Let’s say you’re all set to capture photos of the 2017 solar eclipse with your trusty scope on a Sun-tracking equatorial mount, but clouds thwart your view of the event. Your weather app tells you that conditions are much better several miles from where you’re stationed. What to do? You can race down the road with a few minutes to spare, but accurately following the Sun without polar aligning your mount in broad daylight is next to impossible. If only there were a quick way to align your scope.
You’re in luck, because there is a way to get rough polar alignment that takes about 30 seconds! All you need is your smartphone with a planetarium app installed that automatically aligns with the sky using the phone’s internal compass and accelerometer — and a flat surface on your lens cap or an equatorial wedge. Here’s how it works.
First, check to make sure the app on your smartphone has an equatorial grid function, and possibly either a crosshair or a Telrad field-of-view circle. The brightness settings on the display should be as high as possible, so you can see it in the daylight. (The planetarium apps Sky Safari and SkEye include crosshairs).
Next, set up your mount with the polar axis pointed close to North. If you’re using a German equatorial mount with your lens or telescope, attach your optic to the mount, set the declination to +90°, and keep the lens cap on. Your telescope or lens cover will act as a surface perpendicular to the mount’s polar axis.
Open your planetarium app, and place the phone on the lens cap with its back flat against the cap with some tape or an elastic cord. Because the phone’s display is on top, the phone will effectively be pointing downward, toward the South Celestial Pole. With this in mind, adjusting the fine controls on the polar axis of your mount, and the EQ grid will change accordingly. Move until you see the grid align with the South Celestial Pole. Once you have the Pole centered in the Telrad circle or behind the crosshairs, you’re polar aligned!
This technique is even easier with wedge-mounted telescopes, such as my Meade LX200 and ETX EC-90, both of which are mounted on adjustable wedge-like devices to match the user's latitude. Simply remove the telescope and use the flat surface of the wedge just like the lens cap described earlier; click here to watch a video demonstration of this technique.Once you’ve aligned the wedge, install your scope and you’re ready for action.
With practice, this whole operation should take around 30 seconds. Using this method, you can be sure that your scope will track the Sun for at least 3 or 4 minutes, making that mad dash well worth the effort.