A tool for calculating the position of the sun using historic data

I've expanded the functionality of my moon calculation spreadsheet to include the position of the sun, as well as now the apparent size of both the moon and the sun. This spreadsheet uses Jean Meeus' approximation of Simon Newcomb's Tables of the Sun (developed in the late 19th century) and accurately gives the sun's equatorial coordinates to within about 2 arcseconds and provides altitude-azimuth coordinates as well (with atmospheric refraction accounted for in the latter). Simply enter your longitude and latitude (+ for N and W, - for S and E) and the date and time (in Universal Time). For additional accuracy in computing atmospheric refraction, enter the atmospheric pressure and temperature.



dropcanvas.com...

Enjoy!

reply to post by ngchunter


Hi ngchunter nice work liked the video, does software like Stellarium not do that if you use the time date to look at a past date?

Originally posted by wmd_2008
reply to post by ngchunter

 

Hi ngchunter nice work liked the video, does software like Stellarium not do that if you use the time date to look at a past date?

Stellarium generally uses VSOP87, not Newcomb's tables. Stellarium's end result is quite accurate, there's nothing wrong with it, but I don't know if they let you specify the atmospheric pressure/temperature to increase the accuracy of the atmospheric refraction calculations. I know Cartes du Ciel does have those settings available, but I haven't seen them on Stellarium.

The point of this was more to resurrect Newcomb's old data. It may have been inspired by a desire to prove wrong the claim that NASA and others are lying and that astronomy programs are "being altered to covering up changes to the solar system" so that everything only looks like it's moving normally, but it has uses beyond that. For most purposes it's more than accurate enough, and I rather enjoy dusting off unused books containing historical data like this which used to form the basis of all astronomical almanacs. It's a bit like how some space enthusiasts spend their time restoring an old unused telescope or spaceflight computer. Neither one will perform better than a modern equivalent, and it's much easier to get and use a modern version, but the joy is in the learning process while doing the restoration. In the end there's also an intangible joy that comes from seeing the old data working once again, and the results can be used by others as well.

reply to post by ngchunter


Hi ngchunter

In Stellarium if you have atmosphere on you get two readings for Hour Angle/DE geometric & apparent if you switch atmosphere off you only get one.

You mentioned old telescopes I had the chance to use this one about 30 years ago.

en.wikipedia.org...

Then a few weeks back I got a chance to look through this one.

en.wikipedia.org...

Originally posted by wmd_2008
reply to post by ngchunter

 

Hi ngchunter

In Stellarium if you have atmosphere on you get two readings for Hour Angle/DE geometric & apparent if you switch atmosphere off you only get one.

What I mean is that as far as I can tell, there's no way to fine tune the atmospheric refraction modeling by specifying your local temperature and barometric pressure. The exact amount of atmospheric will vary depending on both those factors, even under otherwise normal conditions.

You mentioned old telescopes I had the chance to use this one about 30 years ago.

en.wikipedia.org...

Then a few weeks back I got a chance to look through this one.

en.wikipedia.org...

Beautiful, both of them. What did you get to see?

reply to post by ngchunter


Hi ngchunter with the first scope I got a chance to see M31.M42 M57 and a few others over a period of a few months when I lived near there also the Moon, Jupiter and Saturn also got a chance to take some pictures but they were lost I a house move a few years later

The second one was at an open night for the public and only got to have a quick look at Jupiter.

Another public observatory has opened up at a deep sky park near were I live the sky's there have a Sky Quality Meter (SQM) scale reading of 21 to 23.6 hope to get there later in the year.

www.forestry.gov.uk...