Well, it’s been nearly the entire month since I last posted anything on here! It’s been an absolute diabolical month for astronomy; only one totally clear night at the beginning of the month. Other than that, it’s been drips & drabs dotted with cloud.
Speaking of the beginning of the month, when I first started in astrophotography I joined many astronomy and astrophotography groups on Facebook. I used these to help me choose my equipment that I purchased, and many people were doing the same at the beginning of the Covid Lockdown. Through these groups, I have made quite a few friends and contacts, and luckily some were quite local to myself.
Myself and one of these new-made friends had been talking quite often, as we had purchased exactly the same equipment just months apart. However, he has taken the next step forward, purchasing a guidescope and camera. He hopes to use Sharpcap to improve his polar alignment routine and make the most of this Bortle 5 skies with longer exposures. However, he was having connection problems with the camera, and so I offered to help him out.
Being not too far away, we decided we meet up in his back garden with our scopes. It was incredible to be under darker skies than my own! The amount of stars visible from his location was insane. And to top it off, he has a clear view of the south-east, so was able to watch Saturn and Jupiter rise. Compared with my 18.96 sky quality magnitude, his 20.05 skies were like black and white. I cannot even begin to imagine Bortle 4 or 3 skies! However, later on in the evening, we were battling with a 94% full moon, which was a bit of a pain. Luckily, both our scopes were facing away from the moon, so didn’t catch much light.
It was a really good evening overall though, just talking again with a physical person after being locked down for 5 months was a welcome relief. Was also good to see two identical telescopes next to each other, we were shooting different targets though. I had my astromodified camera with me so chose another nebula in which to test out the hydrogen alpha response; whereas he was testing out his new guidescope and camera on M81 and M82 with 4-minute exposures.
And what a difference guiding makes to the sub-exposures! As seen on this blog, I’ve previously shot Bodes and Cigar Galaxies myself, and can remember what a single exposure looks like. His single 4 minute exposure was more like my 1 hour stacked exposure from my first night of imaging these targets. It has finally persuaded me to get into guiding myself, allowing me to drop my ISO to reduce noise, but also get a much better exposed image.
Dylan O’Donnell has done a video, detailing the difference between short stacked images, or much longer exposures. This clearly shows the benefits of longer sub-exposures compared with my usual 300+ 60-second exposures.
Anyway, onto my target. Well, not quite just yet!
I’ve recently discovered a new app that I find useful! However, it’s available only on iPhone and iPad unfortunately. It’s ‘My Astro Journal’, developed by Antoine Grelin from Galactic Hunters; they can also be found on YouTube. It’s a place where you keep track of what objects that you have photographed and observed, upload your photographs and equipment details. They also do a monthly target challenge, which is what made me choose this target – NGC 7635 – The Bubble Nebula.
With my 130PDS and Canon 600D I have quite a wide field of view, allowing me to get two other targets in the same shot as well; to the top left, there is M52 and top right is NGC 7538.
This image was taken over numerous nights, however I’ve been constantly fighting the weather this month as it’s just be constant sun during the days, but cloudy in the evenings.
My first session was on the 6th August, which was the only crystal clear night of the month. I managed to get 95-minutes at ISO800, along with 1-hour at ISO1600. If I had taken these images in my Bortle 6 skies, I would have had to take 6h25m worth of exposures! However, stupidly, I only got dark and bias frames for the ISO1600. Learn from your mistakes I suppose!
The second session on the 18th, I managed to get 31-minutes out of a 2 hour session. I had to use lucky imaging to shoot through the clouds, which lost me ¾ of my images. Again with the third session on the 20th, I only managed to get 9-minutes using lucky imaging. All these were shot at ISO800 as I was back in my back garden with much more light pollution.
In the end, I managed to collect 3h13m of exposure across the entire month! It’s been terrible, and doesn’t seem to be letting up for the last week either! Hopefully it clears up as we head into winter!
Now to critique my own work, I would say that I’m fighting a losing battle with coma, and a coma corrector is fast becoming a necessity. I am aiming to purchase the Baader MPCC MkIII in the next month or so, along with a whole array of equipment ready for the winter months!
Also, you can tell that I missed out dark and bias frames from the ISO800 images from the first session; you can see the dark banding going across the nebula. And I couldn’t use my darks from a later session though to replace them, as the ambient temperature was completely different which makes them invalid unfortunately.
When I have my coma corrector properly installed though, I would like to revisit this image and start anew with it, especially if it’s in the winter months. Cassiopeia starts much much higher in the sky and finishes in the west as the sun begins to rise. This way, I would not be shooting over towards the lightdome to my east, where NGC 7635 is currently situated, so I should get a much darker image overall. Bonus!
Going forward though, I’ve decided to change my imaging thought process. Instead of spending just one or two nights on a single target, and then charging onto another. I’ll be spending an entire month on a single target, gathering as much light as a can, aiming for 15+ hours on each target.
As the nights are getting longer, I might be able to get 6-10 hours in one evening. So depending on the weather heading into winter, and if I feel that I’m reaching diminishing returns on a target, I might be able to get 3 or 4 targets in a month. We shall have to see how things play out in the future! There’s plenty of targets in the night sky to image, and I don’t want to rush to capture them all! I want to get the best images that I can!
Well, we shall have to see how September plays out and hopefully the weather improves, as August has been very disappointing. However, we do now have astronomic-dark back of a night time, so fingers crossed!
Till then, I wish everyone clear skies!