NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Learn the stars, by phone
From: Brad Morris
Date: 2009 May 22, 15:02 -0400
From: Brad Morris
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 Brad -----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 contradictory, but we're not. 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 "Confidentiality and Privilege Notice The information transmitted by this electronic mail (and any attachments) is being sent by or on behalf of Tactronics; it is intended for the exclusive use of the addressee named above and may constitute information that is privileged or confidential or otherwise legally exempt from disclosure. If you are not the addressee or an employee or agent responsible for delivering this message to same, you are not authorized to retain, read, copy or disseminate this electronic mail (or any attachments) or any part thereof. 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