astrophotography

Cyg 30 and 31A & B: Twinkle, twinkle…

/ BrendanC

Sometimes the simple shots are the most effective.

Cyg 30 and 31A & B

Nice, isn’t it? I like the way the diffraction spikes interact, like a Mondrian painting or something.

What we have here are three stars (in case you didn’t know what a star looks like, or can’t count).

30 Cyg, to the right of the image, is officially a white giant star with a blue tint. Given that I’d describe mine as blue with a white tint, this shows the difficulty in accurately representing colours. There are calibration tools that reproduce scientifically accurate colours, and in fact my software (StarTools) has sophisticated colour processing baked in. But sometimes, well, colour is subjective, as seems the case here. Which begs the whole question: is this art, or science? Is it subjective, or objective? I’ve decided just to avoid the question altogether and admire the pretty pictures.

31 Cyg A is a bright orange giant, with a smaller blue companion called 31 Cyg B. They form a binary system which orbits at a distance of a mere 11 astronomical units (1AU is the average distance from the centre of the earth to the centre of the sun, which is 149.6 million kilometres). As they are viewed side-on, every 10.36 years they are in eclipse for 63 days.

I couldn’t really find much about when the next eclipse will happen, but eventually calculated it’s in February 2024. Which brings up an intriguing notion: if I took one shot like this, every session, for the next three years, then put them together to form an animation, what would I see? Could I really make out Cyg 31 A and B coming closer together and then merging for two months, then separating again?

And to go back to the art v science debate, would this actually contribute anything to science?

31 Cyg’s eclipses have been used in the past to help determine some attributes of orange giants, such as mass and outer atmosphere. I wonder whether, if I did this, it could provide any useful data? Apart from anything however, it would enable me to admire the pretty pictures – all 846 of them (and counting, down…)

First light – and a neat way to plate solve the moon

/ BrendanC

I’ve taken shots of the moon before with my bargain-basement Bresser Mikrokular camera, but just invested in a T7C camera – a cheapo version of the ZWO ASI120MC.

So, still pretty much bargain basement, but this is mainly for guiding when shooting DSOs, which the Bresser isn’t sensitive enough to do. Mono is usually best for guiding, but I got the colour version so I had the added flexibility of taking lunar and planetary images if I fancied it.

It took a bit of wrestling but I finally managed to get a shot of the moon – 5000 frames captured in SharpCap Pro and stacked and processed in Registax. Nothing too fancy but a good start.

It’s the Moon alright – but which bit? Click for full size.

However, now I’m all over plate solving from my DSO work, it did occur to me: which bit of the moon did I actually capture? Can you plate solve the moon?

Turns out you can’t. The most common advice is to download an atlas and look for it. But, given that I’m very lazy, I found a workaround: use Google’s Image Search.

So, on uploading my image, I get absolutely loads of results back telling me it’s the Sinus Iridum plain.

Sorted! Or, should I say, solved!

It’s so darned clever. It’s almost generalised plate solving: show it any image and it shows you other similar images, which means that it works for pretty much any other kind of astronomy image too.

So, you can’t solve the moon, but you can ask Google to do the next best thing.

Nerdy stuff:

  • 5,000 frames at 1280×960 resolution
  • Hardware: Sky-Watcher 130PDS scope (F5), Sky-Watcher NEQ6 mount, T7C camera with Meade 3x Barlow
  • Software: capture with SharpCap Pro, stacking and post-processing in Registax, plate solving using Google!

NGC 6992, the Eastern Veil Nebula: Alien or evil grin? (or just a nebula?)*

/ BrendanC

Do a quick search and you’ll find two popular views of the Veil Nebula: the Eastern Nebula, and the Western. They’re very photogenic. The Western Nebula is also sometimes called the Witch’s Broom Nebula, while the Eastern Veil… isn’t really called anything. It’s only ever really referenced by its catalogue which is Caldwell 34. Mr Caldwell was clearly a terribly dull chap.**

I find this odddddd because to my eye it looks exactly like a face. Other people have said it looks like an alien from the film franchise, or an evil grin. What you think?

NGC 6992, the Eastern Veil Nebula. Bit scary. Click for full size (even scarier).
NGC 6992, the Eastern Veil Nebula. Bit scary. Click for full size (even scarier).

I guess most photos show it at a different orientation, which is fair enough, but given that there’s really no ‘up’ or ‘down’ in space, I still think it’s strange that this incredibly evocative object doesn’t have a more vivid nickname.

Anyway, the actual Veil Nebula is quite a large structure in the sky, which is why most people just do the edges. I plan to return to this over the coming months and create a mosaic of the whole thing, which will probably be six panes’ worth.

The post-processing was challenging. That part of the sky is teeming with stars, and it took quite some time before I hit on the idea of using StarTools’s Shrink module. Then, I got feedback from people saying they actually preferred the stars. So, given the choices here – east, west, up, down, stars, no stars – you can see that astrophotography is as much about artistic interpretation as actuality.

Nerdy stuff:

  • 11.5 hours of integration
  • 60 seconds exposures at ISO800
  • Calibration: 25 flats, 25 dark flats, 50 darks, 50 bias
  • Hardware: Sky-Watcher 130PDS scope (F5), Sky-Watcher NEQ6 mount, Canon EOS1000D astro-modded camera with Sky-Watcher 0.9x coma corrector
  • Software: polar alignment with SharpCap Pro, capture with Astrophotography Tool (APT), stacking with Deep Sky Stacker (DSS), post-processing with StarTools and Photoshop CS2
  • View annotated at Astrometry.net
  • View superimposed against the WorldWideTelescope

* It’s just a nebula
** Maybe it went something like this: “I say Caldwell old chap, what are you going to call it then?” “Errr… 34?” “Dashed unimaginative, what?”

M81, Bodes Galaxy: Yes, you can image DSOs with an AZ mount (but don’t freeze your laptop)

/ BrendanC

This was probably the first image I was pleased with. It was also my first all-night session, in March 2020. It’s also the one where I froze my laptop – as in, literally froze it.

It’s M81, the Bodes Galaxy, with M82, the Cigar Galaxy.

M81 and M82. Click for full size.

It was one of my last captures with my old Sky-Watcher 130P AZ mount. I had replaced the OTA with a 130PDS, but was still using the mount. It’s a great starter set-up, but the AZ mount is not really suitable for DSO image capture.

Alt-Azimuth mounts are great for observing. They’re just up/down/left/right – easily understandable. You just point. And if you have a Goto, it will then track that object.

However, while AZ Goto mounts follow objects across the sky, they don’t rotate with those objects. An object will rise in the East, rotate as it moves across the sky, and then set in the West, and all the while, the image you capture from the AZ mount will show that rotation. So, when you come to stack all those images, you find that all the stuff around the edges isn’t really usable. It’s called field rotation.

They’re also not terribly accurate. They’re more intended for viewing than imaging, so absolute pin-point accuracy isn’t as important.

That’s where Equatorial (EQ) mounts come in. They track objects precisely, and keep the camera oriented to those objects too.

There’s also a cautionary tale behind this shot.

The night was wonderful – clear, not too cold, a great time for me to do my first ever full-on, all night imaging session.

Once I was sure everything was set up right and working, I took myself abed, leaving the heavens to wheel above me and my kit to capture them.

I woke up early, noticed it was a bit parky outside. Frost. Everywhere.

A bit panicky, I ran to the setup. It looked ok but there was frost on the laptop. When I started it, it went ‘crunch’. This is not a good sound for a laptop.

After leaving it on the radiator for while, it then went ‘swoosh’ and did nothing. After a bit longer it started to go ‘whirr’ and showed a message about Windows not starting, but suggesting I could try restoring it automatically.

Against all hope, it turned out my system had in fact been backed up automatically the day before, and I gingerly started the restore process. It actually worked. It actually, actually worked…

And that’s when I bought a box to keep everything in overnight. Well, you would, wouldn’t you?

Nerdy stuff:

  • 7 hours of integration
  • 30 seconds exposures at ISO800
  • Hardware: Sky-Watcher 130PDS scope (F5), Sky-Watcher AZ Goto mount, Canon EOS1000D astro-modded camera with Sky-Watcher 0.9x coma corrector
  • Software: capture with Astrophotography Tool (APT), stacking with Deep Sky Stacker (DSS), post-processing with StarTools and Photoshop CS2
  • View annotated at Astrometry.net
  • View superimposed against the WorldWide Telescope