M31 Andromeda Galaxy

Images of Andromeda Galaxy are what got me interested in astronomy and, more specifically, astroimaging. When I began imaging in earnest, last March, it was the tail-end of galaxy season and I really didn’t have a clue about my equipment. Still, my first DSO was a galaxy – it was a blurred, over-exposed image of Bode’s Galaxy but it was my first image and I was so excited. Suddenly, I began to realise what I was getting in to. These objects are so distant, that we really cannot comprehend the distances. We measure them, not in units of length, but by how long it takes light to travel across them. The thought of capturing photons that have been travelling for millions of years is what keeps me absolutely captivated by astrophotography.

I was too late to image Andromeda last season – and to be honest, I couldn’t even find it when I tried! Since then, I have learned a lot about imaging and the equipment I use. I am passionate about my imaging and processing; I refuse to listen to people who tell me that my skies are too light polluted and that I cannot hope to capture and process deep space images unless I am prepared to travel to dark skies. So it was with anticipation that I waited for Andromeda to reappear on the eastern horizons this month.

I also wanted to get back to using my DSLR as it is a lot easier to point and shoot rather than mess around with LRGB filters. I am back at work and so I want to be able to set up my kit mid-week and leave it running unattended over-night. I recently had my DSLR astro-modded (the IR and UV filters removed). I know that this is more for capturing nebulas however I feel it will also help a little on all DSOs. The work was completed by Andy at Astronomiser¬†and I’m delighted with his work and service. I had the camera back within 10 days and in perfect working order.

I found myself with a clear night on the 21st September – the forecast all week had suggested I might have a couple of hours however, on the morning, the forecast opened up and I had 7 hours of clear skies from 9pm through to light at 4am. I opted to use my Skywatcher ED80 refractor rather than a newtonian as I really wanted to set up, lock focus and then go to bed rather than have to worry about the temperature, collimation and so on.

By 9pm, I was polar aligned thanks to Sharpcap’s polar alignment tool (can’t rate this highly enough) and I just had to wait for Andromeda to rise above the tree line. I got my scopes focused on Vega using my Bahtinov mask, before locking off and programming in my session into BackyardEOS.

I haven’t done much LRGB imaging – all sumer I have been honing my skills on narrowband – and so I wanted some advice on settings etc. A quick chat with Trevor from Astrobackyard.com¬†helped me decide to work on ISO800 and use the histogram to find a good exposure duration. I ended up on ISO 800 for 180 secs as it gave me some separation on the left of the histogram, without moving too far to the right. I ended up running 100 exposures as I had the time to do so, and wanted to grab as much signal as I could for stacking.

The processing took me most of Saturday – I wasted quite a bit of time in Pixinsight but the stack it created had come real issues (I think that using bias frames was a problem) so I re-ran quickly in Deep Sky Stacker to see what happened. This time the stack looked good so I moved it back into PixInsight for processing.

The main problem in processing Andromeda is that the core is so bright, so any stretch results in the core quickly becoming white clipped. I worked using progressive masking to stretch in increments, masking each new stretch to ensure that the core or stars never blew out. This is a technique I have started using and I think it works brilliantly in terms of bringing out detail, even from light polluted skies.

I’m really happy with my result – it is probably my best process to date – but there are some issues that annoy me. There is some horizontal streaking that I have since learned is called ‘walking noise’ and is caused by a lack of suitable dithering. Strangely, I had wondered that the final stack didn’t seem to have much in the way of borders to crop, especially as it was a 5 hour stack. Looks now like either the dither in BYEOS wasn’t enabled or, more likely, it was dithering but not by enough. Another lesson learned. I have plenty of time on Andromeda this year so I will be imaging a lot more galaxies this winter.

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M31 Andromeda Galaxy

Higher resolution on my Astrobin account

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NGC 281 – Pacman Nebula

NGC 281 – Pacman Nebula – is an emission nebula in the constellation of Cassiopeia. Right now it is still east of the meridian so I was able to run a 5 hour narrowband session without a meridian flip. The nebula is around 9,200 lys from Earth and almost 50 lys across, and was first charted in 1993 by Edward Barnard. Its common name, Pacman Nebula, comes from its supposed resemblance to the 1980s’ videogame character.

This image is composited from 132 subs of 150 secs each, giving it a total integration time of five and a half hours. I hope to add more to this in terms of data (at least the same amount again) on my next outing.

In terms of my camera, I seem to have ironed out the issues with coma by narrowing down the spacing needed. There is still some slight coma in the outer corners of the subs however, due to rotation during the imaging session, these areas tend to be cropped out anyway.

Image details:

40 Ha x 150 secs
45 O3 x 150 secs
47 S2 x 150 secs

What is becoming more apparent is that I need to integrate a lot more subs to get the detail I am after. Now we have longer dark periods again at night, I will be experimenting in terms of total integration time rather than number of subs to compensate for the lower SNR created by my shorter exposures.

Anyway, this is where I am with my process – as ever, constructive feedback and comments are welcome.

NGC 281 – Pacman Nebula

More details on Astrobin

NGC 281 – Pacman Nebula

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IC 5070 – Pelican Nebula – in narrowband

I’m back at work now so my imaging sessions will really be restricted to weekends, weather permitting. The end of August has been pretty poor weather-wise but last night looked good on the forecast and I had 6 hours of dark to play with. Or so I thought.

I wasted so much time trying to get my guiding sorted – no matter what I did, I couldn’t seem to stop the graph oscillating. Turns out I hadn’t enabled guiding – took me an hour to work that out! Then, I had switched out my old finder / guide scope for a dedicated 60mm guide scope but I just couldn’t get it to work properly – I think it isn’t aligned properly and I really can’t do that until the moon is up in a couple of weeks (unless I want to take my kit out in the car and focus on a distant land object, which I don’t!).

Simple lesson learned is to take my time and don’t change out kit that already works well. I went back to my old guiding setup and it guided like a dream all night.

I chose IC 5070 – the Pelican Nebula – as last night’s target and planned for 20×180 of Ha, S2 and O3. Somehow, while transferring the files over this morning I managed to delete 7 of the S2 files!

Anyway, this is an LRGB process of what I did capture. Total integration time is 159 minutes – I’ll probably add more to this on the next session.

20 x 180s Ha
20 x 180s O3
13 x 180s S2
20 darks, 50 flats

Higher resolution on my Astrobin page

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