Afocal Photography

When doing any sort of public astronomy, showing folks the beautiful sights available to a telescope, I often hear the question “Can I take a photo of that?” The person asking the question is usually holding the ubiquitous compact digital camera. They are often surprised when my answer is “Yes”.

Afocal Photography
Taking a photograph of the Moon using afocal photography

It is indeed possible to manage hand held shots of bright astronomical objects by simply holding the camera up to the eyepiece. There are a few tricks to making it work, but nothing that can not be demonstrated in a minute or two. The resulting photographs can be quite pleasing, definitely worth showing to friends and family along with the rest of the Hawai’i vacation shots.

The method of positioning a camera with a lens in front of an eyepiece is called afocal photography, or sometimes digiscoping. Afocal has been around for a while, but was not considered a practical photographic method by most. The advent of common digital cameras without removable lenses has changed this.

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Light Pollution Filters

Our neighborhood is a somewhat odd case. A large development surrounded by miles of empty land. Get just outside the neighborhood and the skies are quite dark. Inside the neighborhood one has to deal with the usual house lights and a plethora of streetlights. Still, I can see the Milky Way from the driveway, pick out M31 with the unaided eye, and make out a number of star clusters. There is one streetlight directly across the street from my front yard. A notable problem, only partly dealt with by way of a strategically planted Royal Poinciana. A few years old now, the tree has begun to shade the driveway from the worst local light source.

Despite the fact that the neighborhood is disgustingly overlit, there is a mitigating factor. All of the streetlights are low pressure sodium type lights. These lights emit all of their power at 589nm, a sharp emission which can be filtered at the camera. Filters for this and other common light pollution wavelengths are readily available from several manufacturers in a number of sizes and formats.

Light Polluted Orion
One minute Orion without LPR filter

While taking some wide field shots using a 50mm lens I had recent opportunity to see the difference with and without the filter. I did not have a filter that fit the 52mm thread on the lens, but rather simply set my 48mm filter on the front of the lens. I had not performed this simple experiment before as the usual mounting location of the filter is buried inside the setup. On this occasion it was a simple matter to take identical frames with and without the filter.

The resulting frames can be seen at the left. These are taken from the camera raw images, imported with daylight color balance, cropped and sized for display. Both images have been handled identically. Neither is a “pretty” picture, these are unprocessed images, none of the stacking, stretching and sharpening that would vastly improve the visual appearance.

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Shooting in the Dark

A supernova, a comet, a new camera and a dark night.

I have had the Canon 60D for a while now. Since April in fact. It was my main carry camera in Alaska this summer. This was the camera used to produce the laser shots and videos that were published far and wide. But I have never used the camera on a telescope. A new Moon observing weekend is an opportunity to change that.

Astrophoto Setup
The NexStar 11″, the TV76mm and a Canon 60D setup for astrophotography at the MKVIS
I have recently re-assembled my astrophotography rig in the garage. But that rig has some technical issues that need to be solved before it is ready to use. Instead I packed up the NexStar 11″ scope, a scope usually used for public observing, but also a nice photographic platform. Piggyback the TeleVue 76mm atop the larger scope, attach the 60D and I am ready to shoot. Well? Maybe a bit more work than that. With alignments, focusing and more it was an hour before the first exposure.

While my camera was busy shooting sequences, I wandered around and visited with the other folks enjoying the night. A few peeks through other scopes at favorite objects was about all the visual observing I did. There were a couple groups using cameras without telescopes to shoot stars capes under the dark sky. We traded hints as multiple cameras worked the night.

An orange glow in the clouds betrayed new lava flows on Kilauea. Even thirty miles away we could make out bits of a channelized a’a flow. The pair of binoculars I had brought became one of the most popular optical instruments around.

I was using the rig without any autoguiding, as a result guiding errors spoiled a number of exposures. I kept the exposures short, and shot bright objects. I have sequences to process of a lot of old favorites… M31, M42, a few open clusters like M11 and M38, the Pleiades and more. Just before dawn I even shot a sequence of the Tarantula Nebula skimming the slope of Mauna Loa. Two 8Gb SD cards filled and part of a third. I will be some time processing the many images taken through the night. There is even some video of Jupiter and Mars to process into high resolution planetary images.

There were three telescopes still operating when dawn appeared. Maureen, Cliff and myself watched as the sky grew bright and a thin crescent Moon rose above the slopes. Even then we spent a little time observing and photographing the Moon or Mars as the stars disappeared. We were still breaking down gear as sunlight swept the hillsides around us. Tired and yet elated we greeted the Sun.

The usual suspects setting up gear for a great night of observing on Mauna Kea...

Mercury Transit

About a dozen times a century Mercury passes in front of the Sun as seen from Earth. The event is observable with a modest telescope and a solar filter, Mercury can be seen as a small black dot crossing the surface of the Sun. If half of those happen when the sun is below your horizon the average person will have the chance to observe five or six in a lifetime. Since the next opportunity will not occur until May 9th, 2016 I didn’t want to miss this one!

Photographing a Mercury Transit
90mm refractor Violet Haze photographing the transit
I took the day off.

Considering that Mercury never gets very far from the Sun means that most of the time you can observe Mercury it is low on the horizon and is typically seen through a great deal of atmospheric distortion. A transit is one exception to this, during a transit mercury is a sharp disk, very different from the multicolor jello ball that is usually seen.

The 2006 Transit was well timed for observation across western North America, starting just after noontime and ending at 5:09pm MST. This put the Sun high in the sky for all but the last part of the event. Our weather cooperated as well, delivering a cloudless blue sky the entire day in place of the clouds that had been forecast. The air was reasonably steady as well allowing good photographic and observing conditions.

I took advantage of the weather and photographed almost the entire transit, all but the very end when the sun sank below the trees in my neighborhood. I used the Canon 20Da and setup a timer to shoot every 5min. The only issue was the inability to do a polar alignment on the mount when setting up in the middle of the day. The result was I had to manually guide the scope every 10-15 min to keep the sun centered.

I got plenty of good photographic material, enough for a few single photos as well as an animation of the transit. A transit is an impressive demonstration of the scale and arrangement of our solar system. Not hard to visualize the reality of those textbook drawings of planetary orbits after you have had such an opportunity to see the real thing.

No complaints on my second Mercury transit.

Mercury Transit 8Nov2006
The Mercury transit of 8 Nov 2006 in progress. Mercury is about halfway between the center to the bottom, a large sunspot complex is visible on the left edge. Photo with a 90mm APO refractor, a Thousand Oaks full aperture filter and a Canon 20Da camera.