exposure times for star trails

Can someone give me an idea of how long an exposure should be for star

trails? I would like to try some tonight. Searched here but couldn't

fing any. Will be using provia 100 and Kblack and white + 400, and

will have snow background. Thanks.

Exposure times can as long as you want (several hours) but eventually the skylight will build up, unless you are in ideal pristine conditions (like high elevation on a clear night with deep, dark skies) Also, it depends on the lens aperture setting... for really long times you need to "stop down" more. The biggest problem with really long times is "dew" forming on the lens (looks foggy) You might be suprised to see how much skylight builds up, especially if you are close to a city (by close, I mean withing 50 miles) If you can't get far from the city, then go to the edge of town and point camera at the part of the sky away from the city. You say you searched but didn't find anything? There are many disucssion on star trails right here on photo.net so try again, typing in star trails, and also try star-trails. By the way, once you lock the shutter open, don't forget and shine a flashlight into the lens, or use a cig lighter too close. If the moon is up, it will wash out the sky too, but can be used to create "moonlit landscapes", especially cool looking with snow! If you want tips on doing star trails with moonlit landscapes send me an e-mail ( photonut1960@sbcglobal.net ) I'll need to know where you live (approximately) and which direction the camera will be facing (North, South, ect.)

Not sure why your search didn't find it, but Bob Atkins PN article

can be found <a href="http://www.photo.net/nature/sunmoon"

>here</a>. It also has links to some other sites.

Simple astronomy might help you get a grip on the obvious: in 24 hours, the "world" turns around itself once (360 degrees).

 

So in 6 hours the star trails cover a 90 degree angle, in 2 hours a 30 degree angle in the sky, etc. Now compare those numbers with the opening angle of your lens, and you will be able to cover all the frame with a star trail, or a half, or a third of the frame ...

 

Now this inviolves higher than 3rd grade math: fractions. Can you do those? From scratch? Good luck! And do open the lens to its widest for best results.

ee,

 

I use Iso 100 @ f/4.0. plus all the above suggestions. If it is snowy or humid you may get condensation on the lense but if the snow has been on the ground for a few days, the humidity may have dropped enough that your lens won't fog up. It usually takes about an hour and a half until it's really dark and you need to be somewhat remote from city lights as stated.

 

If you want a foreground subject, you can use your flash to walk around and highlight it and as mentioned, point the light source away from the camera lens.

 

If you point the camera somewhat northwest, you might pick up a reddish glow from setting sun even waiting almost two hours until exposure begins.

 

I'm interested in doing more of these myself this year as Velvia 100F supposedly shifts to the red spectrum on long exposures.

 

good luck, and don't oversleep. You need to close the lens before morning light begins.<div></div>

<p> Exposure times for star trails will vary depending on the kind of composition you desire and the condition of the sky. Tonight there will have a slightly gibbous waning moon that rises at 10:22 PM so you will likely want to take your photographs before the moon�s brightness washes out the sky. Star trails become more circular but shorter as the image approaches Polaris, the North star. If you include Polaris in the image, the trails will appear to revolve around Polaris.

 

<p> To be effective, star trail photographs do not have to be lengthy. For example, a five minute exposure of Polaris will show the revolving effect to good measure. Some photographers seem to assume the longer the exposure the more dramatic the effect. The risk you take as the exposure time gets longer is that the sky will wash out and you will lose the fainter trails. A wider aperture will capture fainter stars but also causes the sky to wash out faster. A good starting point is two f-stops higher than the maximum for the lens. In the end, there is no �correct� exposure and it all comes down to subjective preferences. You might want to experiment with different exposure times and f-stops to see what you like.

 

<p> Also, you might want to try some fixed star images using short exposures. For example, at 6:30 PM, the constellation Orion will be at the east-southeast and about 15 degrees in the sky. If you are not familiar with this constellation, it looks like an hour glass with three stars forming a neat line at the center (Orion�s Belt). Use exposure times of 10 to 15 seconds using a 50mm lens at f/2.8 and you should be able to pick up nicely with both Provia 100F and your monochrome film. More information on the nuances of imaging stars with conventional equipment can be found in <A HREF="http://www.krages.com/hb.htm">Heavenly Bodies: The Photographers Guide to Astrophotography</A>.

Frank, in the course of preparing your patronizing response, you neglected to consider the star's declination. It should be obvious that you don't need a 180-degree fisheye to capture a 12-hour star trail of Polaris. You'll need a cos(dec) term in your calculations.

Thanks everyone,

I will come back and read all this tomorrow. Just got back, I did look at some people's photos with trails and was going to try their listed exposures, but it was just too cloudy today.

ps. I have a photo of a lunar halo up. I looked at your exposures Jeffrey for that one, but unfortunately the sky is too light and the moon is all aglow/not clear as it was, anyone have an idea why that happened? I thought maybe I should have tried shorter exposures at 30 and 15 seconds. Will try that next time.

Bill your photo is beautiful.

EE,

 

Thanks for your comment. These are fun to do. As others have said, best time is at new moon.

 

Bert, I checked out your link, great book. I may have to have that one.

 

cheers,

<A HREF="http://www.photo.net/photo/2050816">Here's</A> one with star trails and a structure "painted" by flashlight.

<A HREF="http://www.photo.net/photo/2050827">Here's another one</A>

Those are great Jeffrey,

 

I guess I can't do this with a structure that is has lights on it in the photo though? Bill I assume that you did quite a long exposure if you are worried about oversleeping? I have no plans to stay that long, it's too cold at the moment anyway :-) Bert, your book looks like it would be useful for me. Here is my lunar halo, hopefully.<div></div>

ps. Andrew thanks for pointing me to that article.

ee,

 

I like it. It's different and great framing with the trees.

 

cheers,

Thanks Bill,

 

I wish I had gotten it exposed properly, the moon was very clear and it was much more dramatic than this, the sky darker. There was a lamppost nearby, wonder if this affected things at all?

Hi e e, regarding your comment about exposing for the moon, someone suggested the "Moony 11" rule, similar to th "Sunny 16". Basically use the reciprocal of your film speed as the shutter speed combined with an aperture of f/11. In my experience this does show up quite a bit of detail on a full moon. If you rely on the camera's light meter the moon will be way over exposed because the moon is so much brighter (reflected sun) than the rest of the sky is. Sorry that this is so late.

Regards Brendan