Helix, NGC253, NGC1365 and M16 & NGC6744 ST4000XCM & ST7
Hello,
Here are some results from the recent Qld Astrofest; the good, the bad and the downright ugly! Tak Mewlon 180 F12 with x0.8 Reducer/Flattener giving F9.6 riding on an EM200.
The smaller M16 and NGC6744 images were taken with the ST7E and the remainder, Helix, NGC253, NGC1365 and M16 wide were taken with Gerald’s ST4000XCM binned 2x2 giving an image size 1024x1024 (from 2048x2048).
ST7
M16 – 10 exposures at 300 secs each.
NGC6744 – 6 exposures at 600 secs each.
Dark frames manually subtracted after images acquired.
ST4000XCM 2x2 binned
Helix - 6 exposures at 600 secs each.
NGC253 - 10 exposures at 600 secs each.
NGC3165 - 6 exposures at 600 secs each.
M16 - 15 exposures at 300 secs each.
Dark frames auto subtracted at time of image acquisition.
I’m reasonably happy with the ST7 M16 although the NGC6744 was spoiled by thin, high cloud during the imaging session.
I was surprised at the noise in the ST4000XCM sub frames, which were auto subtracted, whereas I usually take 6 separate Dark Frames and do a Median Combine before subtracting them. Maybe that would have been a better approach?
These imaging sessions were quite helpful in guiding me to the realisation that my future in not in high quality LRGB DSO imaging – it is just too specialised and too time consuming for my style of astronomy, which is more of a generalist rather than a specialist.
M16 and NGC253 are real visual treats Dennis. Top work on those. I'm guessing the ST4k binned gives you nice sampling (around 1.76 arcsec/pixel) with that optical train combo. Something you can't really do well with the ST7 as you simply run out of pixels (array isn't huge and they are 9u if I recall correctly). Thanks for sharing this panel. Well done.
Thanks Jase & Stuart. These imaging sessions gave me quite a valuable insight into just what is required to produce nice looking, long focal length, long exposure, clean LRGB DSO images.
The EM200 was auto guiding so well that as I ran the sub frames as an animation, there was absolutely no drift between sub frames, although some frames did have slightly oval stars. However, I’ll have to look into the topic and practice of dithering as I think with the ST4000XCM in particular, the somewhat noisy background just stacked up and amplified when I combined the sub frames. I did use the hot pixel removal tool in CCDSoft on the original FITs files and that helped some.
I takes me hat off to those long focal length, 10min+ LRGB astro photographers out there; your skills and dedication to this black art astound me, as well as the results you post!
The ST4000XCM with its ST237 guide chip was a real pleasure to use – thanks Gerald. The Real Estate was just enormous at 2048x2048, although I had to bin at 2x2 to increase the flux due to the relatively slow F9.6 speed.
I was beaming all night, right through to 5:15am with the acres of open space on the ST237 sized guide chip compared to my TC211!
Very nice Dennis
I'm hearing you
