Star trails and mega pixels

[jambouk]

Would there be much difference if doing star trails (either with one long exposure, or numerous 30 second exposures) when comparing a camera with 18 mega pixels to one with say 6 mega pixels?

Thanks for any replies.

James

[Cornelius Varley]

Somethings you may need to consider when doing star trails.

1 How much light polution you have. Longer exposures may lead to more orange colour cast.

2 How noisy the camera is.

3 Hot pixels in the camera. These may show up more with longer exposures but can be removed with dark frames.

My method is to take multiple 60 second exposures with a interval of 30 seconds between each exposure.

Peter

[jambouk]

Thank you. But do you think there would be much difference in the end product comparing the two cameras?

James

[Cornelius Varley]

18 mp v 6 mp. I think would be up to you to decide. If the 18mp camera is a lot newer it may have better noise reduction and obviously 18mp images should be better than 6mp ones. The only real way to find out is to do a side by test test and compare the results.

Peter

[jambouk]

It's interesting you high light the noise reduction difference rather than the pixels, per se.

Will there be intrinsic noise reduction on the newer camera, or is that something I should be turning on in the settings?

Thanks.

James

[Cornelius Varley]

Longer exposures can create more noise and hot pixels will become more obvious. The newer sensors can handle noise better and most cameras featuer some sort of noise reduction for long exposuers. This can turned off in most cases to reduce the time between exposures (the camera takes a second exposure (dark frame) equal to the length of the light frame and subtracts it to eliminate noise).

Peter

[jambouk]

So if i enable noise reduction, there will still be only one image, but the camera will have taken two and subtracted the dark frame (with with all the hot pixels) from the one I took?

James

[Cornelius Varley]

So if i enable noise reduction, there will still be only one image, but the camera will have taken two and subtracted the dark frame (with with all the hot pixels) from the one I took?

James

Thats right. The drawback to this is that every exposure takes twice as long.

Peter