POTH Dome Geometery

[Tandum (Robin)]

I changed the computer in the dome and forgot to write down the poth dome settings before I wiped the old one

It's been a long time since I last set it up and I have just rediscovered the trick for accurate slaving. Gem Axis Offset in the Southern Hemisphere needs to be a negative number.

I've spent a few weeks changing numbers and screwing around with it, when I've had time, but a simple minus sign has it back to near perfect.

Now I'll write the numbers on the wall of the dome

[h0ughy (David)]

i thought north was positive as too east? so the others must be negative?

[Tandum (Robin)]

I thought it would have used the co-ords you enter on the same page, doesn't look like it. I set all the others (N/S, E/W, U/D) to zero to try and see what was going on. East and west at 30degrees Alt where fine but south and north where not, the gem offset was reversed. I suppose poth is setup for the mount to be pointing north not south. If that's the case then N/S offset might need to be reversed as well so the dome turns the right way.

It got really bad last night when I swapped out the fs102 for the rc8 with a guider on top. That added about 300mm to the offset.