extender to get images with that eyepiece. When I switch to the 9.7-mm eyepiece (125X), again using
the extender, I get degraded images.

I understand they will be dimmer with less contrast. But they are also less precise: more smushy, diffuse, and sparkly (they do not show the clear diffraction patterns that I have read about). And the image degradation is worsened when I insert a 2X Barlow (which requires that I remove the extender). I am unable to separate the double-double in Epsilon Lyrae, which this
scope should be able to do, because of the image degradation.

As far as I can tell, the scope is precisely collimated, following the instructions in the collimation manual by Menard and D`Auria.
But I sense that the focal planes of the eyepiece and mirrors are not matching precisely as they should, and I suspect that I may need to move the eyepiece and spider/secondary mirror still farther forward. But there is not room on the current tube, so to do this I will have to buy a longer sonotube of the same width. But it seems hard to find them.

Does any body out there have any experience with this kind of problem, any suggestions on how to solve it without going to a longer tube? Or is that really going to be necessary?

Many thanks for your ideas.

Dennis Palmini
Stevens Point, Wisconsin

Follow Ups:

Login to Post
Additional Information
About Astronomy Net | Advertise on Astronomy Net | Contact & Comments | Privacy Policy
Unless otherwise specified, web site content Copyright 1994-2024 John Huggins All Rights Reserved
Forum posts are Copyright their authors as specified in the heading above the post.
"dbHTML," "AstroGuide," "ASTRONOMY.NET" & "VA.NET"
are trademarks of John Huggins