After my visit to the Institute of Astronomy at Cambridge the sky stayed clear and I paid a visit to the observatory to try and assess the tracking problems we’d experienced last weekend. Somewhat strangely, there was no repeat of the alt drift when pointing south although there is still a large periodic error in Az. Frame rotation is also problematic when pointing south so the maximum exposure I could use and still keep a reasonable number of the exposures was 15 seconds.
Abell 70 is faint so I didn’t hold much hope of actually being able to image it with this short exposure and my QHY9 single shot colour camera. To compensate, I took about 60 images. The nebula did not show up at all on any of the individual sub-frames.
Once mis-tracked frames were rejected I was left with 38 images which were bias subtracted and stacked with an SD Mask function. Field flattening was performed with GradientXterminator followed by a lot of noise reduction.
The nebula shows quite nicely along with the background galaxy. The nebula is about 45″ across and magnitude 14.5. The galaxy is magnitude 16 and the central star, 18.6.
