Attempt at NGC 6888 (Crescent Nebula)

NGC 6888 - the Crescent Nebula in Ha.

Last Sunday I had a rare opening in the UK’s rather wet summer weather so I set up my new kit and sequenced a night on NGC 6888; the Crescent Nebula. We are just past the summer solstice here in the UK and, given my rather northerly latitude of over 51N, it isn’t dark until nearly 11.30pm and it starts to lighten around 2.30am so there is a small margin for setting up and imaging. Nevertheless, I have been experimenting recently with automating everything via Sequence Generator Pro as I can speed up acquiring data by using plate solving rather than two or three star alignment.

I’m using a new mount (Skywatcher EQ6-R) and a new scope (Skywatcher 130pds) so I was expecting some issues and I wasn’t disappointed!

I did get polar aligned relatively quickly and by 11.30pm I was plate solving on NGC 6888. SGPro managed to get me on target within 2 plate solves (one less than on my older Celestron GT Advanced mount) so that was a bonus.

From here, the problems began. My camera and filter wheel setup comes in at around 900g which wasn’t a problem on my old ED80 scope as the focuser is at the end of the tube (and I used rubber bands to tension out some of the weight on the focuser draw tube). However, on the 130pds, the focuser is on the side at the top end of the tube and so, depending on where the scope is slewed to, the position of the camera can be below, on the side of, or above the tube!

I was planning an hour of Hydrogen Alpha (Ha) and an hour of Oxygen 3 (O3) narrowband data gathering and had set up SGPro’s autofocusing to refocus in between filter switches. I started off the sequence and the first Ha shot seemed pretty good so I went to bed.

I awoke to a folder full of ‘ok’ Ha data and a folder full of unusable O3 data. The focuser tube had collapsed inwards under the weight of the camera during the filter change and so was completely out of focus. Lesson learned.

I managed to scrape together 8×360 sec Ha data which I have stacked and quickly processed to give the image below. It isn’t pin sharp so I won’t be keeping any of the data for future gathering however it isn’t completely useless. Looks like the new scope is clean and the focal reducer has flattened out to the edges. It is a F4.5 (with the FR on) and so is gathering a lot more light than my F7 ED80. Also, SGPro is getting the target frames bang on centre.

I will be investing in a Moonlite focuser and stepper motor kit soon as I really value precision and the ability to use SGPro to automate as much of my evening as possible.

NGC 6888 – the Crescent Nebula in Ha.

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