"Doink" wrote in message
...
OK Jan, I'll give it another try tomorrow. I wasn't sure how small
these
little discs were supposed to be---I was expecting more definition and
larger circles.

Is a Cheshire the best tool for collimation? Is it worth buying a good
one
or is the concept so simple it doesn't matter---like the laser exiting a
round piece of paper....

I haven't seen one of the Cheshires like you have... Mine is a Tectron
unit. I wouldn't necessarily say one is better than the other. If yours
has a good reflective surface, and is well centered, it doesn't have to be
too fancy... The Tectron Cheshire isn't a mirror surface; it is just a
polished aluminum surface on the angled face, and that works just fine. I
do like the fact that their units ARE well machined, and fit the focuser
or adapters tightly, with no slop.

The Cheshire is a handy tool, for many different scopes... For folks with
a variety of scopes, I recommend the whole three piece Tectron kit, which
also comes with a good booklet on collimating a variety of different
scopes... However, if all your scopes are refractors, you won't need the
other pieces, and the Cheshire you have may well be all you need... On
the other hand, if you have any reflectors, the Tectron kit may prove
quite useful to you...

--
Jan Owen

To reach me directly, remove the Z, if one appears in my e-mail address...
Latitude: 33.6
Longitude: -112.3

Doink
"Jan Owen" wrote in message
news:A2F4f.17310$fE5.3690@fed1read06...

"Doink" wrote in message
...
Ok Jan, I saw those dots and they were not stacked....however, if I
move
the
light source, one of the dots moves and I can get it on top of the
other.
What's the control? This is a crappy, plastic cheshire---probably
matters.
I just came in from star testing. Stars "flare" a bit but that could
be
seeing---and it's early out here ---

Help appreciated...
Doink

Well, I can't totally replicate your situation tonight... But I did
put
my Tectron Cheshire in my Apo just now. Unfortunately, it is in the
dining room, and the light in there is a chandelier; not a real good
light
source... Still, what you are looking for are anuluses. One circle
inside another... With my Apo, this is well defined and perfectly
centered one inside the other. I can move the OTA around and cause
some
stray reflections from some of the other light bulbs in the chandelier
to
move around in there, but the annuli are well defined and do not
move...
Unfortunately, I can't see inside your tube to know if you are seeing
stray reflections like I described, or whether the anuluses are not
concentric...

Look at your brightest dot, or disc. And look real close at it like
you
were looking for subtle detail on Jupiter... Is it maybe more than
one
dot perfectly aligned with another, with a little ring all the way
around
concentrically separating the two discs one on top of the other? Or
is
there only one disc? I would either expect there to be two perfectly
aligned discs, one a little smaller than the other, precisely centered
on
each other, with their edgesm by definition concentric. If not, then
I
would expect there to be two well defined discs that are NOT aligned,
and
if that is the case, adjustment is needed. I would expect that if you
move the light source, and one of the discs moves, you may be seeing a
stray reflection, or the Cheshire is not aligned with the light source
in
the first place...

"Jan Owen" wrote in message
news:YzE4f.17241$fE5.14902@fed1read06...
"Doink" wrote in message
...
OK, since I started that mess about refractors, I thought I ought
to
check
collimation on the 6" Celestron and the Antares f/6.5.

I have a cheshire eyepiece that came with the Orion refractor...

I put it in the focuser and shine some light in it from the side
but
I
see
only 1 tiny point (two points, very small actually) which the
documentation
says to ignore. I do not see a ring or a set of concentric rings.
So,
does
that I'm dead on or way, way off? Or am I doing something wrong?
I
used
the laser from my refractor and shot a beam though. I seemed
centered.
I
don't want to do this in the dark...

Doink


With the objective lens cap installed, the star diagonal removed
from
the
focuser, the focuser at the center of it's travel, and the Cheshire
installed in the focuser, with it's opening toward a good light
source
(but NOT the sun), look into the eyepiece end of the Cheshire. You
should
see two or maybe three dots near the center. These dots are not
big,
and
not bright. If they are not stacked one on top of each other,
adjust
the
objective until they ARE stacked one on top of the other, with
their
edges
fully concentric. Then try it with the focuser all the way in, and
all
the way out... If things move around at the extreme ends of
focuser
travel, or as you move away from the center in either direction,
the
focuser is not square to the tube, and THAT will have to be
adjusted,
too... Pretty much the same process, but this time, you will be
adjusting
the rear cell that the focuser is mounted to...

--
Jan Owen

To reach me directly, remove the Z, if one appears in my e-mail
address...
Latitude: 33.6
Longitude: -112.3