Tripod and 1500mm


sebas77

Link Posted 23/07/2013 - 10:48
Hello,

I finally managed to take a shoot of the moon with my pentax Q and the 80-320mm..at 300mm should be something like 1550mm.
this thread is about the tripod though, I noticed on the screen that the moon was oscillating even if the tripod (a triopo) looked stabled.
With my surprise, adding the weight of my bag made the thing worse. That's because the bag was also swinging adding more movement to the tripod...I found quite tedious stop the bag fluctuating.

what are your thoughts?

froeschle

Link Posted 23/07/2013 - 16:22
Have you tried to use an IR remote?

sebas77

Link Posted 23/07/2013 - 16:43
oh yeah of course all the tripod "tricks" are used...disable SR and IR remote included...
although in this case does not really matter, I was talking about the live view not the shot.

So 1500mm is a little bit extreme, so my question is more about if this behaviour is normal with such tele or I need to check if there is something wrong with the tripod.
Last Edited by sebas77 on 23/07/2013 - 16:43

johnriley

Link Posted 23/07/2013 - 17:13
You need a very, very solid tripod with this much magnification, and the slightest touch to the camera will set things moving.
Best regards, John

sebas77

Link Posted 23/07/2013 - 17:19
how do you think I can improve the stability? Adding weight on the central column does not help

johnriley

Link Posted 23/07/2013 - 17:24
It depends how sturdy the tripod is. I'd make sure the centre column was not extended, close down the legs as much as possible and use the 2 second delay to ensure vibrations were allowed time to settle. Then we need a fairly high shutter speed as well - the moon moves quite fast.

Lastly, an absolutely crystal clear night. Atmospheric pollution will cause problems very easily.
Best regards, John

sebas77

Link Posted 23/07/2013 - 21:18
thanks john...I was not worried about the photo result, which is fairly good, I was worried just about the permanent vibration for other situations (like super long exposures)

xbow

Link Posted 23/07/2013 - 22:02
Can't find the link but there was a site that ran some tests for vibrations in tripods. Wooden ones (as supplied with some long Pentax lenses) came out best as I remember. Next best was Carbon fibre with Aluminium bringing up the rear. For your application the biggest heaviest tripod you can get hold of (or carry!) would seem to be best!?
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sebas77

Link Posted 23/07/2013 - 22:27
weird I read many articles saying that the carbon fiber vibration adsorbing is not more than a myth

gwing

Link Posted 23/07/2013 - 22:43
From sports shops you can get ankle weights designed to make running harder. These are essentially velcro fastened padded bands with lead shot or similar inside. Fastening them around both the tripod and the lens adds fairly rigid and well damped mass rather than something swinging around.

johnha

Link Posted 23/07/2013 - 22:46
The problem with tripods and high magnification (1500mm on a FF camera is about 30x magnification) i.e. a pretty effective telescope. Any vibration is going to be magnified enormously, most tripods will struggle one way or another. With big lenses, any wind can also have an effect.

The problem is increased for astro work because of the inclination angle - many tripod heads can't hold the camera/lens combination at an angle solidly enough - even assuming a solid tripod mount on the lens (where it should be).
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doingthebobs

Link Posted 24/07/2013 - 00:42
Have you tried a brick wall and bean bag? I also have an old cement mixer in the garden that supports the bean bag well.

I wonder if the problem lies with the fact that the attachment of the camera/lens is only small. The tripod offers a stable contact with the ground but then the camera/lens can move on a small point at the top, where it is attached to the tripod. Using a bean bag you support a much larger area of the camera/lens and this stops any movement better.
Bob
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