Hermitry isn’t what it used to be. I used to think the ideal occupation for a hermit would be either astronomy or lighthouse keeping.
The “Sombrero” galaxy, M104.
Credits: NASA and The Hubble Heritage Team (STScI/AURA) –
Plouzane. Credit: David Mark, https://pixabay.com/photos/plouzane-lighthouse-france-landmark-1758197/
Lighthouses are no longer an option. The few that remain, are automated, and run for years with barely any human intervention.
You might think astronomy is still a viable hermit option: you trek up to some icy mountaintop observatory and sit all night with your telescope scanning the skies, every night, for weeks on end.
Not any more.
I got my first inkling of this from my twitter acquaintance, Gary, aka @PoetLiggett. He posted a photo of the night sky, taken through an Australian telescope. Gary lives in the north of England.
“You were in Australia, Gary?”
Robotics, automation, and the internet have changed astronomy. You sit in the comfort of your kitchen and open your web browser. Then you schedule a time slot on some Australian or Spanish telescope or wherever; you enter the celestial co-ordinates of the galaxy/nebula/star/constellation you want to photograph; you tell the internet and the robot telescope how many exposures you want and the duration; and then you carry on with life as normal. You can even sleep at night.
When the robot telescope has finished its work, it uploads your images to a web folder. Perhaps while you sleep. You look at the images at breakfast with a cup of coffee. Hermitry be damned, and a good thing too: old-style lighthouse keeping had its share of danger(1). (Strangely, old-style astronomy very occasionally did too.(2))
This new way of doing things sounded far easier than the last time I photographed the night sky. On that occasion I left an anxious family late at night and drove 50 miles/80 km each way, including 30 miles/48 km up (and later down) a steep, narrow, hairpin road to the top of a volcano. It was 4°C/40°F on the volcano rim, and the wind was so strong that I had to hold down my tripod. (3)
I had to try this new, comfortable, remote, robot-telescope photography.
I found several organizations making robot telescope time slots available to Joe Public. I settled on https://www.remoteskies.net/. It offered a telescope in rural Texas, another in Australia, and was building one in the mountains of Chile. The rates were competitive, I didn’t need to subscribe, and the equipment looked very fancy.
I noticed several things in the image above. It’s a whopping-great telescope; it’s got a motor that will let it track whatever object it’s aimed at, as the earth turns; it’s got a secondary guide camera that double-checks and corrects the accuracy of the tracking motor; it’s mounted on a flat concrete slab for stability; the main camera is cooled to avoid random, heat-generated bright spots on the image and it’s all housed in a dome to protect against the elements (or elephants if you make my kind of typo, or live in Africa).
Spouses of astrophotographers often wince at the expense of astrophotography, and then comfort themselves with, “at least it’s not a 40-foot yacht.” With this kind of equipment, it might be a close call.
There was a bonus to my choice of Remote Skies. Dustin Williams, the man behind the organization, was extremely helpful with my newbie email questions. He answered them rapidly, made additional suggestions, and rescheduled my photography for me on nights when the viewing was poor.
Next decision: how to choose a target? Answer: https://telescopius.com/. Telescopius suggests targets for your astrophotography based on your telescope location, the time of year, the weather, the time of night, etc. Of course, you can input your own target or do an exhaustive search. Telescopius will also simulate how large your target will appear in a telescope of any given size.
I settled on the Pelican Nebula as my first target. Telescopius gave me the rise and set times for the Pelican Nebula, along with a visibility forecast, moonrise, moonset, sunrise and sunset. I love Telescopius.
I picked the Pelican Nebula because a) it’s dramatic looking, and, b) its gas clouds are shifting. In a few million years it won’t look like a pelican. Photograph it soon if you don’t want the hecklers shouting: “That doesn’t look like a pelican.”
A little bit of techy stuff next in blue italics. Skip it if it bores you:
Astrophotographers typically use long exposures, repeat them and stacks them on top of each other. This amplifies faint sources of light, like the Pelican Nebula, and diminishes random bits of transient light – passing satellites, etc.
You can do astrophotography with a colour camera, but you lose detail. Let’s say you have a 16-megapixel colour camera fixed to your telescope. But your fancy colour camera only has 4-megapixels for capturing red, 4 for blue and 12 for green. Judged by that, it’s no longer a 16-megapixel camera, and you’ve lost a shocking amount of detail.
For detailed work, astrophotographers mainly use black and white cameras (black, white and shades of gray). The Remote Skies telescope in Texas is no exception, it uses a 16-megapixel black and white camera. If you want accuracy AND colour, then you need to take three or four times as many photos, each time filtering for either just red, just blue or just green light. That way you get one 16-megapixel image from red light only, one 16-megapixel image from green light only and one 16-megapixel image from blue light only. You colour the images accordingly and merge them into a full-colour image.
What about those colourful Hubble images? Same story. The images are black and white, the colours are added after the fact.
The Pelican Nebula is a glowing hot gas cloud that emits light in specific frequencies according to the gases in the cloud. On Dustin’s suggestion, I asked the robot telescope to use three narrowband filters – SII, Ha, and OIII – one at a time, to catch the light emitted by respectively the sulphur, hydrogen and oxygen gas in the nebula. Each filter allows a specific frequency band of light to pass and blocks out light from other sources. Two of the filters even block out moonlight. After photographing the nebula with each filter in turn, I coloured each image with just one colour per filter.
For instance, the black and white image taken with the Ha filter became a green and white image, the image taken with the OIII filter became a blue and white image, and so on. I then merged the single-colour photos to produce a composite multicolour image. And if I deviated a little from traditional colour mapping – well, that’s why I pay the big artistic licence fees every year. (Hint: if you don’t know where to get your artistic licence, just mail me your fee and I’ll get you your licence.)
Two other challenges astro-photographers face are:
- the images need to be calibrated against known flaws (biases/dark spots/bright spots) in the camera and telescope. This is a process known as “calibration” and the details make my head spin.
- the finished images need to be further adjusted to brighten the light areas without lightening the dark areas. The process is known as “stretching.”
I was delighted to find that Remote Skies sent me both raw images and images that were already calibrated, and stretched. Wow.
End of techy discussion
Results, results, results: so, was my armchair astrophotography any match for images from the Hubble telescope?
OK, OK, that photo above is from the Hubble telescope, not from me. Perhaps I shouldn’t have shown it for comparison, but I still feel pretty good about mine. Bear in mind that the Pelican Nebula is a magnitude 8 object, meaning it’s too dark to be visible to the naked eye. It’s also 1,800 light years away, and, at that distance even if it was bright enough to be visible to the eye, it’s tiny – less than 1 square degree of arc(4). Remote Skies and I juggled some cloudy nights, some nights when the atmosphere was turbulent, some nights when the moon was up, and ended up with this. This one’s mine:
I took six photos of 20 minutes exposure each, on each of the three narrowband filters. I.e. that’s a total of 18 photos and six hours of telescope time spread over three nights of telescope time. I colourized and merged the images in PhotoShop(5),(6).
The detail in this newbie image astounds me. If you want a larger view open it up in https://www.photo.net/photo/18627683 . The bright green/yellow back of the pelican’s neck – as I understand it – is an edge of hot gas expanding out into a colder area. The little dark break in the bright – you’d think a child had dragged a wet finger through a watercolour – isn’t a flaw. It’s a detail called a Herbig-Haro object. Who knew that I could capture this level of detail? Thanks Dustin and Remote Skies.
It may not be the Hubble, but every time I look at my image I’m amazed that I could do that. And I didn’t have to drive that god-awful, twisty, steep, hairpin road up the volcano.
Your comments, questions or corrections are welcome.
If you’ve got questions, comments, or corrections to any of the above, or want to share your own experience/photos, please let me know. The comments section awaits.
Notes and Rabbit Holes
(1) See e.g. https://en.wikipedia.org/wiki/Flannan_Isles_Lighthouse#Disappearances_in_1900. Not strictly related to the body of this post, but I’m a sucker for marking rabbit holes for later exploration. We’re in Stephen King territory here.
(2) See e.g. https://en.wikipedia.org/wiki/Saint-%C3%89tienne-en-D%C3%A9voluy_cable_car_disaster#Accident_details. Not strictly related to the body of this post, but I know the area and think of this incident whenever I walk by the cable car that leads up to the observatory.
(3) Miserably cold though it was, I’ve re-used the night sky image from that volcano-top photography several times. See, e.g.: https://gallery.staadecker.com/?image=28 and https://gallery.staadecker.com/?image=21
(4)A typical single letter on a paperback page, held at a typical reading distance in good lighting would be about 5 square degrees of arc. So – the Pelican Nebula – a far darker object in a far vaster black “page” is about 25 times smaller to the naked eye.
(5) I used Photoshop because it’s what I have and know, but the pros and regulars are more likely to use purpose-built programs like PixInsight.
(6) In the image version I’ve chosen to post, I moved black and white images into their respective RGB Photoshop colour channels instead of colouring them. There were other images where I coloured each B&W image, but I prefer this result.