For the moon to appear so large and the observatory to be so small, how far away from the observatory did the photographer have to be?
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thanks,
dull dave
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Google maps (satellite) would indicate that this picture is taken from due west of the original James Lick Telescope building which has north-south dimensions of ~ 75 meters.dull dave wrote:For the moon to appear so large and the observatory to be so small, how far away from the observatory did the photographer have to be?![]()
I measure the 75' dome to be 1/14 the size of the Moon. That means it is subtending 0.035 degrees, and the distance to the photographer must be about 23 miles. That puts him on the west side of San Jose. Pretty remarkable to look horizontally across an entire city and not see more distortion from air currents.dull dave wrote:For the moon to appear so large and the observatory to be so small, how far away from the observatory did the photographer have to be?
Nope. The Moon illusion is purely an eye/brain thing, that fails completely under measurement (even so simple a measurement as comparing the low and high Moon sizes to your fingernail). This distance comes from measuring the relative size of the Moon and dome, and no illusion can change the simple math.Indigo_Sunrise wrote:30 Km...? That's pretty far away. Not saying you're wrong, art, just sayin'.
I think it's more likely one of those Moon Illusion things that we read about here from time to time.
Actually, it is probably closer to Chris's 20 miles (=32 km) than my 30 kmIndigo_Sunrise wrote:30 Km...? That's pretty far away. Not saying you're wrong, art,
The moon appears big to us in this photoIndigo_Sunrise wrote: just sayin'.
I think it's more likely one of those Moon Illusion things that we read about here from time to time. Or maybe using a telephoto lens adds to it, as in this beautiful image.
The full moon on Wed 2008 Oct 15 1:30 UT (Tues 2008 Oct 14 17:30 PT)Chris Peterson wrote:I measure the 75' dome to be 1/14 the size of the Moon. That means it is subtending 0.035 degrees, and the distance to the photographer must be about 23 miles. That puts him on the west side of San Jose. Pretty remarkable to look horizontally across an entire city and not see more distortion from air currents.dull dave wrote:For the moon to appear so large and the observatory to be so small, how far away from the observatory did the photographer have to be?
However, on 2008 Oct 14, the Moon rose at an azimuth of 66°, so the bearing of the photographer would have been 246°, not 270° (due west). Given your distance, that would put him in the hills on the southwest side of Los Gatos.neufer wrote:The full moon on Wed 2008 Oct 15 1:30 UT (Tues 2008 Oct 14 17:30 PT)
was at a distance of 58.3 ER = 106.78 x the moon's diameter.
75 x 14 x 106.78 / 5280 = 21.23 miles
Ortega Park in Sunnyvale is almost exactly 21.23 miles due west of the Lick Observatory
I'm trying my best, Chris.Chris Peterson wrote:However, on 2008 Oct 14, the Moon rose at an azimuth of 66°, so the bearing of the photographer would have been 246°, not 270° (due west). Given your distance, that would put him in the hills on the southwest side of Los Gatos.neufer wrote:The full moon on Wed 2008 Oct 15 1:30 UT (Tues 2008 Oct 14 17:30 PT)
was at a distance of 58.3 ER = 106.78 x the moon's diameter.
75 x 14 x 106.78 / 5280 = 21.23 miles
Ortega Park in Sunnyvale is almost exactly 21.23 miles due west of the Lick Observatory
(BTW, what we're engaged in here is called forensic astronomy; if you're good, you can command excellent fees as an expert witness.)
How did you derive this azimuth? By my reckoning, at that time, from Mt Hamilton, the Moon's azimuth was 74.3°. That also makes sense to me- I often take pictures of the full Moon rising behind Pikes Peak, and I know that in October the Moon rises north of east.neufer wrote:The time is probably the most accurately defined item:
1) At a distance of ~ 21.21 miles the moon was ~ 300 ft
over Lick Observatory at 17:26 PT Oct 14, 2008
This places the moon at an Azimuth of 106° (ESE)...
Plenty.apodman wrote:How much fun can you have with an un-timed test?
Chris Peterson wrote:Plenty.apodman wrote:How much fun can you have with an un-timed test?
Bill Kerchen (for Commander Cody) wrote:I ain't never had too much fun.
Hedonism and indulgence everywhere.Daryle Singletary wrote:I ain't never had too much fun.
And there ain't nothing like a hedonistic physicist!apodman wrote:Hedonism and indulgence everywhere.
I see what's going on. The Fourmilab site is using a non-standard definition of azimuth (rather, they're using an obsolete astronomical definition that uses south as the origin). Their value isn't 106°, it is -106°, which is a true azimuth of 74°. As we would expect for October, the Moon is rising north of east.neufer wrote:1) At a distance of ~ 21.21 miles the moon was ~ 300 ft
over Lick Observatory at 17:26 PT Oct 14, 2008
This places the moon at an Azimuth of 106° (ESE)
Chris Peterson wrote:How did you derive this azimuth?neufer wrote:The time is probably the most accurately defined item:
1) At a distance of ~ 21.21 miles the moon was ~ 300 ft
over Lick Observatory at 17:26 PT Oct 14, 2008
This places the moon at an Azimuth of 106° (ESE)...
Code: Select all
http://www.fourmilab.ch/cgi-bin/Solar
Solar System: Wed 2008 Oct 15 1:26 UT
(Solar System: Tue 2008 Oct 14 17:26 PT)
Right Distance From 37°25'35"N 122°0'43"W:
Ascension Declination (AU) Altitude Azimuth
Sun 13h 21m 34s -8° 35.5' 0.997 0.244 78.967 Up
Moon 1h 25m 53s +14° 4.7' 58.3 ER 2.306 -106.007 Up
You are quite right...I guess I was having a senior moment.Chris Peterson wrote: By my reckoning, at that time, from Mt Hamilton, the Moon's azimuth was 74.3°. That also makes sense to me- I often take pictures of the full Moon rising behind Pikes Peak, and I know that in October the Moon rises north of east.
Well...so much for forensic photography for me; but it was fun while it lasted.Chris Peterson wrote:That would place the photographer on a bearing of 254.3°, which if we use your adjusted distance of 21.2 miles would mean Saratoga, just NW of Los Gatos. Perhaps around N37.25878 W122.01293, without being too precise <g>. It also seems that the observatory structure itself is imaged from south of west.