Exposure Times and ISO Settings Question

[pfitzgerald]

Hi Folks

I have a portable set up and have gotten better at getting a decent PA. To that end the last few times I've been out imaging I've been able to successfully take repeated 7.0 minutes subs at an ISO of 800 with no elongation of the stars in my subs. Now for the question. ;-).

With the current warm weather (I'm in country Victoria at present) is it worthwhile trying for longer subs - eg 10 minutes at ISO 800 on the Canon 60 Da? I'm really tempted to have another go at imaging Thor's helmet.

I'm still very new at this and finding my so any advice would be much appreciated.

Paul

[Spookyer]

Paul, it would depend on the noise that you are getting on each sub. Generally the longer the subs the better for faint targets. If you are not getting objectionable noise then keep going with longer subs.

Brett

[pfitzgerald]

Thanks Brett

I'm still learning about "noise" and SN ratio. Am I correct in that with increased air temperature the noise level in an image increases?

TIA Paul

PS I suspect it will be a try it and see activity.

[raymo]

All other things being equal, the higher the ambient temp, the more
thermal noise you will get, which is why DSLR using imagers frequently
try to find convenient ways to cool their cameras, and dedicated CCD
cameras are normally cooled.
raymo

[batema]

Go long, chuck in a stack of darks, go the noise reduction software and have a ball.

Mark

[pfitzgerald]

Planning to Mark - just got back from watching the 'Desolation of Smaug' with my daughter. Lovely dark skies but too much strong wind at present. I'll give it half an hour then pull the pin if it doesn't improve. The forecast is for clear skies again tomorrow night.

Thanks for your input Ray, not having 'traveled' this far with DSLR imaging until now I was curious as to how far you can go exposure wise until the thermal noise swamps the data gathered.

Paul

[Jon]

I found 10 min was pretty much the max with my 60Da. 800 ISO is also the "sweet spot" for this camera. Using a higher ISO doesn't get you any more signal - in fact it lessens the SNR a little.

[pfitzgerald]

Thanks for that Jonathan.

I'm actually trialling some 10 minutes subs as I type on the Horse Head and Flame Nebulae to see how they come out.

Paul