Thursday, September 24, 2009

Moon Illusion explained (my attempt)

I and others have been aware of this particular illusion concerning the moon where the angle of illumination on the moon during a phase does not match what you'd expect by drawing a straight line to where the sun is in the sky. When I encountered this at Jerry Lodriguss' site here: I thought about it, sketched a few crude pictures and came up with these seemingly obvious observations (which may or may not be true).

In the first diagram, I replaced the moon with a pole that has 3 spheres impaled upon it and a screen upon which the shadows might be cast. But in actuality, this is wrong because although the sun is to the RIGHT of the pole, because it is so distant the rays almost entirely render the spheres (and tree) backlit, and the shadows would miss the screen completely. And even if the sun were further to the right so the shadows would fall on the screen, they would not appear to be lit at different angles nor have their shadows spaced more widely on the screen in accordance with lines drawn from the sun through the spheres and onto the screen. The second diagram better illustrates what we'd see. How does this apply to the moon?

In the third diagram, the moon replaces the spheres. Although the moon IS far away and much larger than it appears, for all intents and purposes it is (I imagine) closer in scale to the model spheres ON the earth RELATIVE to the size of the sun-moon-earth system. The third diagram shows a large angle between the sun and moon - and I don't even know what this angle between the horizon and the sun/moon signifies, but it seems to play a part in the illusion. In the final diagram I consider the true distances and sizes involved (not to scale!) and, even though the numbers and scale are wrong, you can see that INCREASING the sun from the earth and moon results in a SMALLER angle of (apparent?) separation, compared to how we see th eillusion ON EARTH. I'm not sure, but I think I'm on to something...

Thursday, July 16, 2009

Jupiter and Neptune

Between 2:00 and 4:00 a.m. EST early July 5 I took a series of photos of this close planetary alignment. Jupiter was about a half a degree from Neptune and approaching a third of a degree four nights later. I was currently in Wellfeet, MA, on a very windy beach lot, so getting a steady image was difficult. Although both planets were visible in my 35mm Panoptic, I was unable to frame both planets shooting through my attached Canon Digital Rebel. I should have taken an even lower powered photo without an eyepiece simply to orient the separate photos into the correct arrangement, but I had to do it the hard way, and I might be incorrect. The star, Mu Capricorni, is definitely brighter than Neputune, and so easy to establish visual separation. I drew a triangle of the two planets and star from on online map of that night and placed that over my screen, reducing the view size until they matched the sketch and then distanced them the correct amount and angle from Jupiter. The orientation of the moons should be about right since I lined up frame of the Neptune photo parallel to Jupiter's, since I had not turned my camera. In other words this was a painstaking reconstruction, but I am not sue how accurate. The relative magnitudes are exaggerated; I overlayed a shorter exposure of Jupter to eliminate overexposure and show cloud bands, and the moons appear more bloated than in reality, but this was the closest I could get the image to match what I remember seeing.

Friday, February 27, 2009

Comet Lulin & Regulus

Single 15 second shot from a tripod in a very light polluted Burlington, NJ, around 11:15 p.m. on 2/26/09.

Friday, January 23, 2009

Alignment of Venus and Uranus, 1/22/09

My first astronomy photograph in 2009 was on the evening of January 22, 2009 to capture this closest alignment of Venus and Uranus, approximately 1ยบ apart.

Sunday, December 07, 2008

Moon, Venus & Jupiter, one day after close alignment.

Taken on December 2, 2008 at around 5:00 from the side of Rt. 55 at Vineland's Sherman Avenue exit, this photo captures the trio a day after their close alignment. I did see the December 1 alignment but was unable to photograph it before clouds moved in. Magnification of the image shows three of Jupiter's moons.

Friday, April 11, 2008

Crescent Moon Occults the Pleiades, 4/8/08

The following three images document the 3-day old moon occulting M45 (The Pleiades). The photos were taken in Burlington City while overlooking the Delaware River. The moon is setting over the Burlington-Bristol Bridge and the Pennsylvania night skyline, between 9:45 and 10:00 p.m. Each image zooms closer in on the event in question. The first two use a telephoto lens at different settings; the first is wide and the second zoomed all the way in. Some wispy clouds can be seen - it is NOT the nebulosity around M45! The third photo was taken through my 9.25" Celestron SCT, and is a mosaic of a few photos in order to capture as much of M45 as I could (a star or two are out of field) and also some detail on both the overexposed bright crescent portion and the underexposed dark earthglow portion.

Saturday, February 23, 2008

February 20 Lunar Eclipse

This photo was taken along the Delaware riverbank in Burlington City the night of the lunar eclipse, 2/20/2008. The night began with clouds and flurries but cleared up when the moon was halfway through the penumbra. I took 72 photos at two-minute intervals from 9:58 (two minutes before it completely entered the umbra) to 12:20 early 2/21/08 (11 minutes after it had started leaving the penumbra and began to otherwise be unnoticeable to the naked eye). Eventually all 72 photos will be animated to show a quick progression of the majority of the eclipse that I caught, and the particular photo seen below was taken closest to "totality," or the midway point of the eclipse when the moon was halfway (and thus most centrally) through the umbra. Photo was taken with a Canon Digital Rebel 0.8 seconds at 400 ISO through a Celestron 9.25" SCT.
(Note: I reposted the image which in my opinion appeared too bright and "digitally tweaked" on other computer monitors not callibrated to visually duplicate the prints I create.)