why would this happen

[brrttpaul]

Last night I decided to try the pelican nebula in narrow band, I set everything up in sgpro and let it run. This morning now sequence aborted on the last sub (again). I put the subs in blink to see what I acctually got and the last two images are looking like complete star trails? theres a dead centre and virtually a complete circle of stars around it, I cant do nothing now as work calls but any ideas whats doing this? I will put a pic up tonight if I can

[ronin]

Is it always the last sub and only ever the last sub? Just that carries the idea that is is the software that you are (may) be using. If so what is the software? However if it were I would expect others to be using the same and are there reports of similar from others?

Software tends to count from 0 to (n-1) we count 1 to N. Although I cannot see that occuring often these days.

Always remember the kind of standard "First time through bugs" on many a software package. Opposite end to yours but maybe the software is reading what comes next (no obvious reason it should however).

 

[swag72]

Sounds to me like your guiding stopped for some reason..... could it have been some passing cloud that made you lose a guide star, and then the cloud was sufficient in time for the guide star to drift outside of the box in PHD and so there was no star for it to lock onto? 

If it's your last sub again, could it be that by the last sub the target is getting too low and you are losing the guide star through some kind of obstruction, but the main telescope is still able to pick it up? I've certainly had this when using a separate guide scope.

Just as an aside - You do have sticky lock (I think it's called) in the PHD menu ticked?

You could always check the SGP log and see what was reported around the time of the last sub or there's a circled exclamation mark in the sequencer by the targets that you can press (or by the actual event itself) that will give you some hints.

[brrttpaul]

managed to take a quick jpeg of it to put up, now this is suppossed to be the pelican nebula in narrowband, I was always under the impression that the stars would circle polaris so no idea what went on here

[swag72]

Did your mount park in the middle of the sub?

[michael.h.f.wilkinson]

Th image suggests there is a great deal of field rotation, but that the tracking is working (otherwise the centre would not be OK-ish). Is some cable snagging, or is some part of the filter wheel or camera bumping into something causing the camera to rotate?

[AKB]

Just for fun, I ran the image in astrometry.net and, amazingly, it finds it bang on the Pelican...

http://nova.astrometry.net/user_images/1703653#original

 

[RichLD]

Looks like camera rotation to me as well.

[brrttpaul]

wonder if the camera has loosened then? makes sense really as I never tightened it that tight as it was catching the filter wheel slightly

[ollypenrice]

The camera has to have rotated. You'd only get star trails like that around Polaris, otherwise. I'd suspect that a cable snagged and held onto the camera as the mount continued to track as best it could.

Olly

[brrttpaul]

I went out after someone else had mentioned it and it was slightly loose, if i tighten it right up then it catches the filter wheel so I will give the spacer to a mate to shave off half a mill as he works in a factory and can fix this for me. Think Im doomed for all three narrow bands for some reason or another I always capture two not three lol

[AKB]

24 minutes ago, brrttpaul said:

Think Im doomed for all three narrow bands for some reason or another I always capture two not three lol

...bi-colour is nice.