Try Cell Phone Afocal Photography – Especially for Sidewalk Astronomy

There are a great many different ways to take a photograph of astronomical objects. If you are looking through a telescope at a bright object like the moon, it’s possible to take satisfying photos “on the fly” without even having to attach a camera to anything. It’s called afocal photography. It’s very well suited to public or “sidewalk” astronomy events where nearly everyone visiting will have their own camera of some sort.

Afocal photography is the process of shooting a photo with a camera simply by lining the camera up to the telescope (or microscope, or spotting scope, where this technique is sometimes called digiscoping) eyepiece. It does not require attaching the camera to the eyepiece (although there are ways of attaching the camera that makes things much easier. This post is about just trying it hand-held). There’s a nice introduction to afocal photography on Wikipedia (

I thought a demonstration might be fun, using a very ubiquitous and simple digital camera, that built into an iPhone 3GS. If you want to try this with any camera more advanced than that on an iPhone 3Gs, please make sure that you turn the flash off!

On the evening of Saturday 14 September 2013 the Hamilton Amateur Astronomers (  presented a public astronomy evening in the parking area of a visitor centre in Grimsby, Ontario. I went along with my little Meade 125mm Maksutov-Cassegrain telescope, an iPhone 3Gs, and also a Nikon D5100 body. I thought it might be nice to compare two photo methods: afocal (putting the iPhone over the telescope eyepiece) and prime focus (replacing the eyepiece with the camera all together) photography of the moon.

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A public observing night put on by the Hamilton Amateur Astronomers on the evening of 14 September 2013 in Grimsby, Ontario. These events are terrific fun and a chance to see many different types of home telescopes in operation.

After setting up my telescope I was happy to have lots of members of the public come by and take a look at the moon through a wide-angle eyepiece. The Meade telescope has a focal length of 1,900 mm. With a wide-angle eyepiece of 28 mm focal length, the combination had a magnification of 67x (magnification, or “power,” in telescopes is calculated by the ration of the focal length of the tube divided by the focal length of the eyepiece).


My Meade Terabeam (TB) 125mm telescope set up for photography of the moon at the Grimsby public astronomy event. This compact little telescope is very versatile.

In between looks through the telescope, I held the iPhone’s camera over the eyepiece as “flat” as possible – in line with the long axis of the eyepiece, pretty much up against the rubber eye cup. Once I could see the bright light of the moon showing up on the iPhone screen, I moved the phone carefully around a few mm at a time until more and more of the moon showed up.

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A first afocal exposure of the moon taken with the camera built into an iPhone 3Gs. At least one crater is visible – a good, if humble, start!

It takes a little time and patience to line up the camera over the eyepiece, but in a few minutes I got the hang of it and started taking photos.


Getting closer! Nearly the whole moon is visible in this afocal shot, one of many taken to ensure a good one is captured.

After about a dozen images recorded, I captured one that I thought was pretty good.


A pretty satisfying image of the moon, one of about a dozen tried. Hand-held afocal photography is very much a trial-and-error process.

Some shops actually carry devices to hold cameras of various kinds (including cellphones) up against telescope or spotting scope eyepieces. These would be really helpful, especially if you wanted to take video or longer exposures. As it was, in this case I used the default camera app on the iPhone, allowing the camera and phone software to control exposure and focus.


The afocal image above, rotated, and flipped left-for-right. I’ve also adjusted the brightness, contrast, and sharpness very slightly. This compares very well to the image of the moon taken with a Nikon D5100 dSLR body at prime focus, below.

After taking a photo I was satisfied with, I put the iPhone away and set up the Nikon dSLR on the telescope, at prime focus. This is the place where the telescope makes its basic image without an eyepiece. With this 1,900 mm telescope image of the waning gibbous moon, about two or three days past first quarter, just barely fit onto the APS-C sized sensor on the Nikon D5100. I had to rotate the camera to get it onto the sensor.

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A photo of the moon taken a few minutes after the afocal iPhone images, by placing a Nikon D5100 dSLR body onto the same telescope at prime focus (replacing the eyepiece with the camera).

The iPhone afocal image compares pretty well with that from the dSLR once both are reduced down to the same size of image. The dSLR image is more detailed than the iPhone photo taken on the 14th, in part because of the much bigger (16 megapixel) sensor on the Nikon, and in part because of the wide-angle eyepiece used. Put side by side, sections of the images at their original resolution give a good idea of difference in resolution.

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The southern part of the moon imaged with iPhone afocal photography (left) and with a Nikon D5100 at prime focus (right). Both images were converted to black and white, and then a strip 400 pixels wide by 800 pixels high was cropped out of each. The two images here are presented in their original resolutions for comparison. the large round crater with two smaller ones along its edge, toward the bottom of both images, is Clavius. The smaller, circular crater to the north, with a prominent central peak, is Tycho.

Afocal photography is a “quick and dirty” method, but it’s also a lot of fun. One effect you might notice with this method is chromatic aberration, even if you are using a telescope that is an apo-chromat or a reflector that is not itself subject to this problem. It may show up, even on focused images, as colour ghost images or fringes.

As I noted at the beginning, this process is particularly well-suited for public astronomy nights. Nearly everyone (well, lots of people, anyway) has a cell phone or pocket camera with them these days.  If you are inviting the public to try looking through a telescope at something bright like the moon, ask them if they’d like to try to make their own souvenir of the event, too – their own photo of the moon, on their own camera. A few of our guests in Grimsby took away their own photos through my telescope, and they were pretty excited. I’m sure these were sent to a bunch of their fiends by SMS before too many more minutes had passed.

Copyright © 2013 David Allan Galbraith

Consider Being a Citizen Scientist – Amateur Astronomy with a Purpose

There are a lot of different, wonderful reasons to be interested in astronomy. One of the more interesting is that everyone – amateurs anywhere – can actually contribute to science through their hobby. This is not something that is true for many kind of “amateur” activities (those that are done for the love of the thing, not because you’re a professional). Amateurs are sometimes the most interested, creative and knowledgeable people in the fields they’ve chosen. Passion runs high among amateurs, and that’s a wonderful thing.

Recently there was a great example of amateur astronomy brought to my attention. In August a nova appeared in the constellation Delphinus. Given the very straight-forward (if not particularly sexy) name Nova Delphinus 2013, this newly appearing star was discovered on 14 August 2013. At the September 2013 meeting of the Hamilton Amateur Astronomers (, John Gauvreau, HAA’s Observing Director, presented an overview of what’s known about Nova Del 2013. He pointed out that observers all over the world have been looking at the new star and judging its brightness, using the standard way of expressing the brightness of a star, in apparent magnitude. Magnitude is a sort of reversed scale. The fainter the star, the higher is its magnitude. When Nova Del 2013 was discovered by Koichi Itagaki in Yamagata, Japan on August 14, it was at magnitude 6.8. It reached its peak, about 2 days later, at magnitude 4.3. It then started to fade. By the time I took a photo of the nova on 24 August, it was down to about a magnitude 5.5.


Nova Delphinus 2013, imaged from Ripley, Ontario on 24 August 2013. Ten days after the nova was discovered, it had already faded considerably.

As of this date (14 September, a month after discovery) the nova is being reported at about a magnitude 7.5 – pretty tough to see with the unaided eye, but well within the grasp of binoculars or a small telescope.


The light curve of Nova Del 2013, plotted by the data access facility of the American Association of Variable Star Observers on the morning of 14 September 2013. The curve is a representation of thousands of individual estimates of the brightness of the nova, reported by people around the world.

What’s great fun is that you can contribute to observations of things like the brightness of variable stars. There’s a great organized hub for all of this, the American Association of Variable Star Observers (AAVSO) ( Anyone can learn to judge the brightness of a star (that takes some time, but it’s very doable) either with your own eyes, or with the help of a camera, and then submit your reports to the AAVSO database.

There are other ways of contributing your own observations in astronomy, contributions that mean that your own hobby is more than a past-time, but is really helping science. There are also organized groups of amateur lunar and planetary observers, and even some amateurs that get involved with complex observations like recording stellar spectra. You can also contribute through programs like Galaxy Zoo, where you can help classify hundreds of thousands of photographs, helping observational astronomers chart the cosmos.

Copyright © 2013 David Allan Galbraith

Stitching A Lunar Panorama

Astrophotography today is becoming more and more about taking a series of individual images and assembling them into something else. This can be done in two sorts of ways. Very often, astophotographers will take repeated shots of the same area of the sky, and then use software to “stack” them, which has the effect of greatly reducing noise in the final image. As many of the objects in space are extremely faint, long, noise-free images are necessary to find them at all.

It’s also possible to make images of large areas of the sky by taking individual photos and joining them together, or stitching them. This can be a very effective way of using small cameras to produce large, high-resolution images. Despite the trend in some circles of seeking ever-bigger sensors dSLR cameras, stitching means that small cameras – like a web cam – can be used to great effect.

On the night of 16 August 2013 I was doing some observing and photograph form my west-facing balcony in Hamilton, and decided to try to make a large portrait of the moon using a small camera. I tried imaging the moon with several different cameras that night. My telescope was my Meade 125 Terabeam Maksutov Cassegrain catadioptric telescope mounted on an EQ6Pro mount with Synscan. Because of my balcony’s situation, it’s impossible to do an actual polar alignment; I can’t see Polaris. I can get to within a degree or so, which is good enough for taking a few images of bright objects like the moon.

The moon was lovely that night. After a few minutes of general moongazing, I mounted a Nikon D800 body on the telescope at prime focus, and was able to capture images of the whole moon’s face in one shot.


A photo of the moon taken on the evening of 16 August 2013 from an apartment balcony in Hamilton, Ontario, using a Nikon D800 camera on a 125mm Maksutov Cassegrain catadipotric telescope.

I then changed the camera, replacing the big dSLR with a little imager sold specifically for lunar and planetary imaging, a Celestron NexImage 5. This little camera looks like a miniature hockey puck about 2″ across. Inside is a 5 megapixel colour image sensor, which attaches to a computer via a USB cable. In contrast to the very expensive Nikon camera, the NexImage 5 retails for under $200. Because the pixels are quite small compared to the dSLR, it is able to record images of much higher resolution on subjects like the moon, for a given magnification. It is able to do a variety of things, including recording AVI video files that can be used in the stacking process.

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One image captured by the NexImage 5 camera, including the famous craters Tycho and Clavius.

I decided to try making an image of the moon using single exposures with the NexImage 5. I set up the telescope to point at an area along the terminator of the moon, took a single image with the camera, and then manually moved the telescope so that it was pointing to an area that overlapped the first image by about 30 percent. In this fashion I worked my way across the entire surface of the moon, taking 41 individual images.

Having the pictures recorded was just the first step. The camera software had recorded the pictures as bitmap files (*.bmp), and so I used a free image processing software to convert them from bitmap to JPG files. I then used another free software package called Autostitch (downloaded free for personal use at: to automatically bring all of the JPGs together, align them, and blend them together. I ran the program first on about a dozen overlapping tiles to see if it would work at all: Autostitch is designed for landscape photos – not moonscapes!

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A section of the lunar panorama made by using Autostitch to put together a dozen individual tiles.

Autostitch performed better than I could have hoped on my lunar frames! I re-ran the program using the whole set of 41 tiles, and in moments had my portrait of the moon in high resolution.


The moon, stitched together from 41 individual frames using Autostitch.

The final stage in assembling the image was to fill in the grey areas that were not actually captured by the imager.  I used another free software package, Paint.NET (not as capable as Photoshop but a whole lot less expensive!) to adjust contrast and brightness a bit, and paint in the grey areas with black. The results would be even better if each of the tiles had been prepared by the stacking process, which can result in dramatic improvements in such images. For now, I’m happy with yet another photo of the moon!


The final composite image of the moon, captured on 16 August 2013.

Copyright © 2013 David Allan Galbraith

Can Astrophotography be Considered Art?

The debate as to whether photography can be an art – or whether (at least some) photographs are art – has been long standing, and in some circles doesn’t end. The fact that there is some kind of equipment involved, and a process that wasn’t available in Renaissance Times to the great masters, seems to be a sticking point for some. For those that only consider art to be a handicraft executed with traditional materials, astrophotography must seem like arcane technical fiddling resulting in – what? A picture of the moon or stars? How is that art?

That there are now about a trillion photographs per year being taken around the world, most of them with cell phones, doesn’t help resolve anything, I suppose. Then again, art is not about a set kind of process or a formulaic end product. It can’t be. Otherwise, the skillful application of a paint bush to the side of a barn is art just as is the Mona Lisa.

Defining what is and isn’t art isn’t a matter of technology applied. At least in my mind, art is a process of communication in which thought and creativity are combined to express something of meaning. This is of course very open-ended, but in my experience there’s little more specific that can be brought together in one short definition that fits the range of artistic expression I see around me. Art isn’t just about a defined product, because that removes the receptive mind of the person experiencing the art from the equation, too. The receptive, critical mind of the observer/audience is as important to defining art as is the creative, skillful, intent of the artist.

This is nearly as vague as stating that “art is what an artist does or makes,” but even this second idea isn’t all that far off the mark. Who is an artist? Is someone who has great technical skill but does not apply any critical thought to their work, or who never puts that work into the sphere of a receptive audience, an artist? I’m not sure, of course. An interesting case in point is that of the late American street photographer Vivian Maier, who is being recognized as an amazing artist, but only after others found her work and popularized it. Was she an artist? A hobbyist? An obsessive-compulsive photo-snapper hoarder?

Some photographers have rejected the idea that they are artists. One of the greatest living photographic masters, Sebastião Salgado, is a Brazilian photographer whose work is considered as social documentaries. He has stated that he doesn’t think he makes anything new, but instead picks up things around him to tell stories. Yet, when I see his work I am moved, and his work has the qualities I identify as art: great creativity, expression of ideas and passion, and technical mastery. For me, an artist must bring some measure of all of these things together, regardless of the medium being used. I call Salgado an artist even if he is reluctant to do so.

“I don’t know art but I know if I like it,” or perhaps more honestly, “I don’t know how to define art, but I know it if I see it” might be closer to the mark. And perhaps more honest, too.

I am certainly prepared to dispense with the question of whether a photograph can be considered as art. More than anything else, it depends on who is looking at it. One point in favour of the proposition that astrophography can be an art was provided in 2012, when an art museum in the USA put on an exhibit of astrophotographs as art. This step – of having a curated exhibit at a museum – is one of the only widely-recognized measures of whether something that may previously be considered “not art” suddenly makes the jump into the “art” sphere.

“Starstruck: The Fine Art of Astrophotography” ( was an exhibit at the Bates College Museum of Art (Lewiston, Maine, USA), on exhibit from 8 June 2012 through 15 December 2012. This is the first instance of which I am aware that an art museum has taken on astrophotography specifically as art.

Others have approached the question, too. Russell Corman considered on his blog whether astrophotography is art or science (, and describes what he does as a “very technical art.” ( Interestingly, I would argue against amateur astrophography for creative purposes as being science. For me, science isn’t just the application of technology for some activity. Science, like art, is a process that results in interaction with a community, and with the communication of scientific results in a way that the community understands and recognizes. It may be educational, fascinating, and highly technical, but if an activity doesn’t put results into a peer-reviewed journal, for me it’s not exactly “science” either. There certainly can be amateur scientists (Darwin was one), just as there can be amateur artists (most, in fact, are, by definition: someone who does what they do for the love of it, not because it’s a regular 9-5 job). It’s not whether or not you work for some “sciencey” institution that designates you as a scientist – it’s whether you apply the critical thought process of science to a problem that interests you and then disseminate the results so that others can learn what you have learned.

I expect that this question will remain an open one, and that’s encouraging and exciting. I don’t consider all astrophotographs as art any more than I’d identify all photocopies as art. However, could a photocopier be used by an artist as part of her work? Certainly. Could a camera and telescope be used by an artist to create an image that was thought-provoking and moving? Yes. Can it be considered art? Show me and we’ll discuss it. The precedent of the Starstruck museum exhibit opens the door in a serious manner. An examination of some of the images that were included in the exhibit is, perhaps, an indication of where the art is to be found in astrophotography. Some of the images available in the on-line material about the exhibit were in fact taken by NASA spacecraft. They were selected and prepared for the exhibit by artists, using a variety of processes and final media. The show also included images considered historically significant that were created for documentary purposes.

I recall my dear, late mother’s view of art, too, when I approach questions like this. For her, art was something that represented something she recognized. She loved Pablo Picasso’s early works, but hated his cubism. She even kept a print of his Harlequin on her bedroom wall, not knowing who had done the work until I pointed it out to her. If a work wasn’t a skillful, draftsman-like rendering of something she recognized (and liked), my mom wouldn’t give it the time of day.  For her – and for everyone, in reality – the determinant of whether something is considered as art depends on a complex set of cultural expectations and filters. Recognizing that we all have those sorts of filters is an important first step to asking a more difficult question: is my own set of filters keeping me from seeing what others might be seeing? I think that’s where art has one of its strongest roles in society, and it’s where an artist’s contribution is most vital. Bringing things forward that others may not see. In that sense, some astrophotography is art indeed.

Copyright © 2013 David Allan Galbraith