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» Online Classroom   »   » Public Discussion of Cel Nav   » H.O. 249 Volume 1 practice

   
Author Topic: H.O. 249 Volume 1 practice
Lou


 - posted December 12, 2017 11:17 AM      Profile for Lou           Edit/Delete Post 
H.O. 249 Volume 1 practice.
I’m delighted with everything in the Celestial Navigation Course book, except H.O. 249 Volume 1 work. I’ve only found one work form, using Volume 1, example, and it uses 1978 data.
Is there a source for workform practice using current dates?
I do see a government source that provides current data, but I have all the current books and need practice, hopefully including corrected answers available.

From: San Diego
David Burch


 - posted December 12, 2017 11:47 AM      Profile for David Burch           Edit/Delete Post 
You bring up a good point here. We do not have a dedicated form for this, but have simply shown how to adapt our 249 v2,3 form for use with v1. that is in the book, page 187.

However, we could make a custom one for that, and will look into it.

As for latest ver of 249 v1, you can get that at http://www.starpath.com/celnavbook. you can download our forms there as well.

You can also get star data for practice sights at http://www.starpath.com/usno for any time and date, even into the future.

We have frankly not focused much on v1 because—though simpler than v2,3 or 229 or NAO—it does require a special procedure.. and relying on it rules out using best star-planet combo, which is often the best choice.

In the long run, a practical approach these days is to learn the basics from our book, then do some practice with the NAO SR tables, which covers all bodies, all conditions (and is free in every copy of the almanac), and once that is mastered you have all books needed in the Nautical Almanac, which in turn can go into a double zip lock bag and you work the sight reductions with a computer or cell phone app until you for some reason need to get back into the bag. There are tons of free apps for computers and phones that do cel nav.

With that said, I will try to make a new form and generate some current examples for 249v1. There is virtue to it and we have quite a few students who prefer not to touch electronics at all for celestial navigation.

thanks for bringing this up. Hope to be back shortly with some aids for you.

From: Starpath, Seattle, WA
Lou


 - posted December 12, 2017 01:48 PM      Profile for Lou           Edit/Delete Post 
David,
Thanks!
Form 104 works okay, though a dedicated form would be terrific.
I do have all required manuals in paper form and download specifics to mark on, so Hc's ad Z's are readily available, but my location in the Winter Wasatch Mountains, using a (sort of) leveled 12x12 mirror make accurate star shots laborious and cold!
Any help with generating practice problems is greatly appreciated!

From: San Diego
David Burch


 - posted December 12, 2017 05:58 PM      Profile for David Burch           Edit/Delete Post 
We have the new form done and some examples, and way to practice. Hope to write this up tonight.

We appreciate the motivation. We have put this off too long.

From: Starpath, Seattle, WA
Lou


 - posted December 13, 2017 08:27 PM      Profile for Lou           Edit/Delete Post 
Can't wait.
Danke!!

From: San Diego
David Burch


 - posted December 13, 2017 09:23 PM      Profile for David Burch           Edit/Delete Post 
Hi Lou,

Well... you have motivated some work here but this is done now. Thanks for your suggestion.

See a discussion of the process, plus 3 examples, and an outline of how you make an infinite number of your own practice for any time, and into the future.

We are in the process of adding this new Form 111 for Pub 249 Vol 1 to our set of forms, but in the meantime you can download it here. Form_111_Pub_49_Vol_1.pdf

From: Starpath, Seattle, WA
Lou


 - posted December 14, 2017 03:51 PM      Profile for Lou           Edit/Delete Post 
Printed Form 111.
Set up floating mirror and will try some reflected shots tonight, (if it's not too cold).
I will also try the NSO tables for comparison.
Should be FUN!
Thanks, again!!

From: San Diego
Lou


 - posted December 15, 2017 03:59 PM      Profile for Lou           Edit/Delete Post 
New Form 111 is a delight! Quick and simple.
For H.O. 249 v1 Sel. stars, it's an absolute delight!
Thanks!
Floating 12x12 mirror works well, so able to shoot into the night.
Pre comps and reductions a breeze!
I Still have a question about "d" corrections, however.
When not using 249 v1, (i.e. v2, v3), "d" corrections are performed in Box 5, but not Box2.
After reading several times, including NA and 249, I don't understand why, or what the difference is.
Can anyone enlighten me?
Thanks!

From: San Diego
David Burch


 - posted December 15, 2017 07:17 PM      Profile for David Burch           Edit/Delete Post 
There is no d-correction to anything using Vol 1. we do not use star declinations, we are using star names. We are not looking up Hc and correcting it, V1 is giving the final answer. no d-cor, no where. it is a simpler solution.
From: Starpath, Seattle, WA
Lou


 - posted December 15, 2017 09:19 PM      Profile for Lou           Edit/Delete Post 
David, thanks!
I obviously didn't state my question clearly.
When using 249 v1, yes, all "d" values are accounted for.
I was asking what the "d" values correct when using Vols 2&3..
After rereading the Introduction and Entering Arguments in Vol. 2, I've answered my own question: "d" is the "difference" between tabulated and the next higher (or lower?) altitude as corrected by Table 5.
Apologies for the confusion.

From: San Diego
David Burch


 - posted December 15, 2017 09:25 PM      Profile for David Burch           Edit/Delete Post 
No problem. We have unfortunately two "d-values" in cel nav. On in the Almanac which is how much the declination changes in one hour, and one in sight reduction tables which is how much Hc changes when the declination changes 1º. Pub 249 and Pub 229 each handle this latter d cor differently.
From: Starpath, Seattle, WA
Lou


 - posted December 15, 2017 09:34 PM      Profile for Lou           Edit/Delete Post 
For some of us, the learning curve stays pretty vertical!
Enjoying the climb!

From: San Diego


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