Tracking failure

[rkc]

I tried my first stacking tonight (10 exposures of 30s each, ED80, 5DIII, M42) then combined them in DSS, but the results were rather disappointing. In particular all the stars had trailed badly, and comparing the original light frames it looked as though the tracking had not happened at all.

So I'm wondering, which newbie mistake(s) did I make?

1. Was the tracking disabled somehow ?

2. Was the polar alignment WAY out?

3. I realize I forgot to put any counterweights on (been using AZ mode up to now).

The shots I took in AZ mode looked better, in terms of the trailing of the stars,

Richard

[LukeSkywatcher]

Can you post your images. That would help.

[Freddie]

Even with bad PA I wouldn't have thought it would have shown up as you describe in 30secs, but if you can post up a pic it may be easier to determine what went wrong.

[x6gas]

Any chance you could have changed the tracking rate to something other than sidereal?

[rkc]

Can you post your images. That would help.

Even with bad PA I wouldn't have thought it would have shown up as you describe in 30secs, but if you can post up a pic it may be easier to determine what went wrong.

I can't post them tonight - they are on a different machine - but I can try to post them in the morning

Any chance you could have changed the tracking rate to something other than sidereal?

Not intentionally. I wouldn't even know HOW to change the tracking rate...

One strange thing though... I'll have to double check in the morning, but I think the direction of the trailing was / where the motion of the stars at the time would have been \ (just checked with Stellarium).

I wonder if I had forgotten to tighten the clutch on the dec axis.

I had tried and failed to do a 3-star alignment (so did a 1-star instead), but I think that would only affect goto performance rather than tracking ?

Richard

[ronin]

Any chance that to do the alignment and whatever that you have loosened the clutches then not tightened them?

That way the motors do their bit but are not connected to the actual scope and it doesn't move.

Concerning the one star then for any imaging you need it to be accurate, and if the three star failed then something was wrong otherwise it would not have failed. I think if you look through the manual it will say what errors are not compensated for if you do one star alignment so worthwhile looking up what the mount was not doing.

[rkc]

Any chance that to do the alignment and whatever that you have loosened the clutches then not tightened them?

That way the motors do their bit but are not connected to the actual scope and it doesn't move.

That was one of my thoughts, and it is certainly possible, though when I checked this morning the clutches were tight. I may have parked the scope manually then tightened them though, I don't remember.

Concerning the one star then for any imaging you need it to be accurate, and if the three star failed then something was wrong otherwise it would not have failed. I think if you look through the manual it will say what errors are not compensated for if you do one star alignment so worthwhile looking up what the mount was not doing.

When I say that three-star failed, what I mean is that I failed to complete it - a combination of clouds, obstructions, a dewed-up telrad and lack of knowledge of the skies meant I could not confidently locate the alignment stars suggested, so I abandoned the three-star alignment and did a one-star align on Sirius instead.

Richard

[rkc]

I uploaded some images to

There are 4 of the 10 light frames, and the resulting DSS stacked image in there

The trailing seems to go from bottom left to top right, but the stars would have been moving from top left to bottom right, if my calculations are correct.

Richard

[rkc]

After thinking about it some more, I think that the fact that the 'drift' is perpendicular to the movement of the stars is precisely what would be expected if the polar alignment was out. I wouldn't be at all surprised if it was - Polaris was 'on the circle' but whether it was on the right point of the circle, I'm not sure.

It's posible I aligned on the wrong start altogether I guess - there were clouds around Polaris...

I'm a little surprised that poor polar alignment could have this visible an effect on relatively short exposures though.

I think I'll have a play with Alignmaster next time I get a clear night.

[Daniel-K]

here try this http://www.polarfinder.com/ its far easier than align master i have had nothing but issues with that program, not saying it doesnt work but using polar finder you just copy the postion you see on the screen through your polar scope. 6min suns guiding nice round stars HTH