"Chris Taylor" wrote in
:

Shouldn't you mount it on an eq wedge for long exposures, as although
the altaz mount cant hold position, it slowly twists relative to the
universe if running relative to the earth

Hi Mike

Field rotation isn 't really an issue so long as its not prevalent in
any one frame. The stacking software I use takes care of the rotation
whan aligning by using two stars against which to align.

The tracking errors of the goto mount move the image more than a few
pixels over about 15 to 20 seconds causing star trails. My LX90 is
good for about 30 to 60 secs without field rotation (depending where
you aim) and a few minutes when polar aligned.

Wow, it was even worse than I thought!

I'm well happy, just need a couple of bits of ally to make prarper
adaptors, I reckon they'll be as good as store-bought.

The only prob would be balancing the scope front to back, but I don't think
the mount realises there's a scope on at all.

Now I can use the short eyepiece I might try some "real" collimation!

mike