Star trails & pinhole cameras???

Does anyone know if you can capture star trails with a pinhole

camera?..I was thinking this may be a good way to do it as there

would be no dew to form on hte lense as there is no lense?...anyone

know if this can be done at all??? If anyone knows anything about

this subject could they please email me at :

 

terrymccully@hotmail.com

"Use color negative film. Ektar 25 is the best (f/2.8 or f/4 is probably the right exposure). Fuji 100 would be my second choice (at f/5.6 or f/8)."

 

This is from Philip Greenspun's Star Streak Tutorial, http://www.photo.net/astro/star-streak

 

Assuming 25 speed at f/4 is a workable exposure, to use, say, f/200, you would need 2500 times higher film speed, or ISO 64,000 film. In other words, it probably wouldn't be workable.

Interesting question. Seems to me - and I'm just theorizing here, not having actually tried it - that if one wanted to photograph a night scene *without* star trails the solution would be a pinhole camera and slow film. Anything fairly dim and moving wouldn't be recorded well.

 

Seem logical?

well I was hoping that I could capture the trails on film...I hate getting dew on the lense and I was wondering if if could be done with a pinhole picture?

Try using a lens hood to delay the onset of dew on the front element.

I've never tried this, but I've meant to. As far as I understand it,

it's completely workable. Stars are, in essence, point sources

(they're WAY to far away for any camera lens to resolve them),

and so are (I'm told) not effected by aperture. In other threads

the suggestion has been made that chaging aperture from f/4 to

f/8, say, on a night shot will not change the exposure of the stars

(of course, everything else goes down two stops). If that is true,

a pinhole camera should give startails very similar to any other

camera (but softer, of course).

 

But what if a drop of dew covers the pinhole? Surface tension

might actually make a little lens :)

There are several ways to avoid the dew problem. On a breezy or warmer night, dew will be less of a problem. Astronomers use various fans and heaters to avoid the dew. Try a websearch on "star trails" or "astrophotography". You get noticable star movement fairly fast (depends on focal length), and if you don't want to use an hour-long exposure, you may not have a dew problem in the first place.

 

Depending on where you are, you may have a number of "airplane tracks" in your picture, too!

<cite>Stars are, in essence, point sources ... and so are ... not affected by aperture.</cite>

<p>

First part is right, the second part isn't. Ask

any astronomer. Aperture is the single most important attribute of a

telescope, so important that it's the main unit of measurement

used to describe a scope. When an astronomer talks about

a 10 inch scope, he's referring to the absolute aperture, not the

focal length. That's because the absolute aperture

determines the light gathering power, and is the

most important factor in helping to determine what stars

will and won't be visible with a given scope. Stars <em>are</em>

relatively insensitive to focal length -- longer

focal length spreads them out further from

their neighbors, but doesn't make them much brighter

or dimmer if the same absolute aperture is used.

<p>

I doubt that any film is going to be fast enough to record

good star trails with a pinhole, but I'll confess to never

having tried it. I've only done star trail photos from

desert locations where dew was not an issue.

I've tried one of moon with a paper neg (asa 4-6) and it didn't work very well. Haven't got a scan on my PC so can't show you. If you're really interested, yell out and I'll scan and post. I think the aperture (f200 or so) and the slow 'film' mean it's just to slow. Maybe real film might work better.

The moon is a different matter- comparable brightness to daylight on earth. With paper negative, it might smear it out too much. Plus, typical pinhole camera is usually on the wide-angle or normal side, so the moon will just be a round fuzzy dot.

 

But, stars are a whole lot dimmer. Bet that shot of the moon didn't show any stars, either?

yep, no stars that I recall (I'm going to have to go and find this thing soon!). The moon took up a small section of the 5x7" neg and was a smeer as you predicted (and what I was hoping for)

Thanks all who answered my question so fast....LOVE THIS SITE!!!

I doubt you would record much other than a few really bright stars. As others mentioned, aperture rules. It is also what determines the faintest star you can record (for a given length of exposure, everything else being equal). Shoot a frame at wide open (~F/2.8) and then one at F/22 and note the difference. Now think about a pinhole at F/300... Also, I think diffraction would tend to smear out the trails. I'd rather solve the dew problem (astronomers use dew heaters, no reason you can't).