Hi Neal,it's looking good.I put a third 1"long bearing in each of my axies and it improved nicely but not like yours.
By coincidence,I offset my mount and took a few before and after startrails.
The after star trailsARE VERY REULAR AND i TOO USED A 101 POINTED AT THE M31 REGION.I used a 2x big barlow in front of my camera.
My star trails can be described as 2 different appearing trails:
the bright stars look loke a straight linr composed of light balls (stars )connecetd together like a string of pearls.
The dimmer stars leave wavy trails but are much thinner of course than the bright stars.
How would I measure the arcsec error?
I had tried to calculate my arcsec resolution with a 12.5mm ortho eyepiece and on the 60mm scale it took 300 seconds for a star to go end to end.I calculate dthe that give an st-4 pixel is 13.5 x 16 microns that on the ra side,1 pixel at prime focus would be 5.5 arcsecs.The 2x barlow would halve that would it not?
If correct,how then do you extrapolate that to a 4 by 6"photo?
I shot 30 minutes at the pleades and have round stars even under an 8 power magnifier.
Can you shed any light on this for me?
thanks
Jimmy
From: "Neal Barry" <nbarry@...>
Reply-To: Losmandy_users@...
To: <Losmandy_users@...>
Subject: [Losmandy_users] G11 Fix (III)
Date: Tue, 22 Aug 2000 12:55:59 -0700
Hi all,
Well, I'm reasonably pleased with the improvement that I have been able to
achieve in my G11's tracking and periodic error. Take a look at
to see the results.
I am curious how the PE shown on the web page above compares to other G11
mounts out there. I still am not sure if the problems with the mount I
received are typical or a fluke.
I have made the fix permanent since my original post back on 8/13, but I did
risk damaging the mount in the process. Specifically, I pressed in a new
needle bearing with .002" stainless steel shim stock wrapped around the
OUTSIDE of the bearing (I know, I was against it in an earlier post ;-) I do
not recommend this! You can easily damage your mount unless you are VERY
careful. Five things can go wrong.
1. The needles in the bearing can seize.
2. The bearing can easily distort due to the amount of force require to
press it in.
3. The fit can bee too good, and the shaft will bind due to the relative
misalignment of all three needle bearings.
4. You can permanently knock the RA wheel gear bearing sleeve off axis or
bend it.
5. You can expand the OD of the RA wheel gear bearing sleeve so that the
wheel gear will no longer fit.
However, this strategy did cause the ID of the needle bearing to shrink
(exactly the amount needed in my particular case) and I now have a very nice
on-axis fit with no measurable slop. The OD of the RA wheel gear sleeve
bearing did expand slightly (approx .0002") and I needed to lap it a bit to
ensure that it would not bind over an appreciable operating temperature
range.
Anyway, now that the RA shaft was not flopping around, I was finally able to
see how well the mount would track. Now I had a fairly regular PE of about
11-12 arc seconds. After lapping the RA worm and wheel gear it dropped to
under 10 and became even more regular. After training the SkyWalker II PEC,
it tracks within 2 arc seconds. Not too shabby given where this all started.
Neal
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