There are a whole slew of minor inaccuracies that could combine to cause
this, but the only time you use the RA marks is in the initial step of the
LX200's computer-assisted polar alignment alignment method (setting to 0
hour angle), from which the scope does an offset move to Polaris. Since
Polaris is so close to 90° dec, a slight error in RA has hardly any effect.
Specifically, 0.8 degrees (3.2 minutes of RA) would cause an error of about
.6' in polar alignment. Fork flex and atmospheric refraction will both
cause errors larger that that.
For this reason, levelling the tripod is not critical. E/W level error will
cause an error in setting to 0 hour angle (as above), which leads to only
minor error in polar alignment. N/S level error causes no polar alignment
error at all.

Much more important is to make sure your dec setting circle is accurate. An
error here leads immediately to the same size error in polar alignment. A
quick way to check is to set the tube to 90° according to the dec setting
circle, loosen the RA clutch, and look through the scope while rotating the
scope in RA. At 90°, the tube should be parallel to the mount's RA axis, so
when you rotate in RA, the image should rotate around the center of the FOV.

-John



>Subject: [M]: RA Telescope alignment problem?
>Date: Wed, 5 May 2004 21:37:13 -0400
>
>Hi...I just got my Mitty Evolution+ wedge. I carefully leveled the tripod,
>and checked the level on the fork arms to see if they were parallel. It
>turns out that I have to mis-align the RA tick marks from zero degrees by
>about .8 degrees between the fixed housing of the telescope and the
>rotating
>(in the RA axis) part of the telescope.
>
>
>
>In other words, if I line up the RA tick mark with the RA tick mark on the
>part of the telescope that moves, the arms are a little bit off balance.
>Rotating the telescope in RA by about .8 degrees levels the arms.
>
>
>
>A) Should I worry about this? IDEALLY, I'd really like the RA axis to
>read
>dead-on without the need to adjust it by .8 degrees.
>
>B) Any way to fix this?
>
>
>
>Thanks. BTW, initial gotos seem pretty good (dead on for stars off a tad
>for Jupiter) after a interative polar alignment. Going to try a drift
>aligment next time we have non cloudy skies.
>
>
>
>
>
>
>

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