ExploreStars Ephemeris Accuracy Check #ExploreScientific #ExploreStars

Jerry Hubbell - Explore Scientific VP Engineering

Rodrigo Zelada from Chile wrote me recently telling me about his customer's experience using ExploreStars to navigate to Jupiter and Saturn. It is important to know that he is in the southern hemisphere. He told me that the customers were doing the 2 and/or 3 star alignment and going to stars just fine, but when they went to Jupiter or Saturn that the pointing was way off. I thought this was curious as I knew that the ephemeris calculation was generally good to within a few arc-minutes so Jupiter or Saturn should be in the FOV of a medium power eyepiece if the alignment was good. I did a check of the location data provided by ExploreStars as compared to the website https://ephemeris.com and my planetarium Cartes du Ciel. The results showed that for Venus, Mars, Jupiter, Saturn, Uranus, and Neptune the location was within a few arc-minutes. Mercury was within a couple of degrees and the moon was off by less than 1/4-degree.  (See below)

This result made me think that Rodrigo's customers were maybe not recognizing the correct stars when doing a 2 or 3-star virtual alignment with ExploreStars. If you center on the wrong star and Enter its location when doing the alignment, then the pointing will be way off. This should be reflected in the alignment data. To see the alignment data after doing a virtual 2 or 3-star alignment just enable showing it under the settings/preferences.

ExploreStars Ephemeris Check

Date/Time: 2020-08-16 21:40 UTC

Location: W77°46’10” N38°20’15”

Object                  ExploreStars                                       Ephemeris.com                                Cartes-du-Ciel

Sun                        09h38m29s +14°05'21"                  09h47m01s +13°22'04"                  09h46m52s +13°22'50"

Moon                    07h38m50s +23°09'45"                  07h47m53s +22°48'56"                  07h45m29s +22°57'27"

Mercury               09h28m03s +16°43'41"                  09h46m25s +15°16'53"                  09h46m05s +15°18'31"

Venus                   06h27m55s +20°04'22"                  06h37m25s +20°06'16"                  06h37m14s +20°06'16"

Mars                      01h33m09s +05°20'06"                  01h35m54s +05°53'56"                  01h35m51s +05°33'41"

Jupiter                  19h21m21s -22°30'43"                   19h20m36s -22°32'23"                   19h20m37s -22°32'21"

Saturn                   19h56m19s -21°01'22"                   19h55m25s -21°03'52"                   19h55m26s -21°03'50"

Uranus                 02h33m51s +14°36'11"                  02h33m41s +14°35'23"                  02h33m41s +14°35'23"

Neptune              23h26m06s -04°51'32"                   23h25m50s -04°53'17"                   23h25m51s -04°53'15"

Pluto                     18h35m52s -19°50'45"                   19h40m07s -22°30'27"                   19h40m07s -22°30'26"

Jerry Hubbell
Vice President of Engineering

Explore Scientific, LLC.
jrh at explorescientific.com

1010 S. 48th Street
Springdale, AR 72762

Author: Scientific Astrophotography: How Amateurs Can Generate and Use Professional Imaging Data
             Remote Observatories for Amateur Astronomers: Using High-Powered Telescopes From Home

Mark Slade Remote Observatory (MSRO) IAU MPC W54 Equipment
Wilderness, VA
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