Canon 1000d aperture problem!?

[Zendrix]

Hello!

I'm trying to control the F of a Canon 1000d but i can't seem to get it out of a "0" value. I've never touched a Canon, so i'm probably making a newbie stupid mistake... I know the obvious normal procedure of pressing the "Av+/-" button and rotate the dial wheel when in Manual mode or Av mode... but it justs sits on F 0.0!!

Im trying to do prime focus... is the F value only for when you are using lenses? if so, how do people talk about F values in astroimaging if they are using no lenses at all?

Thanks,

Rui

[RikM]

The aperture F value you set on the camera is only for lenses. When used at prime focus is it quite normal so see f/0. When we talk about f values in astroimaging, it is the focal ratio of the telescope (focal length divided by aperture). e.g. (750mm / 150mm gives f/5 for my small Newtonian). As with conventional photography, the lower the f number, the 'faster' the system can gather light.

[Zendrix]

i was already predicting my stupidity! Thanks!

[Auntystatic]

The only stupid question is the one that never gets asked, doesn't stop you feeling like a complete numpty once you've asked a question, and suddenly realise you already know the answer and haven't we all been there before, keep asking away.

[Zendrix]

ok, here goes another one? to picture the moon and planets, shall we be using Focus in Infinity? If so, how do i set it on a Canon?

Thanks ppl,

Rui

[Photosbykev]

If you are using a Canon lens then yes you should be manually focusing at 'infinity'. Live view will give you a good indication when you have got the focus correct.

If the Canon body is connected to a telescope then you should use the focusing control on the telescope to focus at 'infinity'

Also set the exposure dial to manual mode to control the exposure (as the aperture is fixed), if the exposure is a long one i.e >30 seconds then bulb mode will give you the ability to expose for longer.