NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Ho 208 question
From: Stan K
Date: 2014 Feb 24, 12:48 -0500
From: Stan K
Date: 2014 Feb 24, 12:48 -0500
Randall,
Thanks for reporting this. I only have a few pages of H.O. 208, so I am relying on people like you to help get V4.4.0 out of the beta phase. I'll put the update on the web site and send you a copy directly once I figure out what is going on. However, I need more information from you.
First of all, is it only H.O. 208 that gives a bad result? How about the Law of Cosines? It should give answers similar to the USNO site. Also, since 208 works from an assumed position, compare it to another method that works from an assumed position, like NASR.
Since H.O. 208 and all the other methods are sight reduction methods, i.e. in themselves they do not determine LHA, Dec, or Ho, I will need the specific information you entered for the reduction: GHA of Sirius, Dec of Sirius, Ho (after all corrections), DR L, and DR Lo.
A couple of additional items:
1) You say the time was PDT but the ZD was +8. I suspect you meant PST, especially since, sadly, we still have a couple of weeks before Daylight Savings Time starts.
2) Not that it matters for H.O. 208, but you say that the SHA of Sirius is 258º33.21'. I suspect "fat fingers", and it should be 258º33.1'. At least that is what the Nautical Almanac has.
Now I'm curious if I can work backwards to get the data I need. Assuming the time is PST and the ZD is +8, and there is no watch error, the UT would be 04-29-06 on 23 February. The GHA of Aries for 04 hours on 23 February is 212º58.5', what you have for the total GHA of Aries. You seem to have omitted the additional 7º17.7' for the 29m10s. I won't go any further, since the problem might be related to this.
You might want to try the Sight Reduction tool of Celestial Tools. It calculates the Nautical Almanac data, and does a reduction by the Law of Cosines. It might help you locate any other errors that might exist. Just be aware of its accuracy limitations as specified in the Help. Don't forget to enter the actual hs and select Artificial Horizon.
Stan
Thanks for reporting this. I only have a few pages of H.O. 208, so I am relying on people like you to help get V4.4.0 out of the beta phase. I'll put the update on the web site and send you a copy directly once I figure out what is going on. However, I need more information from you.
First of all, is it only H.O. 208 that gives a bad result? How about the Law of Cosines? It should give answers similar to the USNO site. Also, since 208 works from an assumed position, compare it to another method that works from an assumed position, like NASR.
Since H.O. 208 and all the other methods are sight reduction methods, i.e. in themselves they do not determine LHA, Dec, or Ho, I will need the specific information you entered for the reduction: GHA of Sirius, Dec of Sirius, Ho (after all corrections), DR L, and DR Lo.
A couple of additional items:
1) You say the time was PDT but the ZD was +8. I suspect you meant PST, especially since, sadly, we still have a couple of weeks before Daylight Savings Time starts.
2) Not that it matters for H.O. 208, but you say that the SHA of Sirius is 258º33.21'. I suspect "fat fingers", and it should be 258º33.1'. At least that is what the Nautical Almanac has.
Now I'm curious if I can work backwards to get the data I need. Assuming the time is PST and the ZD is +8, and there is no watch error, the UT would be 04-29-06 on 23 February. The GHA of Aries for 04 hours on 23 February is 212º58.5', what you have for the total GHA of Aries. You seem to have omitted the additional 7º17.7' for the 29m10s. I won't go any further, since the problem might be related to this.
You might want to try the Sight Reduction tool of Celestial Tools. It calculates the Nautical Almanac data, and does a reduction by the Law of Cosines. It might help you locate any other errors that might exist. Just be aware of its accuracy limitations as specified in the Help. Don't forget to enter the actual hs and select Artificial Horizon.
Stan
-----Original Message-----
From: Randall Morrow <randall.f.morrow@kp.org>
To: slk1000 <slk1000@aol.com>
Sent: Mon, Feb 24, 2014 11:12 am
Subject: [NavList] Ho 208 question
From: Randall Morrow <randall.f.morrow@kp.org>
To: slk1000 <slk1000@aol.com>
Sent: Mon, Feb 24, 2014 11:12 am
Subject: [NavList] Ho 208 question
The results have improved for my use of Ho 208 but an ususual case is giveing me trouble.
With a GHA of 478* 49.8 and assumed Lon of 118* 49.8 the LHA is 360 or zero.
My circa 1940 .pdf does not have a zero LHA column. If I use 360*60.0' the results are way off. Plugging my sight data into the Ho 208 calculator called "Celestial Tools" I got an intercept of over 1000 miles.
With a GHA of 478* 49.8 and assumed Lon of 118* 49.8 the LHA is 360 or zero.
My circa 1940 .pdf does not have a zero LHA column. If I use 360*60.0' the results are way off. Plugging my sight data into the Ho 208 calculator called "Celestial Tools" I got an intercept of over 1000 miles.
Sight data:
Sirius
Date 22 Feb
Time 20-29-06 PDT
ZD +8
Hs 37*57.5 (Already corrected for AH use)
SHA 258* 33.21
GHA Aries 212* 58.5
Ref. -1.3
IC -0.4
USNO reduction shows Hc 37*56.1 and intercept of 0.3
Sirius
Date 22 Feb
Time 20-29-06 PDT
ZD +8
Hs 37*57.5 (Already corrected for AH use)
SHA 258* 33.21
GHA Aries 212* 58.5
Ref. -1.3
IC -0.4
USNO reduction shows Hc 37*56.1 and intercept of 0.3
As a post script, does anyone have a .pdf version of Ho 208 that has the extra column headings at the top and bottom for 90-180, 180-270 etc.?
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