Playing with field flatteners and sensor distance

June 18, 2020

I'm still running some tests with the new mount as well as clearing up distance issues I had with my narrowband imaging train and the William Optics Flat 6AII field flattener/focal reducer. Everything has to be precisely positioned in order to produce a distortion-free field, round stars, all that stuff. I ended up going back to the stock focuser for the GT81 just to simplify things. And I think it was fairly successful. And the Sky-Watcher EQ6-R Pro continues to make the job easy!

I really like the Framing & Mosaic Wizard in Sequence Generator Pro, and still think this is one of SGP's best features--if only it could function without a net (offline). For one of my test runs I called up IC 1318, the Sadr Region in Cygnus, which contains the Butterfly Nebula, Crescent Nebula (NGC 6888, Caldwell 27), and many beautiful dark nebulae. Using the framing wizard at 6 degrees I centered the sequence on these twists of hydrogen clouds out at the edge--just for something different. My intent was to shoot 50 x 240-second subs, about 3.3 hours of hydrogen-alpha data, but I discovered--too late--that I had a power problem with the dew control gear and the objective on the GT81 started clouding over about an hour and a half into things. I still managed to process something out of the stack, but a better shot will have to wait for another night.

I also took 30 subs of Sh2-54, GUM 84 and 85, LBN 72, that bright emission nebula in the Constellation Serpens. The star cluster NGC 6604 is to the right of it.

And last, just on whim because I had another hour of darkness left in the night, I moved up to IC1396 again, centering on the Elephant Trunk Nebula. I didn't get enough Ha data for a cleaner image, and I had lost some focus by that point too, HFR numbers were climbing over 3 pixels from about 2.25.

We have another fairly clear night tonight, and I'll be returning the William Optics GT 81 to it's modified state, Moonlite Focuser. I may also test things out with NINA again.