Ephemeris: 04/15/2024 – How the Ancient Greeks tried to measure the distance to the Sun

This is Bob Moler with Ephemeris for Monday, April 15th. Today the Sun will be up for 13 hours and 31 minutes, setting at 8:28, and it will rise tomorrow at 6:55. The Moon, at first quarter today, will set at 4:15 tomorrow morning.

The first quarter Moon tonight reminds me of how the Greeks used the quarter Moon to attempt to determine the distance to the Sun. The idea was to determine when the Moon was exactly at first or last quarter, so the angle of the Sun-Moon-Earth was exactly 90°. The next thing to do was to measure the actual angle between the Sun and the Moon at that instant. It’s a difficult observation. Aristarchus tried and got a result that the Sun was about 19 times the distance of the Moon. The Sun-Earth-Moon angle he got was 87°. Hipparchus measured the Moon to be 60 earth radii away which is near the Moon’s actual distance from the Earth. In actuality the Sun is about 400 times the distance to the Moon.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

Addendum

A diagram of the measurement Aristarchus tried to make of the distance to the Sun. He got a distance to the Sun of 19.1 times the distance to the Moon, which correlates to an angle between the Moon and the Sun of 87°. The actual distance to the Sun is on the order, rounded up, of 400 times the Moon’s distance from the Earth. So this angle would be impossible to measure 89.85° for that interior angle instead of 87°. Credit: Ancient Greek Astronomy by Denis Erkal

Ephemeris: 04/12/2024 – GTAS Meeting tonight: Hidden Figures

This is Ephemeris for Friday, April 12th. Today the Sun will be up for 13 hours and 22 minutes, setting at 8:24, and it will rise tomorrow at 7:01. The Moon, 3 days before first quarter, will set at 1:52 tomorrow morning.

Tonight’s meeting of the Grand Traverse Astronomical Society at 8 pm, at Northwestern Michigan College’s Rogers Observatory, will feature the student astronomy group’s movie night with a presentation of Hidden Figures. How female African American “Computers”, made the space program possible. Many of NASA’s facilities were in the segregated South. Back then computers were also people with tremendous math skills, who could work out problems of orbital mechanics by hand and with mechanical calculators. Plus we’ll see if anyone has made it back to report on Monday’s total solar eclipse. The observatory is located south of Traverse City on Birmley Road between Garfield and Keystone roads.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

Addendum

Hidden Figures Promo photo

Hidden Figures actresses with the real women they portrayed. Credit: SEDS-UOC, Sri Lanka

Ephemeris: 04/11/2024 – What is the far side of the Moon good for?

This is Ephemeris for Thursday, April 11th. Today the Sun will be up for 13 hours and 19 minutes, setting at 8:23, and it will rise tomorrow at 7:02. The Moon, 3 days past new, will set at 12:40 tomorrow morning.

The Last Monday when we were having an eclipse of the Sun, the far side of the Moon was fully illuminated. So it can’t possibly be the dark side of the Moon, not permanently. The dark side of the Moon is the night side and Monday that was the side facing the Earth. But what’s the far side of the Moon good for? The Chinese seem to be very interested in it. They have a lander and a rover on the far side, and they’re going to go back and grab a sample from the far side and bring it back to the Earth. The far side of the Moon is one place in the whole solar system in which the cacophony of radio signals from the Earth cannot be heard so it’s a great place to set up a radio telescope. The craters on the far side of the moon might be used to place a dish antenna.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

Addendum

The near side and the far side of the Moon compared. Notice how different they are with the near side dominated by the dark lava seas and the far side by the less dark highlands. The one sea on the far side is at 10 o’clock is the Sea of Moscow, and the other dark spot to the lower lower left about 8 o’clock is the crater Tsiolkovsky named after famous Russian scientist Konstantin Tsiolkovsky (1857-1935)a pioneer in aeronautic, and rocket theory. The Soviets were first to send a probe (Luna 3) around the far side of the Moon in 1959, and got to name the major features they photographed.

A concept for a lunar crater radio telescope . The telescope is in the style of Arecibo, the now collapsed radio telescope in Puerto Rico . Aiming would be accomplished by shifting the suspended receiver. Credit: NASA, Saptarshi Bandyopadhyay.

Ephemeris: 04/10/2024 – Where have the naked-eye planets wandered off to?

This post was updated due to it being uploaded late, and without illustrations. This was due to my recovery from the mad dash eclipse trip Sunday through Tuesday. By the way it was glorious! I shall recount it soon in an Ephemeris Extra post.

This is Ephemeris for Wednesday, April 10th. Today the Sun will be up for 13 hours and 16 minutes, setting at 8:22, and it will rise tomorrow at 7:04. The Moon, 2 days past new, will set at 11:21 this evening.

Let’s find out where the naked-eye planets have wandered off to this week, and see what planets are left. Bright Jupiter is low and in the west, and tonight only can be seen below the crescent Moon. It will set at 10:25 pm. We are getting close to losing Jupiter in the evening sky. Comet 12P/Pons-Brooks is just below-right of it. Though officially naked-eye brightness, one has to have very good eyes, binoculars or telescope to spot it. In my Wednesday blog posts at bobmoler.wordpress.com I have finder charts. In the morning Mars, and Saturn will be very close together in the east southeastern sky at 6:30. They will be fighting the bright morning twilight and low altitude then.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

Addendum

The Moon, Jupiter and Comet Pons-Brooks for 9:30 PM Thursday April 11th 2024. Due to the late post I’m showing this for tomorrow night. Created using Stellarium .

Here is a finder chart for Comet Pons-Brooks for the next week at 9:30 PM. Jupiter is also in the field. The first position is marked with the name, month and day, and the approximate magnitude. The chart shows a comet tail. The tail will probably not be visible visually, however if it is visible, that is the direction it will be pointing. Created using Cartes du Ciel (Sky Charts).

The three day old Moon as it might appear Thursday at 9:30 PM April 11th 2024 through binoculars or a small telescope. Selected features are labeled. Created using Stellarium, LibreOffice Draw, and GIMP.

Mars and Saturn as they may appear side by side tomorrow morning April 12th 2024 at about 6:15 AM. They are probably shown somewhat brighter than they would normally appear in the sky. Created using Stellarium , LibreOffice Draw, and GIMP.

Jupiter as it might appear in a telescope at 9:30 April 11, 2024 in this erect image, showing the position of its Galilean moons. Jupiter’s apparent diameter is 33.54″. Created using Cartes du Ciel (Sky Charts).

The naked-eye planets, Comet Pons-Brooks, and the Moon at sunset and sunrise on a single night, starting with sunset on the right tonight, April 11th 2024. The night ends on the left with sunrise tomorrow morning on the 12th. Click or tap on the image to enlarge it. Created using my LookingUp app and GIMP.

Ephemeris: 04/09/24 – When is the next solar eclipse?

This is Ephemeris for Tuesday, April 9th. Today the Sun will be up for 13 hours and 13 minutes, setting at 8:21, and it will rise tomorrow at 7:06. The Moon, 1 day past new, will set at 9:58 this evening.

I hope you’ve had a good eclipse and were able to view it. I don’t know if you saw the eclipse or if I saw the eclipse since this is being recorded before the events. However, it’s time to look at the next time you might be able to see a solar eclipse. Our next Great American Eclipse isn’t for 21 years on August 12th 2045, which I won’t make, guaranteed. But we have some other minor solar eclipses visible in our area before that eclipse. Our next eclipse will be about 11% eclipse that’ll occur August 12th of 2026, just two years away. It’s not much compared to the 89% yesterday for our area. There will be an even tinier eclipse on January 26th of 2028. Just 2.5% of the Sun’s diameter will be covered. The best of the next three eclipses occurs on January 14th 2029, when the Moon encroaches on 69% of the Sun’s diameter. There are five more partial eclipses visible before 2045.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

Addendum

Eclipse maximum for the Grand Traverse Region, August 12, 2026. Created using Cartes du Ciel (Sky Charts).

Eclipse maximum for the Grand Traverse Region, January 26, 2028. Created using Cartes du Ciel (Sky Charts).

Eclipse maximum for the Grand Traverse Region, January 14, 2029. Created using Cartes du Ciel (Sky Charts).

Ephemeris: 04/08/2024 – Solar Eclipse Today!

This is Ephemeris for Monday, April 8th. Today the Sun will be up for 13 hours and 10 minutes, setting at 8:19, and it will rise tomorrow at 7:08. The Moon is new today, and won’t be visible.

This afternoon there will be a total eclipse of the sun in the United States. But right here it’ll be a very deep partial eclipse, with the moon covering nearly 90% of the sun. For the Grand Traverse Area of Michigan, it will begin at 1:58 PM, mid-eclipse will be at 3:12 PM and the eclipse will end at 4:25 PM. In deep partial eclipses I’ve noticed that the sunlight has a slight yellowish hue. It’s possible effect of the Sun’s edge being cooler than the rest of the disk. Even if it’s cloudy here NASA will broadcast the eclipse from eight points along its route from Texas to Maine. It’s on the Internet on NASA’s YouTube channel, or in an Internet browser type NASA and ECLIPSE. Look for a link for nasa.gov, and you should be able to find out where that feed is. Good Luck!

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

Addendum

Image of the eclipse2024.org overview of its interactive eclipse map showing the path of totality. Click or tap on the image to enlarge it. Credit eclipse2024.org via NASA.gov.

With pinhole projection the Moon will appear to move from the upper right to lower left. Created using Cartes du Ciel (Sky Charts), LibreOffice Draw and GIMP

Ephemeris: 04/05/2024 – A ready-made eclipse projector

This is Ephemeris for Friday, April 5th. Today the Sun will be up for 13 hours, setting at 8:16, and it will rise tomorrow at 7:13. The Moon, 3 days before new, will rise at 6:24 tomorrow morning.

One quick and easy way to view next Monday’s eclipse via projection will be to use a calendar. All those little drain holes are actually pinholes, and will allow you to see multiple images of the eclipsed Sun. Multiple suns will be projected on whatever its shadow falls on. So that’s a quick and easy way of doing it. You may want to plug up some of the holes though, or the images might overlap. The eclipse will start for IPR listening area at 1:58 pm give or take a minute or two, mid-eclipse will be around 3:12 pm and the eclipse will end at 4:25 pm. If you’re wearing eclipse glasses the moon will move from lower right to upper left. If you’re using the pinhole projection method the moon will move from the upper right to lower left.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

Addendum

MARY CLASSEN of Mountain Lake immersed herself in the partial solar eclipse – getting creative with a colander – displaying a whole bunch of eclipsing suns. (Photo courtesy of Mary Classen) via cross-countiesconnect.com.

The projected view of the eclipse will be upside down and reversed left to right. So the Moon will appear to move from upper right to lower left. Created using Cartes du Ciel (Sky Charts), LibreOffice Draw, and GIMP.

Ephemeris: 04/04/2024 – Viewing the eclipse with pinhole projection.

This is Bob Moler with Ephemeris for Thursday, April 4th. Today the Sun will be up for 12 hours and 57 minutes, setting at 8:14, and it will rise tomorrow at 7:15. The Moon, 3 days past last quarter, will rise at 6:01 tomorrow morning.

If you have eclipse glasses and even if you don’t a good way perhaps the best way to view the solar eclipse is to use projection specifically pinhole projection the pinhole can act like a lens and with something as bright as the sun can cast a good visible image of the sun. Probably the best way to do it is to find a long box and cut a hole in one end. Have one long side open or partially open to view the Sun’s projected image. Cover the hole with aluminum foil and then make pinholes of various sizes, about half inch apart. The bigger the pinhole the brighter the Sun’s image but also the fuzzier it will be. The smaller the hole the sharper and dimmer the sun will be. For the IPR listening area the eclipse will start around 1:58 pm, and end around 4:25 pm.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

Addendum

Pinhole projection is the simplest way to project the Sun’s image.

A long box can be used to project the image inside. The diameter of the pin hole is a compromise between sharpness and brightness of the image.
…The farther the image is projected the larger it is.

The throw of the image can be increased by using a mirror masked with a quarter of a inch or larger hole and sending the image 10 or more feet away.

Telescope projection of the Sun. Use the lowest power eyepiece. Cover the telescope finder. Point the telescope using its shadow. Photo by Eileen Carlisle.

With pinhole projection the Moon will appear to move from the upper right to lower left.

Ephemeris: 04/03/2024 – Where have the naked-eye planets wandered off to this week?

This is Ephemeris for Wednesday, April 3rd. Today the Sun will be up for 12 hours and 54 minutes, setting at 8:13, and it will rise tomorrow at 7:17. The Moon, 2 days past last quarter, will rise at 5:33 tomorrow morning.

Let’s find out where the naked-eye planets have wandered off to this week, and see what planets are left. Mercury is now too close to the Sun to be spotted. Bright Jupiter is due west at 8:45 pm or a half hour after sunset. It will set at 11:05 pm. We are getting close to losing Jupiter in the evening sky. Comet 12P/Pons-Brooks is right of and a bit below Jupiter in the evening. Though officially naked-eye brightness, one has to have very good eyes, binoculars or telescope to spot it. In my Wednesday blog posts at bobmoler.wordpress.com I have finder charts. In the morning Mars, and especially Venus and Saturn may be impossible to spot, in the east-southeast in the bright twilight. Mars will rise at 6:10, and will be very low in the east-southeast at 6:45 am.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

Addendum

Jupiter and Mercury as might be seen at 9:00 PM, or nearly three quarters of an hour after sunset, tonight April 3rd 2024 . Also Comet Pons-Brooks is in the same general area of the sky. It is 5th magnitude, and probably not visible without binoculars or a small telescope. Mercury is definiotely not visible wothout a telescope. Created using Stellarium.

Here is a finder chart for Comet Pons-Brooks for the next week at 9:30 PM. Jupiter is also in the field. The first position is marked with the name, month and day, and the approximate magnitude. The chart shows a comet tail. The tail will probably not be visible visually, however if it is visible, that is the direction it will be pointing. Created using Cartes du Ciel (Sky Charts).

During the solar eclipse on the 8th, during totality, the comet will be located around the 2nd to the last position of its track. However, unless it is obviously noticeable, totality time is too short to use trying to find it. Enjoy the glory of the sun’s corona for the brief time you have.

The Moon, Mars, and Saturn as they might appear about 6:45 in the morning about 1/2 an hour before sunrise low in the east-southeast to southeast. Mars and Saturn are shown brighter than they might appear, so don’t be discouraged if you can’t see them. Created using Stellarium.

The moon as seen in a pair binoculars or telescope around 6:45 tomorrow morning April 4th 2024. Selected features are labeled. Montes Jura or the Jura Mountains on the terminator surround 3 sides of the Bay of Rainbows (Sinus Iridium). The crater J. Herschel is named after John Herschel, son of William Herschel, a more famous astronomer, who has a small crater near the center of the disk of the moon just north of crater named for Ptolemy and near another crater named for the Greek astronomer Hipparchus. Created using Stellarium, LibreOffice Draw, and GIMP.

Jupiter as it might appear in a telescope at 9:30 this evening in this erect image, showing the position of its Galilean moons. Jupiter’s apparent diameter is 33.93″. Created using Cartes du Ciel (Sky Charts).

The naked-eye planets, Comet Pons-Brooks, and the Moon at sunset and sunrise on a single night, starting with sunset on the right tonight, April 3rd 2024. The night ends on the left with sunrise tomorrow morning on the 4th. Click or tap on the image to enlarge it. Created using my LookingUp app and GIMP.

Ephemeris: 04/02/2024 – Availability of and checking out eclipse glasses

This is Ephemeris for Tuesday, April 2nd. Today the Sun will be up for 12 hours and 51 minutes, setting at 8:12, and it will rise tomorrow at 7:18. The Moon, 1 day past last quarter, will rise at 4:59 tomorrow morning.

In six days there will be a total solar eclipse, if you’re right place. Northern Michigan is not the right place. We get a pretty good chunk of the Sun being covered by the Moon, about nearly 90% around here. This means that you will still need protection if you want to view the eclipse. My daughter reports that there are places around Traverse City that you can get solar eclipse glasses. However, to make sure that they are the proper eclipse glasses they will have a globe symbol with ISO in it for the International Organization for Standardization. Also, they must state that they conform to and meet the transmission requirements of ISO 12312-2, filters for direct observation of the sun. That doesn’t keep someone from making counterfeit ones. A way to check is with laying one lens onto a smartphone flashlight, which should be barely visible through it.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

Addendum

This is an image of solar eclipse glasses placed on a smartphone to test their effectiveness with its light, which is used as a flashlight and as a flash, turned on and note that it just barely shows up in the lens or the filter. Also note the ISO 12312-2 requirement of the ISO filters for direct observation of the sun. These glasses pass the test. Now these solar eclipse glasses are for just viewing the sun without optical aid. Do not use them with binoculars or a telescope. They’re just for viewing the sun having ambient sunlight fall on them. Anything more than that will burn through the filter and cause eye damage.