Star trail - excessive noise - suggestions?

[niko]

Hi,

I took this trail photo a few weeks ago and was surprised to see so much noise.

Could anyone offer any suggestions as to why?

Many thanks

niko

http://www.flickr.com/photos/6638216...in/photostream

[DavidU (Dave)]

Were you in jpg mode? was it a hot night?

[RobF (Rob)]

Nick, there is software available for combining lots of short'ish exposure images into trails, I'm sure. That would keep your long exposure noise down signficantly.

Aha, found it - cunningly hidden on a webpage called "Startrails"!
http://www.startrails.de/html/software.html

[niko]

Thanks guys.

Ah yes, it was a hot night. I did take a raw as well but the results are just as bad.

Really? A warm night can do that! Wow!

Thanks Rob - I have used startrails but find it creates quite a jagged/stepped trail and wanted to see if I could do better with a long exposure like I used to do with film.

cheers

niko

[Poita (Peter)]

If it is a hot night, then consider some form of cooling, the sensor gets hot and noise becomes an issue.
Can you post a RAW image somewhere? What ISO were you shooting at, and how long was the exposure?
Are these the jagged trails you meant with the software?
http://www.flickr.com/photos/6638216...n/photostream/
The jaggies can be as a result of having VR/Image Stabilisation turned on, or the tripod being to lightweight.

As for the noise, I make sure the camera starts off rested and cool, and set it to ISO 200 and try a 10-15 minute exposure. Turn the camera off for 30 seconds to cool the sensor back down and then take another 10 minute one. Seems to work okay and be low noise.

[niko]

Thanks Peter - I'll check the stabilisation and perhaps weight the tripod down.

ISO was pretty low from memory - probably 100 and the exposure was probably close to 2 hours (maybe a bit long)

Would be delighted to post the RAW if you can suggest where.

thanks again

niko

[skysurfer]

Looks very grainy. Do you have exif info ? Looks like 6400 or more asa. A hot night cannot be the main problem I have taken many pictures in Bali at 27ºC with iso1600 and virtually no grain. But the exposure time was always short, no more than a few minutes. I don't have experience with *hours* of exposure time that might be the problem. Did you set the 'long exposure noise reduction' on ? In that case the camera will take another picture (darkframe) with the same (which means hours in your case) exposure time.

[niko]

termia kasih skysurfer! I'll check the exif info

[luigi]

If you plan to take a single shot then turn on long exposure noise reduction in your camera. The shot will take twice as long but the noise will be reduced.

[jjjnettie (Jeanette)]

Definitely noise caused by heat.
Give Star Trails another go. I too notice exaggerated jagged edges while viewing the image within the program. But in a full res image, they aren't as bad.
Try doing 5 minute subs instead, with 1 second between shots.
You can try to clean up this image though, using the "dust and scratches" filter in Photoshop. A very small increment is all that should be needed, then fade it back if necessary.

[niko]

thanks again for all the advice

we have clear skies (sorry to those in the north) but that giant bright thing in the night sky is a terrible interference!

[alistairsam]

Originally Posted by niko

thanks again for all the advice

we have clear skies (sorry to those in the north) but that giant bright thing in the night sky is a terrible interference!

I know, someone needs to turn it off!!

[niko]

LOL!

Don't get me wrong I love the moon but perhaps if it could only ever get to about 65-70% full we could all be happy. The terminator would be there so we'd get nice views and the lunar month could be that little bit shorter.

Terry did such a good job with the comet - maybe his powers extend to objects a little closer....?

[Terry B]

I think that star trail pics is one area where film cameras still have the edge. The star trail software is good but not as simple as a single long exposure.

[niko]

I agree with you Terry - probably the single area where film stll holds the edge in astrophotography.

Also, so much easier to focus on infinity.

And for that reason I unearthed an old Minolta at my Mum's on the weekend (mine has mould in the lens) and bought some film from Ted's yesterday.

Look out for a whole host of postings when the film comes back from the chemists!