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JayBee
Well-Known Member
Re: Celestial Navigation - Pro Forma
Hi Brian
Here's a link to my old proforma for reducing two sights on one side of A4, using the cosine-versine formula to obtain a single position line by the Marc St. Hilaire method.
If you can find Burton's 5-figure or 4-figure Tables there is an explanation of the method in the Notes.
The 4-figure tables give slightly less accuracy than the 5-figure tables and also use versines instead of haversines - makes no practical difference to the method or to the result. The azimuth is calculated using ABC tables - also included in these publications, and very simple to use.
These tables might be hard to find.
Alternatively, you could also get hold of George Bennet's
Complete On Board Celestial Navigator, which uses what is basically a "cleaned up" version of the formula and also has a useful long term almanac.
Cheers and good luck!
Hi Brian
Here's a link to my old proforma for reducing two sights on one side of A4, using the cosine-versine formula to obtain a single position line by the Marc St. Hilaire method.
If you can find Burton's 5-figure or 4-figure Tables there is an explanation of the method in the Notes.
The 4-figure tables give slightly less accuracy than the 5-figure tables and also use versines instead of haversines - makes no practical difference to the method or to the result. The azimuth is calculated using ABC tables - also included in these publications, and very simple to use.
These tables might be hard to find.
Alternatively, you could also get hold of George Bennet's
Complete On Board Celestial Navigator, which uses what is basically a "cleaned up" version of the formula and also has a useful long term almanac.
Cheers and good luck!
Talbot
Well-Known Member
Re: Celestial Navigation - Pro Forma
The book you want is IIRC "Norries Tables". This includes Haversines, and Transverse tables and explanations on how to use them.
The book you want is IIRC "Norries Tables". This includes Haversines, and Transverse tables and explanations on how to use them.
calamitys38
Well-Known Member
Re: Celestial Navigation - Pro Forma
My proforma for Marc St Hilaire as follws:
GHA body
+ incr
= GHA Body
+/- DR Long (E + /W -)
= LHA Body
Dec Body
+/- DR Lat
= Diff between Lat and Dec
A - (Tan Lat / Tan LHA)-Named Opposite to Lat A if LHA is between 90 and 270)
B - (Tan Dec / Sin LHA)- Always named same as Dec
= C - (to find C, if A and B same names - Add. If is Different names - Difference
=> Az/Brg of Body (From table C or Tan Az = 1 / (C x Cos Lat)
Log Hav LHA
+ Log Cos Dec
+ Log Cos Lat
= Log Hav
=>Nat Hav
+ Nat Hav L diff D
= Nat Hav CZD
S Alt
+/- IE
= Obs Alt
- Dip
= App Alt
T Correction
= True Alt
- 90
= TZD
CZD
= Intercept (If TZD less than CZD - named towards or down rgthe Brg (True Tiny Towards))
Using Traverse tables (or Plane Sailing) calcutalte Lat and Long of the Intercept (or by far the easier method - plot the DR lat Lat Long on a chart and draw on the Bearing and Intercept and draw the Position line at 90 degrees to the Brg).
Another method is to do Longitude by Chronomter, hoewever, it becomes too insenitive to use if the LHA is within 30 degrees of the Meridian.
Methodology for doing Long by Chron however is as by finding LHA and TZD as above, then:
N Hav TZD
Nat Hav Lat diff Dec
= Nat Hav
=> L Hav
Log Secant Dec
Log Secant Lat
= Log Hav LHA
=> LHA
+/- GHA
= Long (E/W)
As you can see, having got the LHA, you can now work out the Longitude that the Position Line (the one that is at 90 degrees to the Brg previously calcultaed) cuts the DR Lat.
Very long winded (both methods) but good fun and with practice, shouldn't take longer than about 20 mins to work out three sights simultaneously so as an average Intercept can be used.
If any other postes see fault with above method, please don't criticise too heavily, I have had to drag out my notes from 1983 to answer this and I am sure the standard proforma has been updated since then. However, i found the above useful as it could be written in the marging of an A4 piece of paper and then the sight(s) could be kept to a single page.
If preferred, there is a s calculator method for Marc St Hilaire as follows:
Cos CZD = Cos Lat x Cos Dec x Cos LHA +/- Sin Lat x Sin Dec
(Lat and Dec Same names - Sum (add). Different names - subtract (difference).
Sin Azimuth = Sin LHA x (Cos Dec / Cos True Alt)
Anyway - hope above helps.
My proforma for Marc St Hilaire as follws:
GHA body
+ incr
= GHA Body
+/- DR Long (E + /W -)
= LHA Body
Dec Body
+/- DR Lat
= Diff between Lat and Dec
A - (Tan Lat / Tan LHA)-Named Opposite to Lat A if LHA is between 90 and 270)
B - (Tan Dec / Sin LHA)- Always named same as Dec
= C - (to find C, if A and B same names - Add. If is Different names - Difference
=> Az/Brg of Body (From table C or Tan Az = 1 / (C x Cos Lat)
Log Hav LHA
+ Log Cos Dec
+ Log Cos Lat
= Log Hav
=>Nat Hav
+ Nat Hav L diff D
= Nat Hav CZD
S Alt
+/- IE
= Obs Alt
- Dip
= App Alt
T Correction
= True Alt
- 90
= TZD
CZD
= Intercept (If TZD less than CZD - named towards or down rgthe Brg (True Tiny Towards))
Using Traverse tables (or Plane Sailing) calcutalte Lat and Long of the Intercept (or by far the easier method - plot the DR lat Lat Long on a chart and draw on the Bearing and Intercept and draw the Position line at 90 degrees to the Brg).
Another method is to do Longitude by Chronomter, hoewever, it becomes too insenitive to use if the LHA is within 30 degrees of the Meridian.
Methodology for doing Long by Chron however is as by finding LHA and TZD as above, then:
N Hav TZD
Nat Hav Lat diff Dec
= Nat Hav
=> L Hav
Log Secant Dec
Log Secant Lat
= Log Hav LHA
=> LHA
+/- GHA
= Long (E/W)
As you can see, having got the LHA, you can now work out the Longitude that the Position Line (the one that is at 90 degrees to the Brg previously calcultaed) cuts the DR Lat.
Very long winded (both methods) but good fun and with practice, shouldn't take longer than about 20 mins to work out three sights simultaneously so as an average Intercept can be used.
If any other postes see fault with above method, please don't criticise too heavily, I have had to drag out my notes from 1983 to answer this and I am sure the standard proforma has been updated since then. However, i found the above useful as it could be written in the marging of an A4 piece of paper and then the sight(s) could be kept to a single page.
If preferred, there is a s calculator method for Marc St Hilaire as follows:
Cos CZD = Cos Lat x Cos Dec x Cos LHA +/- Sin Lat x Sin Dec
(Lat and Dec Same names - Sum (add). Different names - subtract (difference).
Sin Azimuth = Sin LHA x (Cos Dec / Cos True Alt)
Anyway - hope above helps.
sticky
Well-Known Member
Re: Celestial Navigation - Pro Forma
If anyone would like copies of the step by step sight reduction forms I have, send me a pm and I will email them to you. I posted this message yesterday, but it disappeared!
Sticky
If anyone would like copies of the step by step sight reduction forms I have, send me a pm and I will email them to you. I posted this message yesterday, but it disappeared!
Sticky
co256
Well-Known Member
Re: Celestial Navigation - Pro Forma
I completed my Yachtmaster Ocean theory some years ago but have lost most of any knowledge I gained long before I had a chance to put it in to practice.
Does anyone offer a short "refresher" course in sextant use/sight reduction???
Without dragging myself, kicking and screaming, through the whole course again!
Many thanks.
I completed my Yachtmaster Ocean theory some years ago but have lost most of any knowledge I gained long before I had a chance to put it in to practice.
Does anyone offer a short "refresher" course in sextant use/sight reduction???
Without dragging myself, kicking and screaming, through the whole course again!
Many thanks.
sticky
Well-Known Member
Re: Celestial Navigation - Pro Forma
I may be able to help, if you would like to pm me your email address we can chat.
Sticky
I may be able to help, if you would like to pm me your email address we can chat.
Sticky
co256
Well-Known Member
Re: Celestial Navigation - Pro Forma
E-mailed through your website, thanks!
E-mailed through your website, thanks!
