Bob Moler
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mrephemeris.bsky.social
Bob Moler
@mrephemeris.bsky.social
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Retired computer systems engineer, programmer; current amateur astronomer, volunteer radio program producer. Most posts point to my blog postings, which illustrate my short Ephemeris radio programs on astronomy and space.
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mrephemeris.bsky.social
Ephemeris: 02/16/2026 – The Dog Star
bobmoler.wordpress.com/2026/02/16/e...
The Egyptians used the heliacal rising of Sirius as a signal that the flooding of the Nile was imminent, starting their agricultural year. The Greeks called the star Sothis, while the Egyptians themselves called it Sopdet, a goddess, and consort of the god Sah, our Orion. Part of my presentation on ancient Egyptian astronomy.
February 16, 2026 at 7:06 AM
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Ephemeris: 02/16/2026 – The Dog Star
bobmoler.wordpress.com/2026/02/16/e...
The Egyptians used the heliacal rising of Sirius as a signal that the flooding of the Nile was imminent, starting their agricultural year. The Greeks called the star Sothis, while the Egyptians themselves called it Sopdet, a goddess, and consort of the god Sah, our Orion. Part of my presentation on ancient Egyptian astronomy.
February 16, 2026 at 5:03 AM
mrephemeris.bsky.social
Ephemeris: 02/13/2026 – The real cause of a planet's retrograde motion
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A diagram showing the Earth and Jupiter and above, the appearance of Jupiter in our sky and the retrograde motion as the Earth in essence passes Jupiter in our orbital motions around the Sun. When the sight lines from earth to Jupiter are trending counterclockwise, moving to the left, the planet appears to be moving eastward in its normal motion. As we pass Jupiter, at our closest point to it, the sight lines tend to rotate in the clockwise direction, which causes the appearance of retrograde motion of Jupiter in our sky. The plotting intervals on the top diagram is 10 days, 20 days on the bottom one.
February 13, 2026 at 5:03 AM
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Ephemeris: 02/11/2026 – Taking our weekly look at the whereabouts of the naked-eye planets
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Jupiter as it appears tonight, February 11, 2026, in its orientation at 9:00 PM moving against the stars of Gemini. Also shown is its track from last July to next July, and the retrograde loop that is currently making, slowly moving to the West which it will do for the next 27 days until it stops on March 10th. Then it will resume its eastward motion. The inset shows a magnified view of the west end of the retrograde loop. Created using Stellarium, LibreOffice Draw and GIMP.
February 11, 2026 at 5:49 AM
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Ephemeris: 02/10/2026 – Artemis 2 is delayed until at least March
bobmoler.wordpress.com/2026/02/10/e...
For all but one of the proposed launch dates, the Artemis 2 mission launch window opens up after sunset to just after midnight. Each launch window is 2 hours long. For the April 30th launch date, the launch window opens about 2 hours before sunset. Photo from Scitechtimes.com, no attribution, possibly NASA.
February 10, 2026 at 5:02 AM
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Ephemeris: 02/09/2026 – Orion's amazing belt stars
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A close up look at the stars and nebulae around Orion's belt and sword. The only nebula not visible visually with optical aid is the Horsehead Nebula. Photo credit: Daniel Dall'Olmo.
February 9, 2026 at 5:03 AM
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Ephemeris: 02/06/2026 – GTAS tonight, Annual Telescope Clinic
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February 6, 2026 at 5:02 AM
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Ephemeris: 02/05/2026 – The celestial unicorn
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February 5, 2026 at 5:02 AM
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Ephemeris: 02/04/2026 – Taking our weekly look at the whereabouts of the naked-eye planets
bobmoler.wordpress.com/2026/02/04/e...
Jupiter as it appears tonight, February 4, 2026, in its orientation at 8:00 PM moving against the stars of Gemini. Also shown is its track from last July to next July, and the retrograde loop that is currently making, slowly moving to the West which you will do for the next 34 days until it stops in March. Then it will resume its eastward motion. Created using Stellarium, LibreOffice Draw and GIMP.
February 4, 2026 at 6:34 AM
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Ephemeris: 02/03/2026 – Canis Major, Orion's greater hunting dog
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February 3, 2026 at 5:12 AM
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Ephemeris: 02/02/2026 – Groundhog Day's significance
bobmoler.wordpress.com/2026/02/02/e...
I'm no artist, so I asked AI to draw a Groundhog Day cartoon. Last year I had Microsoft's Copilot do it, this year I asked Google's Gemini. While I asked for a whimsical cartoon, I didn't really mean that the shadow that the Groundhog cast was the direction of the sun and not away from it, among other things. Gemini got the nightcap I asked for correct. Copilot gave me a knit winter cap instead. The nightshirt is a nice touch.
February 2, 2026 at 5:01 AM
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Ephemeris: 01/30/2026 – Previewing February skies
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Star Chart for February 2026, (9 p.m. EST February 14, 2026).
January 30, 2026 at 5:02 AM
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Ephemeris: 01/29/2026 – After Artemis 2 comes Artemis 3 and the landing
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rtist's visualization of a Starship HLS on the Moon,near the Moon's South Pole, where both the Earth and the Sun are low to the horizon. Credit: SpaceX.
January 29, 2026 at 5:01 AM
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Ephemeris: 01/28/2026 – Taking our weekly look at the whereabouts of the naked-eye planets
bobmoler.wordpress.com/2026/01/28/e...
Jupiter as it appears tonight, January 28, 2026, in its orientation at 9:00 PM, moving against the stars of Gemini. Also shown is its track from last July to next July, and the retrograde loop that is currently making, slowly moving to the West which you will do for the next 41 days until it stops in March. Then it will resume its eastward motion. Created using Stellarium, Libreoffice Draw and GIMP.
January 28, 2026 at 5:03 AM
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Ephemeris: 01/27/2026 – Orion's heat shield problem
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Heat shield damage from the Artemis 1 reentry. :Credit: NASA.
January 27, 2026 at 5:01 AM
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Sorry guys, the Age of Enlightenment ended.
Sorry guys, the Age of Enlightenment ended.
January 27, 2026 at 1:56 AM
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Ephemeris: 01/26/2026 – Artemis, not just flags and footprints
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An artist's impression of what a moon base might look like. Credit: ESA (European Space Agency).
January 26, 2026 at 5:03 AM
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Ephemeris: 01/23/2026 – The new space race
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A 1/10th scale model of the China's Long March 10 rocket, purported to be their Moon Rocket. It is supposed to be ready for a human landing attempt on the Moon by 2030. Credit: Shujianyan.
January 23, 2026 at 5:01 AM
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Ephemeris: Taking our weekly look at the whereabouts of the naked-eye planets
bobmoler.wordpress.com/2026/01/21/e...
Jupiter as it appears tonight, January 21, 2026, in its orientation at 8:00 PM, moving against the stars of Gemini. Also shown is its track from last July to next July, and the retrograde loop that is currently making, slowly moving to the West which you will do for the next 48 days until it stops in March. Then it will resume its eastward motion.
January 21, 2026 at 5:54 AM
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Ephemeris: 01/20/2026 – What's happening inside the Great Orion Nebula
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The lower part of Orion with the Great Orion Nebula. Created using Stellarium.
January 20, 2026 at 5:08 AM
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Ephemeris: 01/19/2026 – Follow the drinkin' gourd!
bobmoler.wordpress.com/2026/01/19/e...
Shown are the positions of the Big and Little Dippers in relation to Polaris, the North Star in the evening sky, early in each season. The dippers themselves, even though there are four sets of them, are in the same quadrant defined by the pointer arrows, and that dippers seem to pour into each other. Created using my LookingUp app, GIMP and LibreOffice Draw.
January 19, 2026 at 5:03 AM
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Ephemeris: 01/16/2026 – Comparing Orion's two brightest stars
bobmoler.wordpress.com/2026/01/16/e...
Orion's named stars. Betelgeuse means "Armpit". Bellatrix means "Female warrior". The names of the belt stars refer to belt or girdle, Rigel refers to Orion's foot. Saiph means sword, however Orion's sword is the line of three stars below the belt stars. In binoculars, there's more than three stars here. Around the second "star" of the sword is the Great Orion Nebula, barely visible here. Created using Stellarium.
January 16, 2026 at 5:02 AM
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Ephemeris: 01/15/2026 – Orion's great cloud
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Orion is lousy with gas and dust. A regular star factory, or nursery. The red nebulae shows the predominance of hydrogen in here. The white nebulosity to the right of Rigel is the Witches Head nebula, probably the reflection of Rigel's light off a dust cloud. Base image by Bernal Andreo, via Wikipedia.
January 15, 2026 at 5:01 AM
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Ephemeris: 01/14/2026 – Only two naked-eye planets are visible this week, both in the evening
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This is a photograph of the Sun, Venus and Mars taken through the Solar and Heliospheric Observatory‘s (SOHO) C3 coronagraph last night at 7:54 PM or 0:54 today Universal Time. Venus and Mercury are heading to the left, while Mars is heading to the right. They are all beyond the Sun. Venus will be entering our evening sky, and should be visible in about a month. Mercury too should be visible in the evening twilight by mid-February. Mars will be moving into the morning sky and it will take several months before it will be visible then. Credit: NOAA/ESA.
January 14, 2026 at 5:01 AM
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Ephemeris: 01/13/2026 – Orion is too preoccupied to notice Lepus the hare
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January 13, 2026 at 5:08 AM