NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: UNK
Date: 2017 Jan 30, 09:59 -0800
Brad,
You must have never looked at a Rude Starfinder 2102-D, or at the instructions that you posted (unnecessarily).
You wrote:
"In not one place can I find where I can sum Right Ascension (whose units are hours, minutes seconds) on a device which is demarcated in degrees with a resolution of 1/2 degree. "
The author probably assumed that any user who has the need to convert between the units knows how to do so. If you can't do it in your head, there is a handy table for that in the yellow pages of the N.A. (The very first one, right after p. 325). If you need more help, I will guide you through a worked example. I don't know about the air almanac, but users of the N.A. won't have that conversion problem anyway, because it uses SHA, given in degrees, to describe star positions. In order to check the accuracy of the starfinder, you therefore only need to add the SHA to the right ascension, also marked in degrees on the starfinder.
And yes, the instructions clearly explain this under the heading "To plot the sun [...] OR ADDITIONAL STARS" under item (2).
And you wrote:
"If you can identify an actual flaw, when using the device as designed, I would be very receptive to listening to and understanding your point."
Well, have you actually checked what Frank said? Did you take out your 2102-D and measure the position of any star? One at least?
I did. Applying a ruler to Hamal, I find a RA of 30 d 45' for Hamal on the starfinder. I retrieve its SHA of 328 deg from the N.A. of 2017. Adding these two values (AS PER THE INSTRUCTION ON THE 2102-D!!) I obtain 358d 45'. No conversion needed! After this spot check, I have no reason to doubt that the systematic error that Frank has found indeed exists. It is normal to expect that, after all there is such a thing as precession. The SHA of Hamal was half a degree larger, half a century ago when the starfinder was designed. In other words, Frank is saying is that the starfinder is outdated. To me, the reason is obvious: There is no demand for an updated version.
Herbert
