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Thanks Simon,
before plunging into 30 min subs I did experiment with 15 min, 20, 25 and 30 minutes and I found that the temperature of the sensor was very similar in all.. even the noise level was not that much higher in the 30 minute sub as in the 15 minute.
I'm thinking of targetting a very faint object, such as the outer nebulous whisps of the Helix nebula but perhaps going for a hour sub... ISO100/200 just out of curiosity...
I'm thinking that the length of the sub exposures would be dependent of how of a faint object I'm imaging. That said I do seem to get crisper, higher detailed images when using lower ISO sensitivities... although not much difference between ISO200 and 400.
I'm thinking that the longer subs at ISO200 would pick up more fainter detail as opposed to half the time at ISO400 due to the sheer time that the sensor is collecting real photons per sub... Then there is also the balance of how long to expose before the frame gets over exposed due to ambient light... hopefully that is not a issue with narrowband, as I have found so far. With visible light at my location 10 minutes is about the limit of a sub at ISO100.
The Filter wheel I use is the Orion filter wheel with openings for 5 filters... not electronic, just a standard manual type... with auto guiding working so well, I thought I'd leave a few things where I can still be a part of the hobby, namely filter changes and focusing.
Mariusz
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