A productive daylight observing session

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A productive daylight observing session

Unread post by Pete »

Friday, Oct 23, 2015

Most of the members of my class are off on vacation somewhere, but Dave B came by at 11 AM and the sky cleared. So we set off to observe planets. There’s a lovely conjunction for early risers. I caught Venus/Jupiter naked eye at 6:30 AM today. But the objective for this particular effort is to view Venus, Jupiter, Mars and Mercury in the daylight.

Venus will be 0.7 AU distant, -4.5 magnitude, 50% illuminated and 25 arc-seconds in size.
Jupiter will be 6 AU distant, -1.8 magnitude, and 32 arc-seconds in size.
Mars will be 2.3 AU distant, 1.7 magnitude, and a tiny 4 arc-seconds in size.
Mercury will be 1.2 AU distant, a bright -.9 magnitude, 80% illuminated and a tiny 6 arc-seconds
in size. (May not be possible as it’s leading the sun by only 16°.

Sitting on the deck and using the observatory to shield us from direct sunlight we unsuccessfully attempted to find Venus with binoculars. It’s leading the sun by 46° and while it’s clearing there’s light cloud in and out. There’s an airplane amazing high up there but no Venus. Even using a cell phone app that pointed out the position of the planet we were unable to identify it.

So the observatory 14” was slewed to Venus. And came up at least 10° behind where Guide 9 and Dave’s cell app said it should be positioned. Venus was not in the guide scope. Meade software sometimes loses the planets or gets confused with daylight savings time. Slewing west in azimuth located Venus. Since we were trailing by 15° I suspect that I might have canceled the daylight savings time function. Anyway, there’s Venus. 30X in the 80mm finder scope and 115X in the 14”. It’s waning at 49% phase.

Centering Venus and synchronizing the scope on Venus, we next slewed to Jupiter. Jupiter has a blueish tinge when seen in daylight. Cloud banding was very visible at 115X in the 14”. I suspect that using color filters would have pulled out more detail, but nighttime’s best for viewing Jupiter.

Next step: Mars. Mars is a relatively small round object at 115X. I thought it looked white but Dave though it looked red. He’s probably right. Although viewing through miles of daylight atmosphere does impact color.

Mercury's dangerously close to the sun. Slewing to Mercury while the scope was fully shielded by the dome, we then inched the dome to the east until direct sunlight fell within 6” of the corrector plate. About 1/3 of the view thru the 14” is blocked by the side of the shutter but there’s little Mercury. We have to play around with focusing a bit as it doesn’t look “right”. Shifting to 284X in the 14” it still doesn’t look right. Finally looking at it in Guide 9 we can see our problem – it’s only 80% illuminated.

Slewing back to Venus we observe at 284X. And then pull out the binoculars again. This time, looking out of the dome and using the big scope as a pointer it’s obvious that the airplanes we’d been observing were Venus seen through moving cloud. It really is brilliant in a binocular. And it shows tack sharp in my new Nikon AE 10X50.

Now, setting aside the binoculars we begin observing Venus naked eye. Dave seems to catch a momentary sight of it first but loses it. Then I’ve got it. It’s difficult to focus the eye at infinity when there’s nothing obvious to see. But after a bit both of us were viewing it consistently, with the dome shading us from direct sunlight.

Cool daylight session lasting from 11:00 to 12:15.

hgp 23 Oct 2015
Pete P.
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Apollo XX
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Re: A productive daylight observing session

Unread post by Apollo XX »

Great report, sounds like it was a lot of fun!
"The purpose of life is the investigation of the Sun, the Moon, and the heavens." - Anaxagoras