(meteorobs) advice needed to shoot meteors

[Chris Peterson]

Hi Jeremie-

How bright a meteor appears is largely independent of exposure time, 
since the meteor sets its own exposure time by how long it spends on any 
one pixel. Longer exposures do slightly decrease the sensitivity by 
adding more noise, but the effect is small for typical camera exposures. 
So why limit yourself to 5 seconds? You're going to need to take an 
awful lot of images, and there is dead time between each while the data 
is saved. I'd consider something like 30-second exposures. That gives 
you a much better chance of catching a meteor, and a lower percentage of 
your time spent inactive. You're not going to see much sky movement in 
30 seconds using a 50mm lens unguided. You might also consider a cheap 
tracker for the camera.

You get some advantage with the smaller DSLR sensor, because it sits in 
the central region of the lens image plane, where the optics are better. 
Even so, very few lenses are capable of producing pinpoint images out to 
the edge of the chip unless you take them down one or two stops from 
wide open.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message ----- 
From: "vaubaill" <vaubaill at imcce.fr>
To: <meteorobs at meteorobs.org>; "IMO-news" <imo-news at yahoogroups.com>
Sent: Saturday, December 15, 2007 6:04 PM
Subject: (meteorobs) advice needed to shoot meteors


> Hi guys,
>
> Here is a kinda unusual request. Here is the thing: I would like to
> shoot some meteors with my digital SLR (canon rebel XT). I do not want 
> a
> too large FOV because in this case the tracks are so small they can
> hardly be seen. So the focal length I am aiming to is around 50mm
> EFFECTIVE, meaning a lens focal length around 35mm because of the
> correction factor for digital SLR (1.6 for the Rebel XT).
>
> Now I really need a FAST lens, since I'll shoot 5sec max., so forget
> about anything slower than f/2.0
>
> So you may think of the 35mm f/1.4 by canon, BUT for ~$1200, man 
> that's
> kinda a stretch for my wallet!
>
> I saw the sigma 30mm f/1.4 for ~$400. Since I don't know wnything 
> about
> this brand, my question is to know if anybody here has ever tried this
> one for astro-photography please?
>
> Thanks for any advice ;-)
>
> Jeremie