Date
1 - 9 of 9
Locked Moon Dx #general
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Mike Black
Trying to determine accuracy of moon distance.
Using WSJTX Astronomy window, PSTRotator and https://www.mooncalc.org All 3 seem to agree pretty well on Az and El but distance is off by about 5000km comparing WSJTX to the others. As of 13:00 or so I see WSJTX 383,115 PSTRotator 388074 MoonCalc 388199 The equatorial radius of the moon is 1,738km so that doesn't explain the difference (of about 1.3%). It seems the code in wsjtx was done with certain deliberation so I'm hoping WSJTX is more accurate. But how to resolve who's right? Mike W9MDB |
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Svend, OZ7UV
Hi Mike.
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I just got this answer: PstRotator v17.28. The displayed Moon distance is now the distance between your location and the Moon surface. It is still a difference around 100km between PstRotator and WSJT-X, and I will try to find the reason. Codrut - YO3DMU \Svend, OZ7UV man. 26. sep. 2022 01.02 skrev Michael Black via groups.io <mdblack98= yahoo.com@groups.io>: Trying to determine accuracy of moon distance. |
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Dave w6de
They could all be correct depending on the assumptions. Your position on the earth and the distance to the to the moon constantly varies. Examine what each of the three programs assume for the reflection point on the moon and your position on the earth.
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73, Dave, w6de -----Original Message-----
From: main@WSJTX.groups.io <main@WSJTX.groups.io> On Behalf Of Michael Black via groups.io Sent: Sunday, September 25, 2022 22:31 To: WSJTX Group <main@wsjtx.groups.io> Subject: [WSJTX] Moon Dx #general Trying to determine accuracy of moon distance. Using WSJTX Astronomy window, PSTRotator and https://www.mooncalc.org All 3 seem to agree pretty well on Az and El but distance is off by about 5000km comparing WSJTX to the others. As of 13:00 or so I see WSJTX 383,115 PSTRotator 388074 MoonCalc 388199 The equatorial radius of the moon is 1,738km so that doesn't explain the difference (of about 1.3%). It seems the code in wsjtx was done with certain deliberation so I'm hoping WSJTX is more accurate. But how to resolve who's right? Mike W9MDB |
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Julian
I recently looked into this. There is no simple answer. The Apogee and Perigee vary considerably over time.
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See the following paper from NASA: https://eclipse.gsfc.nasa.gov/SEhelp/moonorbit.html Over the period 2008-2010, the radius of the orbit varies between 356,568 and 406,602km. Over a 5000 year period, it varies between 356,355 and 406,725km. It depends on what the programmes have assumed... Julian, G3YGF On 26/09/2022 00:52, w6de wrote:
They could all be correct depending on the assumptions. Your position on the earth and the distance to the to the moon constantly varies. Examine what each of the three programs assume for the reflection point on the moon and your position on the earth. |
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This probably doesn't answer the question but it's pretty interesting!
https://en.m.wikipedia.org/wiki/Lunar_distance_(astronomy) -- John P. WA2FZW |
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Mike Black
I had an older version of PSTRotator and they agree much better now with 17.28 -- differing by around 100km as of right now so only 0.026% between them.
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WSJTX 390620 PSTRotator 390506 MoonCalc 386676 MoonCalc is now the odd one out and off by approx 3900km but I imagine they are doing the orbital distance and not surface-to-surface. Mike W9MDB On Sunday, September 25, 2022 at 06:51:13 PM CDT, Svend, OZ7UV <spanget@...> wrote:
Hi Mike. I just got this answer: PstRotator v17.28. The displayed Moon distance is now the distance between your location and the Moon surface. It is still a difference around 100km between PstRotator and WSJT-X, and I will try to find the reason. Codrut - YO3DMU \Svend, OZ7UV man. 26. sep. 2022 01.02 skrev Michael Black via groups.io <mdblack98= yahoo.com@groups.io>: Trying to determine accuracy of moon distance. |
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Charles Suckling
Hi Mike
Yes, I think its the difference between geocentric and topocentric calculations. If you look at Moonsked, the 'Range' changes continuously in one direction (today centre of moon is moving closer to centre of earth). Watch' Dist' in WSJT-X and you should see it increase again after transit, as the observer moves away from the moon. For comparison, I suggest using JPL Horizons to provide definitive data for comparison. At the present time, JPL and WSJT-X differ at my location by about 5-6km. 73 Charlie DL3WDG On Mon, 26 Sept 2022 at 10:57, Michael Black via groups.io <mdblack98= yahoo.com@groups.io> wrote: I had an older version of PSTRotator and they agree much better now with |
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Charles Suckling
Hi Mike
I forgot to add, that discrepancies may arise between programs that use a 6 character grid locator to define your home location, and JPL Horizons where you can enter your exact location, due to the potential inaccuracy in determining your exact location from a 6 digit Maidenhead locator. We see this sometimes on microwave EME, where the computed Doppler shifts may be a few Hz out. Similar effects might well happen with moon distance. Its all negligible, however! 73 Charlie On Mon, 26 Sept 2022 at 10:57, Michael Black via groups.io <mdblack98= yahoo.com@groups.io> wrote: I had an older version of PSTRotator and they agree much better now with |
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Lawrence Godek
Extremely interesting!
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On 9/25/2022 8:03 PM, John P wrote:
This probably doesn't answer the question but it's pretty interesting! |
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