• Dale Hill

Towers and Telescopes

Updated: May 9

Date: May 1, 2021

Distance: 16.64 miles

Total Elapsed Time: 11h 24m

Total Moving Time: 8h 44m

Summit Elevation: 5,709 feet

Elevation Gain: 5,147 feet

Trailhead: Mt Wilson Trail, Sierra Madre

Previous Ascents:

  1. March 18, 2021 (Observatory gate locked, Elev 5,671 ft)

  2. March 15, 2020

Notes: Peakbagger Peaks - 2

  • Mount Harvard (1st Summit)

  • Mount Wilson

Survey Marks - 12 (4 previously observed)


Challenge Check-in


I have been systematically tackling the remaining peaks on the SoCal Six-Pack of Peaks Challenge, last Saturday I hiked Mount San Jacinto as #8 on the list of 11 (San Bernardino Peak is still closed due to last year's fires). Today's hike to Mount Wilson checks off Peak #9.

Mt. Wilson Summit Recap


The last time I was on the Observatory grounds was March 15th last year, I did the loop trail up from Chantry Flats, Sturtevant Trail, and back down the Upper Winter Creek Trail, the weather was challenging with a cold rain most of the day. The fog at the summit limited visibility dramatically, so much so, that I had a difficult time locating the trailhead because I could only see 10 to 20 feet in front of me!


When I hiked Jones and Hastings Peaks this past March, I made it all the way up to the front gate of the Observatory via the Mt Wilson Toll Road, but the grounds were closed due to the pandemic AND were still included in the Bobcat Wildfire Closure order. My plan to recover the survey marks I had missed (or wasn't aware of) in 2020 would have to wait.


Today's weather conditions were absolutely perfect, bright and sunny, mild to warm temperatures and light winds. I started out on the Mt. Wilson Trail a little after 0600 with the objective of bagging the peak at Mount Harvard on my way up to Wilson to search for survey marks.


Historical Plaque Recognizing Nobel Scientist Albert Michelson for Measuring the Speed of Light

Since I had just hiked this trail in March, I didn't spend a lot of time stopping to take pictures, I wanted to make sure I had ample time to wander around the summit and find the marks on my list. However about 4.7 miles into the trail, at 3,840 feet elevation, the trail was blocked by some recent rockfall and blowdown. I had watched a couple ahead of me trying to navigate through the fallen tree and it looked like they were about ready to turn around, then they made it through. When I reached the site, the trail was completely covered so I spent about 15 minutes clearing all the rocks and tree debris that I could move by myself, clearing a path up around the broken tree trunk. It wasn't perfect because there was just some stuff that was too big for me to handle by myself 🤷🏻‍♂️, but I did make the trail more obvious and a little safer to navigate through.


Mount Harvard - 5,441 Feet Elevation


Moving on, I reached the trail junction where I'd turn and head up to Mount Harvard right at 1000. I'd covered 6.7 miles in 3h 49m, even with the brief delay to clean up the trail. I only had 3/10ths of a mile to the summit of Mount Harvard, and fortunately, both sets of gates were open.

Mount Harvard is a communications tower site with all sorts of different types of towers. I was hoping to locate a survey marker quickly and then head over to Mt. Wilson.


The NGS does not list a survey marker on Mount Harvard, nor are there any clear indications on the Topo Map that there is a disc at the summit. I headed to the high point as identified by the Peakbagger App which happened to be underneath the northmost tower on the site. Nothing. I headed to the other end of the site near a single building with a smaller tower and looked around. Nothing. I went back toward the main building, a guy was walking across the pad so I asked him if he was aware of a survey marker on the site. It turns out he was on the original crew that built the building and installed the towers back in 2000, he said he'd never seen a survey mark on the peak.

After chatting with him for a while about the history of the towers, I returned to the small building and looked in the direction of Mount Yale. There were power cables that stretched down the hill behind the building and disappeared over the edge of the mountain, the cables were secured beneath a raised, narrow grated gangplank system and there were cables and ropes along the side. Wondering if the mark was on the little hill below the tower, I used the ropes to get down to the saddle, then up the other side.


Of course, there was no mark 🙄, but I did get a good look at the route down to Yale and decided IF I ever go back to recover the Yale survey mark, it will be an approach from the South! Retracing my steps using the rope and cable as needed, I covered the short distance back up to the road and headed down to the junction of the Mt Wilson Trail.


On Your Mark, Get Set, GO!


Prior to March's trip, I had loaded all the survey marks on Mount Wilson into my GAIA GPS by dropping pins at their known (or expected) location and transferred my notes to the app, I was ready but the mountain wasn't. Today once I hit the lower parking lot I went straight to work.



Wilson Memorial

Last year I found two marks in the Southeast corner of the parking lot very close to the monument to the memory of the mountain's namesake, pioneer trapper, and settler, Benjamin Davis Wilson. One was an L.A. County Survey Control System Triangulation disc (PID: EW7221) and the other was a Horizontal Control Mark.


I took advantage of the good weather today to update my photos of the Triangulation Station disc. I probably should have updated the TLRS-90 picture too and maybe added some chalk to call out the letters better, but it really wasn't on my radar (maybe next time I'm up there). Here are the two that I recovered last year:

Unbeknownst to me at the time, the Mount Wilson E 10A station had a reference mark located 75 feet to the WNW along the edge of the gravel parking area, in an iron pipe well, with a cover stamped County Engineer Monument. Looking at my GPS track from last year, I almost walked right over this cover, I passed within two feet of it! As I may have already mentioned, it was raining and extremely foggy, visibility was next to zero, and at the time, I didn't know to look for marks hidden under these mini-manhole covers. Today, it was a simple recovery.


I spent all of 15 minutes in the lower parking lot prepping the disc and getting my photos, since it was right before noon, I headed up to the Pavillion to have lunch before continuing on with the rest of my recoveries.


Compass Inlay at the Pavillion

The Observatory grounds were still closed, that included ALL the facilities too, most notably, the restrooms and the Cosmic Cafe. I had packed an ample lunch, but I was hoping on the outside chance that the Cafe would be open as I've never eaten there. I settled for my own picnic table in the North corner of the Pavillion, the closest table to the water bottle refill station (which was turned on and provided reasonably cold water!) The restrooms being closed was an annoyance. If you're heading up there while everything is still closed, just plan your "nature breaks" accordingly.

Several picnic tables were spaced out around the perimeter of the Pavillion and there were a couple of other groups there when I arrived and people came and went as I ate. This was kind of a luxury lunch for me since it was in a covered Pavillion, with a smooth concrete floor, and a water station nearby. I just kicked back and spent an hour there 😂... I took my boots off, changed into a dry shirt, and leisurely ate my lunch.


Telescopes Galore!


The self-guided tour map identifies 15 different telescopes on the mountain top (however, there are a few more that aren't listed): 3 solar telescopes, 6 optical interferometric telescopes in the CHARA (Center for High Angular Resolution Astronomy) Array, 3 that comprise the Infrared Spatial Interferometer (mounted in a truck trailer over by Echo Rock), the Hooker 100-inch telescope, a 60-inch, and a 16-inch telescope!


Last year I went into the viewing area of the 100-inch telescope, to get out of the cold, wind and rain, and to eat my lunch. I remember it well, I had brought a thermos of hot soup and a thermos of coffee, it was a lifesaver that day! The Hooker Telescope is also a survey mark labeled as the Mt Wilson Observatory Dome (PID: EW7225).


Today's new recovery of an Observatory Dome survey mark was the 150-Foot Solar Telescope, listed in the NGS database as the Mt Wilson Carnegie North Observation Tower (PID: EW7223)



The Michelson Station


While researching the NGS Data Explorer for listed survey marks on Mount Wilson, I came across the Michelson Station with its two Reference Marks. The description and recovery comments all indicated that all marks were 'recoverable' and in good condition. The station is located about 260 yards down a road that leads through an area where resident scientists live; the mark sits just north of a 10-inch telescope. As I approached the island that was formed between the road and a driveway to the 10-inch telescope, it was easy to spot the first of three concrete monuments that would hold the survey discs. I stopped at the first monument, Reference Mark 2, to prep it for photos, as I was taking my "view" pictures, I could see a larger concrete pad up the embankment, at first I figured this was where the Station disc was mounted.



When I got up to the pad, the first thing I saw was a rectangle bronze plaque centered in the pad then I noticed a disc centered on the South end of the pad. Still thinking this was the station disc, I went around to examine it closer and realized I just recovered my FIRST Gravity Control Mark! This was stamped "Mt Wilson 1924 1995", once again, I was blown away that after recovering more than 300 survey marks, I am still finding new stuff! Since that wasn't the station, I made a quick scan of the area and easily found the monuments with the station disc and reference mark 1 (both also had witness poles nearby).

The plaque (larger photo at the beginning of this post) commemorates Nobel Scientist (Physics, c1907) Albert A. Michelson and his achievement of measuring the speed of light in 1926 where he shot a beam of light to Lookout Mountain, a lesser ridge on Mount San Antonio, and reflected it back to this site.


Side note: the Gravity Control Mark is set so when you stand at the end of the pier and can read the disc, you're facing North.

I'm still researching the Gravity Control Mark and Gravity Surveys, but according to the NGS, this type of disc started being used around 1979 and is set during gravity surveys. Factory stamped “GRAVITY CONTROL MARK” with a crossed slash in the center, the surveyor would stamp the name and date on the disc before mounting it. Interestingly, this type of mark was usually set indoors flush with the floor. Gravity is measured in units of acceleration and there is highly specialized equipment used to measure it (along with a lot of crazy math!). Precise GPS stations can be operated as gravimeters since they are increasingly measuring three axis positions over time, which, when differentiated twice, give an acceleration signal. Hmmm, so I'm guessing this is how the Gravity Control Mark comes into play.


As I finished up, I took one last look around before heading back up the road when I noticed a cylindrical concrete monument on the West side of the road, perfectly aligned with the Station Disc, well THAT'S a no-brainer! Turns out it was an L.A. County Survey Control System Reference Mark (unstamped) that clearly pointed to the Michelson Station.


This was a jackpot recovery! Five survey marks all in really good condition, plus an unexpected historical monument that precipitated a few hours searching the interwebs and learning about Michelson, measuring the speed of light, and the use of gravity control marks in Gravity Surveys. I've mentioned this many times before, I'm not really a "science" guy, but am always fascinated by the educational directions my recoveries lead me. 🙂


Echo Rock - Trail Closed due to Bobcat Fire


Last year I had hiked up to Mount Wilson on the Sturtevant Trail and Echo Rock was the first part of the summit that I reached, it is located just off the East end of the Observatory Campus (past the Infrared Spatial Interferometers). Coming up the trail through the fog, there's a walkway with pipe railing and some plastic chairs that make up a viewing area at the lookout. Mounted in a concrete monument near the end is a survey mark set by the Los Angeles County Flood Control District...I remember laughing about a mark set by the Flood Control District on top of a mountain 😂 These are my photos from last year...as you can see, not much of a view on that day! If you look closely at the mark, you can make out the name stamped as the innermost line of text at the top.


I had hoped to recover the two Echo Rock reference marks and the Azimuth Mark today, however, this point is located at the terminus of the Sturtevant Trail which is still under the Bobcat Fire Closure order. The entrance to the trail was chained off with multiple warnings not to enter the fire area. These marks will remain on my "to do" list until the closure restrictions are modified or fully lifted.


The Tower Farm


I walked back along the road through the telescopes and museums toward the lower parking lot to pick up the Mt Wilson Trail and head back down. The Northwest end of the summit is where all the towers are located, one, in particular, is registered with the NGS as a survey mark (type: 42-Radio/TV Mast). It was originally the KRCA Tower but is now owned by KNBC and is located in the area known as Mount Alta, the highest point, and the first area to be used as a tower site. There are actually five distinct groups of towers that populate the mountain top, even though from a distance it looks just like one big collection. My "official" photo of the mark was taken from the Mt. Wilson Trail as I was heading down, the other two photos were taken from the lower parking lot not too far from the trailhead.


Wow! The day was everything I had hoped it would be and MORE! I recovered 8 new survey marks and as a byproduct of logging those into my database, learned a lot of cool science stuff that I probably never would have explored otherwise. It was a perfect day for a hike and I met some cool folks on the trail, which is always a good thing 🙂. Heading down the trail, I caught up with a group that I had met early at the summit while I was looking for marks. One of the gentlemen in the group was intrigued by what I had been doing and we had chatted briefly at the summit.



When I reached their group on the trail, he dropped to the back of the group to talk with me so more, we must have talked for 2 or 3 miles! As it turns out he was the leader of their hike, a local resident who organizes frequent hikes with his friends. They were a pretty impressive group, there had to be at least a dozen (maybe more) on today's outing. Since I usually hike solo, I don't always get the chance to meet up with and talk with others on the trail. I love the solitude of solo hiking, but it's never a bad thing to make new friends 😉


Relive® 3D Video of Today's Hike



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