NGC 891 - First Light

[Hicks]

First light is a stretch as it's really just first light with my new focuser setup and technically it's 2nd light but I'd rather forget the first light having put the focal reducer in the wrong way round and getting a complete mess, so, first light it is! Found out later that the LBT also selected NGC 891 as their first light target

I picked NGC 891 on what was a very hazy night with only an hour or two "clear" before 100% cloud and sleet was predicted. I didn't realise just how hazy it was until the moon started coming up and was a bright glowing blob in the sky.

Despite the conditions, we've had only a couple of good clear nights since November so I wanted to make the most of it and check that the focal reducer switched around inside the focuser sorted all my issues (it did). I got to try out that CCD drift align method (forget who posted it on here but it's great :P) where you image 5 seconds, then guide east for X seconds then guide west X seconds and look at the resulting star trails, making alt/az adjustments until the two overlap. That worked well and saved me a great deal of time and guesswork compared to visual drift align.

As for the result, I'm both happy and not at the same time. Considering the conditions and only getting 40 minutes of exposures (not all usable) I'm pleased but at the same time I think processing wise there's much more to be done even with this limited amount of data.

In the end I took ~18x120s and 2x180s to see if I could push my guiding a little more. Didn't have time for more than that due to clouds

After calibration with 25 dark frames, 60 bias and 118 flats (had little to do waiting for clouds to clear so took more than I normally would :), I stacked and stretched the image in pixinsight as well as tried a de-noise pass. I don't really like the de-noised version, although I was probably too aggressive with it. Both are shown below.

De-noised Version:

Integrated and stretched only version:

I've also attached a single raw 180s fits exposure. Is it worth me trying to push my exposures longer or would 180s be sufficient if I take more of them ? I'm still not happy with my guiding but it has improved of late so I should be able to do 180s and perhaps longer now, but i'm not sure if that will help reduce the impact of light pollution or make it worse?

Thoughts/criticisms/advice more than welcome, especially any advice regarding processing*. Can I really hope to get the noise reduced with so few exposures without it looking too fake like the above noise reduced version does?

Please bear in mind this was taken from near leeds/bradford so a reasonable amount of light pollution and taken through a layer of high cloud on a not too transparent night

*Getting Warren's PixInsight book so hopefully I'll improve my processing a bit more before too long

Light_180_secs_2017-01-14T20-11-19_001.fits