Tracking motor speed

[S Fletcher]

Hi All, Newbie here, living in a great dark sky region of Spain. Ive been following the forum for a while now, and am amazed at the knowledge and degree of help given by the members here.

I have just bought a cheap setup, a Celestron Astromaster and EQ2 motorised mount. The reason for not spending more is that here we have very hot days, and equally hot nights, so i thought a cheap setup would show atmospheric fluctuations without shelling out too much and then be impossible to use. As a professional wildlife photographer, i know just how much the heat haze can be restrictive, meaning the summer months are impossible for any photography using any sort of long lens.

I have a question though. When drift aligning, does it matter if the motor speed is correct, does the drift align not worry about motor speed and can be adjusted later, or does the motor speed have to be bang on before drift aligning ?

Regards

Steve

www.extremaduraphotos.webs.com (http://www.extremaduraphotos.webs.com)

[alistairsam]

Hi Steve,

Welcome to IIS
While drift aligning, you need to ignore drift in RA for both the meridian star and the east star. You just need to observe drift north and south.

Any east west drift in RA would be due to tracking rate errors and will need to be adjusted separately.
It's best you align your camera such that moving the ota in north south moves the star on screen north south as well. Then watch for N S drift.
Adjust azimuth for the meridian star and elevation for the east star, in both cases you're looking for drift in north south only. Ignore east west drift.
Best to align the drift along a reticle or grid line.

Do a search on drift aligning in this forum and you'll get plenty of pointers.
Cheers

[RobF]

Hi Steve! Welcome to IIS :welcome:

Most drives are already adjusted to run at "sidereal speed" which is the rate the earth is turning relative to the stars. If your motor has a (RA) speed adjustment that's to get the rate of motion in RA adjusted. Drift aligning for polar alignment is all about minimising drift in DEC under controlled conditions to get your mounts azimuth and altitude sorted. Hope that helps rather than confuses.

[S Fletcher]

Many thanks guys, that was how i thought it worked.

Typical though, i set everything up yesterday, and we had the first cloudy night for 4 months last night !!!!!

[Poita]

I think I had my first *clear* sky night in four months last week. I'm coming over to visit!