Field of view
Ron Brecher on the nocturnal behaviour of imagers and eyepiece astronomers
For nearly a quarter century I’ve been studying astronomers – including myself – ‘in the wild’. I’ve noticed some interesting differences between my fellow astronomers, depending on whether they are catching photons with their eyes, a camera, or both.
Let’s start with who’s talking and when. Eyepiece astronomers can be downright chatty while setting up their relatively simple equipment (I’ll get to that in a moment). But once the serious observing starts, they tend to go quiet. They often observe in small groups and speak in whispers, occasionally consulting a star chart with a dim red flashlight. Imagers are exactly the reverse. Although quiet during setup, they can be downright boisterous while the cameras do the observing. They may hang out in large groups. Or they may just go to sleep…
With relatively simple equipment, visual astronomers don’t need much power. One small battery for my red dot finder is enough for many nights of observing with my 10-inch (254mm) Dobsonian telescope. For my 20-inch (508mm) Dobsonian I also use a 9V battery for a fan to cool the primary mirror, but that’s about it. When I’m doing astrophotograpy it’s another story: I need power for a mount, two cooled cameras, a guidescope, two electronic focusers, a PC and two dew heaters. And all that gear means much more can go wrong too; I’ve never had to quit looking through the eyepiece because of an unplanned Windows software update!
However, there are some conditions that put a damper on a visual observing session, the most important being extreme cold. In my locale, winter observing tends to be brief, even for the hardiest astronomers. Cold doesn’t have to affect imaging, since most imagers can find shelter while their equipment carries on. Excessive heat and intermittent clouds are the opposite. Clouds at the wrong place and time can cause the failure of automated focusing or autoguiding, which can stop an imaging run in its tracks. On very warm nights, camera sensors and optics can be harder to cool and stabilise for imaging. Meanwhile, the visual astronomers are in T-shirts, happily pointing their scopes between the clouds at their favourite objects. Another interesting dichotomy between visual and imaging astronomers is the length of the target list for a given night. I usually have a slew (pardon the pun) of targets in my visual observing plan; I once viewed 15 globular clusters in the constellations of Ophiuchus, the Serpent Bearer, and Sagittarius, the Archer over a three-hour period. As an imager, I think in terms of nights-per-target rather than targets-per-night, having learned that my best photos come from the patient acquisition of photons over multiple nights.
We’re fortunate that we can choose to enjoy visual astronomy, astro imaging, or both. For me, nothing can replicate the experience of photons hitting my retina and activating my brain after a trip across space and time, and into my scope. But images reveal so much more detail and colour, and can be enjoyed by people who will never climb a ladder in the dark at –20⁰C, or whose vision won’t let them see well at the eyepiece. After considering everything, I’m going to keep doing both – usually at the same time!