Astronomy Adventure – Afocal Astrophotography
In response to my series on globular clusters, a reader asked just how difficult these kinds of astrophotos are to take. I’d be happy to answer as the whole point of this adventure has been to show that basic astrophotography like this is far easier and more available at a relatively reasonable price than it has ever been.
Having been inspired by the work of Andrew Symes and Mike Weasner using iPhones for afocal astrophotography, my initial goal was to be able to do some basic astrophotography quickly and easily at a cost of under $500.00. I described my initial purchases and the reasons for them here, which cost somewhere between $400 and $500. Since then I have added a 6.3mm and a17mm eyepieces which added another $80 to my total. The 6.3mm was mainly for planetary viewing and the 17mm was the best fit for capturing non-planetary images, primarily because it was eyepiece with the most magnification that fit the smartphone adapter without using a Barlow lens and best matched the size of the camera lens.
In terms of actually taking these photos, there are two main difficulties. First, the tracking alt-azimuth mount needs to polar aligned, which simply means pointing the telescope at the North Star. This requires some degree of guesswork on my part because Polaris is not visible from where I usually set up my scope, but I can do this relatively well pretty consistently now just because I’ve done it so many times. The precision of polar alignment will determine the exposure times that I will be able to use. The more precise, the longer the exposure and the more detail the photo will have. But even in the worst cases, 20 second exposures will work without showing significant star streaking.
The second issue is getting the proper focus. Because the camera lens may be a little farther from the eyepiece than your own eye, or vice versa, means that what may look like perfect focus to you through the eyepiece may be slightly out of focus through the camera. This is usually easily fixed when photographing clusters, galaxies, and nebula. It is more difficult when photographing the planets or, less so, the moon mainly because seeing is never usually steady enough to get perfect focus.
But by far the biggest obstacle to doing even this basic astrophotography is the quality of the seeing. Dark skies and steady air are by far the biggest factors between the best and worst photos.
Because of these issues and the limitations of the equipment I’m using, open clusters and the moon provide the best photographs. But you can get some decent photos of globular clusters, nebula, galaxies, and occasionally even the planets. Of course, they are not going to compete with the Hubble Space Telescope or those with more powerful scopes and equatorial mounts with tracking scopes that can take hours-long images.
If you already have a scope, get a smartphone adapter and download NightCapPro or similar software and give basic afocal astrophotography a try. You’ll be surprised at what you can do. Even if you have no tracking available, a 5 second image will still be sufficient to create some nice photos. And if you have nothing yet but are interested in doing some basic astrophotography, just know that you can now do it relatively cheaply.
Here’s one of my better photos of Jupiter taking on a night of steady seeing way back in June:
