Sunday, November 10, 2019

Shot Planning: Full moon rising behind Lick Observatory (Mt Hamilton) Monday November 11?

This is an email thread and some associated notes. The original idea expanded quite a bit.

Email from Chip, 10/28

Fred Larson is putting together some full moon shots up in SF next month, but we have some good opportunities closer to home. I tried a couple of times a few years ago to shoot the full moon rising behind the observatory, but never got the alignment right. Now our tools our better. This shot requires parking on Skyline Rd between Hwy 9 and Castle Rock, and hiking 0.5 mi., partly on the Skyline Trail and some of it off-trail to clear the trees. The parking is legit, though we're supposed to be gone at sunset. Anybody interested?

Here is the setup in TPE:,-122.105669&dt=20191111170400-0800&z=11&spn=0.38,0.71&center=37.2933,-121.8473&sll=37.341132,-121.643070

Here is the location and trail in Google Earth:

I've hiked this trail before, but not the off-trail part. If anyone is interested, I'll check it out beforehand.

There's an even easier setup the night before, Sunday Nov 10. The shot would be from right off Skyline in the Long Ridge area. The moon is 97.6% lit, and the shot is at 16:35, a half hour before sunset. So the observatory would still be in direct sunlight. Here is the TPE setup:,-122.152554&dt=20191110163500-0800&z=14&spn=0.05,0.09&center=37.2871,-122.1497&sll=37.341132,-121.643070

Email from Bill, 10/29

From the Santa Cruz mountains you are pretty far away from Mt. Hamilton. How long a lens are you planning to use? With my 200mm and the crop factor on my Canon 50D, that is still going to be a small image of the observatory. Is that what you are after? Another option is going to Mt Hamilton Road and getting an upwards looking picture from there. (Attached is an example of the shot without the moon.)

Email from Chip 10/31

You have a great point about the tele. I went back and looked at some shots I took a few years ago from the hills above Los Gatos, this one is at 400mm full frame (200 with 2x converter). Yeah it's a lot smaller than I remembered it. I have a 500mm lens now and would use the doubler, but it would still be relatively small. Nice big moon though.

Email from Chip 10/31

Hey Bill,

Yes, there are several more setups along Mt Hamilton Rd and in Grant's Ranch park. Because of the elevation of the shots (we'd be looking up), the shot time is somewhat later, and the moon would probably be less orange because it is higher.

Moon ephemeris and geographic data below are mostly from TPE ( Their elevation data does not have as much resolution as I'm giving it credit for, which will lead to some errors in the ideal time and azimuth for the shot. The shot time has to account for the elevation angle between the shooting location and the target (the observatory). The moon moves relatively quickly toward the south as it rises so the shot time affects the azimuth quite a bit. A flat location with room to move north-south will have less error and be easier to correct.

For comparison, my first idea of the shot from the Castle Rock area has an angle of elevation of 0.42 degrees. The moon's radius is 0.26 degrees, so ideally we want the moon to have risen 0.42+0.26 or 0.68 degrees above the horizon to be centered behind the observatory. This occurs a little after 17:03 at an azimuth of 76.0. This distance, as you pointed out, is quite far, 42km. The observatory building is 85m long (the dome plus the flat part). The dome itself is about 24m. At that distance it has an arc of 0.116 degrees if my rusty trig is correct (asin or atan of 85/42000), or only about 20% of the diameter of the moon. I still think that would be cool but my 500mm lens has a horizontal FOV of 4.1 degrees or 2.06 with 2x. The observatory will occupy 5.6% of the horizontal. My 5DIII sensor provides 5760 horizontal pixels so the observatory would be only 324 pixels wide. So maybe not.

I worked on several alternatives. The first two are interesting, the last two don't work.

Grant's Ranch #1 (Hall's Valley Rd).

6.6km from the observatory. Angle of elevation to the observatory is 6.59 degrees. The ideal elevation for the moon is about 6.84 degrees above the horizon, which occurs at 17:35 at an azimuth of 80.8
At this distance the observatory building occupies 0.74 degrees and the dome itself 0.21 degrees. With the 500mm lens, the building occupies 18% of the width of the frame, or 1040 pixels. Usable but not great. With a 2x doubler it's pretty good. But do you only have a 200?,-121.716545&dt=20191111173600-0800&z=18&spn=0.00,0.01&center=37.3316,-121.7162&sll=37.341132,-121.643070
This should be a very easy spot to shoot from, just off the road near Hall's Valley campground, with some room to adjust north-south. I would need to check vegetation first.

Grant's Ranch #2 (Canada de Pala Trail).

3.6km from the observatory, angle of elevation 7.85 degrees. Ideal elevation for the moon is 8.1 degrees above the horizon which occurs at 17:42, azimuth 81.8.
The observatory building occupies 1.35 degrees at this distance, the dome 0.38. The 0.52 degree diameter of the moon would be smaller than the building but still larger than the dome. This could be a great shot, but there is more risk that if the azimuth is slightly wrong it won't line up.
With the 500mm lens, the building occupies 33% of the frame width, or about 1900px. I wouldn't use my doubler here. If you shoot Canon I could lend it to you.,-121.682245&dt=20191111174200-0800&z=16&spn=0.01,0.03&center=37.3355,-121.6814&sll=37.341132,-121.643070
This is a relatively easy location, accessible via a well maintained trail 1km from a parking area. It is officially closed at sunset (17:00), however, and the parking area does have gates. Parking on the road here may invite a ticket, I don't know. I like this spot so I may inquire whether I can get permission.

Mt Hamilton Rd #1.

835m from observatory, angle of elevation 11.95 degrees, ideal moon elevation 12.21 degrees, occurs at 18:03, azimuth 84.8.

This close, the dome itself occupies 1.64 degrees, the building 5.85, both much larger than the moon. I don't think this works.,-121.652249&dt=20191111180200-0800&z=18&spn=0.00,0.01&center=37.3404,-121.6532&sll=37.341132,-121.643070

There are turnouts right here, but then we'd be crossing a barbed wire fence to climb a little hill. The fence may be broken right here.

Mt Hamilton Rd #2.

425m from observatory, angle 18.35 degrees, ideal moon elevation 18.61, occurs 18:36, azimuth 89.5.

This is a non-starter because it is too close. The moon will be tiny.,-121.647628&dt=20191111183600-0800&z=19&spn=0.00,0.00&center=37.3410,-121.6483&sll=37.341132,-121.643070

There is a turnout right here, then we climb a little hill. Doesn't appear to be fenced.

Email from Bill, 11/2

Okay I did a little research today. Attached you will find a couple of doctored up photos showing the observatory today plus old moon images. I wanted to see how big the observatory would be in both places you listed using my equipment (my Canon 50D with 1.6 crop sensor).

The first one, with the fuller moon, is at the Grant Ranch entrance (I didn’t go in because I would have had to pay), and was done with my 300mm lens (a not-very-good 70-300 kit lens). It fills the image well enough. I added an old moon image using the 300mm lens to show the relative sizes.

The second one, at the other parking lot and 15 minutes up the trail, I used my 200mm lens and superimposed an old partial moon also at 200 mm. Again the observatory fills the image well enough, but you can see the moon image is smaller relative to the size of the observatory. There is plenty of room to move left and right to accommodate where the moon might actually rise.

So I guess it depends on what you want to get. The observatory is at the same angle and looks pretty much the same in both photos. So if you are after the orange color, then you might want to go back to your original plan from the Santa Cruz mountains where you will get a lower angle and therefore more color. With your 500mm + doubler, you will get a nice large moon and the observatory might be big enough for you.

I am thinking that for me, I would prefer to use my 200mm lens and therefore want to get closer to the observatory. Also given the sunset time issue (having to leave the park), I may want to go a day or two earlier and get a mostly full moon in more daylight.

Email from Bill 11/4

I have been trying to figure out what to do. I called the park and they said the park does close at sundown although there “may” be a half hour grace period before they lock the upper gate and issue citations. (They also said some nights the rangers don’t actually get there.) Looking at the timing for Sunday night, it seems risky. The moonrise is at 16:26 and sunset is 17:00 so that seems good, but we need to wait until the moon rises a bit, take some photos, then hoof it back to the parking lot. It may be a 20 minute hike back to the parking lot. It doesn’t seem possible to get back before 5:15. If there really is a half hour grace period, then all is good.

So I guess after all my pondering, I think the safest thing for me is to go on Saturday the 9th. Then the moon rises at 3:59. I can easily get my shots and be back at the parking lot before 5:00. Unfortunately I have to hike further, the moon is not as full (93.7%), and it won’t be orange, but I don’t have to worry about closing time.

I think your idea about camping is the way to go, but I don’t want to go overnight.

P.S. Attached is a picture I took on the other side of the valley at Mt. Umunhum with a crescent moon.

Email from Chip 11/4

I appreciate the dilemma for Sunday night. With a little more advance planning we might get a special Park Use Permit which might solve the problem, but I'm doubtful there is enough time now.

If you do want to shoot Monday from Hall's Valley (site #1), you could join me and then head out afterwards -- the main gate only closes for people entering, but the exit lane is still open (with 1-way tire spikes). You'd be welcome to stay of course, but I understand wanting to get back.

Another option is in Hall's Valley on Sunday night, just north of site #1 at 17:07. This would avoid the possible ticket and would get you home sooner. It's a long shot for your 200, but I could let you use my 2x and just shoot with the 500.,-121.717795&dt=20191110170700-0800&z=17&spn=0.01,0.01&center=37.3367,-121.7165&sll=37.341132,-121.643070

Email from Bill, 11/10

Bill emailed his results from shooting last night (Saturday) with the following "lessons learned:

  • I wasn’t in the right place. When the moon appears I had to run a ways to get to the spot I wanted. Even then I didn’t quite get the angle I wanted. Be ready to move!
  • The observatory is orange but the moon is white. I guess that’s the smoke being low in the valley.
  • Due to the angle of the shot, it wasn’t until 45 minutes after “moonrise” that I got the shot. So don’t bother to go on the trail tomorrow as you won’t get see the moon before sunset. Speaking of which…
  • I got to meet the ranger at my car since I didn’t get back until 5:15. I didn’t get a ticket, but she might not be as nice next time. (And yes, they do lock the parking lot.)
  • Based on my timeline, tomorrow should be good from your campsite, but Monday may be too late to get any light on the observatory. Perhaps a silhouette only?

Shot Planning Spreadsheet

I made a spreadsheet to help with my shot planning. I was mostly looking for a way to use more precise elevation data than TPE. It also automates some of the other calculations I was doing. 

The primary inputs can be captured using Google Earth, from the URL when centered and zoomed on the points.  The property editor can also be used: use 2D mode, center it on the point, and zoom in.

  • Subject Location and Elevation, 
  • Shooting Location and Elevation
There are optional inputs for subject size, lens focal length and crop factor, and camera sensor width.

Given the locations and elevations, the sheet computes
  • Bearing to subject (degrees)
  • Actual range to subject (kilometers)
  • Angle of elevation (degrees)
  • Apparent subject size (degrees)
  • Lens angle of view (degrees)
  • Relative subject size (percent of frame and pixels)

Final Shot Planning

Sunday Night 2019-11-10

Nominal Moonrise: 16:26 at 81.0 degrees.
I used to TPE to determine a shot location just off Grant Rd near the first bathroom. The TPE parameters are
  • Sunset 17:00
  • Shot time 17:06
  • Moon: 86.7, +7.0
  • shot location + 472 m | 37.3377°N 121.7186°W
  • subject (dome): 86.69, +6.79
Checking the locations using Google Earth I determined:
And my spreadsheet then computes:
Bearing to subject86.698degrees
Horizontal Range6.690kilometers
Actual Range to subject6.738kilometers
Angle of Elevation6.894degrees
Apparent subject size0.204degrees
Lens Angle of View2.062degrees
Relative subject size:
Percent of frame9.9%
Sensor pixels569.944pixels

Comparing to TPE this is spot on in bearing, as I had hoped and expected. The angle of elevation is 0.1 degree higher. The ideal moon elevation is +7.15 , which makes my ideal shot time a little closer to 17:07. At 17:07 the moon azimuth is 86.8, indicating a small adjustment northward.

Here's my final TPE setup. The location is 37.33782131,-121.71885617,478.36830055.

Monday Night 2019-11-11

In the original TPE setup for this I have
  • Sunset 16:59
  • Shot time 17:35
  • Moon: 80.8, +6.8
  • Location + 509 m | 37.3315°N 121.7165°W
  • Subject (dome): 80.66, +6.59
From Google Earth I'm using:
  • Subject (dome): 37.34110674,-121.64305876,1285.25634598
  • Monday night shot location: 37.33156539,-121.71649342,510.55247654
My spreadsheet computes:

Bearing to subject80.697degrees
Horizontal Range6.578kilometers
Actual Range to subject6.624kilometers
Angle of Elevation6.716degrees
Apparent subject size0.208degrees
Lens Angle of View2.062degrees
Relative subject size:
Percent of frame10.1%
Sensor pixels579.781pixels

Again, the bearing is fine but TPE gave me an angle of elevation 0.12 lower than my calcs using Earth data. Using the Earth elevation of 6.716 to the dome, my ideal shot elevation is 6.98, pusing the shot time back about a minute to just before 17:36.  Moon azimuth is now 81.0, which is small adjustment northward, and I think smack in the middle of campsite #14. It is a small adjustment. Here is the final TPE setup. The location is
  • 37.33174796,-121.71663604,510.51296615

Other Shots 

I looked into doing a sunrise shoot, but the sunrise Sunday at 6:40 is at azimuth 111, much further south than the moon.  So to get an alignment with the dome one must get much further north.  There is a shot about 4km up the Canada de Pala trail at 7:15 (TPE setup link).  There's only about 40m altitude gain difference from the parking lot, but it involves some up and down. I'm sure it would take me at least an hour to hike carrying my bag, maybe 90 minutes. And there are questions about parking before sunrise. Sunrise Monday is essentially the same.

This would be a good shot for using an electric bike!!

I browsed around on the web, besides weddings, the main shots are landscapes of rolling hills, shots around the lake, and wildlife including bobcats and boar, and the historic Grant home.


Grant Ranch


These go into my Shot-Planning Spreadsheet.


No comments:

Post a Comment