How Could I Move My Mount By A Fixed Amount?

[russellhq]

I've been using Astrotortilla to check my polar alignment. It takes 2 images a short distance apart, plate solves both then gives an error in alt or azi for your polar alignment.

When i do this, I usually have PHD open with the grid display on. I try to move the visible star a certain amount of squares using the adjustment bolts and try and match the magnitude of the error. But this involves a lot of guess work on my part!

Now, if I could get the mount to move the distance reported in Astrotortilla, it should then just be a simple case of adjusting the bolts to bring the star back to the original position marked on PHD.

Currently I know of no way of moving the mount by a fixed amount to offset for it's current position. So any pointers on how to do this would be greatly appreciated!

[Merlin66]

Comes down to knowing the "angle of dangle".....

You need to measure/ calculate the pitch (mm/ rev) of the adjusting screws and the length of the effective tangent arm ie the distace from the centre of rotation and the screw...once you know these things you can calculate the # of turns required to move yyyy sec/min of arc.

[russellhq]

Thanks Merlin but I'm tackling it from the other direction.

I have the mount connected to the laptop and I have a star centred in my finder camera. I've done a polar alignment check with Astrotortilla and it tells my I'm pointing say 5' North of the polar axis. So I want to send a command to the mount to move it say 5' North. The star in my finder is now off-set by 5' north. I can then adjust the Alt screws to bring the star back to the centre. This would, I assume, have moved my mount 5' South and I should then be pretty close to aligned in Alt?

Where I'm struggling is sending a command to the mount to tell it to move 5' north.

[NickK]

It would be good if, after two plate solves, it moves to one of the stars (offset by the Alt, then by the Az). That would then give you the right positioning.

The real pain is that the alt-az on my EQ6 isn't the most linear when adjusting - even when it's spirit levelled - however this only really becomes a problem beyond 1000mm fl in my book.