12-22-2020, 11:40 PM
pabrides,
Yes, have been doing more cn than usual.
The times since March haven't been good at all for most of us. A lot of unemployment and the destruction throughout the cities and the economy have been horrific. "Hoax" is the perfect word. And we put up with it! Awful.
But to answer your question....
I'm in a similar situation and have never exactly known why my LOPs are consistently off assuming I don't make an error in the initial observation getting Hs.
The following may be helpful;
1- If your AH has any kind of glass "tent" over it that could be causing refraction. That's the first thing that comes to my mind and what I often blame for these errors.
2- Your method of bring the Sun down is correct- the sun "in the sky" sits on the reflected Sun in the AH (LL- Lower Limb). If you had the them inverted you'd be off a huge amount and it would be obvious.
3- The Sun Altitude Correction table takes into consideration SD, parallax and refraction. Yes, it's true that CelNav's Altitude Correction table is dated 2003 but the figures in it for the planets Venus and Mars are the only ones that significantly change from year to year. The Altitude Corrections for the Sun and stars only vary in tenths of a minute of arc or at most 1 minute of arc from year to year.
4- Index Error. That might be what's causing the trouble. I'm sure you know the rule- "if it's on the arc- take it off" or "if it's off the arc- put it on". I use the Sun for determining Index Error. My III-B stays consistent with 2 minutes off the arc. Those two minutes will indeed amount to a good error that should be accounted for.
5- Side error. My sextant does have side error which I zero out once in a long while but it always sneaks back in.
6- Time- make sure your time is correct or you know what your chronometer error is.
7- When in doubt- suspect your GPS. There are a number of online services that provide maps that'll help you determine the longitude and latitude of your location.
8- Lastly, post some of your Hs figures and let's see if we can reduce them to an Ho that's in agreement with yours.
Merry Christmas,
Fred
Yes, have been doing more cn than usual.
The times since March haven't been good at all for most of us. A lot of unemployment and the destruction throughout the cities and the economy have been horrific. "Hoax" is the perfect word. And we put up with it! Awful.
But to answer your question....
I'm in a similar situation and have never exactly known why my LOPs are consistently off assuming I don't make an error in the initial observation getting Hs.
The following may be helpful;
1- If your AH has any kind of glass "tent" over it that could be causing refraction. That's the first thing that comes to my mind and what I often blame for these errors.
2- Your method of bring the Sun down is correct- the sun "in the sky" sits on the reflected Sun in the AH (LL- Lower Limb). If you had the them inverted you'd be off a huge amount and it would be obvious.
3- The Sun Altitude Correction table takes into consideration SD, parallax and refraction. Yes, it's true that CelNav's Altitude Correction table is dated 2003 but the figures in it for the planets Venus and Mars are the only ones that significantly change from year to year. The Altitude Corrections for the Sun and stars only vary in tenths of a minute of arc or at most 1 minute of arc from year to year.
4- Index Error. That might be what's causing the trouble. I'm sure you know the rule- "if it's on the arc- take it off" or "if it's off the arc- put it on". I use the Sun for determining Index Error. My III-B stays consistent with 2 minutes off the arc. Those two minutes will indeed amount to a good error that should be accounted for.
5- Side error. My sextant does have side error which I zero out once in a long while but it always sneaks back in.
6- Time- make sure your time is correct or you know what your chronometer error is.
7- When in doubt- suspect your GPS. There are a number of online services that provide maps that'll help you determine the longitude and latitude of your location.
8- Lastly, post some of your Hs figures and let's see if we can reduce them to an Ho that's in agreement with yours.
Merry Christmas,
Fred