Drift problem...

[cybereye]

Morning all!

Last Friday evening I set myself the task of imaging M4. I got the alignment to be what I thought was good and took some 30s exposures. I then tried some longer exposures - 1 minute seemed OK but 2 minutes showed definite trailing.

When I examined the 30s photos on my PC, I noted that, although the stars were nice and round, they had moved between exposures. However this movement was not always in the same direction. A few shots would show movement in one direction and then all of a sudden the next 4 or 5 would shoe movement at right angles to what I'd seen before.

I'm assuming that the movement I was seeing was in RA and then DEC or vice-versa, but haven't been able to track it down. Do I need to start PEC training or is there something else I need to investigate?

I know this is a bit of the old "how long is a piece of string" question but any ideas would be gratefully accepted.

As for my image of M4 - I would say it needs longer exposures as the core wasn't very visible in the 30s ones. I'm not posting it because I think it's a dud! :lol:

Cheers,
Mario

[bmitchell82]

what it sounds like is flexure mario, have a look into if everything is tight, i have only ever seen the stars round but moving between frames when this happened the newt i was using the spider had come loose and as the mount was tracking the secondary would move as well. round stars all smeared.. :( go back though you'll find something amiss ;)

[Moon]

Mario
Was it unguided? What was the rest of the setup?
James

[cybereye]

James,

I have an 8" reflector, 1200mm fl, on an HEQ5 Pro mount and the problem occurred when the scope was unguided.

I'm working on guiding but at the moment I'm stuck on getting the Windows 7 driver working for my USB to serial cable.

Baby steps, baby steps...

Cheers,
Mario

[Moon]

Mario
A look at one of your images would help - but I would say if you can already go 1 min unguided at that focal length, then the next step is to get guiding working.
The movement could be, and probably is, caused by many things. Guiding can fix a lot of different issues for you, including PE, polar misalignment, mechanical issues etc etc.
You need to have guiding working before you try to train the mount for PEC. That would be the next step after you get guiding working.
Keep at it...
James

[M_Lewis]

XP Mode for windows 7 will solve your USB problems. Google search for it, download the files from microsoft and all will be good after that.

[Manav]

different direction - Could be vibrations/bumping, check if there isnt something hitting or bumping the mount during photography? Furthermore, are you taking photos remotely? My setup requires I leave it untouched until all vibrations and stopped before I take photos remotely. Pressing a camera button/making adjustments and taking photos straight away use to cause such problems....Just a thought!