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Old 09-10-2020, 01:52 PM
hamishbarker
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hamishbarker is offline
 
Join Date: Mar 2017
Location: Nelson, new zealand
Posts: 49
the jig looks good. I see you have both north and south sectors rather than just a north end pivot. this keeps your platform shorter and stiffer, fine.

slippage should not be an issue as long as everything is arranged to put the CoG on the polar axis, or just a smidge to the west of it in order to just balance out friction so that the motor hardly has to do any actual work and just regulates the movement at precisely the drive speed.

I found it well worth spending some time getting my head around drift alignment. I remember it by using an acronym: LEN. LOW EAST NORTH as follows:

if the polar axis of the platform is to LOW (when looking at a star near the eastern horizon),

or is too far EAST of due south (when looking at a star on the meridian near the celestial equator)

then it will appear to drift NORTH in declination when viewed in the eyepiece. Nudge the scope north before watching for drift so that you can tell which side of the field of view is to the north.

using a crosshair eyepiece with the lines rotated so that any RA error is along one line makes it possible to immediately see any DEC error as the star will deviate one side of the line or the other.

I keep a few shims with the platform as I was too lazy to add adjustable feet (and also worried that they would make for flexure).

Quote:
Originally Posted by Greggles View Post
Hey all,

Apologies for not replying in a while i've been busy working on my sectors.

I ended up swapping the steel out for aluminium and ground down the sectors using a jig. Photos attached

Crappy weather in Sydney so untested but hopefully get some testing in and some photos of mars!

Bojan, in regards to my sectors not being on the same plane, i believe this is part of the VNS design and the angle is calculated so at a right angle it intersects the the polar axis. although i don't know if I'm explaining this properly.

Regards,

Greg
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