Photoclubalpha

Hopefully one of you guys can give me some info' about taking star trail photos.

I'm wondering if I need a shutter release cable for taking long exposures, or whether just setting the camera's two-second timer will work okay.

Also, I saw on YouTube that one guy - using film - placed a black hat in front of the lens just before and after pressing his remote shutter release. I can't figure out if I need to do this or not.

Thanks in advance.

I haven't tried for star trails myself as yet but have done a few night street light/city/firework scenes. I have noticed camera shake is amazingly easy to get even on these long shutter openings. I prefer to use a cable for these and have learnt the hard way bridges/structured walkways and most hotel balconies are no use as tripod bases. Generally A mode, f8 or f11, ISO 100 seems to give good results. Full manual for street/fireworks is probably just making things unnecessarily hard, obviously shutter needs to be open a lot longer for startrails and you will estimate for yourself. Regarding the black hat, I think that is perhaps going a little far but see how you go.

Hi Cycladelic, my understanding of photograhing star trails is that you need very long exposures (e.g. 30 minutes, or even hours) on a tripod. The longest 'automatic' exposure that most dslrs will take is 30 seconds. After that you need 'bulb' mode where you have to press the shutter to start exposure, and again to stop. The 2 second timer mode would still require you to touch the camera to stop the exposure. If you use bulb mode with a remote cable you don't have to touch the camera and therefore do not risk moving the camera, even ever so slightly. To be ultr safe you could use 2 sec timer and a remote cable .

I can't work out the black hat bit. I can see you may use something like that to 'interupt' a long exposure. or use it to restrict light entering through the viewfinder, but don't understand it as you describe.

I was going to try this on my next clear night wich could come this week. i've done a few 15 minute ones but I wanted to go for 30min or longer. Anyone have any idea how long dark frame noise reduction can work for on an A700?

The black hat can block out the effects of camera shake. If you open the shutter, wait for vibrations to cease, and then remove the covering, you have no camera shake in your photo. Do the same at the end so that the shutter doesn't shake the camera as it closes. Well, it will shake the camera, but it the lens is blacked out, it won't show up!

Dusty

Many thanks for the replies.

Birma - as Dusty stated, the black hat - or whatever item you use - will cut out any sign of vibration caused by the shutter opening and closing.

I'll have to check my a850 to see what the max' exposure time is. How about the Sony cable release gadget - are there more options with that, does anyone know?

There are quite a few tutorials on YouTube. Many talk about stacking - taking numeorus photos and then merging them into one image. It sounds a bit complicated. It seems the benefit is that the consequences of camera shake are reduced as the shutter is open for less time.

I'll have to wait for a clear night and just have a go. However, it'll be hard to get a good shot where I live as there is so much street lighting.

Ah, that makes good sense Dusty .

For cable release, I bought a cheap one of eBay - very low risk of it damaging the camera (imho) and it doesn't need to be gold plated for the job it has to do. There is the Sony wireless (IR?) remote control (was free with the A700 ) but you need to be in front of the camera ideally for this.

I have a cheap programmable one off e-bay too. it works really well and was very inexpensive.

The main problem you have with long exposures (over 30s) is from light pollution turning your skies orange and so loosing the faint stars. Plus the need to do a dark frame image with the lens cap on of the same length in order to remove hot pixels.

The common trick now is the take many 30s exposures, putting the camera into 'continuous shooting' mode and using a locked on cable remote. Also turn off 'long exposure' noise reduction to stop the camera taking a 30s dark frame after each exposure. At the end of your series of shots then put the lens cap on to get a few (say 5) dark frames.

The processing then can be done in Photoshop or Paint Shop Pro, to combine your shots using 'lighten' mode to add together all the short star trails. This could be a lot of work so there is a handy utility - available at http://www.startrails.de - which takes your exposures and your dark frames and does all the hard work for you!

This image is the combination of 120 frames totalling an exposure of 1 hour. Sony A700 / Samyang 8mm Fisheye.



Revolution - Lovell Telescope by Ant_H., on Flickr

Cheers,

Ant.

Nice image and great instructions Anthony_h, almost makes me want too try, but for me the real point of star trails is too see the colour of the stars as they really are, and I can't figure out what combination of WB, ND filter ISO etc. (whatever) would possibly do that, they move slowly enough that they actually burn their colour out, so yellow (like the sun) stars end up white etc. There are some high carbon/silicone red stars as well (r Lepus typeshttp://en.wikipedia.org/wiki/R_Leporis) and it would be really good too be able to get them show up as actually red also. I see in your image there are actually some blue (very hot) stars so your settings are on the verge of actually getting the colour/spectral type to show up. It's all complicated by what magnitude some of the more interesting stars are as well, some of the yellows and most of the rare reds are a lot fainter than the whites and blues so that makes life even more difficult, (too get them all in the same exposure that is).
Greg

Very nice instruction Anthony_H. Thanks.

Cheers Greg, Dr Harout.

One technique to reveal the colours is to defocus the camera, hence spreading the light over a larger area and avoiding over saturating the pixels. One example of doing this is in this shot by David Malin (AAO).

Though of course this only works for the brighter stars, the faint ones just get lost in the noise as you spread their light over more pixels.

Ant.

Thanks Anthony_H - a very useful approach to start trails. I hope to give it a try some time.

Nice antony. was this a series of Low Iso small or aperture shotes or are you exposing for sky on every shot?

The individual shots were taken at ISO 160, 30s, but as it was a manual lens I do not have a record oft he aperture, most likely f/4.5 or so. All were done at the same settings.