Mak cone error

[jambouk]

My 180mm Mak is mounted on the standard Skywatcher dovetail, like this http://www.skywatche...BK180MAKSPZ.jpg (I can't find 216mm ID rings anywhere).

Anyway, I checked for cone error in accordance with Dion's video last night ("hello again....").

There is loads. If I get Polaris in the centre of the field of view in the finder scope (9x50) and in a reticule eye piece (12mm) in the OTA, then flip the OTA 180 degree on the RA axis, and adjust the dec axis, Polaris is miles off; it's no where in the FoV in the scope, and roughly in the position shown in my diagram in the finder scope.

Can I reduce the cone error given how my OTA is mounted to the dovetail? I'm still hunting for tube rings which I think would make reducing cone error easier.

Thanks for any replies.

James

[knobby]

Hi James... A bit heath Robinson but until you (if you) get tube rings maybe try loosening the dovetail and shimming between the dovetail and ota.

If it works out you can then make neater... Not so visible shims

[JamesF]

Do you really need to worry about it? It's a pain if you want to shoot all over the sky with a short focal length eyepiece in, but otherwise it's not that much of a problem, surely?

James

[jambouk]

It is annoying that the goto isn't that accurate, and doing PAE just makes it worse as everything not in that area of the sky is then messed up.

I'm potentially going to try stuffing foil under the dove tail at the weekend, unless i can find any rings at the show tomorrow

James