Orthogonality

[GrampianStars (Rob)]

My 2005 LX200GPS Meade 12" hasn't seen stars 4 weeks now & is covered by it's shroud in it's observatory, mounted on a Wedge/pier combination.
I suspect that the orthogonality may need to be corrected. (never done)

Is there a basic method without removing from the wedge?
I do have a tripod if needs dictate......
also what equipment will I need?...
a trip to visit Barry Gerdes in NSW would be a 3 day round journey @ least.

[AndrewJ]

Gday Robert

To do it properly requires a 2 stage process.
The first is to get the DEC axles perpendicular to the RA axle.
The second stage is to get the OTAs optical axis parallel to the RA axle.

Stage one isnt a simple exercise and cannot be done properly on a wedge.
Stage 2 can be initially validated by doing a spin test whilst looking at the triangular asterism at the pole.
Ie set the OTA to DEC = -90 and DEC axles horizontal
Note position of stars on either side ie L and R sides of the EP relative to the stop.
Rotate in RA by 180deg so that the DEC axle is again horizontal
and again note position.
You may need to tweak the DEC slomo to get the OTA perfectly at DEC = -90 whilst doing this spinning.
Once done
If they are the same relative distance away
then your "second stage" alignment is OK.
When its truly correct, you can actually spin the scope in RA
and the stars of that asterism should trace circles inside the EP.

Note. Stage 2 aligning can be achieved, even if stage1 aligning is incorrect, but unless stage1 aligning is correct, gotos will still be off.

Andrew

[Barrykgerdes]

Hi Robert
Andrew has covered it well.
Getting the forks correct is the first thing to do but if you have the latest one piece "U" section with the bolt on dec bearing carriers I have not found the need to make any corrections to these yet.

If you have the old type where the Dec arms are bolted onto the base with a spacer. It is a considerably more complicated job to do and measure.

Getting the OTA is done as Andrew says. There are a couple of #4 tapped holes that can help with this but whatever you do don't try to make adjustments with them directly. Just use them as reference stops.
I work out which way the tube needs to go and let the weight of the tube do most of the work after loosening the one side where the adjustment is made and settin the #4 screws to a suitable stop position.

I have stoped doing corrections to all intents and purposes due to the physical requirements. But if someone brings me a scope to do and will do all the necessary lifting I can still provide the expertise.

Barry