Why can't I get beyond 20 seconds?

[ollypenrice]

One other thing though, other people with the same scope say they get up to a minute of exposure, now I don't know if they drift align but I doubt it, am I right in assuming that normally with wide field you shouldn't need to?? Surely there must be another reason for my problem that doesn't involve needing the palaver of drift aligning adding into the equation. Loads of people I've read, say they don't bother with drift aligning, so why do I need to, there must be something else wrong with my set up, isn't there?

It depends on your imaging scale but in effect this means your focal length, as Ags says. It also depends on where in the sky you are working. 

Olly

[kens]

Thanks, the polar scope is every so slightly out at the bottom compared to the top but it really is fractional. I might try and see it I can get rid of that fraction to see if that helps. Thanks for the DERV tip, I'll look into that, however as I understand you need a southern view for drift alignment and unfortunately I don't have this as my house and next door neighbours house are in the way.

You need to be able to see the East or West Horizon at around 0 degrees Dec and the meridian also at around 0 degrees dec. For you, that would be about 40 degrees above the southern horizon but you only need to be within about 20 degrees.

I find I can get around 30s at 70mm FL with a rough alignment. At 200mm its obviously only a third of that. And as Oily says that depends on where in the sky one is pointing. I'm normally some way off the celestial equator

[wxsatuser]

DARV will at least show you how far out you are.

You don't have to be bang on the celestial equator, get as near as possible east and south.

The more you move away from the equator...... your DARV should be longer.

Use the not so good nights for practicing DARV in no time it will get you results.

Here is a DARV frame......if I remember right this was a 10minute exposure, 5 in 5 out, as you

see it went out of frame then came back perfectly on top.

This was done on a cloudy night with varying amounts of cloud.

DARV

http://www.cloudynights.com/page/articles/cat/articles/darv-drift-alignment-by-robert-vice-r2760

[bendiddley]

Thought I'd up date you guys. I decided to cut my losses and buy another motor, I was very suspicious about my old one as it was temperamental, slowing down, stopping completely and I knew my setup was good, polar scope reticule well aligned, polar alignment done properly so it had to be the motors. Well I am now pleased to announce that I can now get 1.5 minutes of exposure before the Stars begin to stretch!! Yay!!!