HELP: whats caused this

[PNJ]

Hi All,

I was imaging last night, my first 3 - 4 frames were spot on and my guiding very good, then i downloaded a few bad frames as per example here.

Could not work out what caused it, as my guide star was still guiding very nicely.

I suspect maybe balance or vibration issue, but as you can see its only on the brighter stars were i get the streak

Also when using Maxim Dl, the progress bar while in the middle of a sub, was behaving strangely too, the blue progress bar was flashing on and off.

Maybe a driver or power problem !!

Paul J

[JamesF]

My first thought is that guiding failed briefly at the start or the end of the subs.  Perhaps the end of one and the start of another if they're the only two affected and they're consecutive subs.  Power issues might account for that too, I guess.

Could be that only the bright stars have apparent trails because the lower mag ones weren't bright enough to make it obvious.  A hard stretch might show up more, perhaps.

James

[Zakalwe]

It could be lots of things, but if the guide graph doesn't show any peaks, then I'd be suspecting some slop or looseness in the imaging scope (I'm assuming that you are using a guidesope and not an OAG?). If the guide graph isn't picking it up then it means that the guiding system is tightly coupled to the mount and the imaging train is shifting somewhere.

It could be a loose focuser, extension tubes not fully screwed in, OTA loose in the rings, camera moving in the compression rings. This is one of the reasons why I like a fully screwed connection between the focuser and the imaging camera...I have a pathological fear/hared of compression clamps on drawtubes.

If the guide graph has a large peak in it,, then it is down to something else- backlash, knocking the scope, a cable catching, a gust of wind.

[chrisvdberge]

I see this quite often. Mostly due to (very) brief vibrations often in combination with bad balancing and/or awkward mount positions. 

Then the mirror of the DSLR can already cause enough vibrations to see something like this. Make sure you have enough time in between exposures

Also, this could be due to (brief) gusts of wind.