Pacheco State Park, especially Whiskey Flat

[Jamie Dillon, DDK]

Here's a fresh topic thread for Pacheco (with an ahem from the listowner).

Brief history. Peter and I were both Bull Goose Head Gatekeepers at Dinosaur Point, over quite a few years, following Albert Highe who got us down to that lot along the lake in the first place.

Before we started going down the hill to Dino, TACos often observed at Whiskey Flat, by some horse paddocks, to the right before the gate that leads down the hill. There's a sign there saying Pacheco State Park. It was decently dark. No one complained about the lights on the highway. But there were a couple epic nights for dew there, that I missed. Stories of water sloshing off of primary mirrors.

Tony, I guess that was before you started coming around. Brad, you've mentioned observing at Pacheco over the past couple of years, and I've lightly scratched my head over that, because there are several large houses that have been built in the immediate area, since we observed up there. Those people love their floodlights. One night leaving Dinosaur Point about 3 years ago, I counted 14 bright lights on one house  to the right and its outbuildings, off to the right. There are other lit-up houses to the left as you leave; I have no idea what effect they have on Whiskey Flat.

But no permits needed, nor previous permissions nor phonecalls nor nothin'. Ranger Nathan's a good guy, thoughtful of him to suggest Whiskey Flat, to give us an alternative.

[Brad Templeton]

Where I would go was the open parking lot to the left.   Did not get floodlights there, but I have not been for a couple of years, maybe it's more than I remember.   The best darkness is to the south, of course, and in fact this area is the closest Bortle 3 to the south bay -- right on the B4 to B3 border.    It is about the same amount of driving time as the Coe park location, but it is further away from the lights because the driving is all highway.   But it's still an hour each way from my home.

This is the location I've used.  Maybe it's been longer than I remember if those houses to the north are the ones that have put on floodlights.

https://www.google.com/maps/place/Pacheco+State+Park/@37.0652387,-121.2112777,3a,75y,70.22h,81.36t/data=!3m7!1e1!3m5!1ski1L9qeT-s-OcXT9sBlNjg!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D8.644046917385964%26panoid%3Dki1L9qeT-s-OcXT9sBlNjg%26yaw%3D70.2166637131096!7i16384!8i8192!4m6!3m5!1s0x80918562e258762f:0x7726b06f9b9bbe79!8m2!3d37.0650751!4d-121.2116388!16zL20vMGNyZ3cw!5m1!1e2?entry=ttu&g_ep=EgoyMDI1MTEyMy4xIKXMDSoASAFQAw%3D%3D

I did shoot this there in 2020.

[Mark Wagner]

Down the hill at Dino was a pretty good spot, but the access is not free and open.  Problem for some, not for others.  Just needs a few coordinators to step up, Jamie knows who and how.

The thing I didn't like up at Pacheco State Park was noise from the hwy 152 traffic.  I haven't been in many years, but I've also heard the development (homes) created a direct site light issue. It could also be a bathtub.

[KG]

Hi all, happy Turkey day to all. I have been to Dino point few times, but looking at satellite images, is it not possible to drive down towards the Dino windmill farm area by the Mammoth lake - appears open with no houses ? 

GK

Sent from my iPhone -made in China😴

On Nov 27, 2025, at 7:13 AM, Mark Wagner <itsmar...@gmail.com> wrote:

Down the hill at Dino was a pretty good spot, but the access is not free and open.  Problem for some, not for others.  Just needs a few coordinators to step up, Jamie knows who and how.

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[Peter Natscher]

The access road to the windmills is accessible 'after' passing through the main park gate. Not sure if driving to the winmdmills area is even allowed nor what horizons that area offers.  The park's main gate closes and is locked at sunset.  It is not an automatic gate that will allow an exit after sunset.  Gate reopens the next morning.

[Mark Wagner]

The supervising ranger (Dooley) at the time I used Pacheco took me and Rich Neuschaefer for a Jeep ride back there.  He said (IIRC) we could get permission.  I found it unacceptable, the towers were so obtrusive and terrain not great.  But that's 25 years ago I'd guess.

Mark

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[Jamie Dillon, DDK]

About Dinosaur Point, Mark was all -

"Just needs a few coordinators to step up, Jamie knows who and how."

That's past tense. What Ranger Nathan was politely telling Peter was that we can forget nighttime access to Dino. No gate mojo, as Turley would say.

[Mark Wagner]

Jamie - too bad.  I don't subscribe to all the TAC emails so I missed that.

Perhaps it's possible at PSP.  I camped there a few times observing.

Another site bites the dust.  Guaco and the other free range spots look even more valued.

Mark

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[Brad Templeton]

As noted, this area has the virtue of being the closest (by drive time) Bortle 3, similar drive time to Coe.     As such, I've been wondering about all the other locations around there.    For example, there is an adjacent area which appears to have no gates, and while it does have some houses, there appear to be some lots that are either vacant, or might be public land or otherwise usable from the side of roads.   That includes places like this pond area, which if you look at the property lines is just an empty parcel

https://www.google.com/maps/place/37%C2%B002'49.2%22N+121%C2%B014'15.3%22W/@37.04701,-121.2387803,666m/data=!3m2!1e3!4b1!4m4!3m3!8m2!3d37.047008!4d-121.237588?entry=ttu&g_ep=EgoyMDI1MTEyMy4xIKXMDSoASAFQAw%3D%3D

I don't know, though, if there are lights from the houses, or people who would be bothered by astronomers doing late night sessions. 

On the other hand there are various roads which are gated but lead to public land where it might be possible to beg somebody for a gate code or lock.    For example, Pacheo lake reservoir has a gate, and is owned by the water district, but who knows, maybe they would be friendly?    Perhaps access to Kaiser Aetna road (health insurance road?) which goes to the southern visitor center of Henry Coe park (which is only open rarely) could be used, though there isn't a great pull off spot, other than the visitor center parking which is a fair bit of drive (removing the benefit of the short highway drive.)    That visitor center is normally only open in spring and the road is closed in wet season.

[Steve Gottlieb]

Here’s the 2022 Light Pollution Map showing Light Green (Bortle 3 starts at Blue): https://www.cleardarksky.com/lp/Dino_CAlp.html?Mn=CCD

Steve

[Aris Pope]

Brad that's a nice capture of Neowise. 

Aris

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[Brad Templeton]

Yeah, maps differ in their estimates.  On the map at https://www.lightpollutionmap.info/#zoom=14.20&lat=37.0747&lon=-121.1780&state=eyJiYXNlbWFwIjoiTGF5ZXJCaW5nUm9hZCIsIm92ZXJsYXkiOiJ3YV8yMDE1Iiwib3ZlcmxheWNvbG9yIjpmYWxzZSwib3ZlcmxheW9wYWNpdHkiOiI2MCIsImZlYXR1cmVzb3BhY2l0eSI6Ijg1In0= it's right on the 3-4 border, but more to the point, if you look at the SQM or total brightness estimates, this is darker than Coe, and about the same driving time, which is why it's interesting.   If matters where your targets are.   Coe sucks to the west, Dino is not great to the east, but really good to the south.    It's clear from the bigger map that this is the darkest place within an hour.   Pacines is the darkest at about 1:15 from me, Panoche and Big Sur are darker but farther.      An hour is pushing the limit for where you want to go for an evening trip to return home, with over 2 hours round trip driving.    Otherwise half an hour can get to the top of Page Mill or to Oak Ridge.      Indeed, the winner, if we could find it, would be a spot near 17 and Skyline, not because that's the darkest sky around but because you can be there really fast up 17 if it's not too far from that bridge.  Used to have a friend with a house up there.   I found an empty lot up there which was promising but they put a chain over the entrance, though I've debated asking the owner.   There are darker skies, but Pinnacles (even when they were nice) is too far from the south bay.