At last! September has come around again and we can actually start imaging before 10:00 p.m. hooray!! Less baggy eyes at work the next morning 🙂 This Month’s imaging object is the mysterious-looking NGC7023, a reflection nebula known as the Iris nebula in the constellation Cepheus. From my notes I started imaging this one around 9:45 p.m. so not that much before 10:00 p.m. but sufficiently early in the evening for it not to feel too painful.
You need to go deep on this one in order to do justice to all the dark nebulosity that surrounds the Iris. Look carefully and you’ll see a huge “clover-leaf” pattern surrounding the Iris nebula where most of the stars are missing – this is the massive dark nebulosity that fills this region. In order to get that rich brown colour that is often associated with dark nebulae you need to go deep, and that means 5-10 minute sub exposures with the Hyperstar and 10-20 minute subs with an f#4.5 instrument like a Sky 90. For total exposure times you’d like to get around 4-6 hours with the Hyperstar which translates to in excess of 24-hours with the Sky 90, which is bordering on silly. This example shows the power of Hyperstar imaging where you can download quality data 6 times faster than is possible with a very popular imaging refractor.
The Iris nebula lies at a distance of 1,400 light years in Cepheus, and it’s not an easy one to process as the core is so bright it is hard to control it and not having it “blow out”, while at the same time trying to show the dark nebulosity at its best. You’ll know you’ve got quality (deep) data and that you’re processing is top-notch if you manage to bring out the little pink region lying very close to the core of the Iris.
Hooray!! The earlier evenings have returned – we now have (hopefully) another 7 months of great imaging ahead of us.
I wish you clear, dark, Moonless September skies.