Quote:
Originally Posted by GrampianStars
G'day Coolhandjo
Before visiting Bazza
try this out
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Hi
I checked out that doc. It is quite a standard method of doing a polar alignment and is similar to most that I have seen. It will work quite well if the telescope rotational axes are orthogonal.
If they are not it will produce the errors so many people find. The older method of attaching the fork arms to the base in Meade telescopes was often quite poor and produced the condition where the arms were not the same height or tilted to the left or right. This was often compensated by adjusting the OTA in its brackets to make it appear perpendicular to the base. The newer method now supplied uses a one piece lower fork that is much more reliable and I have not seen any of these that have the problem of uneven fork arms. This only leaves the OTA to be tested in its brackets.
The method that Meade uses to find the 90 degree position of the OTA will also show up the OTA offset in the amount the test star drifts from left to right and back while finding the 90 degree point. Once the fork arms are corrected.
It is possible to get the axes within an arc minute of truly orthogonal with a little patience and an effective method of measurement. This done even the simplest of polar alignment procedures will present good goto's. On my permanent mount I could goto anywhere at any time and have my object within 4 arc minutes of the centre of the eyepiece.
I have been advocating the necessity of orthogonality in Meade fork mount telescopes for 13 years now and have received all sorts of negative response from the so called gurus on other forums who said it was not necessary and that you could correct the goto problems with the SMT extra or other ways. Good engineering practice says you don't fix an error with another error, you correct the first error.
Barry