star trails

[bucketman]

Hi Guys
Its been a while since ive been on but stuck again so please help
been tring to do some star trails and one web site says you need 200 pics at 20 sec when i take one I get what I guess is an error message so how do i take 200 (camera is a D90 with a sigma 10 20 lens) the message says "job nr r02"

[Donald]

Download this guide to stacking images. It should tell you all you need to know about the 'take 200@20secs' issue.

Sorry, can't help with the apparent error message.

[bucketman]

Cheers Donald
Will have a read thru it but its the error message am worried about if I go down to 8 sec its fine but 10 sec and the camera gives up???

[Colin Southern]

200 x 20 sec sounds rather extreme to me - why not just take 10 or 11 10 minute exposures? (or 5x 20 minute exposures)?

If you're at a low ISO then the noise shouldn't be too bad (expecially since you can push the contrast and kill most of the noise in PP anyway.

[bucketman]

Hi Colin
worked out the error is a noise reduction thing? if I take 1 pic at 30secs it takes about 30 secs for camera to calm down. So after a 10 min exopsure would it
take 10 mins for camera to work again. The 20 sec * 200 is for astro pics so it was on that web site I read it. I have what is called a GOTO Mount that can track a star or planet but my star trails would just be on a normal tripod

[Colin Southern]

Hi Colin
worked out the error is a noise reduction thing? if I take 1 pic at 30secs it takes about 30 secs for camera to calm down. So after a 10 min exopsure would it
take 10 mins for camera to work again. The 20 sec * 200 is for astro pics so it was on that web site I read it. I have what is called a GOTO Mount that can track a star or planet but my star trails would just be on a normal tripod

For noise reduction purposes a camera can take a dark frame (of the same exposure) and subtract what's in common between the two, but it's a feature that can be turned off (called long-exposure noise reduction on Canons) so that there's no delay between frames.

Astro photography is something different though, where they could well take lots of shots, but I thought you were after something else (you won't get many star trails if you camera is tracking them on a GOTO mount

I'm planning to do some shortly, so I'll let you see how I got on. With long exposures I've done in the past there can be a lot of noise - but - it's shadow noise (for the most part) and you can simply raise the black clipping point until it goes away, and then lower the highlight clipping point to increase the contrast - it actually works surprisingly (or perhaps not so surprisingly) well.

[bucketman]

Thanks Colin
yes I have a GOTO mount but I would like pics of star trails then move on to astro I have swiched the mount off to get the trails but my camera sends error message up on multi exposures I will look can if I switch the nr off on my little old nikon
thanks again
rob

[bucketman]

Thanks again Colin
I have swiched the NR off
thanks again
rob

[Peter Ryan]

I have not done star trails with my DSLR (so not sure bout the noise) but with film I used 100 film ISO @ f2.8 for 30 minutes or @ f5.6 for one hour.

Make sure you point your camera to the northern (northern hemisphere) or southern celestial poles (or there abouts) so you get better curvature in the trails. If you point towards the equator you will get straight lines.

Is this the type of shot you are trying to achieve. This was taken @ f5.6 for 1 hour.

[Colin Southern]

I have not done star trails with my DSLR (so not sure bout the noise) but with film I used 100 film ISO @ f2.8 for 30 minutes or @ f5.6 for one hour.

Make sure you point your camera to the northern (northern hemisphere) or southern celestial poles (or there abouts) so you get better curvature in the trails. If you point towards the equator you will get straight lines.

Is this the type of shot you are trying to achieve. This was taken @ f5.6 for 1 hour.

Nice shot Peter - what's your focal length on that one?

[Peter Ryan]

That was shot with an old Pentax film camera with fixed 35mm lens.

[Peter Ryan]

Two additional points if I may.

Star trails should be shot on nights where there is the no moon (or smallest possible). Moonlight will kill star trails.

Try to point you camera away from city lights, even if they are over the horizon, as their glow will show through at the bottom of the shot. The glow in the bottom of the above shot was the lights from Melbourne 90 km away.

[bucketman]

Thanks you all
the sky at the moment has not got one cloud. Cant help the light pollution where i live but will have a try but one last ? would you go wide angle 10mm or zoom 300mm got about 2hr till it goes dark so no pressure and am in work tomorrow so bed by 12

[bucketman]

oh forgot cos of noise jpeg or raw

[Dave Humphries]

oh forgot, because of noise; jpeg or raw?

RAW, always RAW !

[Dave Humphries]

Thanks you all
the sky at the moment has not got one cloud. Cant help the light pollution where i live but will have a try but one last ? would you go wide angle 10mm or zoom 300mm got about 2hr till it goes dark so no pressure and am in work tomorrow so bed by 12

Choose a lens based on what you want in shot - you choose, but that's a heck of a difference, anything in between available?

[Peter Ryan]

Thanks you all
the sky at the moment has not got one cloud. Cant help the light pollution where i live but will have a try but one last ? would you go wide angle 10mm or zoom 300mm got about 2hr till it goes dark so no pressure and am in work tomorrow so bed by 12

The shot above I took with a fixed 35mm lens.

[bucketman]

only took a couple of shots 10 mins and 15 min exposure it just a test but when i had a look you can see star trails but the sky looks like dusk (we have a lot of lights round here) so if i pp them could i get the sky to go darker and if so how. New to all this
rob

[Dave Humphries]

only took a couple of shots 10 mins and 15 min exposure it just a test but when i had a look you can see star trails but the sky looks like dusk (we have a lot of lights round here) so if i pp them could i get the sky to go darker and if so how. New to all this
rob

Hi Rob,

No time to answer now, but need to know what you're using for PP software, or we risk causing confusion by using the wrong terminology.

Thanks,

[Colin Southern]

if i pp them could i get the sky to go darker and if so how. New to all this
rob

Hi Rob,

Pretty easy - in essence, all you need to do is increase the contrast so that blackish things go blacker and whitish things get whiter. In Photoshop you can just add a levels layer and bring in the black and white clipping points ... in Adobe Camera RAW you can just raise the blacks slider.