When the inner planets, Mercury and Venus, pass between Earth and the Sun, it is known as a “planetary transit.” While not as visually spectacular as a solar eclipse, the transit of our inner solar system’s neighbors is a remarkable sight to viewers on Earth. Unfortunately, these events are not visible to the naked eye, so let’s discuss what gear is recommended for photographing and viewing the transits.
Astronomical images NASA/JPL
Before you invest in solar viewing optics, please know that these transit events are rare.
Mercury transits are visible around 13 times every 100 years and, interestingly, they only happen in May or November. Even more rare, there is a long wait of either 121.5 years or 105.5 years between a pair of Venus transits separated by 8-years. Isn’t our Solar System’s celestial clock absolutely amazing?
The rarity of these events should definitely make you want to view and/or photograph them. If you do not want to invest in solar viewing gear, look for local viewing parties coordinated by your neighborhood astronomy clubs, observatories, science museums, and more.
SAFETY FIRST
To view a transit, you will be viewing the sun. All precautions needed for viewing and photographing a solar eclipse, or doing standard solar viewing and photography apply to planetary transits. DO NOT use non-certified solar filters. DO NOT use solar viewing glasses in conjunction with magnified optics like unfiltered telescopes or binoculars. And, DO NOT point an unfiltered camera lens or look through an optical viewfinder when a non-solar filtered camera is pointed at the sun.
50x
When it comes to viewing optics for planetary transits, most experts agree that you will want an optic that offers magnification of at least 50x for prime transit viewing, so keep that number in mind as we discuss the options.
Solar Telescopes
By far, the best way to view and photograph the transit of Mercury or Venus is with a solar telescope. B&H carries many brands and options in this product category with different apertures, focal lengths, and features. Some of these scopes are suitable for nighttime viewing (white light/broadband viewing), as well, because they include a solar filter for when the scope is pointed at the sun. And, some of these scopes have specialized Hydrogen-Alpha wavelength filtration for detailed viewing of the Sun’s surface features. As amazing as a Hyrdrogen-Alpha-filtered viewing experience is, these scopes come with premium prices and are not usually suitable for nighttime celestial observations. One exception is the newly re-engineered Coronado SolarMax III family of H-alpha scopes—the filters moved to the exterior so they can be quickly and easily converted to nighttime use. Also, most H-alpha scopes come without mounts and often without many (or any) accessories, so you’ll need to build your rig à la carte.
The math for calculating magnification is simply the focal length of the scope divided by the focal length of the eyepiece. For example, the Meade EclipseView 60mm f/13 AZ Achro Refractor Telescope with Solar Filter has an 800mm focal length and comes with a 26mm eyepiece that gives 31x magnification and a 9mm eyepiece that provides 89x magnification.
For digiscoping through your telescope, be sure to be familiar with how to connect your camera to your scope or telescope eyepiece before the big day! Digiscoping setups and ease vary between cameras and telescopes.
Spotting Scopes
The spotting scope is one of my favorite tools for casual astronomical viewing and a great tool, when properly filtered, for solar observation. Also, digiscoping with a spotting scope can be much easier than connecting a camera to a telescope.
Most spotting scopes come with native magnification that exceeds 50x and, many spotting scopes also have threads for mounting front filters. This makes it easy to add a round screw-in solar photography filter. If your scope does not have threads, you can still use a universal solar filter.
NOTE: When using a spotting scope lens with a solar photography filter, DO NOT view the sun through the scope with your eyes when using a simple neutral density (ND) filter. These ND filters are for photography ONLY. If you wish to view the sun and transit with your own eyes through your spotting scope, be certain that you are using a solar viewing filter for your optics. Look for “Safe Solar Viewing and Photography” in the product description.
Just as with the binoculars, a tripod and panning head will be crucial to getting the best viewing experience.
Superzoom Cameras
If there is one camera that was made for photographing a planetary transit, it is the superzoom or bridge camera. These point-and-shoot cameras have incredible magnification and are relatively small, light, and easy to use when compared to a telescope. On the Web, I have found some great footage of the 2016 transit of Mercury captured with the Nikon P900 and now we have the even more powerful Nikon P1000 with its 3000mm equivalent lens providing 60x magnification. Like the spotting scopes, many of these superzoom cameras have threads at the front for adding filters. Because these superzoom cameras do not have optical viewfinders, you may use solar filters designed just for photography—not viewing and photography.
Because you’ll likely be shooting at maximum magnification through a dark solar filter, I would strongly recommend using a tripod when photographing/viewing the transit with a superzoom camera.
Telephoto Lenses
I hesitate to mention super telephoto lenses, but you can certainly try to photograph the transit using a very long telephoto lens and solar filter. What focal length lens gives you 50x magnification? Well, if you use the basic formula that a 50mm lens is 1x, you will find that 50x comes from a 2500mm lens.
B&H is fresh out of 2500mm lenses, but you could theoretically use a lens with a focal length of 600mm or more (maybe with a teleconverter?) and hope that you have sufficient resolution to crop the image to see the inner planet’s transit. Remember, the sun is 150x larger than a transiting Mercury (Venus is larger and closer, so a larger transit subject), so the planet is going to be extremely small—likely smaller than some sun spots—when viewed through a camera lens.
However, if you have a long lens with or without a teleconverter, you are welcome to give it a try! With today’s high-megapixel cameras, you might have sufficient resolution to “zoom” into the image to see the transit.
NOTE: When using a telephoto camera lens with a solar photography filter, DO NOT view the sun with your eyes when using a simple neutral density (ND) filter. These ND filters are for photography ONLY. If you wish to view the sun and transit with your own eyes, through your camera’s optical viewfinder, be certain that you are using a solar viewing filter for your optics. Look for “Safe Solar Viewing and Photography” in the product description.
Binoculars
First, the bad news: B&H carries a full line of solar viewing binoculars, but, unfortunately, none of these optics have sufficient magnification for planetary transit viewing. As far as non-solar viewing binoculars, there are several pairs of zoom binoculars that will take you to and beyond the magic 50x number. If you want to use a pair of big magnification binoculars, you will need to properly filter them for solar viewing.
NOTE: Again, don’t even think about looking at the sun through a pair of unfiltered binoculars or using eclipse viewing glasses in conjunction with a magnified optic.
To get the correct filters for your binoculars, be sure to determine the outer diameter of your optic’s objective lenses and get the correct size of universal solar filter to place over the front of the binoculars. Also, with this much magnification in a binocular, you will want to mount them on a tripod with a panning head to steady your view.
For more information on safe solar photography, click here. Also, check out our B&H in Space page for more information about astrophotography, celestial events, and more!
0 Comments