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: George Huxtable
Date: 2009 May 22, 20:13 +0100
From: George Huxtable
Date: 2009 May 22, 20:13 +0100
Frank Reed wrote "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. " Frank is trying hard to find a bit of "wriggle-room" here. But that wasn't the contradiction. In [8254] he wrote "These compasses, aided, of course, by software models of the Earth's magnetic field, can determine true direction in three dimensions in most parts of the world to an accuracy of one degree or better." and when that was questioned as seeming implausibe, he reduced the claimed error even further, stating- "The Skyscout ... includes a GPS chipset, two magnetic chipsets, and accelerometer chipsets. With the output from those, it can determine where you're pointing in the sky from anywhere on Earth at any date and time (probably limited to a few decades out for planet positions) with an accuracy of about 0.5 degrees." That seemed even less likely, and as I could find no such claim currently being made by the makers , I asked where it had been made, and got this seemingly authoritative reply "It refers to the SkyScout, which I have tried out myself. That half-degree claim comes from the official specs. It's a believable claim, based on performance, but the exact level of accuracy (whether it's 0.5 or 0.75 or 1.0 degrees) is not critical in any way to the device's use." So, again, I asked- " That is why I've been trying to find out- 1. Who makes such a claim? 2. Under what environmental circumstances is it claimed to apply? Such as magnetic latitude, acceleration, sensitivity to local magnetic deviation, temperature range? 3. What are the snags, if any?" but got no further response. Since, then, I've found a statement, hidden away on a shadowy corner of the Celestron website, which belies Frank's claim for half-degree accuracy, stating "" Pointing accuracy and using my SkyScout The SkyScout has a pointing accuracy of 2-3 degrees (a thumbtip at arms length). It is not as accurate a pointing device as an optical finderscope with crosshairs, a pair of binoculars with a reticle ..." There's the contradiction. Frank informed us his quoted half-degree "came from the official specs". Well, did it? Did Celestron make such a claim at some time, then diluted it? That would be interesting, in itself. Or did Frank imagine it? He should either withdraw, or back it up, not try to sweep such a significant discrepancy under the carpet. George. contact George Huxtable, at george@hux.me.uk or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---