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Solar / Polaris Ephemeris
Anyone know of a source for solar and polaris ephemerides? Last one at Cadastral.com was 2017 and I’m not finding others such as Lietz/Sokkia easily. Are they still publishing them? The USNO has some information but it appears to be a software item which may or may not be available.
Asking for a friend – really!
Tyler Parsons
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18 Replies
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Tyler,
Here is the link to Kurt Wurm’s web site that has the 2019 solar and Polaris ephemeris.
Solar and Polaris Ephemeris files
I also checked Jerry Wahl’s web site and he has a link to this online calculator.
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Thanks Gene. I didn’t see that on Jerry’s site.
I just sold one of my older total stations, prism pole and prisms to a retired chemistry professor friend who also has a small tree farm that he is using RTK GPS and a drone to determine the location of tree tops, along with miscellaneous other projects. While were discussing the total station, I just threw out “do you need a solar filter and elbow”? not thinking he would be interested., He thought about it and bought it the next day. Ok, I need to get him started and looked for ephemerides. Oops. Well, today he brought his Naval Observatory Ephemeris book (1972) when he came to pick up the filter and elbow today. I told him that that wouldn’t work. He knew that but had a lead on a program referred on the USNO site. Wow. A real “Ball of Fire”! I think of him as the Energizer Chemistry Bunny. ???? I told his wife that this would keep him off the streets for a while.
Tyler
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I use (worked last I checked) S P A D E (SOLAR & POLARIS AZIMUTH DETERMINATION) by Michael R. Craymer.
This is an old DOS based program and likely requires running in a DOS Box or similar, fairly easy to use and has an ephemeris built in.
https://mcraymer.github.io/software/spade/
SHG
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Spade works in Windows 7.
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SPADE hasn’t been updated in quite a few years so is extrapolating far past actual earth behavior data. Has anyone checked how accurate it is now?
I compared it to the popular astronomy program Stellarium (check that out if you haven’t) for a recent Polaris azimuth and found differences of up to 13 arc seconds. That was good enough for this task, but raised the question of which is better.
The task was to help friends in a local astronomy club get a telescope mount oriented within its adjustment range of true, so some fraction of a degree was sufficient.
It’s good the requirement is loose, because it was a whole lot more difficult to work in that space than outdoors. We’re almost 42 deg latitude, very near the limit for looking up with my Topcon without a right angle eyepiece. But I couldn’t set up high as I wanted and be able to see the floor 5 feet away to place marks.
I didn’t have a starting azimuth or focus setting good enough to find the star until almost an hour darker than I should have needed. Then lighting the reticle externally added to the clumsiness, as I think the Topcon had an internal illuminator that’s burned out.
Someone moving around in the cramped area bumped the tripod twice during the transfer to floor marks.
So what should have been a 15 minute project took over 2 hours. But I’m reasonably confident the line is good enough for their purpose.
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There is a paper by Robert Fink and Jerry L. Wahl on Jerry’s web site on how to shoot Polaris day or night. Daytime observations require an azimuth within 5 arc-minutes and proper focus. The paper suggests focusing on a distant object and then marking the barrel of the telescope since most modern instruments can focus “beyond” infinity.
THE ADVANTAGES OF POLARIS OBSERVATIONS IN LAND SURVEYING
I have several older theodolites and found the following method is a great way to set the focus for daytime observations of Polaris. I set up a second theodolite nearby and sight on each instrument. I then focus each instrument until both see the other’s cross hairs clearly. I’ve done this numerous times with my Wild T-2 as a quick check of the field observations and computations of my solar observations.
And yes, I still do solar observations with my T2. The accessories include a Wild Roelofs solar prism, a Casio “atomic” watch that I can manually update to the atomic clock in Ft. Collins, CO, and my trusty old HP-41CX with the Elgin, Knowles and Senne solar reduction program that I also use as a stop watch. With a little practice one can get the points of the Roelofs “diamond” to be coincident with the horizontal and vertical cross hairs. Using both the hour angle and altitude reduction formulae provides another check on the solar reduction. ????
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I do need to mark my focus setting.
But neither my instrument optics nor my eyes are of Wild quality. I recall finding Polaris one morning and watching until I couldn’t see it in the scope any more about an hour after official sunrise. Maybe the air wasn’t at its clearest? I’m below 1000 ft elevation. A black tube extending the sun shield made no difference. I have also set up in the evening with a good backsight angle and had to wait until 3/4 hour before sunset to find the star.
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Gene – are you talking about the ASTRO*ROM module?
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from NASA JPL
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No, I’m referring to the HP-41 code that was printed in the annual ephemeris.
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I have been using the iPhone i41CX. And I came across ASTRO*ROM for the i41CX. It returns only about 3? different than my software.
I have been using USNO AA, I get 366 days and it??s a cut and paste into Excel. I retrieve about 8, Stars, Sun, Jupiter Saturn.
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The USNO web site is going offline for 6 months for “modernization”. This seems to me like a totally unreasonable action, why wouldn’t they leave the website up until the new one is ready?
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Looks like the USNO site has gone down early
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That’s code for “If we don’t get enough complaints, it’ll stay down for good.”
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AA USNO is online for now.
But JPL Horizons is now problematic. Is there a new URL for its web interface?
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I used the JPL horizons site the other day (Saturday?). It was still up, but I could not get it to work via telnet.
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The error reported was bad gateway. So that was probably the WiFi I was on.
Fortunately USNO AA was online today and I pulled all of the 2020 data that I wanted.
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