NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: FWD: Star Finder "2102E" spreadsheet
From: J Tiffany
Date: 2009 Feb 19, 14:58 -0800
From: J Tiffany
Date: 2009 Feb 19, 14:58 -0800
Hi Brad, I've been looking at your 2102-E spreadsheet - this is a great idea! This is a potentially amazing tool for teaching the use of the starfinder. Thanks for sharing it; I'm sure that you have a significant amount of effort in it. I worked with it for quite a while. I have a few comments/suggestions if you don't mind my input. I hope these comments are useful and help you improve the tool (you called it a toy, but no, not a toy at all in my view). 1) I think the ability to rotate the star field and also the way you show the display of the sun position are both wonderful ideas. But I noticed that when you rotate the star field, the vernal equinox on the sun display does not rotate with them, which it should. The VE (Aries) should always be at SHA=0 deg. 2) The GHA slider is not aligned correctly with Aries. Try this: Set the latitude to 45 degrees N to deform the blue overlay enough to identify the centerline which is 180 degrees or due south (this is the blue line that points directly away from the north celestial pole - on your real 2102-D it has an arrow on it that points at the LHA). Next, set "day of year" to 79 which is the day of the vernal equinox (March 20), then adjust the GHA slider so that the 180 degree line of the blue overlay crosses the center of the sun. Note that the GHA value is shown as 102 degrees, but it should read 0 degrees in this case. 3) Again regarding the "GHA Aries" slider, I think this should be labelled "LHA Aries", and the range of the slider should be 0-360 deg with the blue overlay rotating once (currently it goes from 0-180-0-180-0 and the blue overlay rotates twice through the slider range). 4) The star "Alphard" is misspelled "Alpharad" - (finally, an easy fix!) 5) The star field is displayed differently than on a 2102-D - it is reversed. The spreadsheet display is like a planisphere "facing North" view and shows the stars as they would appear in the sky - the 2102-D shows what the geographic positions (subpoints, if you prefer) of the stars would look like if plotted on the (flattened) surface of the Earth. Try this: Rotate the star field until Archernar is at the top. Notice that Ankaa is displayed to the lower left of Archernar. Now take out your 2102-D star base (North side) and likewise turn it so that Archernar is at the top. You'll see that Ankaa is displayed to the lower RIGHT of Archernar. Compare the other stars and you will see that they are all reversed in regards to their positions between the spreadsheet and the 2102-D. Some people who are accustomed to using planispheres think that the 2102-D is "backwards", but it just uses a different viewpoint, one that is better for celnav. 6) Would be nice if the correct hemisphere (for the stars) could be taken from the latitude slider rather than the N/S radio buttons, so you don't accidentally have the latitude slider in the S hemi and acidentally leave the stars in the N hemi configuation (yes, this is getting picky, sorry). 7) The Blue overlay doesn't seem to work correctly in S hemisphere latitudes. Again, I think you have created something really significant here. Regards, John Tokyo, Japan On Feb 14, 5:23�pm,wrote: > Here is my version of the 2102-D, upgraded to the 2102-E. � > > Some general directions for use. > 1) Just play with the slider bars, don't attempt to type in your desired values, as that has no effect > 2) You can adjust the Day of Year, which places the solar disk > 3) You can adjust the Latitude (most fun) to see ANY latitude clear overlay > 4) You can adjust for Aries > 5) You can rotate the stars > 6) You can select northern or southern hemisphere. > > PLEASE DONT USE THIS FOR ACTUAL NAVIGATION. �Its just a toy. > > Depending upon your settings, you may have to enable content. � > > For those who want to see how I made it work, you will have to unhide worksheet elements. �There is no password protection, I just hid the sheets so it wouldn't be destroyed immediately by "poking around"! > > The key to the entire deal is azimuthal equidistant. �The mathematics are published in many places. > > Enjoy! > > Best Regards > Brad > > Linked File:https://www.NavList.net/imgx/2102e.xls --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---