Bulb (long exposure) night photography

benjyman345 · Sep 26, 2006

hello,
I want to take a long exposure photo of the night sky and stars so that you can see the movement of the stars in the photo.

What is the best settings to use to achieve this?
Shutter time? (30mins, hour etc?)
Appeture?
What film? (100, 200, 400?)
What ISO should i set the camera to? (the same as the film or diffferent)

Anything else i should know or consider?
(I have a remote shutter release button and lock and tripod)

thanks

Big Mike · Sep 26, 2006

Welcome to the forum.

I haven't done much of this really long exposure stuff...but I seem to remember that low ISO film works best. After a minute or so...it's actually more sensitive than faster film. As for aperture, I don't think that matters too much...your DOF will be at infinity anyway.

I think that trial and error seemed to be the way in which people found the right exposure time...you may be able to find a starting point if you search around.

Good luck.

fightheheathens · Sep 26, 2006

well....I like to use the Lowest ISO film possible.
like 50 or so
i would say for starters, go f/8 and then what ever you want for your shutter.
you would get good stuff after 30 min. but i personally have done 4+ hours with my camera.

JDP · Sep 26, 2006

There's someone on this forum who has taken a LOT of space pictures, I can't remember who - but he did a wonderful job and has plenty of info on his site - I *hope* he sees this and lets us all know!

benjyman345 · Sep 26, 2006

if I use 100 film should i leave the ISO setting at 100 or set it to a lower setting such as 50?

If i do change the ISO setting for one or two photos out of the roll of film do i need to notify the people processing the film?

thanks for all your responses so far.

astrostu · Sep 26, 2006

I doubt I'm the person that JDP is referring to, but I've done a lot of astrophotography (and I have some star trails on my photosite in my signature). The exposure time will depend upon how long you want the trails to be. One hour will give you arcs that are 15° long (2 hrs will be 30°, 20 minutes will be 5°, etc.).

One issue in exposure length, however, is how much light pollution there is where you are. Near a city, if you expose too long (even for a half hour), the sky is bright enough that it could wash out all of the stars. Hence, really trial and error is the only way to really figure out what's best for you.

Big Mike · Sep 27, 2006

benjyman345 said:
if I use 100 film should i leave the ISO setting at 100 or set it to a lower setting such as 50?

If i do change the ISO setting for one or two photos out of the roll of film do i need to notify the people processing the film?

thanks for all your responses so far.

Don't worry about over-riding the ISO setting...just leave it the same as the film.

JDP · Sep 27, 2006

astrostu said:
I doubt I'm the person that JDP is referring to, but I've done a lot of astrophotography (and I have some star trails on my photosite in my signature). The exposure time will depend upon how long you want the trails to be. One hour will give you arcs that are 15° long (2 hrs will be 30°, 20 minutes will be 5°, etc.).

One issue in exposure length, however, is how much light pollution there is where you are. Near a city, if you expose too long (even for a half hour), the sky is bright enough that it could wash out all of the stars. Hence, really trial and error is the only way to really figure out what's best for you.

Wrong! It WAS you I was responding too! I have an odd love for space, though I let other people to the dirty work - you have some wonderful pictures Stu, you should be proud!

astrostu · Sep 27, 2006

JDP said:
Wrong! It WAS you I was responding too! I have an odd love for space, though I let other people to the dirty work - you have some wonderful pictures Stu, you should be proud!

Alright, I just figured it was someone else since I've only been on this forum for under a month ... but I'm glad that I'm already making a good impression - thanks! :blushing:

rmh159 · Sep 27, 2006

How about a lens for these shots? I have a 18 - 55mm... would that do it or would it work better with a telephoto?

astrostu · Sep 27, 2006

rmh159 said:
How about a lens for these shots? I have a 18 - 55mm... would that do it or would it work better with a telephoto?

It depends upon the effect that you're going for, but I would think you'd want a pretty wide-angle lens in order to capture more stars. All of the trails on my site were done with an 18 mm lens.

mortallis288 · Sep 27, 2006

somone did this in the AP art class at school. they did it for an hour and a half exposure time, im not sure about the other settins

Torus34 · Sep 28, 2006

It's not possible to give you exact information as the exposures you will use will depend on your night skies -- light pollution, haze, scattered light from the Moon, etc.

An ISO 100 film will do the job. Very grainy films do not give satisfactory images. Color slide film is best as there is no loss of contrast/sharpness in a printing process. Set lens at infinity and use one stop down from your widest aperture. Then try a range of time exposures. You will find, when you examine the results, that stars have different colors. Your first roll of film, if you take notes of the exposures, will tell you lots of things. Exposure is a trade-off. If you stop down, you can expose for a longer period of time before the background sky light will fog the image. This will provide longer star trails, but you'll lose the fainter stars. The choice of focal length, aperture and exposure time depends on just what sort of an image you're after.

Learn your sky. Free download-able star maps are available from several sites. The 2.7 Meg Basic Program from this site will get the dog walked, and then some:

http://www.stargazing.net/astropc/download.html

Pick out stars of various magnitudes [1 through 4] as references. Some nights, all you can see are mag 2 and brighter. Other nights, mag 3 and brighter, etc. By knowing the magnitudes of a few reference stars, you can accurately judge the photo conditions. There's a nice series to be found in Ursa Minor and the stars are visible at all times of the year. For brighter stars, either Ursa Major or Cassiopeia are visible each night. Right now, Cygnus and Lyra are overhead in the early evening. All five are easily-recognizable constellations.

Try including an Iridium satellite flash in a photo. They can be very bright -- up to mag -8. There are other satellites visible almost every night with various magnitudes. Here's a site with information on them -- just log onto it and enter your longitude and latitude. It will provide nightly predictions. [It's a freebee, too!]

http://heavens-above.com/

As a side note to anyone reading this: catching an Iridium flare or seeing the space station or shuttle is worth the effort, IMHO. About all you need is your longitude and latitude, a decent view of the night sky, a timepiece and the above site. The nature of satellite viewing is such that you don't even have to stay up late. Binoculars of not more than 7X are a nice aid.

astrostu · Sep 29, 2006

Torus34 said:
As a side note to anyone reading this: catching an Iridium flare or seeing the space station or shuttle is worth the effort, IMHO. About all you need is your longitude and latitude, a decent view of the night sky, a timepiece and the above site. The nature of satellite viewing is such that you don't even have to stay up late. Binoculars of not more than 7X are a nice aid.

True, but they're somewhat difficult if you have a lot of obstruction around your observing site. And an accurate timepiece is necessary, since passes usually last only 1-3 minutes, and most watches/computer clocks will disagree up to 10 minutes from each other.

The space station is especially neat to see since it's usually quite bright (mag -3 when I saw it).

For those non-astro people here, the magnitude scale is really weird, where brighter objects are smaller numbers. Naked eye at a dark site has a limiting magnitude around 6, cities closer to 2-3, with NYC closer to 0 or -1 (I saw one star, Sirius, when I was there last, and Sirius is the brightest star in the sky (other than the Sun)). The Moon is usually around -12 by comparison, the Sun -26. "Standard" bright stars, such as Vega, are defined to be 0, and the magnitude scale is a logarithmic scale where every increase of 2.5 in magnitude is a decrease of a factor of 10 in brightness.