A smartphone lunar atlas

I have covered the topic of basic smartphone astroimaging on two previous occasions (“Cellphone imaging” in November 2011 and “Cellphone digiscoping” in October 2012). I had little choice. Both of those issues were astroimaging-themed, and I was asked to do my part.

It was a daunting task, as my experience with astrophotography was limited to taking 20- to 30-second exposures of constellations with a tripod-mounted, single-lens reflex (SLR) camera and 35mm slide film — and that was back in the late 1970s.

For the first time in my life, I’d be putting camera to telescope. I took a deep breath and gave it a try, and discovered that lunar imaging with a smartphone was a lot easier than taking constellation slides with an SLR camera.

This past winter, I returned to lunar astroimaging in a big way by deciding to put together my own small-scope Moon atlas. Each night (and early morning when the Moon was in its waning phases), I’d trudge outside with my smartphone and a 4.5-inch f/8 reflector rigged with a 16mm wide-field eyepiece, and take a whole Moon snapshot. Setting up the scope, aligning it with the Moon, getting a decent shot with the smartphone, and putting everything away took 15 to 20 minutes.

The hardest part came in finding the “sweet spot,” where the smartphone can capture a lunar image from the eyepiece. Not only does the phone have to be positioned precisely both up-and-down and side-to-side, but it also has to be at a 90° angle and the right distance from the eyepiece. The process can be simplified with smartphone adapters, like the ones featured in Tom Trusock’s “Turn your smartphone into an astro-camera” article in the March 2017 issue.

Not owning such an adapter, I had to hold my smartphone in my hand and keep it as steady as possible. This took a lot of practice and patience. Fortu­nately, I could quickly review each shot and delete it if the result was less than satisfactory. My earliest attempts required a dozen or two takes, but eventually I was able to capture a workable image in the first half-dozen tries.

Once I got an image I liked, I emailed it to myself. At the computer, I retrieved the image, transferred it to a Word document where I did some fine-tuning, and then ran it through the printer. I referred to a Moon map to label the main features, then slid the sheet into a page protector and placed it in a three-ring binder. I used to curse the Moon for making it difficult to conduct deep-sky observing. Now, I welcome the opportunity to add another page to “Chaple’s Small-Scope Lunar Atlas.”

Enter the neophytes

If you have a smartphone and have never taken astroimages through a telescope, I urge you to give lunar imaging a try. Even a rank beginner can do it. At a star party for a local elementary school, I brought my 4.5-inch reflector and invited parents with smartphones to try their luck taking an image of the Moon. After a quick demonstration with my smartphone, I put one of the parents in charge of the scope and went to my 10-inch reflector to conduct the main part of the star party.

Eventually, a girl walked up and proudly showed me a stunning lunar image she’d just captured. Here was a person who had likely never even seen the Moon through a telescope, and she was about to go home with an image of it that she had taken herself — from novice to lunar astroimager in less than an hour!

Questions, comments, or suggestions? Email me at gchaple@hotmail.com. Next month: Why I won’t recommend a particular restaurant, movie — or telescope!