# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Learn the stars, by phone
Date: 2009 May 22, 15:02 -0400

```The Skyscout just has two flat lenses, through which you observe the object.
You are expected to observe the object in the center of the objective, a
reticle would have been nice, but is not part of the kit.

When we talk about pointing accuracy, I think we must bifurcate the discussion
to azimuth and elevation.  Since the inclination of the Skyscout is far more
readily obtained than the azimuth, I would suggest that the elevation is of a
very high accuracy, much finer than the 0.5 degrees.  There are several
electronic devices which can provide inclination, here are several
http://www.leveldevelopments.com/inclinometer-sensors.htm Note that the
quoted resolution is on the order of 1/100 th of a degree.

The azimuth is a far different matter.  The internal magnetic variation map
(absolutely required for the device to work) cannot be infinitely fine in
resolution, leading to an approximation right from the start.  Why is it
required?  Since the variation of the compass will clearly affect object
identification, we have no choice but to account for it. If your variation
was 10 degrees, then the object pointed at would be wrong by 10 degrees, thus
mis-identification would occur. Next, we must sense the local magnetic field,
determine (via gps) where in the variation map we are, and then compare to
see if we are in range (yielding that 'magnetic error message') and finally
determine azimuth by correction.

To me, this azimuth solution sounds much like the longitude method whereby the
longitude would be found by the variation of the compass.   If the variation
was mapped to a very fine level AND we had a way to sense azimuth, then we
probably could get a fairly good approximation to longitude.  Problems: the
variation map changes all the time, the sensitivity isn't there and local
disturbances would yield some highly wrong results.

------

On the topic though, of attracting Celestial Navigators because they have the
Skyscout or a Smart Phone is upside down.  If you have a Skyscout, you have a
GPS, no need for Celestial.  If you have a Smart Phone, between the cell
tower localization and the probable on board GPS, you have no need for
Celestial.

They may make the connection that it is Celestial turned inside out, but they may not.

But that can be turned to our advantage.  Suppose the display would show a
graphic, explaining how the object's light intersects the earth's sphere and
showing that classic circle of equal altitudes.  Then click on the next
object, with its circle of equal altitudes shown super-imposed on the same
sphere, showing the intersection!  In other words, Sumner's Lines of
Position, graphically, based on the objects the user selects!  That brings
the attention to how celestial "could" have shown the same thing...

Best Regards

-----Original Message-----
From: NavList@fer3.com [mailto:NavList@fer3.com] On Behalf Of frankreed@HistoricalAtlas.com
Sent: Friday, May 22, 2009 1:53 PM
To: NavList@fer3.com
Subject: [NavList 8381] Re: Learn the stars, by phone

I wrote previously that the SkyScout has a pointing accuracy of 0.5-1.0
degrees. George found a FAQ saying 2-3 degrees. If we were talking about a
sextant or other measuring instrument, those statements would be

Under good operating conditions, I wouldn't be surprised if the SkyScout has a
pointing accuracy at the high end of accuracy. And under marginal operating
conditions (for example, just before its software complains about magnetic
interference), I wouldn't be suprised if the pointing accuracy is near the
low end of accuracy. For a device with no magnification, none of this makes
any difference, of course.

It will be interesting to see if the mobile phone engineers who are attempting
to add this pointing capability to a device with a more hostile environment,
both internally and externally, can get reasonable accuracy out of it. They
have a lot more money than Celestron (now there's an understatement!), and
they've had a few more years to work on it, but we will have to wait and see.

-FER

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