Daylight Polar Alignment Made
Easy
By: Spencer R. Rackley IV | May 19, 2017
Aligning an Apogee fork mount using an iPhone running
Sky Safari 5.
Sean Walker
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).
Attaching your smartphone over the front of your polar finder works just as well. For German equatorial mounts
without a
polar scope,
set the
Declination
to +90° and
attach your
smartphone to
your
telescope or
camera's lens
cap.
Spencer R.
Rackley IV
Next, set up
with the polar
close to North.
using a
equatorial
your lens or
attach your
mount, set the
to +90°, and
cap on. Your
lens cover will
surface
perpendicular
mount’s polar
your mount
axis pointed
If you’re
German
mount with
telescope,
optic to the
declination
keep the lens
telescope or
act as a
to the
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.
CATEGORIES
Astrophotography: Tips & Techniques, Observing, Stargazer's Corner: Adventures Under the Night Sky, The 2017
Total Solar Eclipse
About Spencer R. Rackley IV
Rackley is an amateur from Charlotte, North Carolina, who goes by the handle "Astronerd."
View all posts by Spencer R. Rackley IV →
4 thoughts on “Daylight Polar Alignment Made Easy”
1.
Grr8063 May 25, 2017 at 5:37 pm
The article says that Sky Safari 5 has the Telrad field-of-view circle, however, it appears that the Pro or
Plus versions of the program is required.
2.
Monica Young May 26, 2017 at 9:38 am
Yes, that’s correct – I have the regular Sky Safari app (not Pro or Plus), and it does not provide a Telrad
circle.
Log in to Reply ↓
1.
Trevor May 27, 2017 at 10:59 am
SkEye free on Android has 8deg and 16 deg circles that would do the trick. Going to try this
on my Meade LX90 next time I get the wedge out. Only limitation I can see would be the
calibration accuracy of the phone used.
Log in to Reply ↓
1.
Spencer R. Rackley IV Post authorMay 27, 2017 at 1:40 pm
Trevor,
SkEye free is used in the video. There is some concern about magnetic offset to true
north that I have heard about. The developers at SkEye say they correct for magnetic
declination and have assured me that accuracy is based on “…the location you enter
and the world-geomagnetic data built into the Android system.”
Remember that this technique is intended for a fast setup for solar eclipses if you
have to move on short notice.