What Fake Astrophotography Can Teach Us

What Fake Astrophotography Can Teach Us

The New Zealand Herald has an article today about a cool and very popular image of the Moon positioned perfectly within a radio satellite, produced by astrophotographer Chris Pegman: Supermoon image goes into media orbit

Image by Chris Pegman
Image by Chris Pegman

The article talks about how there has been debate online about whether or not this could be taken without resorting to Photoshop. It concludes that “the verdict was that it might be, but it would require an incredible amount of planning” but this isn’t strictly correct.

The apparent rotation of the Moon changes as it travels through the sky. When it rises, it will appear to be “on its side” relative to when it is at its zenith, and when it sets it will have rotated further still.

This is most obvious with a crescent Moon. Depending on if it’s waxing or waning, the Moon will rise with the crescent facing either down or up, then when it’s at its zenith the crescent will be facing sideways, and as it sets it will have rotated around further. Of course, the lit side of the Moon always faces the Sun. It’s the fact that the Earth rotates beneath us that makes it look like the Moon is rotating as it travels across the sky.

Here’s an example of this which I took with my phone in July, showing a waning crescent Moon shortly before sunset:

We can see from the lunar maria (the dark areas) that the Moon in Chris Pegman’s picture is rotated how it would be if (when viewed from the southern hemisphere) it were near its peak, not near the horizon, so his picture couldn’t be produced without artificial manipulation.

Mark Gee is a fantastic astrophotographer from Wellington. In October he captured a time lapse of a full moon rising, in which you can clearly see that angle of the Moon is not the same as in Chris Pegman’s image when it rises: Supermoon rises over New Zealand timelapse.

There’s a Twitter account called Fake Astropix, which tweets fake astronomical images with the reasons why they are recognised as fake (well, as much as can be given within a tweet).

I find these reasons can be very educational and thought provoking. For example, it’s impossible to take a photo from Earth where the Sun and Moon don’t appear to be roughly the same apparent size. Also, the full moon can’t appear next to the Sun in the sky (remember the lit side faces the Sun). So “debunking” these fake astronomical images can be a good educational exercise that makes you think a bit more carefully about how things work in our solar system.

Do you have any fake astronomical images that you can share, along with the reason why you can tell it must have been faked?

Have you seen any astronomical images that you think might be fake but you’re not sure? Share them here and let’s investigate, and see if we can learn something.

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Stargazing

As I mentioned in an earlier post, after looking up at the night sky through binoculars for the first time over my summer holiday, I decided to buy a telescope this year. On the 27th of January, I went to see a show at the local observatory, Stardome, and ended up talking to one of the staff about the telescopes they had on sale. I came home the excited new owner of a “Celestron Powerseeker 114EQ”.

My new telescope
My new telescope

It’s a “Newtonian” telescope, also known as a “reflector”. It uses a mirror to gather light, as opposed to a “refractor” that uses a lens. The light comes in the front of my telescope and hits a concave mirror 114 mm in diamater at the other end of the tube, where it is bounced back up to a flat mirror near the opening that reflects the light out the side into the eyepiece. I have 3 eyepieces that give 45x, 90x, and 100x magnification.

My first target was Jupiter, which I’d got a brief glimpse of from one of Stardome’s much more expensive telescopes after the show I saw. When viewing it from home, I was thrilled to be able to make out its 4 Galilean moons, and tried taking a photo. It turns out, as you might be able to guess, that holding an iPhone 4 camera up against the eyepiece of a telescope in the dark, then holding it steady and pressing the “take a photo” button without bumping the phone, is actually pretty hard. I got very lucky though, and the first photograph I took clearly showed an overexposed Jupiter and its 4 largest moons:

Jupiter and the 4 Galilean moons. In no particular order: Io, Europa, Ganymede, and Callisto
Jupiter and the 4 Galilean moons. In no particular order: Io, Europa, Ganymede, and Callisto

Some time later, I was also lucky enough to take a recognisable photo of Saturn using the same technique:

Saturn. It appears on its side because of the angle I was viewing it from. Click through to see the full image.
Saturn. It appears on its side because of the angle I was viewing it from. Click through to see the full image.

That picture was taken with the highest magnification eyepiece, which has a lens only about 6 mm in diameter. It was really difficult to hold my phone steady for this, even with the trick I’d learned of using the iPhone headphones’ volume buttons as a remote for the camera app. After this, I decided I should look to see if I could buy an adapter to fit my iPhone directly onto my telescope, but while searching for one I found an article about how to make your own adapter. I didn’t follow the steps in that article, but I did decide to give it a shot. I found a piece of plastic, an old cover for part of a swimming pool pump, that fit perfectly over my telescope’s eyepiece, and put it together with a bunch of foamboard and glue to get the final product. Here are a few pictures of the process:

The first layer
The first layer
The plastic backing
The plastic backing
The second layer
The second layer
The 2 pieces combined
The 2 pieces combined
Trying it out. It was a bit heavy at this stage, and overbalanced my telescope
Trying it out. It was a bit heavy at this stage, and overbalanced my telescope
Cutting it down to size
Cutting it down to size
All trimmed down. After this I sanded the edges and it was good to go
All trimmed down. After this I sanded the edges and it was good to go

Using this new adapter and some astrophotography image processing software called Registax that lets me combine multiple images or frames of a video to form a single clean image, I’ve been easily able to take some clear images of Jupiter, the Moon, and Saturn:

Jupiter, with some of the cloud bands clearly visible. Click to see the full image.
Jupiter, with some of the cloud bands visible. Click to see the full image.
The waxing crescent Moon. Click to see the full image.
The waxing crescent Moon. Click to see the full image.
Saturn, rings and all. Click to see the full image.
Saturn, rings and all. Click to see the full image.

Registax also allows for a bit of processing to remove noise and sharpen the image. I’m not sure what I think of this yet, as I’m pretty much flailing blindly and to be honest it feels a bit like cheating, but here’s what came out the other end when I applied some of its filters to that Saturn image:

Processing image of Saturn to remove noise and sharpen it. Click to see the full image.
Processing image of Saturn to remove noise and sharpen it. Click to see the full image.

I also took some photos of Mars, but they’re all horribly overexposed and not really worth looking at. I’ve been having trouble seeing anything aside from just a circle of light when it comes to Mars. It’s tough using an iPhone 4 as a camera. It’s not possible to manually change settings like focus or exposure, and in order to take photos and videos of Jupiter that weren’t overexposed I had to lock the camera’s settings on the brightest part of the Moon (done not by tapping to focus like usual but by holding my finger on the spot for a second or so). Luckily Jupiter and the Moon are quite close in the sky at the moment so that wasn’t too much effort, but moving the telescope back and forth between the Moon and Mars was quite annoying. I’m sure there’s a better way that I’m yet to find. It possibly involves buying a decent camera.

One other thing I was finally able to do last night is resolve the Alpha Centauri system (the outermost of the 2 “pointers” that show the way to the Southern Cross) as a binary star system. I wasn’t able to photograph it though, the stars still appear very close together and my phone overexposed them to look like a single star. I guess that’s a challenge for another night.

I’m also quite looking forward to the upcoming total lunar eclipse on the 15th of April. Although I’ve read that the Moon is meant to turn a dark red during the totality of the eclipse, I’m not really sure what to expect when it comes to viewing or photographing it, which I find pretty exciting.