[AZ-Observing] Re: DA14 ephemeris?
- From: Dan Heim <dan@xxxxxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Wed, 30 Jan 2013 16:24:01 -0700
Thanks for the info Bob. I share your confusion. I'm beginning to wonder
if the orbital elements are being updated as DA14 approaches, since its
orbit will be changing due to Earth's gravity. But my understanding is
that updates are only done at opposition. Couldn't find anything on the
JPL site about that. I think I'll just wait a week, and see what's
online then. -Dan
On 1/30/2013 3:24 PM, Bob Christ wrote:
> I can shed some light, but I am totally confused as well Dan. It has been a
> while since I used Horizons so when I inputted the time offset I
> inadvertently (my bad) used the convention "-7," when it should have been
> "UT-7." I regen'd the ephemeris in Horizons and then generated it using
> Starry Night Pro + and the results are totally inconsistent" UGH! Here's
> the SNPP output for 5-hours on the evening of the 15th.
> Local Time Az Alt RA
> Dec Constellation
> 2/15/2013 8:00:00 PM 41.5° 19.2° 11h 58m 49.8s 50° 25' 29" Ursa
> Major
> 2/15/2013 9:00:00 PM 42.0° 28.6° 12h 01m 14.5s 53° 54' 20" Ursa
> Major
> 2/15/2013 10:00:00 PM 41.2° 37.4° 12h 02m 23.0s 56° 29' 30" Ursa
> Major
> 2/15/2013 11:00:00 PM 38.3° 45.4° 12h 02m 32.0s 58° 27' 19" Ursa
> Major
> 2/15/2013 12:00:00 PM 32.7° 52.4° 12h 01m 59.1s 59° 57' 40" Ursa
> Major
> 2/16/2013 1:00:00 AM 23.2° 57.7° 12h 00m 59.4s 61° 07' 11" Ursa
> Major
>
> So, within the same time band, Horizons relates 2012 DA14 will be in UMi and
> Starry Night says it's in UMa and the values are not close. At this point I
> am at a loss to understand the discrepancy:
>
> Horizons: 2013-Feb-15 20:00 m 14 35 54.57 +82 00 47.8 5.7909 27.2193 UMi
> SNP+: 2/15/2013 8:00:00 PM 41.5° 19.2° 11h 58m 49.8s 50° 25' 29"
> Ursa Major
>
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