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Old 04-09-2013, 09:43 PM
Carl
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non aligned star trails

After some advise. just took 30 images in a row to do a star trial image. Everything locked down and using an automated remote timer so i am not touching anything. Sequence was 5min exposure with 1 second gap.

But here's the problem. Every second image, the entire image has shifted by the same amount. For example 15 even number files are perfectly aligned with each other,and all 15 odd numbers align with each other but the even and odds have shifted by the exact same amount.

Any thoughts as to what the hell is going on

Regards
Carl
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Old 05-09-2013, 02:31 AM
dp297 (Dimitris)
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Maybe u should give some more info on your mount and how u performed alignment
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Old 05-09-2013, 03:40 AM
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iceman (Mike)
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And post some test images!
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Old 05-09-2013, 08:15 AM
Carl
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Non aligned star trails

Hi Guys
Thank's for the reply.
My tripod is pretty solid and i have not had any issues before. The series specs were 5min exposures x 20 with a 1 second interval.
If the tripod was too lightweight or things were not tight then i could expect random movement but this is uniformed movement; every second image has shifted by exactly the same amount. I put all the images into layers in Photoshop and checked the movement pattern.

I then did a test in my study late last night and increased the interval time to 5 seconds, This time the movement was random throughout the exposure list. My third test was better but this time i turned off image stabilsation and only allowed 2 seconds interval

This still doesn't account for the uniformed movement in the first series of exposures. I haven't changed anything from my earlier attempt at star trails that worked.

I'm at a loss, does the interval time have anything to do with it?

regards
Carl
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Old 05-09-2013, 11:31 AM
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sil (Steve)
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What I think may be happening is there is not enough time in that 1 second gap for the data to be processed and saved. I've seen similar oddities with intervalometer and tethered shooting. Can't say for certain unless you explain how you are taking the photos.
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Old 05-09-2013, 02:56 PM
mg (Mitchell)
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Were you using an image stabilising lens?
I have had a similar effect when doing a time lapse and forgetting to turn off IS. Some images were shifted just slightly - the ones where the lens IS obviously kicked in. All shifted by the same amount. The affected images weren't in an exact pattern like you explain though.
Maybe every second pic the lens detected slight tremor from the mirror/shutter or something and IS activated.
But if stabilisation was turned off my whole theory is nonsense!
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Old 05-09-2013, 05:10 PM
Carl
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non aligned stars

Thanks guys
I'm going to give it another test tonight in the house just to see whats going on. Very strange.
Do you leave the mirror locked up? and how long do you give intervals?

regards
carl
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Old 05-09-2013, 05:35 PM
mg (Mitchell)
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Last time lapse/star trails I did I used 20 sec exposure, mirror lock up on, and took a shot every 25 secs. This was at 18mm focal length. If you leave a big interval between pics, you'll get gaps in the trails, but it depends on the focal length how long you can leave.
5 secs was plenty on my camera for it to write to card and then the mirror locks up 2 secs before the next image.
There's possibly a way to leave the mirror locked up for the whole sequence but I didn't do that.
I used the pics to make a video and also stacked the images in startrails to get the pic with the trails.
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Old 05-09-2013, 05:42 PM
mg (Mitchell)
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Forgot to add, I took short exposures because I was making a vid and didn't want trails in each individual pic. If you are just doing the trails, save yourself heaps of trouble and stack 50 x 5 mins, rather than 500+ x 20 secs.
Sorry if you knew this already.
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