I figured out how to collimate (or align?) the optics of my Celestron 114GT
after I thought I knew better than the factory how to do it. I goofed it up.
Then I had to redo every part of the alignment.
The biggest factor is, of course, the path of light through the focuser tube.
This is because that is where the on-board Barlow lens is. You have to make
sure the light passes directly through the center of the lens, and perpendicular
to it no matter where you position it by doing the focusing (moving it in and
out).
I did the following:
Removed the main mirror.
Put cross-hair threads across back of tube, crossing at mechanical center of the
main tube.
Removed the secondary holder.
Passed a laser beam through the center hole in the spider, from behind the main
tube, past the crosshairs, along the mechanical axis of the main tube.
Unscrewed the barlow lens from focuser tube.
Inserted the secondary, adjusted at a true 45* angle. This reflects the laser
beam up through the focuser.
Adjusted the beam, using the tilt and rotation of the secondary, so that it
passes through the focuser and it doesn't move side to side as the focus is
changed. I use a plastic film can with lid, pair of holes in center of bottom
and cap.
Fixed the screws tight on the secondary.
Removed cross threads from back of main tube, put center mark (white paper
donut) on main mirror, put main mirror back in tube, tightened cell screws to
tube.
Put laser in the focuser, shining down to secondary, and it shines to the center
of the main mirror. Any side-to-side adjustment of the main mirror's center
should be done with shims inside the main tube, or in the main mirror cell, not
the secondary adjustment screws.
Adjusted the main mirror tilt screws (collimation screws) at back of cell so
that laser beam goes back up to center of secondary, and into the focuser tube,
through its center. Tightened jamming screws in back of cell.
Put barlow lens back in focuser tube.
Went out on a very calm night to see if star test was off. It was close to
being concentric rings at very high power (300X). If off a little, slew scope
in direction where the rings are concentric around central star image. Then
adjust main mirror collimation screws so that image of star goes back to center
of field. Repeat if not done far enough yet. You should not have to move more
than two fields of view at 300X.
The only degrade of perfect Airy disk image will be 6 faint spikes from spider
bars, and 3 small wings evenly spaced around central star instead of complete
rings.
I can now use up to 80X per inch (325X) of the 114GT on bright objects like the
Moon and planets. I have tried a 3X Televue barlow and a quality Televue Nagler
7mm eye lens on planets and bright stars. That is an effective 2.3mm fl eye
lens, and giving 410X magnification with the 1000mm EFL main tube optics. No
matter where I run the focus tube in and out, there is no change on the image.
While the optics are not as good as a true 1000mm newtonian with no barlow, the
500mm spherical mirror and internal barlow is a good combination and low and
medium powers.
The alignment to the stars is a bit more of a trial, as that depends upon the
motors, gears, setup of the computer information correctly.
I can get it on most nights to be quite close in the finder, and within the
field of view of a low power eye lens when I slew half way across the sky. I
think that is about the best that can be expected without paying five times as
much as I did ($190 at Costco in 09/2003).
I can suggest a good used or a new Meade ETX125-EC or an even larger Newtonian
on an LX75 mount if you wish to spend that much.

--- In Meade-Uncensored@yahoogroups.com, "hankellis@..." <hankellis@...> wrote:
>
> What you advise a newbie with a budget of 1,000 to 1,500? New or used, I need
it to be able to easily find things. I'm sick of trying to align this Celestron
114gt.
>