If spring has been a mixed bag of poor weather and few targets for you, as it has been for many of us, things are looking up as May rolls in. A total lunar eclipse highlights the list on May 15-16.
2022 Total Lunar Eclipse
This eclipse favors the eastern part of North America and all of South America. Observers on the west coast of North America will see moonrise with the eclipse in progress, while western Africa and Europe will see the Moon setting before the end of the eclipse. Check this site for your local eclipse circumstances.
If you’re on the west coast of North America and not able to set up up your equipment the night before, the rising Moon will give you little chance to set your exposure and focus, especially if you are using a telescope and want to capture a shot of the eclipsed Moon against the eastern horizon.
Prepare to bracket your exposures and use at least a single-axis tracking mount. A tracker or astronomical mount will free you from having to adjust pointing during the eclipse, which will last several hours. During the fully eclipsed part of the event, you will also want to take exposures up to a few seconds long to also capture stars in the background. And by the way, even though lunar eclipse is easily visible even in light-polluted cities, being able to see the stars in a dark location adds much more to eclipse photos.
May also opened with a nice lineup of planets just before sunrise. Venus and Jupiter were close enough to be caught in a single frame shot through a medium-sized telescope. As May progresses, Venus and Jupiter will grow apart, but the entire array of planets will still make a good wide field composition for a few weeks.
The usually active Lyrid meteor shower was largely a bust with the full moon limiting visibility, but the early morning Eta Aquariid meteor shower (dust from Comet Halley) seems to be showing some decent activity. Wikipedia lists the peak as occurring on May 6, but with activity actually spanning April 18 to May 28, we might as well put our wide field cameras to use whenever we’re out shooting at night in May.
Galaxies Far, Far Away
Spring is an in between time for many astrophotographers because the target-rich areas near the Milky Way are either setting early in the evening or rising late in the morning. Since we’re located towards the outside edge of our own galaxy, during this time, we’re looking in the opposite direction from the galactic core. We’re thus able to see objects outside our galaxy without the interference of dust and gas. The downside is that these objects are very small, so a long camera lens or moderately-sized telescope are the minimum starting point for astrophotography, and a tracking mount is a must.
On the shorter end of the equipment range, all but a few galaxies will show as more than fuzzy spots in the vast emptiness of space. But it is possible to photograph some nice combinations of galaxies, such as the “Leo Trio,” so named because three galaxies (M65, M66, and NGC3628) can be photographed in one shot. Even better, a camera modified for H-alpha sensitivity is not necessary to see the detail in the galaxies.
Or, try for Markarian’s Chain, a nice arc of galaxies.
Markarian’s Chain lies in a relatively compact cluster of galaxies called the Virgo Cluster, located in the constellation Virgo, of course. Most of the galaxies will appear as fuzzy spots in small telescopes, but a few can be photographed with an amazing variety of forms, some actually gravitationally interacting. The shot below was done on 6x7cm medium format film, scanned, and shown in negative form, which makes seeing the tiny galaxies a bit easier. Markarian’s Chain is near the center of this shot.
The scope used was a Borg 100ED (100mm aperture, f/4). The shot is from a single 45-minute exposure on (no longer available) Kodak PPF400 negative film. I used the Millennium Star Atlas as a reference to hand-label the galaxies one rainy weekend. These days, it’s easier to use Astrometry.Net to get a labeled photo. This site allows you to upload an image and, after a few minutes, returns to you a notated version of your shot (among other info). Use a JPEG image and give the program some hints about where you were pointing to speed up its processing.
Finding Small Faint Targets
Photographing small faint targets like galaxies brings a whole new set of challenges because you can’t see your target even in a wide angle finder scope. The modern solution is to have a computerized go-to mount. Ideally, if properly set up (aligned on two or three stars on each side of the meridian), a go-to mount should point your scope at a target and have it in the field of view of your camera. In practice, especially when moving a large distance across the sky, a lightweight mount may not be very accurate, so the best thing to do is to first go to a nearby bright, easily identified star to synchronize the computer’s pointing. An older mount with analog setting circles would need the same sort of synchronization procedure on a nearby bright star first.
Once the target is in the field of view, I turn the ISO on a DSLR or mirrorless camera to the maximum value and take a framing shot of a few seconds. This allows the pointing to be tweaked for best framing as well as gives me an idea of how long an exposure can be used when the ISO is turned down to its best setting. As for all deep sky objects, multiple frames will be needed, so an intervalometer for the camera is needed.
For advanced astrophotographers with very sophisticated setups (who need not read this article), a fully computerized imaging camera, mount, and pointing software can move to the approximate target point, take an image, determine exactly where it is pointing (equivalent to using astrometry.net), and adjust the pointing so the framing is exactly as specified by the user. But my own preference is to not use such a fancy (complicated) setup, especially for portable setups, so I use the procedures described earlier.
Whichever is your preference, spring brings a whole new level of challenges for your astrophotography. Happy shooting!