NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Eye problems and IE, IC
From: Bill B
Date: 2006 Jul 14, 03:32 -0500
> Bill,
> Thanks for posting the numbers.
>
>> 13 July, 2006
>> 15:06 to 15:40 EDT (breaks for cloud cover)
>> Hc 66d to 61d
>>
>> Vertical Vertical Horizontal
>> Upright Inverted
>>
>> 32.0 31.8 31.7 HU
>> 31.8 32.0 31.8 HD
>> 32.0 31.9 31.3 HU
>> 32.0 31.9 31.6 HD
>> 31.9 32.0 31.4 HU
>> 32.1 32.0 31.4 HD
>> 32.0 32.1 31.7 HU
>> 31.9 32.0 31.8 HD
>
> You do not say whether these are on or off the
> arc and which eye was used, but I suppose this
> table contains the data for one eye and either are
> all off or all on.
Alex
You are correct. A sin of omission. All are on the arc. I take meeting the
4SD test as a given at this point (like a 1" putt in golf) and with 17 holes
ahead of me did not do off the arc. If the on-the-arc figures were
significantly different than typical on-the-arc figures for the body
elevation, I would have explored. If the inverted figures were off the
upright figures, I would have certainly explored. Perhaps not very sound
scientifically, but lacking any evidence of a problem and a long road ahead
I moved on. (Candidly, at that point it was hot, and I was imaging that I
should gather temperature and humidity figures so I could state that instead
of "hot" should I be called on it. Or at least put on a light-colored shirt.
<G>)
>
> The first and second columns look perfect to me.
> (To confirm this, I would need both off and on readings
> so that theiur sum san be compared with 4SD from the almanac).
> The horizontal observations look somewhat biased,
> and I experienced this with my SNO too.
> It is possible that sextant rigidity in this transverse
> direction is less than in the normal, vertical direction.
> (Which is not surprising with the usual sextant construction).
> That HU observations deviate most also has an easy explanation:
> this is so-called "inconvenient position", and it is well
> documented that observations with such sextant position
> are substantially less precise.
First and second columns are too perfect. So perfect I reviewed them
several times. I don't trust perfect. I have not checked, but I have a
sense that if I take the figures from the first and second columns and rank
them from lowest to highest, they will exactly match line for line. Which
if I wasn't there and tape recording the readings with no idea of the
outcome, would have me screaming, "Fudge."
Some other excellent thoughts. As you may recall when I first purchased the
Astra, I had real discrepancies between vertical IE and horizontal IE
observations (horizontal recommended so refraction does not come into play.)
At that point my skill sets were so relatively poor, and I was switching
eye-to-eye while running around with my new toy, it was hard to make a case
for anything.
The posting after the one you noticed has figures that explore the vertical
and horizontal relationships between my eyes and perhaps relates them to eye
defects. My contention is that if gravity is the driving force behind the
vertical/horizontal deviation, it will also have the same trend if I switch
eyes. Surprise (or not), the trend is exactly the opposite as I perceive it
now and matches the astigmatism of my eyes.
As for inconvenient positions, I thank you for teaching me that early on
(when I could not get myself into position to do a short star-to-star on
your balcony). My first posted results between vertical and horizontal
shots (a few days ago) were very good from a tight-scatter stand point.
Vertical or horizontal, handle up or down, did not seem to matter much. All
groups 0.1' STDV or under. Today I was (relatively) all over the map on
horizontals. I have not taken a hard look at the data for up vs down in
later tests, but at first blush up or down did not appear to matter much, I
was either in the groove for the 10 or 15 minute segment or I was not.
That in itself boggles my mind. In right-eye observations I was really
struggling (reviewing the results with horizontal on-the-arc separations
handle up and handle down). My worst, if I recall, STDV of the day, 0.26'.
Doing five off-the-the arc, flipping the sextant handle up and handle down.
29.0, 29.0, 29.0, 29.0, and at last 28.9. What changed? In the old days my
separations were always more consistent than my merges. Now it was too
perfect to believe. I stopped at five each, too weird.
I was very surprised at how well the right eye performed today. Maybe it
has felt neglected for the past year or so and needed some attention ;-)
This being human thing can be such problem at times.
Bill
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To , send email to NavList-@fer3.com
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From: Bill B
Date: 2006 Jul 14, 03:32 -0500
> Bill,
> Thanks for posting the numbers.
>
>> 13 July, 2006
>> 15:06 to 15:40 EDT (breaks for cloud cover)
>> Hc 66d to 61d
>>
>> Vertical Vertical Horizontal
>> Upright Inverted
>>
>> 32.0 31.8 31.7 HU
>> 31.8 32.0 31.8 HD
>> 32.0 31.9 31.3 HU
>> 32.0 31.9 31.6 HD
>> 31.9 32.0 31.4 HU
>> 32.1 32.0 31.4 HD
>> 32.0 32.1 31.7 HU
>> 31.9 32.0 31.8 HD
>
> You do not say whether these are on or off the
> arc and which eye was used, but I suppose this
> table contains the data for one eye and either are
> all off or all on.
Alex
You are correct. A sin of omission. All are on the arc. I take meeting the
4SD test as a given at this point (like a 1" putt in golf) and with 17 holes
ahead of me did not do off the arc. If the on-the-arc figures were
significantly different than typical on-the-arc figures for the body
elevation, I would have explored. If the inverted figures were off the
upright figures, I would have certainly explored. Perhaps not very sound
scientifically, but lacking any evidence of a problem and a long road ahead
I moved on. (Candidly, at that point it was hot, and I was imaging that I
should gather temperature and humidity figures so I could state that instead
of "hot" should I be called on it. Or at least put on a light-colored shirt.
<G>)
>
> The first and second columns look perfect to me.
> (To confirm this, I would need both off and on readings
> so that theiur sum san be compared with 4SD from the almanac).
> The horizontal observations look somewhat biased,
> and I experienced this with my SNO too.
> It is possible that sextant rigidity in this transverse
> direction is less than in the normal, vertical direction.
> (Which is not surprising with the usual sextant construction).
> That HU observations deviate most also has an easy explanation:
> this is so-called "inconvenient position", and it is well
> documented that observations with such sextant position
> are substantially less precise.
First and second columns are too perfect. So perfect I reviewed them
several times. I don't trust perfect. I have not checked, but I have a
sense that if I take the figures from the first and second columns and rank
them from lowest to highest, they will exactly match line for line. Which
if I wasn't there and tape recording the readings with no idea of the
outcome, would have me screaming, "Fudge."
Some other excellent thoughts. As you may recall when I first purchased the
Astra, I had real discrepancies between vertical IE and horizontal IE
observations (horizontal recommended so refraction does not come into play.)
At that point my skill sets were so relatively poor, and I was switching
eye-to-eye while running around with my new toy, it was hard to make a case
for anything.
The posting after the one you noticed has figures that explore the vertical
and horizontal relationships between my eyes and perhaps relates them to eye
defects. My contention is that if gravity is the driving force behind the
vertical/horizontal deviation, it will also have the same trend if I switch
eyes. Surprise (or not), the trend is exactly the opposite as I perceive it
now and matches the astigmatism of my eyes.
As for inconvenient positions, I thank you for teaching me that early on
(when I could not get myself into position to do a short star-to-star on
your balcony). My first posted results between vertical and horizontal
shots (a few days ago) were very good from a tight-scatter stand point.
Vertical or horizontal, handle up or down, did not seem to matter much. All
groups 0.1' STDV or under. Today I was (relatively) all over the map on
horizontals. I have not taken a hard look at the data for up vs down in
later tests, but at first blush up or down did not appear to matter much, I
was either in the groove for the 10 or 15 minute segment or I was not.
That in itself boggles my mind. In right-eye observations I was really
struggling (reviewing the results with horizontal on-the-arc separations
handle up and handle down). My worst, if I recall, STDV of the day, 0.26'.
Doing five off-the-the arc, flipping the sextant handle up and handle down.
29.0, 29.0, 29.0, 29.0, and at last 28.9. What changed? In the old days my
separations were always more consistent than my merges. Now it was too
perfect to believe. I stopped at five each, too weird.
I was very surprised at how well the right eye performed today. Maybe it
has felt neglected for the past year or so and needed some attention ;-)
This being human thing can be such problem at times.
Bill
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
