Major tracking problem......?

[stan26]

Hi folks,

Not sure what was going on with my mount last night, but basically after imaging M31 for around 2 hours I never got a single sub without star trailing

It's an EQ3-2 mounted on my new 8" square concrete filled pier, with no guiding using dual axis motors. The mount was drift aligned Monday night and its spot on. It not like it has moved since. As it happens I took a single 30sec sub of M31 on Monday to show my mate what can be done with a DSLR and the stars where perfectly round etc.

All subs where 30secs long. I have used my EQ3-2/ST102 combo for DSO imaging many times now using 30sec subs and I usually get at least about 30% success rate with round star subs, not great but it is only an EQ3 after all....

The star trailing seemed to constantly change direction during the 2 hours. First they would trail north/south and then it would change to east/west. Flicking quickly through the subs on my dslr screen shows this happening in a fairly consistent circular fashion.

What could be causing this? M31 was close to the meridian last night, but I have image M51 this close with the above setup with no problems. The only thing I can think of is that I think that possibly I had the balance set up wrong. I think that the weight may have been bias on the scope side, not the counter weight side, thus not loading the RA motor correctly when pulling it up....Would this cause this sort of tracking problem....?

hmm.....

[stan26]

Just to add, the tracking was so far out that M31 almost ended up off the screen towards the end of the session. Wonder if the mount battery is any good.....

[barkis]

What kind of battery is powering your mount. Is it a Power Tank?

Seems as though your drive is struggling, and it may well be your supply. Is your imaging rig outside, or in an Observatory.

It would be better to use a PSU but as it is mains supplied, it must only be employed in a very safe environment, and with RCD protection too. Don't take any risks.

Ron.

[stan26]

Thanks for reply Ron. I'm not using a power tank, I'm using a small motorcycle sized 6v sealed battery that was use with a hunting lamp. Have never had a problem using it before, and it has got charge. I'v currently got the rig set up with the correct (i think) weight balance taking some 30sec subs to see what i get. After re-checking the alignment tonight it seems that the alt was ever so slightly out. A combination of all those things now put right I hope......