On the right track?

[Roy Batty]

Last night I tried using ISO800 with my EOS clip CLS filter, instead of my usual ISO1600 - but pushed up sub length from 60 to 90 seconds (unguided setup). A cursory look at the subs has I think reduced the noise & amp glow considerably - my aim to improve the signal to noise ratio. I think i'm right in my assumption that by upping the ISO on a DSLR actually just increases the amplification of both signal and noise? I've also read somewhere that for a canon 350D ISO800 is considered the optimum for astro work.

Any thoughts welcome.

RB

[ianporter13]

Sounds about right to me Roy,

at 1600 you'll get more data but much more noise so you'll need to take more subs to average it out.

I'd stick with 800.

Ian

[jcm]

With my 130mm telescope I have found 800 ISO as the best overall setting. With light pollution effecting most of us the CLS filter seems to compliment the Canon cameras and remove a good proportion of the pollution. Some colour adjustment is often needed usually to reduce the amount of red. This time of year the background sky is quite bright and at F6 about 5mins at 800 ISO is about the max exposure time I use. ( often 4 mins has to be used)

John

[Roy Batty]

Thanks for the feedback guys, it's nice to know my conclusions are consistent with your thoughts - I'm now looking forward to see what results I have got from last nights session - M95 & 96 and also a grouping centred on M86

cheers

RB

[steppenwolf]

I have always found that upping the ISO above 800 is counter-productive but 800 gives the best overall balance of signal to noise - for greater saturation (for the Moon for example) then you can't beat ISO 100.