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"--
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
Mounts: ES PMC-Eight G11 + Telescope Drive Master (TDM)
Scopes: ES 165 FPL-53 ED APO CF, ES 102 FCD100 ED APO CF
Cameras: QHY174M-GPS + FW, QHY163C
Misc: 3-inch 0.7x Focal Reducer Field Flattener, Filters: Luminance,
Red, V-band Photometric, Diffuser, 200 lpmm Spectral Grating
Software: MaxIm DL 6, Cartes du Ciel, Astrometrica, AstroImageJ, AutoStakkert!