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Astron Excel sight reduction manual almanac
#1
Gentlemen, 

I just tried to use Sight reduction Astron spreadsheet / manual option and can't locate Altitude correction for Sextant sight.  Also, Index error shows only minus option. But if it is (-) should I add it instead of subtracting it from Hs? . When I entered the Height of eyes in meters the spreadsheet calc simply subtracted this number from Hs, not the data I saw in Nautical Almanac ( hard copy).  Anyway, I got a little bit different results for azimuth and intercept.

My question is: should I blindly trust the spreadsheet or paper/pencil approach? Yes it is much faster.

Again, difference about  +/- 1.5 deg. in azimuth and tolerable in the intercept results. Thank you.
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#2
I just want to clarify my previous message. In the Nautical Almanac there is a TAble of Altitude correction. Based on Apparent altitude you get correction for Sun sight, Stars, and Planets.. It is written over there Apparent Altitude=Sextant altitude corrected for index error and dip. Now, using the spreadsheet, I got corrections for dip. Also I have index correction. But in the case of the Sun I also need to have Apparent altitufde correction for low /upper limb. And that's what I can't locate in the spreadsheet. Am I missing it?
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#3
Rumata,

You'll find the Lower, Upper, Center limb area of the reduction around column I and row 27. Enter in column cell I31 (eye 31) L for Lower, U for Upper or C for center.

I assume refraction is calculated using the figures for temperature and barometric pressure in cells G31 and H31.

Does that help?

Ed
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#4
Ed, thank you. I wasn't too attentive and missed that cell. I'll put in real numbers and check it against my paper calcs. Also, I wrongly considered that index error was "sign-indifferent".  It wasn't.  As soon as I entered (-.6) as IC the spreadsheet correctly added it to the sextant's measured altitude. So, if I'll see that altitude correction number is considered in the final result-great.

Thank you again for straightening me into the right direction.

PS. Still find more fun doing all those jazz by the traditional methods, means tables, paper, and pencil.  It gives me some feeling that I'm a little bit in control. ;> ;>;>
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#5
(10-01-2017, 07:03 AM)Rumata Wrote: Gentlemen, 

I just tried to use Sight reduction Astron spreadsheet / manual option and can't locate Altitude correction for Sextant sight.  Also, Index error shows only minus option. But if it is (-) should I add it instead of subtracting it from Hs? . When I entered the Height of eyes in meters the spreadsheet calc simply subtracted this number from Hs, not the data I saw in Nautical Almanac ( hard copy).  Anyway, I got a little bit different results for azimuth and intercept.

My question is: should I blindly trust the spreadsheet or paper/pencil approach? Yes it is much faster.

Again, difference about  +/- 1.5 deg. in azimuth and tolerable in the intercept results. Thank you.

Rumata,

Astron does a good job and I've not found it inaccurate so far.  Compared to the USNO's site- [/url]

Celestial Navigation Data for Assumed Position and Time

...it's very good and equivalent.  However, electronics and computers, like anything that's complex will fail you when you need them the most.  That's why I tend to use paper only and not electronics.  But, Astron is useful and helpful for many purposes and good in helping to verify your paper based sight reductions.

Astron is good is when experimenting using hypothetical data from different latitude and longitudes so one can get a good idea of how to reduce a sight from a Contrary latitude and Eastern hemisphere.  Those of us in Northern latitudes and Western longitudes often think that there is no other part of the world except ours. Astron helped answer several problems I had when attempting a hypothetical sight reduction based on Eastern longitudes;

Remember- to obtain the LHA in Eastern longitudes- round up the GHA figure to the next higher degree

figure and add the whole degree DR. Longitude to it.

The italicized text is from- [url=https://www.thenauticalalmanac.com/Complete%20Sun%20Sight%20Reduction%20Procedure-%20Ocean%20horizon.pdf#page=6]Eastern Longitude LHA rules

There is no virtue or vice in using electronics for sight reduction.  We're looking to get the correct answers.  While "on the hard" it's often easiest to use the method you're most comfortable with and when using Astron you can reduce a lot of sights quickly.  But....paper is much more enjoyable.


Clen
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#6
(10-02-2017, 10:36 PM)c_davidson Wrote:
(10-01-2017, 07:03 AM)Rumata Wrote: Gentlemen, 

I just tried to use Sight reduction Astron spreadsheet / manual option and can't locate Altitude correction for Sextant sight.  Also, Index error shows only minus option. But if it is (-) should I add it instead of subtracting it from Hs? . When I entered the Height of eyes in meters the spreadsheet calc simply subtracted this number from Hs, not the data I saw in Nautical Almanac ( hard copy).  Anyway, I got a little bit different results for azimuth and intercept.

My question is: should I blindly trust the spreadsheet or paper/pencil approach? Yes it is much faster.

Again, difference about  +/- 1.5 deg. in azimuth and tolerable in the intercept results. Thank you.

Rumata,

Astron does a good job and I've not found it inaccurate so far.  Compared to the USNO's site- [/url]

Celestial Navigation Data for Assumed Position and Time

...it's very good and equivalent.  However, electronics and computers, like anything that's complex will fail you when you need them the most.  That's why I tend to use paper only and not electronics.  But, Astron is useful and helpful for many purposes and good in helping to verify your paper based sight reductions.

Astron is good is when experimenting using hypothetical data from different latitude and longitudes so one can get a good idea of how to reduce a sight from a Contrary latitude and Eastern hemisphere.  Those of us in Northern latitudes and Western longitudes often think that there is no other part of the world except ours. Astron helped answer several problems I had when attempting a hypothetical sight reduction based on Eastern longitudes;

Remember- to obtain the LHA in Eastern longitudes- round up the GHA figure to the next higher degree

figure and add the whole degree DR. Longitude to it.

The italicized text is from- [url=https://www.thenauticalalmanac.com/Complete%20Sun%20Sight%20Reduction%20Procedure-%20Ocean%20horizon.pdf#page=6]Eastern Longitude LHA rules

There is no virtue or vice in using electronics for sight reduction.  We're looking to get the correct answers.  While "on the hard" it's often easiest to use the method you're most comfortable with and when using Astron you can reduce a lot of sights quickly.  But....paper is much more enjoyable.


Clen

Thanks, Clen. Agree. As you 've mentioned, I also tried to use Astron for hypothetical calculations. Yes, East longitude, Southern Hemisphere, crossing Date Line back and forth and so on. And yes, it is a very good tool to check paper-written calcls for the sanity. I wasn't too attentive in input for manual almanac calc and therefore asked for the advice. Thank you, Clen, and to Ed for the fast response. I found it very satisfying when my humble result is very similar to the Astron's. It means some patches of the grey matter in my brain are still functioning. ;>
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#7
Rumata, you're right- that work is good for practice and keeping us sharp. It's surprising with the St. Hillaire method if there's an error in the reduction the intercept comes up as preposterous. That is, "how in the world did I come up with that one?! Something must be wrong."

Astron does speed up the process.

Good luck,

Ed
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