hello everyone,

 

this is more like a simple curiosity, yesterday night I took some pictures of the stars with my camera.

the first picture was aimed at Capella and the field of view was diagonal, longitudinal and the exposition was 20 seconds, everything went fine.

for the second and the third picture I wanted to grab a bigger slice of the sky, so I just put the camera on the ground facing upwards, with the focus to infinity, so the field of view was completely vertical. for the first attempt I set the shutter to 30 seconds and the stars left a trail, for the second attempt I set the shutter 15 seconds and the stars left half the trail relative to the first attempt. of course I immediately blamed the terrestrial rotation (at the first attempt) but what puzzles me is that the diagonal-longitudinal shot was perfectly still.

 

what happened?

 

thanks in advance.

15 seconds would equate to movement maxiumum of 15/240 of one degree - which would not leave a trail. You probably moved the camera - sorry.

 

1. use remote control - as you may be moving camera ask you hit shutter release

 

2. If it wasn't you maybe the flick of the shutter itself was enough to move the camera. If you want to avoid this use a bulb exposure (ie press once to open and twice to shut. And before you open place a piece of dark card right infront of the lens blocking out all light - open the shutter, remove the card without jolting the camera at all, wait, wait some more, and some more, get bored, finally replace the card still without actually banging the camera, close the shutter. It does make a difference and take no time at all to get used to.

If it's an SLR you can probably lock the mirror up. When the mirror is flicked up it causes more movement than just the shutter on its own.

 

If the camera could wobble then any movement of the floor could cause the camera to move enough to create the track.

Mirror not shutter - you are completely right. And regarding the floor - yep, first rule of photography "get a decent tripod"

This post led me to check out my camera's capabilities. It's a standard digital camera that images to an SD card, and has a USB port for image transfer to PC.

 

It turns out that many cameras with USB ports can do an awful lot via those ports. In particular, there's a

USB-controlled switch that allows you to activate the shutter without moving the camera.

 

This post led me to check out my camera's capabilities. It's a standard digital camera that images to an SD card, and has a USB port for image transfer to PC.

 

It turns out that many cameras with USB ports can do an awful lot via those ports. In particular, there's a

USB-controlled switch that allows you to activate the shutter without moving the camera.

 

Very cool - I hope to see some posts with the stars above New Hampshire very soon (I presume the NH is New Hampshire - if not I apologize)

After some hunting around, here is what I have learned:

 

For Canon digital cameras, there is a set of free software called CHDK, the Canon Hack Development Kit, which allows you to do all kinds of hackery to your Canon but without making any permanent changes. This includes enabling remote control, i.e., using the Ricoh remote USB switch (above) to click the shutter so you don't move or even touch the camera.

 

I have personally followed all the steps to install CHDK on a separate SD card and enable the remote USB switch feature, and taken pictures with a Ricoh USB switch. I can take a picture without touching the camera, and have done so aplenty. Currently I'm having trouble half-clicking the USB switch -- which focuses the lens -- but that's my clumsy fingers.

 

This doesn't solve everybody's problem, but most Canon cameras have CHDK kits ready for download. It helps to have Java on a PC to correctly process the SD card.

Can you not focus with the camera button and then change the lens to manual focus to take the photo?

In something like astrophotography using the self-timer to avoid vibration will suffice I would think.

Can you not focus with the camera button and then change the lens to manual focus to take the photo?

 

Yes. Better yet, I can focus with the camera button and then use the USB switch to take the photo. A quick snap (all that I can do right now) will then not change focus. Of course, we are talking about shooting stars...pity CHDK doesn't have a "focus to 1620l.y." command. Hell, maybe it does; I'm just getting started here.

 

The right thing to do of course, is practice so I can do a half-click with the USB remote. It can't be that hard...