City DSLR AP: Messier 4

[Phisci]

4 hour stack of 1min ISO200 subs using Samsung NX500 on 10 inch F5 newtonian. EQ6 mount guided using PHD2; Stacked and processed in PI. this is one of two closest globular clusters to the Solar System. Estimated age of 12.2 billion years!

[Placidus]

Nice work. It looks very M4.

ISO 200 sounds a bit low. Ideally one wants to set the ISO so that one photon equals at least one count in a 16 bit image. Setting it less than that is a bit like trying to measure the length of a grasshopper to the nearest kilometre. It might be worth trying a higher ISO. Use the highest ISO that doesn't burn out the stars in a single sub.

Keep them coming. Looking forward to your next image.

MnT

[Phisci]

Thanks for the feedback MnT and for the encouragement. I run at low ISO because I'm in redzone suburbia, so quickly get washout of images at higher iso given light pollution. I could run at say ISO800 but would then have to use much shorter subs. I'm giving the processing another bash to see if I can extract a bit more.