Night photography - need a little advice

Calina

For reasons too long to go into, am going somewhere that I might be able to take nightsky photographs without any/too much light pollution. I'm thinking dusk/stars all that kind of thing.

I'm not a night photography person - I've done a handful of nice things with an eclipse but apart from that, nada. I want stars.

Advice on the subject of exposure times would be appreciated.

TJM

Try turning off noise reduction. I've found relatively little benefit (at least on my camera) in return for doubling the length of each shot & eating battery life. YMMV.

whyulittle

How remote are you going to be? You'd be surprised how far light travels. Took the pic below looking out over Lough Ree, thinking it would be nice and dark. Ended up with light from Roscommon, Lanesboro and Ballymahon pouring into the shot!



EDIT: Plenty of experienced photographers over here, who are always happy to give advice.

magicbastarder

do CCDs and CMOS sensors suffer from reciprocity failure?

Calina

Dahkla in Morocco. I've seen one photograph from there that looks nice which is why I want to go give it a try.

nilhg

To get a decent shot you will need a long exposure, if the camera is on a tripod the stars will appear as streaks, with a very long exposure they will be star trails.

To get sharp pictures of stars you need the cameras mounted on a guided polar aligned equatorial mount, not the type of thing you usually bring on your holliers.

But you probably knew all that already.

My feeling is that if you can't get the sharp pictures you should go for the longest exposures you can manage, to get some nice star trails.
Could be quite long though, it will depend on the area you are in though,,how you feel out after dark.

The sky will be dark though if its anything like Tunisia when we were there last year, no lights at all once you left the towns.


http://www.astropix.com/HTML/I_ASTROP/TRIPOD/TRIPOD2.HTM

Thirdfox

http://www.flickr.com/photo_zoom.gne?id=962978013&size=o

thumbnail here:


This was taken near my house in our public field - hence the massive light reflection off the ground.

22 minute exposure (the sky was even lighter and I had to darken it in photoshop to get a semi-blackish colour).

Benster

If you want just stars and not star-trails, keep the exposure to about 20-30 seconds. After that, you start to see the stars as elongated blobs. If you want star-trails, the longer the exposure the better, as then you get those big sweeping arcs which look cool. You might have to get a cable-release/remote-release with a lock that will enable you to do exposures of over 30 seconds with the shutter speed set to "BULB".

Find the Pole star and keep that in frame too, as you can see in ThirdFox's pic, it can act as an anchor around which everything else is racing around.

Keeping a ground object in the bottom of the frame can give a nice composition,eg a tree or a mountain. It will more than likely come out as a silhouette against a bright sky.

Finally, batteries may be a problem, as if you are doing a long-exp for several minutes, followed by noise-reduction for several more minutes, that will eat battery power, even more so as you'll be in the middle of Morocco at night, which will probably be freezing cold. Batteries do not like cold, so either keep the camera inside your coat til you need it, or else take the battery out and keep it in your pocket.

My effort recently:
[the clouds are lit by Dublin light, the levels of the stars were boosted and the darkness was toned down]

Thirdfox

^ lovely shot - the tree has a surreal glow around it (I'm assuming that's the clouds right?)

Be aware that bulb apparently doesn't mean unlimited in digital photography anymore - I've been told the limit on both Nikon and Canon is 30 minutes.

I'd say this is one of the few areas where film has an advantage - no hot spots worry, noise reduction times and you can hold the shutter open for hours.

pete4130

@magicbastarder

I think reciprocity only affects colour print film IIRC? You have to increase the exposure length by a certain amount or precentage to counteract this AFAIR?

I think it was to do with the way colour print film recorded images onto the film due to the dyes and structure so I'd imagine that CCD's and CMOS sensors wouldn't suffer from it too.

Correct me if I'm wrong though!

magicbastarder

it affects all film, colour print and slide, and b&w. happens at the short end of the exposure range (shorter than 1/10,000 sec) as well as the long end.

Fenster

I preface it by saying we have some beautiful skies over the desert here, but the constant amount of dust that gets kicked up means that light pollution is a bigger problem than it was over say Galway county, even though the region is much more sparsely populated.

Light pollution is going to be a problem no matter where you go in Ireland as a city like Galway or Limerick can light up the sky anything up to 50km away.

Anyways, desert. There's nothing like watching the moon climbing over a desert ridge, but that's a tale for another day.

Your camera innately isn't suited for astro-photography due to it's infrared baffle; most telescopes both on the ground and in space image much further into the infrared spectrum than you'd imagine, mostly as infrared light cuts through haze and dust better than plain light.

Rather than a single long exposure, if you're feeling brave you could try to stack photos. It's a very key technique in any space photography; to sum it up you take a lot of short exposures and digitally composite them.

The advantages are that light pollution won't affect the image, star trails will be brighter and more prominent, and faint constellations will come to the fore. The disadvantage of stacking is that it's extremely labour and time intensive, both in shooting and in post-processing, as well as very stressful on your camera and it's battery.

Here is the one real stacked photo that I've had the opportunity to create:



The sky is black and the stars are vibrant. Off the top of my head it was comprised of about 20 30 second exposures stacked and composited through specialized software. There's software for every OS; I think I composited it under Linux as my desktop box was free at the time. Clean-up was in Photoshop under OS X. Total processing time was a little under four hours.

I'll see if I can drag an astronomer in to give some tips.

ThOnda

I have read somewhere that I should avoid exposures between two and five minutes. In that range the stars or the moon get smudged or unsharp and it is not visible that it has been caused by rotation of the earth.
Some open shutter to BULB with lens covered with black cloth, remove cloth, put it back after exposure and after that release the shutter again. It is to prevent shaking of the camera by mirror movement or the shutter itself.

Roen

magicbastarder wrote: »

do CCDs and CMOS sensors suffer from reciprocity failure?

Nope, they don't, that's a character of film. They can heat up during long exposures and create image noise that way though. CCD's more so than CMOS.