Practice sights for a beginner.

[Simon]

Hi! I am real new to this and i don’t live on the coast so i can take regular sights. So it would be much appriciated if some of you could post some old sights that you have taken so i can calculate on.

[Joe Langone]

Have you tried an artificial horizon? I have not used one but they are not that expensive and you can use them anywhere.

[Jason]

Get the phone app “GPS anti-spoof” You set a few things about your setup, such as object, limb, horizon, dip, even index correction. It then tells you, in real time, the altitude of the body from your current GPS location. You can use a natural horizon, a bubble level, or an artificial horizon.

The app is designed to allow a person to detect anomalies in the GPS system, but is also a great tool for a quick practice.

[Ken Gebhart, Jr.]

@langedrag, I ran across this site the other day. It looks interesting. I haven’t really gone thru it yet. If you do, let us know what you think.
https://celestialnavproblems.wordpress.com/

[Philippe]

Hello,
To create exercises for celestial navigation, I use Stellarium, a wonderful freeware you can get freely here: Stellarium
With this program, you can choose the place you are on the earth, the date and time of your sight, and the celestial body you wish to use.. The software tell you the altitude of this body and the azimuth you would get at the end of your computations.
And more : this software give you a realistic image of the sky, and will help you to understand the movement of all the bodies.

[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

[Jason]

Peter:

Well put. I was planning on coming back and explaining exactly what you have here.

Everyone should check out GPS Anti-spoof

Jason

[true]

For my beginner exercises I got a practice bubble that replaces the telescope on the sextant. I ordered a 5 year old almanac (pretty cheap). If i’m correct, I think I read that the sights come close to repeating every 5 years (?). My first noon sight try got me within 15 miles and I was sloppy with the timing. Any suggestions on timing? I tried to use my phone stopwatch. but cumbersome, so I’m thinking a regular old stopwatch.

Has anyone had a problem with sunlight leaking through the bubble horizon from celestaire? I got a pinpoint flash of bright light that was disturbing, even with the sun shades in place. Maybe reflecting from the glass level on top of the sight?

Thanks for any input and corrections.

[Jason]

True:

1. You can get the current almanac online for free.

2. Get the free app mentioned above. “GPS Anti-spoof” It will eliminate the need for an almanac AND timing when taking practice sights.

Jason

[pmaclearn@verizon.net]

True:
I recommend that while you are learning you get a 2020 Almanac. The practical duration of an NA is one year as described in the “Explanation” section of the almanac (pg 261). You can use the 2020 almanac for 2021, with corrections, but it cannot then also be used for the Moon or planets. HO 249, Vol 1 is good for +/- 4 years on each side of the Epoch. Perhaps that is what you are thinking of. Purchase the “Commercial Nautical Almanac” (perhaps from Celestaire, for less than $30.00, which is less than half of what the Gov issue is).

In regards to the bubble sextant attachment from Celestaire. When you replace the sextant scope with the bubble sight attachment you will notice that the attachment more resembles a tube rather than a scope. The narrow, optical entry point for the attachment, being smaller than the scope’s optical entry point does not physically block the reflected light from the horizon mirror from your eye as does the scope. Also the other end of the attachment (the ‘eyepiece’) also does not have an eye shield as does the scope. If your eye is not fully on the scope( properly lined up with the eyepiece), it may be possible for you to see reflected sunlight directly from the horizon mirror as you move the sextant about. I have noticed this, but it has not been a problem as it occurs rarely. Light is supposed to leak into the bubble sight attachment to help illuminate the bubble and depending upon sextant position it will sometimes appear brighter than at other times. This is by design and is not a problem. Hope this helps.

The technique I often use with a watch, when timing my sights, is to start counting immediately after saying “Mark”. In other words, “Mark one-thousand-one, one-thousand-two…etc until I can look at my watch, stopwatch, time display, etc. This works quite well for me. When using my smart phone with an app I find it easiest to have the phone standing-by on a flat surface, within easy reach, with the app active, so that I am not holding the phone, and that I can get to it quickly.

In regards to electronic aids of any kind, as an aid to classical, traditional Celestial Navigation. Ultimately you must be very proficient in determining your position without any additional electronic assistance. Learning independently, and while learning, I would recommend getting the latest paper almanac and reduction tables to learn how to use them and to appreciate all that they offer. Study them as stand-alone separate tools. Non-electronic tools such as the Starfinder, star charts, etc, are invaluable as well. Use these tools as you primary sight package components to work your sights, and then, as required, augmenting the accuracy of your results by using a calculator, apps such as “GPS Anti Spoof”, etc to hone your skills to the point that you have the confidence to take quality sights and to then determine your position accurately. After this you can start playing with old Almanacs and tables to your hearts desire with the developed ability to decide for yourself whether the extra work is worth it to you.

By the way, there is always something to learn or to improve upon when doing CelNav….the sky is the limit (poor pun intended) Like the rest of us, you will always be a student. Good luck!

[Bill]

The almanacs repeat every 4th year for the sun and stars but not the moon or planets which have their own unique orbits. There is a bit of error over time but it takes many years for it to be a problem and for practice, old almanacs are fine.

[pmaclearn@verizon.net]

Bill:
What you say is correct, but it is not clear which almanac year “True” has. Why search for an old almanac when you can get a new one to learn from? ‘True’ is getting results that are marginal for a person standing onshore, on solid ground, and from a known position, in good weather. Is the issue with his sight taking? Is the issue with the corrections he applies? Is the issue with the tables themselves? Are there multiple errors such that a stack-up of errors make his sights look better or worse than he is actually getting? I submit that as a self-learner, and self-evaluator, this may be difficult for ‘True’ to decipher. The point is to reduce the uncertainties in the process/procedures, and the learning curve, as much as possible and to avoid undue confusion and discouragement.
When first learning I would advocate for acquiring the best tools that you can afford so that you take as many of the unknowns out of the process as possible. Also, while taking sights of the sun is a good starting point, the ability to move on to the moon, planets and stars when, and as you are able, should be as a straight forward and easy step. This can be done most easily with the current almanac (for a little over $25).
I’m trying to help ‘True’ out here. Obviously he, or anyone else can do what ever he/they please(s).

[true]

Thanks for all your help everyone!

[true]

A reexamination of the bubble horizon instructions suggested putting a piece of tape over the bubble to shade the sunlight leak. A piece of masking tape did the trick.

[David Williams]

I live not far from a Pacific Ocean beach, so I often go there to practice my celestial navigation using the Astra III pro sextant. But on occasion at home from my driveway, I use a Celestiare artificial horizon. Everyone must concede that it takes practice, lots of it, to achieve honorable results. At the beach, I record less than 2 nautical miles error. At home I usually record less than 5 nautical miles error, unless I have wine. The artificial horizon is not as rewarding as the true horizon.
I use the Celestaire # 0511 practice bubble horizon. To it I attached the slip-on rubber eyecup #0505 over a small piece of snuggly fit PVC pipe. I wear a long-billed hat to keep the above sources of light out. There are internal bubble reflections. Over the hole that illuminates the bubble, I attached a red LED, with a 48 ohm resister and a 5K pot to adjust LED brightness, all mounted on a well-shaped block of wood to prevent slippage of position. The block can be moved back and forth to enable adjusting of the bubble reflected brightness. To provide power to the LED, I tapped into the handle’s battery wire with a small connector. With this assembly, I can do late evening sextant practice. It may not be ideal, but it works! With a good wine, I reliably achieve my 5 nautical mile error. Careful calibration of the instrument error with the bubble horizon against the true ocean horizon ( with dip) is necessary.
I programmed my HP-35 calculator with the sight reduction formulas to make the practice of sight reduction more efficient. I use only the current Nautical Almanac because there are slight changes year to year, especially with the planets.
I formally urge all interested to practice celestial navigation just to preserve history. Teach others to do it. Use the GPS only to measure accuracy of the fix. I find doing the plot on a NOAA navigation chart quite revealing.

[Author]

Posts