question on astrophotography

[howado (Howard)]

Hi all,

I had taken this picture last night, with 10-22mm, 15 sec. exposure. The picuture appears to have trails on the stars. However, with 15 second exposure, and set at the wide angle end, it should not have such visible star trails. Initially I thought it might be casued by camera movement, however, the trails appear in different directions.

Does any have explanation for this?? thanks

shutter speed: 15s
aperature: f/5.6
iso: 500

[[1ponders] (Paul)]

Hi Howard.

Can you upload a larger and clearer image? What were you mounted on? A tripod or motorized mount?

[that_guy (Tony)]

the trees also look all shaken up, so i dont think its star trails and did the camera have a remote shutter or was it taken with a timer?

[howado (Howard)]

Originally Posted by [1ponders]

Hi Howard.

Can you upload a larger and clearer image? What were you mounted on? A tripod or motorized mount?

here is the image in the original resolution.
the camera was mounted on a tripod

https://picasaweb.google.com/1164722...77835193006242

[[1ponders] (Paul)]

It looks like a simple rotation around one point, near top left center, but I can't say how that would happen on a tripod.

[howado (Howard)]

Originally Posted by [1ponders]

It looks like a simple rotation around one point, near top left center, but I can't say how that would happen on a tripod.

true... but with such short exposure (15s) and mount on a tripod, I am wondering how it happened... since other images I took with the same exposure time, didn't leave a trail

[[1ponders] (Paul)]

weight of the camera drooping? One leg slipping or sinking? Not sure but it is a strange one

[ballaratdragons (Ken)]

Looking at the whole image you can see rotation.

When you blow up the trees you can see that the camera has rotated in R.A.

Somehow your camera has self rotated or has been knocked. but due to the brightness of the stars and the solidity of the trees at the end of the movement (or the start) it tells me that the camera rotated for about 10 seconds then sat still for about 5 seconds, or sat still for about 5 seconds then started its rotation and 10 seconds later the image was finished while the camera was still slowly rotating.

I hope that makes sense.

Look at the trees in this crop from your pic:

[adman (Adam)]

does your tripod have an adjustment where you can turn the camera 90 degrees into 'portrait' orientation - if so that may be where the rotation came from. It wouldn't have needed to move much.

Adam

[pproctor (Paul)]

Just a quick thought.

As you said the lens was a 10-22, could it have possibly been the zoom slipping during the exposure?

[[1ponders] (Paul)]

Good thought Paul, but if it was the zoom the stars would most likely move radially towards the center .

[desler]

My bet is Tripod head movement.

Did you turn the tripod head to fit/secure the camera?

Darren

[howado (Howard)]

Thank you so much for the explanations. I think the most likely scinario in this case, might be that the tripod head was not properly secured.