Re: New JPL Format for Horizons Ephemeris #APCC - Format Causes Issue #APCC

Michael 'Mikey' Mangieri

Thanks for the insight. I had verified both and they are OK. What I did find is that the problem is with Stellarium. A photo of where Ceres should be according to Stellarium didn’t show the dwarf planet. When I slewed to the coordinates given by JPL she was in the field; not perfect but well within the FOV. So now I guess it’s time to contact the Stellarium folks. Maybe the Solar System plug-in isn’t all that accurate for asteroids and comets. 

On Nov 20, 2021, at 1:27 AM, Brian Valente <bvalente@...> wrote:

Two things come to mind

First is to make sure you solve and recal ahead of time so your pointing is is as accurate as possible

Second is Comet/satellite tracking is very sensitive to accurate time, many people (myself included) invest in a gps system with realtime clock updates using something like NMEATime

On Fri, Nov 19, 2021 at 8:25 PM Michael 'Mikey' Mangieri <mjmangieri@...> wrote:
Well, after some trial and error I finally got Horizons to work using the beta release of APCC and the instructions given by Ray to change the header text.  But now I have an interesting question ...
In testing out this feature I decided to target Ceres since it was placed high in the sky during the early evening hours. I wanted to test out the horizons tracking for comet Leonard but it doesn't rise above my tree line until 2:30-3:00 in the morning.  I ran the JPL ephemeris for Ceres and loaded it into APCC.  All went well. I then set my mount (AP1100) to track Ceres starting at 10:30pm.  When the mount slewed to Ceres it was not at the correct location according to Stelarium which I use to target objects and control the mount's initial slew. The location given by Stellarium is RA:  04h 23m 37.6s;  DEC:  +16d 45m 16.2s.  But the JPL data is giving  RA: 04h 22m 57.7s;  DEC:  +16d 39m 30.4s.  This is a considerable discrepancy. APCC Horizons thus points the telescope to a location well out of the FOV of the camera.  
Not sure this is the proper place to discuss this, but has anyone experienced this issue?  This makes setting up a planned tracking impossible since the coordinates are not correct.  I've checked my location (Lat/Lon), and the settings on all the software and they are correct. J2000 vs 'on date' may contribute some of the error, but not nearly the amount I'm seeing.


Brian Valente

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