|
Alex it all depends on how dark your sky is. The darker the sky, the lower ISO you want to use to utilise the dynamic range available.
In summer, you probably want to find a compromise, as the longer the exposure the worse the thermal noise will get.
As a stab in the dark, I would dial it up to ISO1600 for 2, maybe 3, minutes and see how you go. When the weather cools down a bit, and if you have a really dark sky, I’d try dialling it down a bit.
Just be aware that some sensors have their quirks - I think the sensor in the D5500 is the same as in my Fujifilm, and these Sony sensors have what’s called high conversion gain mode, which kicks in above ISO800...and reduces read noise, and thus the all-important signal to noise ratio.
|