Arch Rock, Joshua Tree National Park, CA, June 7, 2018

For having visited Joshua Tree as often as I have, I somehow managed never to make it to Arch Rock. Arch Rock, as the name implies, is a rock arch. Unlike most arches (that I am aware of), this one is composed of granite. However, for whatever reason, Joshua Tree granites are often pretty crumbly, which is, I assume, how this arch formed.

Just a few weeks ago, I came across a Milky Way shot with Arch Rock, and decided that I would have to not only visit this place, but visit it at night, with the summer Milky Way as a backdrop. This last weekend was going to be my chance: I was coming to the area for some astronomy outreach at Sky's the Limit, a private observatory just outside the North Entrance to Joshua Tree National Park (literally, just outside, as it is surrounded on two sides by the park boundary). I could then drive up here after the event.

Of course, I wanted to see the place in daylight, first to make sure my plan was feasible.

The trailhead for Arch Rock is within White Tanks campground. It's a small, 15-site campsite, with vault toilets but no running water, and no ability to make advanced reservations. Well since I couldn't guarantee myself a spot there, I had to reserve a motel room. The Motel 6 in Twentynine Palms was my choice, as it's relatively cheap, and quite close to the North Entrance.

So I checked into my motel room in the mid-afternoon, after coming through a brief but tremendous downpour, that had mud and standing water across parts of Highway 62. Drove to the campground, which is on Pinto Basin Road. From the North Entrance, you drive about five miles, then make a left at the road that goes all the way to Cottonwood Springs, and I-10. But you only need to drive a little over 2 1/2 miles to get there. You'll pass Belle Campground on your left, first. Then there's Twin Tanks backcountry trailhead, on your right. A half mile after that, White Tanks Campground is on your left.

If it's between 7am and 10pm, you can drive into the campsite and park as a day user in a small lot across from the trailhead, which is near site #9. Otherwise, you should park off, but adjacent to, the main road, at the entrance to the highway. There's room for a few cars just east of the turnoff, and room for several more cars a bit further east. Alternatively, it's only about 1/2 mile past the large, paved lot that's at the Twin Tanks backcountry trailhead.

From the trailhead, it's an easy 1/2 mile to the arch. Take care to stay on the actual trail, as use trails cut all over the area, and the desert is slow to heal from these detours.

At the arch, I took a few cell phone shots from both sides of the arch, then launched my planetarium app (Sky Safari 5 Premium) so I could see where the Milky Way would be later that night. I determined that, yes, I could manage a shot of some interest later that night.

Came back around 10:30pm, parked outside the campground and walked in, then took about 30 shots around the arch, mostly from just a few vantage points, but with a couple of different lenses and different ISO and exposure times. The fastest ISO I used was 6400, which looks okay at laptop computer screen size, but shows significant grain very quickly, if you zoom in. With very wide angle lenses, I shot between 15 and 30 seconds. Again, at computer-screen sizes, even up to 30 seconds with the Tokina 11-20mm zoom shows pretty sharp, untrailed stars. With the 14mm Sigma, I shot only up to 20 seconds.

I wore a cheap headlamp to light the way during my walk, and the red light function of the headlamp, handheld, to quickly "paint" the arch for foreground illumination in some of the pictures.