Reply To: Practice sights for a beginner.

[pmaclearn@verizon.net]

Simon (Jason & Ken):
First of all, Stellarium Astronomy and GPS Anti Spoof are two entirely different tools. For brevity I am only going to discuss the GPS Aniti Spoof tool. First of all it is an App and is best used on a smart phone for convenience. A limited subset of the full app is free, but I jumped right to the full app for a one-tijme charge of less than $20. The full app provides data on the Sun, Moon, Planets and the 57 Navigational stars. The main screen provides time-active data on the celestial body you have selected (on the second page – Settings:) Universal time, your location Lat/Lon out to 3 decimal places (the app automatically knows your location), Hs (you set up the parameters on the second page (Settings), and Azimuth. There is a pause button near the center of the screen.
As there are only two screens (pages) to this app it is extremely easy to use and set up.
Not withstanding the original purpose of the app that Jason mentioned, the ability to practice CelNav on many different levels is unbelievable. I won’t go into any of the details because once you try the app it will instantly become self-explanatory, but below is a list of how it can be used:
1. After setting up for a particular body (lets go simple here and use the Sun), and setting up your site notebook for taking sites, you simply hit the pause button, record the time (UT), the Hs and the Azimuth. Hit the pause button again to resume active data. After doing this three to five times you now have all the info you need to work the sites and plot the LOP. This is great for learning how to use or reacquaint yourself with the NA and any given Table set as it takes out any personal sextant errors you may have and gives you good input data to start your worksheets. Since you don’t actually use a sextant, or horizon of any kind, this work can be done at your table/desk, at your convenience (and those of the celestial bodies) without ever going outside, and so can be done as the mood strikes even if there is a blinding snowstorm going on outside.. With this tool you can do single body LOPs, meridian passages, two-body fixes, three-body fixes, etc, all to be practiced while never leaving your desk. This practice data can of course be used to plot your LOPs if you need practice with that as well.
2. OK, so now you’ve mastered the NA/Tables of your choice, and now you need/want to practice with your sextant. So after checking your sextant for errors, you simply go outside with your sextant and your smart phone. and set up the app for your horizon (Sea, Bubble, Art. Hor, True or geocentric), with all corrections done for each in the app. Every time you “mark” a sight, you hit the pause button on the app and compare your sextant reading with the Hs on the app. You continue this process until you now have worked out the bugs in your technique, and then you’re done. Since you are just practicing your sextant technique, there is no need to record you times, take notes, or work the sites.
3. For actually taking sights, including multiple body fixes you can now move onto the full site-taking process with confidence in your abilities. If you want you may still get the UL time from the app easily by using the pause button and maybe sneaking a peak at the app’s HS.
This app is very cool, and so simple to use. There are other uses for this app, but what I discuss above may keep you busy for quite a while.
Peter