+- Forums (https://thenauticalalmanac.com/Forum)
+-- Forum: Main Forum Area (https://thenauticalalmanac.com/Forum/forumdisplay.php?fid=1)
+--- Forum: The Sight Reduction process (https://thenauticalalmanac.com/Forum/forumdisplay.php?fid=8)
+--- Thread: Why Polaris isn't listed? (/showthread.php?tid=107)
Why Polaris isn't listed? - Rumata - 04-20-2017
Greetings,
I tried to to use intercept method in solving some problems from a book and found out that despite the fact that Polaris is one of the most easily recognizable stars in the Northern Hemisphere Nautical Almanach of 2005 and earlier versions did not have SHA for it. Now, 2017 they do. So, my question is, why Polaris wasn't included in the list of observable stars in Pub.249 and NAutical Almanacs and is it any way to guess it SHA without jeopardasing the accuracy of plotting too much?
I wanted to place the question as the new one but am not not sure how to do it. So I just place it in Sight Reduction forum.
RE: Why Polaris isn't listed? - c_davidson - 04-20-2017
Rumata,
I can't exactly answer your question. However, while Polaris is easily found in the sky, Pub. 249 Vol 1 includes the Polaris tables 6 & 7 on page 353 (the last page of tha volume).
The Air Almanac also includes the Polaris tables and can be found here-
Polaris- Correction for (Q) (2017)
I think that version is included on the TheNauticalAlmanac.com since it's the most up to date version though the one found in Pub. 249 Vol. 1 will not yield a significantly different result.
Polaris is typically used just to determine latitude. Using the Polaris Tables 6 & 7 only require LHA ♈ (Aries) and not the additional SHA of Polaris to solve for latitude. Thus, you can determine latitude quickly using Tables 6 & 7 than the lengthy process of using Polaris's SHA and drawing an LOP.
While Polaris is a useful, my guess it's not listed in the Pub. 249 Vol. 1 stars as it's not very bright. But there could be other considerations that I'm not familiar with.
The Nautical Almanacs found on TheNauticalAlmanac.com provide Polaris's SHA & DEC for each year on the daily pages.
You can get the procedure to determine latitude using Polaris here- Determine Latitude using Polaris
Polaris also has the Latin name of a Ursae Minoris
You can also get the principle navigational stars SHA & DEC from the Air Almanac here-
SHA & DEC of stars
Clen
RE: Why Polaris isn't listed? - Rumata - 04-20-2017
(04-20-2017, 12:32 PM)c_davidson Wrote: Rumata,
I can't exactly answer your question. However, while Polaris is easily found in the sky, Pub. 249 Vol 1 includes the Polaris tables 6 & 7 on page 353 (the last page of tha volume).
The Air Almanac also includes the Polaris tables and can be found here-
Polaris- Correction for (Q) (2017)
I think that version is included on the TheNauticalAlmanac.com since it's the most up to date version though the one found in Pub. 249 Vol. 1 will not yield a significantly different result.
Polaris is typically used just to determine latitude. Using the Polaris Tables 6 & 7 only require LHA ♈ (Aries) and not the additional SHA of Polaris to solve for latitude. Thus, you can determine latitude quickly using Tables 6 & 7 than the lengthy process of using Polaris's SHA and drawing an LOP.
While Polaris is a useful, my guess it's not listed in the Pub. 249 Vol. 1 stars as it's not very bright. But there could be other considerations that I'm not familiar with.
The Nautical Almanacs found on TheNauticalAlmanac.com provide Polaris's SHA & DEC for each year on the daily pages.
You can get the procedure to determine latitude using Polaris here- Determine Latitude using Polaris
Polaris also has the Latin name of a Ursae Minoris
You can also get the principle navigational stars SHA & DEC from the Air Almanac here-
SHA & DEC of stars
Clen
Thank you, Clen. I know about the tables which are used to determine the latitude by Polaris. And yes, I think you're right, Polaris isn't the brightest one in the sky. As I've mentioned, I worked on some intercept problems and the input included Polaris among other stars. Then, by accident I found out that even in Nautical Almanac 2005 for instance, which doesn't list Polaris SHA per se, on page 272 it does includes it as alpha Urse Minor ( surprise ;>) and gives it SHA and declination. But you really need to search for it to find it out. Not in the middle of nowhere, for sure.
Anyway, thank you again for the response.
RE: Why Polaris isn't listed? - EdCa - 04-20-2017
Rumata,
Welcome aboard!
It's a further curiosity to notice on the USNO's Navigational Star Chart that Polaris, while it's listed with a general SHA of about 328° that there isn't a number next to it which indicates, I assume, that it's not included as one of the 57 navigational stars.
Get the Navigational Star Chart here- Navigational Star Chart
Anyone have other ideas about this?
Ed
RE: Why Polaris isn't listed? - Rumata - 04-20-2017
Thank you. It is n't listed as one of the 57 navigational stars. Another strange thing is that it isn't the dimmest star from 57. And its almost nailed position should kind of suggest it as a default star for intercept method. I hope it has nothing to do with any superstitions or alike. I worked on several problems concerning intercept and Polaris was listed among suggested stars for LOPS quite often. Majority of problems ( book) are around 1993 and there was no way to find Polaris SHA and declination.
Another thing is that azimuth angle for Polaris usually within .1 of degree from True North. Which make LOP just a perpendicular to Lat. line ( using universal plotting sheet).
Anyway, I'm just curious was Polaris used for intercept method in real conditions years ago? If yes, how?
Rumata,
Welcome aboard!
It's a further curiosity to notice on the USNO's Navigational Star Chart that Polaris, while it's listed with a general SHA of about 328° that there isn't a number next to it which indicates, I assume, that it's not included as one of the 57 navigational stars.
Get the Navigational Star Chart here- Navigational Star Chart
Anyone have other ideas about this?
Ed
[/quote]
RE: Why Polaris isn't listed? - CelNav57 - 04-21-2017
Rumata,
I made a 1993 Nautical Almanac for you.
Get it here- 1993 Nautical Almanac
Please let me know if that works alright for you.
CelNav57
Johannes H.
RE: Why Polaris isn't listed? - Rumata - 04-21-2017
(04-21-2017, 01:03 PM)CelNav57 Wrote: Rumata,
I made a 1993 Nautical Almanac for you.
Get it here- 1993 Nautical Almanac
Please let me know if that works alright for you.
CelNav57
Johannes H.
CelNav57, thank you very much. This is great. it even has Polaris in daily pages. I'wondering why in the excellent book "100 problems in Celestial Navigation" by Gray, the excerpts from daily pages don't have Polaris. But it is of no importance for now. Thanks again
RE: Why Polaris isn't listed? - CelNav57 - 04-22-2017
Rumata,
I'm glad it worked out alright for you. Let me know if you ever need a Nautical Almanac for a specific year not already found on TheNauticalAlmanac.com and I'll make it for you in the format you wish- compact or regular.
CelNav57
Johannes H.
RE: Why Polaris isn't listed? - Rumata - 04-22-2017
(04-22-2017, 12:14 AM)CelNav57 Wrote: Rumata,
I'm glad it worked out alright for you. Let me know if you ever need a Nautical Almanac for a specific year not already found on TheNauticalAlmanac.com and I'll make it for you in the format you wish- compact or regular.
CelNav57
Johannes H.
Thank you, CelNav57. So far all the problems related to 1993. But I know whom I need to contact if I need some bizarre year's data. And I use Pub.229 for intercept solutions. I found out that working with LHA of a specific star/planet but not on LHA Aries is fine. For declination correction I go to the Table 5 in the end of NA "Correctionb to TAbulated Altitude for minutes of declination." I used Pub.249 for a while but found for some reasons 229 more convenient. Personal preference, of course.
RE: Why Polaris isn't listed? - Rdutton - 04-22-2017
Rumata-
Working with paper is more enjoyable than electronics but lugging around Pub. 229 wouldn't be so bad if I considered that, no, I'm probably not going to sail around the world so all volumes aren't needed. Only, at my latitudes of sailing, Vol 3 is necessary.
What has kept me from using 229 for stars with declinations over 29° is using the Hc and the Z formula and a calculator. Hc can be calculated using the simple Casio fx-300ES (about $10) in about 8 seconds. Z takes around 10 seconds. Whenever using those formulas and calculator a thought passes through my mind when looking at the device that, "one of these days when you're most needed you wont work".
You can find the formulas here-
https://thenauticalalmanac.com/Formulas.html
Roland
RE: Why Polaris isn't listed? - Rumata - 04-22-2017
(04-22-2017, 10:55 AM)Rdutton Wrote: Rumata-
Working with paper is more enjoyable than electronics but lugging around Pub. 229 wouldn't be so bad if I considered that, no, I'm probably not going to sail around the world so all volumes aren't needed. Only, at my latitudes of sailing, Vol 3 is necessary.
What has kept me from using 229 for stars with declinations over 29° is using the Hc and the Z formula and a calculator. Hc can be calculated using the simple Casio fx-300ES (about $10) in about 8 seconds. Z takes around 10 seconds. Whenever using those formulas and calculator a thought passes through my mind when looking at the device that, "one of these days when you're most needed you wont work".
You can find the formulas here-
https://thenauticalalmanac.com/Formulas.html
Roland
Yes, Roland, I'm with you. For practical purposes-definitely YES. For years I liked to hike and climb mountains and deserts ( hike, of course ;>). More than once there was no GPS signal inside canyons where 70-100 feet walls for some reasons blocked the reception. No map-no go. Because the maze of dry washes looked amazingly like trails. I consider celestial navigation as the science developed and advanced over centuries. For instance, nobody, I'm sure, from practicing sailors would use Ageton method but it is very interesting to see how somebody despite all those baggage of knowledge available, still was able to develop a workable system.
Bottom line: agree with you.
RE: Why Polaris isn't listed? - Rumata - 05-01-2017
(04-21-2017, 01:03 PM)CelNav57 Wrote: Rumata,
I made a 1993 Nautical Almanac for you.
Get it here- 1993 Nautical Almanac
Please let me know if that works alright for you.
CelNav57
Johannes H.
CelNav57,
I tried to use Pub.249 for Hc for Polaris, LHA =227. It isn't listed. Yes, I can use NA-93 and find SHA but how can I use Pub.249? In 229 no questions, just LHA of the object and Decl. But Pub.249 just lists selected stars. Meaning I need to use 229 in this case. Am I missing something? Thanks.
RE: Why Polaris isn't listed? - Rumata - 05-02-2017
CelNav57,
I tried to use Pub.249 for Hc for Polaris, LHA =227. It isn't listed. Yes, I can use NA-93 and find SHA but how can I use Pub.249? In 229 no questions, just LHA of the object and Decl. But Pub.249 just lists selected stars. Meaning I need to use 229 in this case. Am I missing something? Thanks.
RE: Why Polaris isn't listed? - Rumata - 05-04-2017
(05-02-2017, 04:19 PM)Rumata Wrote: CelNav57,
I tried to use Pub.249 for Hc for Polaris, LHA =227. It isn't listed. Yes, I can use NA-93 and find SHA but how can I use Pub.249? In 229 no questions, just LHA of the object and Decl. But Pub.249 just lists selected stars. Meaning I need to use 229 in this case. Am I missing something? Thanks.
Greetings,
I found kind of answer to my question. I found the formula for Hc . Still don't understand why it isn't listed in Pub.249. But calc is not difficult. So be it.
RE: Why Polaris isn't listed? - CelNav57 - 05-05-2017
No, you're not making any mistakes.
Pub. No. 249 Vol 1. (7 varied navigational stars) provides stars that are brightest and best for producing an LOP with sharp angles between them. The magnitude (brightness) of Polaris is such, I suspect, that it's not a good choice. Pub. No. 249 Volumes 2 & 3, of course, do not cover declinations over 29° so Polaris can't be used.
If using a calculator Hc can be determined in about 10 seconds. Zn is a little more time consuming- maybe 30 seconds.
The formulas for Z have been updated in the 2017 Nautical Almanacs and here-
https://thenauticalalmanac.com/Formulas.html#Determine_Z
The "rules" to determine Zn had been omitted as I assumed, incorrectly, that most people knew the rules.