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All,

Having purchased a new hp 15c calculator I quickly keyed in a program for sight reduction. Worked great. Now inspired, I thought it would be fun to drop in a simple algorithm to determine sun GHA and declination.

I went to MS Copilot and asked for "A simple alorithm to determine the GHA and declination of the sun for 2025". Copilot returned about a page and half of nicely laid out equations that seemed perfectly reasonable to drop into the calculator. BUT! When I checked the equation it gave me to convert a date and time to JD for the algorithm, the trouble began. I could not get my calculation to match what Copilot gave me as an example conversion. I assumed I made some sort of input/equation error so I checked carefully until very annoyed!. So, time to dig deeper.

I tried checking against other online converters and found that they did not match my calculation or the example calculation I was working with.

I finally figured that the NASA converter should be good and indeed it matches what I had set up perfectly for all the examples I tried (but did not agree with the Copilot example). So, either I made the same mistake as NASA or we are correct. All of this has left me with a couple of questions:

1. What formula have members who have had occassion to work with JD used for almanac work?

2. Have other members expereinced the inconsistencey in conversions online that I have?

3. I was really surprised that the equation(s) to convert to JD Copilot gave me agreed with NASA but then Copilot gave me an incorrect conversion. Anyone else experience this.

Being quite capable of screwing up my own work, this was really annoying.

Thanks in advance of any comments.

Cheers,

Jim