Progress Report on ongoing Astro work.
Location: NGS Station aa8189, back sight to NGS Station aa8188.
Late afternoon/evening...Sun, Jupiter, Arcturus, Polaris
Results analyzed by my esteemed Astro Mentor, Larry Scott.
Inverse 175-25-56.8 (from INVERSE3D).
Each observation set consisted of 8D/8R, and averaged D/R on the back sight before and after each set.
Sun 175-25-58.9 (previously done on 24-Apr) best
Polaris 175-26-01.6 good
Arcturus 175-25-59.7 same as best
Sun (175-26-05.4) questionable
Jupiter....Observed but not reduced
Average: 175-26-00 (ignoring 31-May sun)
Difference from inverse 3.2" (Interestingly, ALL measurements were on one side of inverse. Hmmm.)
Didn't realize until it was too late that during the Sun set, it passed through a fat telephone cable 30' away (causing refraction). Pulling a few more observations affected by that brought that one down to 175-26-04.4. Scintillation (irradiance) was also a factor on the back sight on that one.
Superior spreadsheet: Excellent
Orthometric measurements converted to Geo, time: Excellent
Environment: Good to Excellent
Acuity: Good for stars/sun; Fair to back sight
Equipment: Adequate to Good
Procedure and methodical discipline: Fair
Leveling: Sucks to Fair
You'd think that after reading all the threads on FIRMLY planting tripod legs into the dirt; making sure that all equipment comes up to even temperature before observation etc., that I'd have that part down. Definitely need to work on that.
Overall (self designated) grade: B-, but I did increase my rank to Senior Grasshopper:stakeout:
Glad to see you got promoted.
And if you look at the network uncertainty of the NGS points I think your azimuths may be superior.
Cool following along. Thanks.
I looked at Bob's observations, and some advice on observation and reduction.
This isn't a whole lot of data, but the repeatability looks good.
The question is "how close to geodetic is his onsite azimuth observations?"
All astronomic to geodetic conversions applied,
UT1 time source internet NTP (feedback loop, network time protocol)
To repeat Bob's summary:
the off-site control points. (Laplace -2.8")
inverse between published NGS pts
175-25-56.8 pub
Very clean data,
175-25-58.9 (2.1" to inv) sun
175-25-59.7 (3.1" to inv) Arcturus
These had some apparent issues reported in the notes, and noted before reduction:
175-26-01.6 (4.8" to inv) Polaris
175-26-04.4 (7.6" to inv) sun
________________________________________________________
On site, repeat azimuth observations. No GPS inverse comparison. (Laplace 4"):
327-58-33.7 sun
327-58-32.6 sun
327-58-32.3 sun
327-58-32.3 Arcturus
327-58-32.7 average
Additional observations, very good looking data, however, 5" different. :
327-58-37.7 sun morning
327-58-37.3 sun afternoon
Too soon know which is more accurate No apparent reason for the 5" difference
Sweet Avatar.
Also...thanks for the entertaining and educational threads.
Excellent work.
You're definitely a bona fide "Celestial Azimuth Determinatior"
JBrinkworth, post: 375286, member: 6179 wrote: Sweet Avatar.
Also...thanks for the entertaining and educational threads.
ditto
Note on plat:
BEARINGS BASED ON GRASSHOPPER OBSERVATIONS
Keep up the good work,
DDSM:beer:
Basis of bearings: by stellar observation.
Larry Scott, post: 375325, member: 8766 wrote: Basis of bearings: by stellar observation.
Ya, I like that one better.:-D
Larry Scott, post: 375271, member: 8766 wrote: I looked at Bob's observations, and some advice on observation and reduction.
This isn't a whole lot of data, but the repeatability looks good.
The question is "how close to geodetic is his onsite azimuth observations?"All astronomic to geodetic conversions applied,
UT1 time source internet NTP (feedback loop, network time protocol)To repeat Bob's summary:
the off-site control points. (Laplace -2.8")
inverse between published NGS pts
175-25-56.8 pubVery clean data,
175-25-58.9 (2.1" to inv) sun
175-25-59.7 (3.1" to inv) ArcturusThese had some apparent issues reported in the notes, and noted before reduction:
175-26-01.6 (4.8" to inv) Polaris
175-26-04.4 (7.6" to inv) sun
________________________________________________________On site, repeat azimuth observations. No GPS inverse comparison. (Laplace 4"):
327-58-33.7 sun
327-58-32.6 sun
327-58-32.3 sun
327-58-32.3 Arcturus
327-58-32.7 averageAdditional observations, very good looking data, however, 5" different. :
327-58-37.7 sun morning
327-58-37.3 sun afternoon
Too soon know which is more accurate No apparent reason for the 5" difference
And to round it out, Bob's observation to Jupiter has been reduced:
175-25-54.6 (2.2" to inverse.)
So, Astro to Geo seems to be a lot better 7-10".
Larry Scott, post: 375566, member: 8766 wrote: And to round it out, Bob's observation to Jupiter has been reduced:
175-25-54.6 (2.2" to inverse.)
So, Astro to Geo seems to be a lot better 7-10".
Advantage of Jupiter is that, like the sun, it's pretty easy to do during daylight hours. Not sure though it'd be reliable throughout the year, as it might become gibbous then "new". I centered both limbs between the two wires; not sure I could do that if it "wasn't all there".
Too bad they don't make total stations with zoom lenses; wide angle for stake out; telephoto for astro.:-D
However, I think it's reasonable to assume that Saturn would return as good a result as did Jupiter. And between the two, you have options. So, using the outer planets, is as viable as solar. Textbooks have always held that position, but this is a practical, classroom demonstration. And again, we're not talking 10-15" to Geo or GPS. But more like less than 5", which is acceptable in almost all situations.
By demonstration, solar, stellar, planetary azimuth observation, in this location and using this total station, using NTP time source, has returned azimuths consistent with Geo, better than expected. Astro az has been much maligned as 'approximate'. However, attention detail and repeat observation, concurs with textbook expectation.
(And all azimuth observation data were reduced by a one-off excel spreadsheet using hour angle formulae from textbook.)
