Another Doozy of a Question (star trails and bulb mode)

[Brownbear]

Doozy (instead of the term dumb)

I just purchased an outdoor photography magazine, which states the following about photographing star trails which I have never attempted (and that's about all it says)

Point your widest lens towards the northern sky so you include the Pole Star (Polaris?), lock your camera's shutter on Bulb for 2 hours at f4 on iso 200 and see what happens... you will be amazed by the results!

I have a Nikon D80 and a Sony alpha 200.. with both cameras I believe I have to keep my finger on the shutter button for long exposures... And I don't think it is possible for anyone to hold the shutter button down for 2 hours.. Do I just set it to bulb, and come back 2 hours later and then press the shutter button?

Does anyone know what will happen? What is the idea behind this technique for photographing stars?

Thank you.

[Donald]

Christina

To get a 2 hour exposure, you cannot be expected to hold the shutter open for that period of time with your finger. You need a shutter release cable. You plug that into the camera, press the shutter release, lock it in open position and then go inside and watch TV for 2 hours.

The other way of doing it is to take lots of shorter exposures (say 12 x 10 minutes = 2 hours) and then blend them. That gives you a 2 hour exposure, but you'd still need a cable release.

[davidedric]

Mind you, Polaris will be a whole lot lower in the sky in Mexico than it is in my and Donald's part of the world!

[dubaiphil]

Like all great TV chefs:

"Here's one I prepared earlier"

I decided on a different route - using a remote intervalometer I shot 30 second exposures for around 2 hours, aiming roughly North.

If you are in the Northern Hemisphere then stars will appear to revolve around the Pole Star. As a rough estimate, your latitude in degrees above the Equator (if that's right - I'm always muddling my Lat and Long) should relate to the degrees above the horizon that the Pole Star will appear.

This was from The Maldives, around 2 degrees North, so with a low Pole Star.

[dubaiphil]

So there are several methods of attack:

1 - take one single long exposure. To remove hot pixels, you should run a 'dark' image with the same shutter time to clean your image up in post. This will drain your battery big time

2 - in camera noise reduction - again, this will do pretty much the same thing as 1, but in camera. Again, your battery will drain big time.

2 - take multiple exposures - if you're shooting over a long time period, then small gaps between images don't really matter, depending on your focal length. If you're zoomed in at 200mm, then a 5 second gap may create gaps in your trails. If you're at 35mm or wider it's not noticable. You then only take 1 'dark' image, but that is the length of your individual exposures (so if you're shooting 1 min exposures for 3 hours, you only need 1 x 1min 'dark' exposure) so your battery won't be drained so much. You can then blend in Photoshop or a free bit of software (which is what I used in the above example) called startrails.exe (worth googling)

If you're going down route 3, then you can get a cheap remote release and lock the remote shutter button down. If your camera's in continual high but your manual exposure settings are for 60 second exposures, it'll just keep going until you're run out of patience. Or you can use an intervalometer which is a more expensive option.

[ktuli]

Christina,

The remote shutter release is also good for reducing vibrations... on a long exposure, pressing the shutter button will actually shake the camera slightly even mounted on a tripod.

I am a fan of the Satechi remotes as they are much cheaper than the manufacturer's offerings... http://www.satechi.net/index.php/cam...timer-shutters

- Bill

[Brownbear]

Thank you Donald... Will buy a shutter release cable (and I appreciate the extra advice), especially after seeing Phil's photo.. Amazing!

Dave, I am now in Bragg Creek, Alberta... Freezing my butt off, and learning to take photos in snow... Lots of stars outside every night, if I can muster the courage to head out into the cold night. All the birds are in hiding.

Thank you Phil for all the photography tips.

Thank you Bill.

[oleleclos]

A little useful information from a navigator: As the Earth spins at 15 degrees per hour, a two hour exposure will give you 30 degre circle segments of each star.

Nice shot Phil, but those clouds?

[Dave Humphries]

Nice shot Phil, but those clouds?

The ones behind the stars you mean?

Sorry Phil, couldn't resist

[dubaiphil]

I know- a bit surreal!

There were little white clouds constantly blowing through the scene over the night! Seeing as for once I had the equipment with me and very little light pollution I thought I'd give it a go.

[Brownbear]

So in other words... I will have to learn how photograph star trails, and use layers to create a similar photo? ie the clouds are not real? I thought they were.

[dubaiphil]

Yes - they're real. Ole and Dave are just ribbing me because the star appear in front of the clouds!

[Brownbear]

Thank you for confirming...

[Donald]

. or a free bit of software (which is what I used in the above example) called startrails.exe (worth googling)

Phil

Had a look. Is that software as easy to use as the 'blurb' for it suggests?

[dubaiphil]

It's a piece of cake and you watch the trails grow as it stacks...

[Andrew76]

Just downloaded - was even bright enough to figure out how to get the English version! Now to just wait for a clear night. Not tonight I'm afraid.

[DanK]

Christina,

A few other suggestions:

You can get wired remote releases very cheaply on eBay, for perhaps $15. (It's been a while, so I don't recall exactly.) I have bought two different brands, for two different cameras, and both were fine. My current one is a Yongnuo. If you end up getting into long exposure night photography, you might want an electronic release with a timer function. It is a pain to try to read a watch in the dark to figure out when to release the shutter on a cable release. I have a Hahnel Gigabit T pro II. However, you might want to wait to find out whether you do much of this.

A second point: you can probably forget about 2 hour exposures, unless you have a camera with a very forgiving sensor. Long exposure noise reduction (NOT the standard noise reduction) will allow you to take reasonably long exposures with a lot of cameras, but I doubt you can go that long. On my camera (Canon 50D), I have been successful with a 20 minute exposure (plus 20 more for the long-exposure noise reduction to finish), but the one time I tried hour-long exposures, the sensor overheated, creating big bands of distorted colors. Some night photographers still use film for very long exposures. Of course, using an intervalometer for repeated exposures can help by letting the sensor cool down.

If you don't want the whole sky but want star trails, don't use your widest lens--use the longest lens that will get you a field of view that you like. That will make star trails appear more quickly (because less rotation of the earth is required for any given proportion of the FOv).

For an easy-to-read and practical how-to on night photography that starts at square one, I would suggestion an e-book titled Light of Midnight by Mark Bowie, http://www.markbowie.com/latest.html.

Dan

[Andrew76]

Quick question - maybe a silly one, but I don't have the answer! We are heading into what appears to be a very beautiful, cloudless weekend, starting tonight, and I'm very interested to take a few pictures and try out my fancy new star trails software, but I'm leery.

Temperatures will be dropping to about -8C, which is not terribly cold, but is it OK to leave the camera out there for 1+ hours in that temp? I know the battery will probably drain quickly, but should I heed the warning of all electronics about not leaving in temperatures below 0C, and above 30C?

Thoughts please?

[tybrad]

Quick question - maybe a silly one, but I don't have the answer! We are heading into what appears to be a very beautiful, cloudless weekend, starting tonight, and I'm very interested to take a few pictures and try out my fancy new star trails software, but I'm leery.

Temperatures will be dropping to about -8C, which is not terribly cold, but is it OK to leave the camera out there for 1+ hours in that temp? I know the battery will probably drain quickly, but should I heed the warning of all electronics about not leaving in temperatures below 0C, and above 30C?

Thoughts please?

Probably not a problem on strong batteries but you could buy a chemical hand warmer from an outdoor gear dealer and use it for the time involved.