An Accidental Lunar X

When I took this shot of the moon on 9 PM 18 May 2021 from my balcony in Hamilton, Ontario (with a Nikon CoolPix P950 at 2000 mm zoom) I was pretty happy with the detail along the terminator – the zone between sunlight and shadow. Lots of lovely craters, some clear enough to see central peaks. Contrast is important: when I took the photo the sky was still blue to the unaided eye. The moon is so bright that to photograph it for surface detail usually means tricking the camera to under-expose the shot; automatic camera settings are not designed for this kind of thing. I always shoot astronomical subjects with the camera on manual. This photo was taken at ISO 560, 1/150 sec, f 6.5, hand-held with on-camera image stabilization. Normally you should only try hand-held shots with the shutter speed at the reciprocal of focal length (for example, 1/500 of a second if the focal length is 500 mm), but the stabilization in this camera is very good.

A nice photo of the moon. taken with a Nikon Coolpix P950.

What I did’t notice until pointed out by John Gavreau of the Hamilton Amateur Astronomers is that I accidentally captured the famous Lunar X in the photograph.

The Lunar X is visible in the middle of this cropped frame.

The Lunar X is a transient feature caused by oblique sunlight falling on the rims of adjacent craters.

Clear skies!

The 2024 Total Solar Eclipse, Part 1

Observing the 8 April 2024 Total Solar Eclipse at the Arboretum of Royal Botanical Gardens (Canada) in Hamilton, Ontario.

The total solar eclipse of 8 April 2024 that swept across North America caused an enormous public and media sensation. Millions of people were able to take in this beautiful natural phenomenon.

Here at Pine River Observatory (which is both virtual and portable) I’m going to post a couple of blog entries about my experience with the 2024 eclipse. I had the wonderful opportunity to participate in preparation for and leading the programming of a visitor experience for the eclipse at Royal Botanical Gardens (Canada), in Hamilton, Ontario, where I serve as Director of Science. In this first blog post describe the preparations for the event, which was held in the Arboretum of Royal Botanical Gardens (Canada) on the afternoon of April 8th.

Preparations for the event actually began about three years ago. I had traveled to the United States to witness the 2017 total solar eclipse that was sometimes called the Great American Eclipse. I joined friends south of St. Louis, MO, and experienced my first total solar eclipse. I also had the honour to serve as interpreter and observation guide for the group, which included members of The Explorers Club, St. Louis Chapter.

Members of the St. Louis Chapter of the Explorers Club and my little telescope set-up watching the 2017 total solar eclipse in Missouri.

The 2017 eclipse was a chance to prepare solar observation telescopes and some camera equipment to record the event. That event went pretty well, and I was excited to capture a variety of images. I also demonstrated that my small telescope, a 5 inch Meade Terabeam Maksutov-Cassegrain OTA with a two inch Jim Weggat optical back, performed very well for visual observations and photography when equipped with a mylar solar filter from Kendrick.

One of my telephoto images of totality in 2017.

In 2021 I first started bringing the 2024 eclipse to the attention of the interpretive and planning staff at Royal Botanical Gardens (Canada), with information about the path of totality and its duration. The Arboretum at University of Guelph was just inside the path of totality, with eclipse websites indicating 87 seconds of totality could be expected there. It was not hard to work with online ephemeris sites and get the direction and the elevation expected for the sun and moon at totality. This would be just about southwest, at 45° elevation.

Serious planning for the event at the Arboretum began in mid 2023, when our director of business development and I started to discuss just what was practical and possible on the day. While the astronomical portion of the eclipse was very predictable, the wildcard in all of this was the weather. We were expecting a 60% probability of being clouded out on the day of the eclipse. Historical weather information, however, is proving to be somewhat unreliable in the era of climate change we are now experiencing. The two days before the eclipse the weather turned out to be cloudless and beautiful. Of course, we did not know this in our planning.

Prior to the eclipse itself RBG organized a presentation by eclipse chaser David Makepeace, of Toronto, a videographer who has identified himself as The Eclipse Guy. David has traveled the world many times to take in eclipses, and gave a wonderful presentation on eclipse chasing at RBG two weeks before the event itself.

We also teamed up with two other institutions in preparation for the eclipse. The Ontario Science Centre in Toronto included RBG in some of its own planning, and sent a team to RBG for the day of the eclipse. This was done in part because the Ontario Science Centre was to be outside of the path of totality. The other partner was McMaster University, which made the wonderful donation of several thousand eclipse glasses to RBG for distribution during our programming. In total McMaster University had over 600,000 pairs of eclipse glasses prepared and distributed free in Hamilton to give people a chance to observe the eclipse in safety.

To set up for the eclipse, it was decided that the Arboretum on the North Shore of Cootes Paradise Marsh would be the best place for an RBG eclipse viewing. It’s not that the Arboretum is anything particularly special, but it does present a large grassy area with a good view to the southwest. Our food services department set up a food truck, and our operations and events people set out chairs, tables, and even fire pits across the Arboretum so that visitors could relax and enjoy the event in style.

I decided to set up a couple of cameras and my five inch telescope 5 inch telescope so that people could take a look at the eclipse in its partial phases through the filtered telescope. On 7th of April, the day before the eclipse, I set up all of my equipment in the Arboretum and did a practice run with solar imaging, producing a decent visual light image of the solar disk.

The sun’s disk on the afternoon of 7 April 2024, just 24 hours before the total solar eclipse was to begin. Taken at the RBG Arboretum with the Terabeam telescope and a Nikon D5100 at prime focus.

I disassembled the equipment and packed it back up into my car for the overnight wait, and then arrived at the Arboretum around 11:30 on the morning of 8th April. It took a while to set up the equipment, but I decided to do a very simple thing with my telescope. Critical to any observed observations with a telescope is the telescope mount. In my case I have an old mount of about an EQ3 size (I’m not even certain), and I decided I was going to use it simply as a manually-moved German Equatorial manual mount. I made a rough north alignment, and then set up the optical tube assembly, the mylar solar filter, and eyepiece.

For camera equipment I had a Nikon D 7000 with a 150 to 500mm telephoto lens and yellow plastic solar filter. I used the handheld camera to take pictures of the sun and moon at various times. At totality, I removed the filter so that I could get photographs of the totality event.

And that was about it. I set up my relatively simple telescope, and during the day I was aided by several RBG volunteers, a wonderful group who come out to help at nearly every event. The wait was on to see if we would get an eclipse, because early on the morning of the 8th of April the weather forecast did not look very good. We had solid cloud until at least 1:00 PM, with totality scheduled for about 3:20 PM.

I’m going to pick up the story of the actual eclipse event in our next blog post. I’ll review the programming and experience of eclipse day, observations and the interactions with all of the public who joined us on the event, and share some photographs. We had at least 400 people attend. It’s not giving anything away at this stage to say that we did see a wonderful eclipse, the clouds cooperated in a rather dramatic fashion, and it was my impression everyone was very excited and satisfied that day.

Get Ready! A Quick Guide to Observing the 8 April 2024 Total Solar Eclipse in Canada

A time-series of the August 2017 Total Solar Eclipse I photographed in south of St. Louis, Missouri.

The April 8, 2024 total solar eclipse presents a once-in-a-lifetime opportunity for amateur astronomers in Canada to witness an extraordinary celestial event. By planning ahead, selecting the right equipment, following safety guidelines, and keeping an eye on weather conditions, you can maximize your chances of experiencing this breathtaking phenomenon. Remember that the memories and awe-inspiring moments you’ll capture during the eclipse will be cherished for years to come.

This blog post gives you general suggestions about viewing or photographing the eclipse, based on my personal experiences with the August 2017 total solar eclipse that I saw in Missouri.

1. Where Will the Eclipse Be Visible?

The April 8, 2024 total solar eclipse will be visible across a large portion of North America, offering Canadians an incredible opportunity to witness this phenomenon. The path of totality—the region where the sun is completely covered by the moon—will stretch across several provinces, allowing observers to experience the eclipse in its full glory. In Canada, the path of totality will traverse regions including Newfoundland and Labrador, Prince Edward Island, Nova Scotia, New Brunswick, southern Quebec, southern Ontario.

Totality – the period when the sun is completely blocked by the moon – varies from place to place. It will cover a narrow band of about 160 km across. The differences can be stark. Totality will not be visible in downtown Toronto, but will be in Hamilton. Even if you are not in the path of totality the sight of the moon obscuring the disk of the sun can be very dramatic.

Here’s a good guide for the details on-line: https://eclipse.aas.org/eclipse-america-2024

2. Recommended Equipment

A 5″ Terabeam telescope (the white ETX-125TB Catadioptric Maksutov-Cassegrain telescope on the left) and a Nikon digital camera and telephoto lens on an Eq-5 tracking mount, both equipped with mylar solar filters suitable to photograph a solar eclipse.

To fully appreciate the grandeur of a total solar eclipse, it’s crucial to have the right equipment on hand. While a total solar eclipse is a mesmerizing sight to behold with the unaided eye, using proper eye protection is essential to avoid permanent eye damage. A pair of certified solar viewing glasses or eclipse glasses are an absolute necessity during all stages of the eclipse, except for the brief period of totality when the sun is completely covered.

For those looking to capture the eclipse’s stunning moments, a digital camera or smartphone can be used to take photographs, but it’s important to use appropriate solar filters to prevent damage to the camera’s sensor. Solar filters designed for cameras or telescopes can help capture the intricate details of the eclipse’s corona.

If you’re an amateur astronomer with access to telescopes, consider using a solar telescope or a telescope equipped with a solar filter. These devices allow you to observe the eclipse in even greater detail, revealing sunspots, prominences, and the solar corona during totality.

There are also some very simple ideas that can make for a fun viewing experience. These include pinhole “cameras” that project an image of the sun onto a white panel or card from a small hole in a solid sheet.

3. Viewing in Safety

Safety should always be a top priority when observing a solar eclipse. Even a partially eclipsed sun can cause permanent damage to your eyes if proper precautions are not taken. Follow these safety guidelines:

Use Certified Solar Viewing Glasses: Regular sunglasses, no matter how dark, are not sufficient for observing the sun. Only use certified solar viewing glasses or eclipse glasses that meet the ISO 12312-2 international safety standard. Check for any damage or scratches on the glasses before use.

Inspect Your Equipment: Ensure that any equipment you use to observe the eclipse has the appropriate solar filters in place. Telescopes, binoculars, and cameras all require specialized filters to prevent harmful sunlight from damaging your eyes or equipment.

Monitor Children: If you’re observing the eclipse with children, make sure they also have proper eye protection and are aware of the importance of not looking directly at the sun without it.

4. Weather Considerations

While regions of Canada offer prime viewing opportunities for the April 8, 2024 total solar eclipse, weather conditions can play a significant role in determining whether you’ll be able to witness the event. It’s crucial to keep an eye on weather forecasts in the days leading up to the eclipse and to have a backup plan in case the weather takes an unfavorable turn. As the eclipse is taking place in early spring, for example, the chance that it will be obscured by cloud in Ontario runs about 50%.

If you’re planning to travel to a specific location to view the eclipse, consider selecting a spot with a history of clear skies during the month of April. Coastal areas may be prone to fog or marine layer clouds, so it’s wise to research local climate patterns before finalizing your viewing location.

5. Potential Challenges

While parts of Canada are fortunate to be within the path of totality for the 2024 solar eclipse, there are a few challenges to keep in mind. The farther you are away from the path of greatest totality, the shorter the duration of totality will be. Be prepared for a potentially brief but incredibly intense experience. At most it will be about three minutes. During that period the entire landscape will become dark – not quite night, but very dramatic none-the-less. You may also experience a distinct cooling during the eclipse as the warming rays of the sun are cut off. Also, if you are in a popular area during the event traffic may be heavy!

6. Final Thoughts

I travelled from Hamilton, Ontario to St. Louis, Missouri in 2017 to view the total solar eclipse with friends from the area. This was one of the most moving experiences I can remember. It was well worth the time and travel. And, I prepared for the photographic experience by reading and practicing with my equipment before I left for the trip. If you can take in the 2024 eclipse I highly recommend it.

My First Try at Photographing the International Space Station

The idea of being able to take a photograph of the International Space Station is enchanting. Here’s one of humanities’ greatest achievements, passing by very frequently and yet so far out of reach to those of us on the ground.

Taking photos of the ISS is perfectly possible from the ground, but it requires some preparation. First, you have to know how to find it. There are several smartphone apps and on-line sites that allow you to predict when and where the ISS will be visible from your location. I use ISS Spotter on an iPhone, which I find very handy.

Once you know where it is going to be you have to think about how to capture it. The ISS typically crosses a section of the sky at a rate of between 1 and 3 degrees per second. This doesn’t sound too fast, but when you realize that it’s about 100x faster than computerized telescope mounts move you get some idea of the challenge. Even a large consumer telescope on a computer mount just can’t keep up.

It IS possible to follow the ISS and other satellites using computerized telescope mounts, but they’re not off-the-shelf gear. An absolute master at this kind of photography is Thierry Legault, an engineer based in Paris, France. Thierry’s systems include modified mounts that can turn at the phenomenal speeds needed to track a satellite. Take a look at his images and his methods at: http://www.astrophoto.fr/

My equipment isn’t up to that sort of approach, but you don’t need to that way. Instead, I’ve tried mounting my 125mm Meade Terabeam Maksutov-Cassegrain telescope on a photographic tripod. This arrangement (see the photo) is easily carried in one hand. It depends on being able to use the finding device (in this case a Rigel Systems QuikFinder reflex sighting device) to follow the target. Using this simple set-up it’s possible to follow the target and take numerous photos or shoot video, and them examine the resulting images later for any that worked out. This is an approach related to “Lucky Imaging” that is commonly used in more sane corners of amateur astronomy.

My ISS-hunting rig. I’ve mounted a Nikon dSLR camera at prime focus on a 125 mm Meade Terabeam Maksutov-Cassegrain telescope. This is then set up on a heavy-duty photography tripod. This telescope is equipped with a red-circle Rigel Systems QuikFinder (http://rigel.datacorner.com/rigelsys/quikfinder.html )

Of course I am using the term “sane” in a tongue-in-cheek manner here and mean no disrespect to those suffering from mental disabilities. It’s just the term that came to mind as I snapped away at the space station like a field gunner trying to shoot down an Sopwith Camel during the First World War.

There are a couple of very basic set-up steps that deserve every bit of attention before the pass begins.

First, ensure that your finding device is well-aligned with the telescope itself. You will not be looking through the telescope or camera to take these photos.  You’re flying blind, relying on the finder to set things up. You are adjusting the aim of the telescope throughout the entire pass. The steadier the better, but you still must keep moving to keep the ISS as close to the telescope’s centre of view as possible.

Second, focus is crucial. The ISS is tiny from earth – just a few arc-seconds across. Before the pass focus the telescope as carefully as possible on a star. This is a little easier said than done without having the telescope on a capable telescope mount. I used the moon and also very distant lights to try to focus the spot mac.

While I was setting up to shoot the ISS I snapped this distant jet high over Lake Huron. Possibly 30 km or more away.

 

Keep in mind too that if you are using a dSLR your camera is going to shake like made when the mirror and shutter are activated. Every bit of extra motion is a problem. I think an ideal imager for this application would be a mirrorless camera with a full-frame sensor, but I’m not quipped with one of these.

For my first try I used a Nikon D800 camera on video mode. I started running the video before the ISS came into view, and simply kept the telescope pointed at it, moving as smoothly as I could, throughout the pass. Afterward I then exported all of the images using IrfanView, and threw out everything that wasn’t a recognizable image. In other words, nearly all of the resulting frames.

Just for the focus. I used the moon as a target to focus the telescope prior to the pass of the ISS on 29 July 2017 visible from the mouth of the Pine River. 

Despite all of the make-shift arrangements, at the end of the day I did capture something with structure. Here are a couple of frames:

I’ve seen some authors recommending this approach with telescopes on Dobson mounts. This makes a lot of sense too, as these mounts are intended to allow you to point the telescope by hand with ease. I will try to take more images of the ISS as time and opportunity permits. It’s a fascinating subject!

Copyright 2017 David Galbraith

 

 

The Great Eclipse of 2017 is Just Around the Corner!

One of the grandest spectacles in astronomy is a total solar eclipse. On 21 August 2017 there’s going to be a stunning event, as the shadow of the moon sweeps over the continental USA from west to east. I’ve recently seen suggestions that this might be the most photographed event in history (to date) when it happens. I’ll be in there too, dear readers, making plans for many months about the chance to photograph this spectacle. The next one that will be visible over the North American continent will take place on 8 April 2014.

Alan Dyer’s ebook on the 21 August 2017 eclipse is highly recommended. You can get your own copy here: http://www.amazingsky.com/eclipsebook.html 

A total solar eclipse is, of course, a transient event in which the moon passes directly in front of the sun from the perspective of some location on earth. Because of the coincidence of the similar relative sizes of the sun and moon as viewed from earth, the moon can just about block out the central disk of the sun. A total eclipse, as the name suggests, brings the sun, moon, and earth into alignment. A partial solar eclipse consists of part of the sun’s disk being blocked.

The 21 August event will be a partial solar eclipse in southern Ontario. For observers in a band a few kilometers across running from the west to the east coast of the USA it will be total.

Preparation for watching an eclipse is a must. Not only should anyone wanting to take this in be prepared from the perspective of observation itself, safety is a crucial concern. Although the disk of the sun is blocked by the moon during these events, the sun is still producing a great deal of UV radiation from the corona, the tenuous outer layers of the sun’s atmosphere. Always wear appropriate eye protection during these events, or observe indirectly, such as with a pinhole camera you make make from a simple cardboard box. For safe eclipse observing ideas, see: https://www.space.com/35555-total-solar-eclipse-safety-tips.html

In preparation I’ve been sorting out gear, trying things, and reading up. I highly recommend Alan Dyer’s comprehensive e-book on photography of this specific event. I’m planning on using several cameras to capture different aspects of the eclipse. At least one will be running interval photos that can later be stacked to produce this sort of effect:

A three hour sequence of solar photographs taken at the home base of the Pine River Observatory, at Lurgan Beach, Ontario on 29 August 2017. A Nikon D7000 digital camera was set up to take photos every 30 seconds, and was equipped with a Mylar solar filter and a wide-angle lens. Every sixth resulting photo was then stacked with StarStaX. The last photo, with the sun in the trees, was taken without the solar filter. It forms a background for the otherwise rather dull individual photos of the sun.

Another camera will be set up with a long telephoto lens and a Mylar solar filter. I am not quite sure yet whether or not I will set up any camera on a telescope mount to track the sun – as this trip requires some travel, lugging such things around is always complicated.

If you are able to take images of the eclipse, consider submitting them to SkyNews Magazine, Canada’s own astronomy magazine. They’re holding a contest for the best solar eclipse photo: http://www.skynews.ca/solareclipsecontest/ 

Safe observing!

Copyright 2017 David Galbraith

 

A New Year, a New Night-Time Photography Class!

I’m happy to report that Royal Botanical Gardens has asked me to lead another Night-Time Photography class! If we get sufficient response, we’ll start at 7 PM on the evening of Thursday 26 January 2017, at RBG’s Nature Interpretive Centre. The class will run for a total of four sessions, weekly.

The class will be a hands-on opportunity to take photos at night, with an emphasis on capturing beautiful images of the sky. We’ll cover equipment, celestial objects, post-photography processing, and more. This isn’t an astronomy class per se, but we will talk a bit about astronomy. By the end of the course I am hoping everyone will feel confident going out at night with their cameras and experimenting with capturing beautiful images.

We’ll try to end each two hour classroom experience with a quick dash outside to see be seen. Guidance will also be given on photo opportunities taking place between classes.

RBG’s public program calendar is available on-line at: http://www.rbg.ca/files/pdf/education/publicPrograms/RBGexperiences1116.pdf

You can register on-line for any of the RBG programs at: https://tickets.rbg.ca/PEO/

To find the Night-Time Photography course, just click 26 January 2017 on the calendar on the web site. Registration is limited to 20.

If you are planning to take the course, please contact me ahead of time for more information. It’s recommended that participants bring their digital cameras and tripods to the first class. Digital cameras should be able to be operated completely manually. A wide-angle lens is best for this sort of photography. Tripods should be very sturdy. I can make recommendations if anyone has any questions.

 

 

Night-Time Photography Cancelled

Unfortunately there haven’t been enough takers this year for the Night-Time Photography short course that Royal Botanical Gardens has asked me to present to go ahead. The course has been cancelled.

A stacked star-trails image captured along the shores of Lake Huron.

When I do offer this three night course, the program is all about learning to take photographs of the night sky with a digital camera. Ideal equipment includes any digital SLR and wide-angle lens, tripod, and remote or cable release. Other digital cameras may be usable, but it will depend on whether you can take complete manual control over the camera. Functions like ISO rating, shutter speed, aperture, colour temperature and focus should all be able to be controlled manually to get the most of out night-time photography.

The Burlington Waterfront in December 2013, photographed early one morning.

We talk a little about telescopes, and there’s a chance to try out some telescope photography, too. However, this introductory program is intended to help you take beautiful images of landscapes and the sky at night, especially those with interesting skies and night-time city-scapes. Subjects covered include basic camera operations, composition, planning for photography at night, controlling long exposures, and computer software for various functions such as stacking star trail images.

The Burlington Waterfront and Pier before dawn.

Our first evening together is usually in a classroom. The subsequent meetings are outdoors. Locations are chosen depending on the weather and class interest. Excellent opportunities for interesting night-time photos are often to be had along the edges of Hamilton Harbour (such as at La Salle Park Marina) or along the Burlington waterfront.

Constellation Orion rising over a suburban street in Burlington, Ontario, on the evening of 23 March 2013. Betelgeuse, the brightest star in Orion, is in the middle of the frame and about 1/8th of the way down from the top.

 

The moon photographed early on the morning of 29 August 2013. Yes, this one was taken with a telescope.

I hope the program will be invited once again. I’ll post updates if that happens.

Get ready for AstroCATS 2014: Canada’s Astronomy Trade Show!

The Royal Astronomical Society of Canada – Hamilton Centre is presenting the second annual Canadian Astronomy Trade Show, AstroCATS, on 3-4 May, 2014!

The web site for this exciting event is: http://www.astrocats.ca/

The big show will open at 10 AM on Saturday 3 May, and close at 6. On Sunday it opens again at 10 and closes at 4. AstroCATS 2014 will be held in the David Braley Athletic & Recreation Centre at Mohawk College, 135 Fennell Ave. West, Hamilton L9C 1E9.

Visit the web site to find lists of vendors, special speakers, and all of the exciting highlights planned for the show in May. Hope to see you there!

Public Access Astronomy: the MicroObservatory Robotic Telescope Network

The MicroObservatory Robotic Telescope Network, operated by the Harvard-Smithsonian Center for Astrophysics OWN “Observing With NASA” program allows free, public access use of 6″ reflecting telescopes located at the Whipple Observatory in Amado, Arizona. If you are a teacher interested in introducing astronomy in a hands-on way, a parent wanting to show kids that they can also take astrophotos, or just interested in experiencing with Internet-based remote observatories, making use of this free system is well worth a try. This system has been in use for over a decade and is a lot of fun.

The network can be reached at: http://mo-www.cfa.harvard.edu/MicroObservatory/

Guest users can select from a pre-set menu of target objects. In December 2013 I tried shooting images of several deep space targets over successive nights. The 6″ reflectors (identified as Ed, Ben and Cecilia, Donald) are programmed with a simple web form. Once images are captured, users are sent an email message with instructions on how to retrieve the files. The files are all returned as 650 x 500 FITS files. The network also supplies MicroObservatoryImage, a free program based on Java that processes FITS files, including stacking RGB images, optimised for the small images the system produces.

The web site is well worth exploring, as there are several resources there of interest to teachers, especially.

Here are three images I captured with this system in December 2013. The images I was able to capture did suffer from several artifacts, including diffraction spikes, and “blooms” produced by very bright stars.

The Cab Nebula (Messier 1) imaged with one of the educational telescopes of the
MicroObservatory Robotic Telescope Network. Three images were taken, one each through a red, green, and blue filter, and then they were combined with the MicroObseervatoryImage software supplied by the network.

NGC5457, Messier 101, imaged with the MicroObservatory Robotic Telescope Network. This was taken as a single 60 second exposure, taken at 5:37 AM local time on 31 December 2013. The area imaged is approximately one degree of arc across.

The Great Nebula in Orion (M42) imaged in three colours using the MicroObservatory system. The colour image was assembled as described above for the image of the Crab Nebula. This image is slightly retouched to reduce artefacts created by both diffraction effects (spikes) and also “blooms” or smears produced by very bright stars.

Copyright © 2014 David Allan Galbraith

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 (https://en.wikipedia.org/wiki/Afocal_photography).

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 (http://www.amateurastronomy.org)  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.

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.

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.

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.

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