Proposal

The goal of this tag is to allow for the mapping of good astronomy viewing sites. These are tracked in a very decentralized way, at the moment. Clear Dark Sky is probably the largest repository of viewing sites in the US. I am told that DarkSkyDiscovery.org.uk serves a similar function in the UK.

This is distinguished from man_made = observatory in that it does not involve permanent viewing infrastructure. Rather, it is a site for amateur astronomers to use by bringing a mobile telescope. This does not necessarily preclude it from having amenities such as toilets, however.

Rationale

This is a type of POI which has relatively little tracking online. No other map provider tracks these, and what repositories exist are fairly decentralized. Allowing them to be tagged on OpenStreetMap gives users a convenient way to discover new sites and navigate to them, and additionally might bring new viewing sites to light as people attempt to use this tag.

Verifiability

Because this could have some amount of subjectivity, I propose using the following test to determine if the site is eligible for the tag. Note that it assumes good weather, so that you can actually see the sky clearly.

The site must be accessible by car (minimum walk ~5 minutes) The site must be roughly flat, such that it could accommodate a tripod easily There must be at least a 90-degree horizontal view of the sky, preferably towards the equator when at higher latitudes You must be able to see from the zenith (straight up) to 20-degrees up from the horizon in the above area One of the following must be true: Light pollution yields a 5 or better on the Bortle scale (approx: 19 mag/arcsec 2 or 2.5 mcd/m 2 )

or 2.5 mcd/m ) You can see unaided an object of magnitude 5 or dimmer (ex: M22, M52, Orion Nebula, M41, NGC 6025, Vesta (max), Uranus (max))

It is my belief that with this test in place we can have greater verifiability than with several other tags, such as tourism = viewpoint without names or tourism = camp_site s that are both impromptu and backcountry.

The process of making these measurements can be aided by apps like Loss of the Night (also on iOS) or SkyMap (open source, doesn't list magnitudes).

Measurements taken on different scales can be converted using this handy chart.

Note

One could make a pretty good argument to lower the visible brightness requirement to 5.5 magnitude, but I could find very few examples that would be easily located.

Equivalency

The light pollution test is two-pronged because there are numerous sources of light pollution data already published. I am unsure on the copyright status of these, and whether they are eligible to use as a source for OpenStreetMap, but it seems reasonable to assume that there will be a future database which is eligible, even if the current ones are not.

Examples

Numerous examples can be found at Clear Dark Sky.

Additionally, there are some existing locations tagged already such as this one in Tennessee , this one in New Mexico, and these two in California.

Tagging

Simple tagging

leisure=star_gazing name=

A new tag is used here because in my opinion this does not fit in the purview of tourism = viewpoint for the following reasons:

While it does indicate a good view, it is generally supposed to be for things on the ground Astronomy is typically not a tourist activity, but a leisure one There is no apparent way to distinguish between a normal viewpoint and an astronomical viewpoint

Even if we used a subset of viewpoint, we would still need to add tags to make it work. I am happy with it if we end up settling on a scheme like

tourism=viewpoint type=astronomy

Advanced tagging

leisure=star_gazing name=Ice House Observation Plateau 1 weather=https://www.cleardarksky.com/c/IHOPCAkey.html access=public|private|customer (defaults to public) fee=no|yes (defaults to no) dark_sky=no|yes (defaults to no) direction= seasonal= ele=

Directions here should be tagged as in tourism = viewpoint

The rationale on weather is that many of these viewing sites have associated astronomical weather tracking, including specialized conditions which affect the quality of images that you could take. This way if someone discovers the site via OpenStreetMap, they can see whether it is worth going to the site.

It is a similar story with directions. If you only have certain fields of view, having a rough idea of what that is will tell you whether you can see any astronomical objects you might be interested in.

The dark_sky tag should indicate that a site is in a Dark Sky Park.

Potential Conflicts with Campsites

Many observation sites are also campsites. It is my impression that none of the tags here overlap except fee. If there is a fee to camp, but not to stargaze (or vice versa), you should use the syntax:

fee=yes (campsite value) fee:conditional=no @ star_gazing

If you are not tagging it in tandem with another object type, fee should refer to the observation site, and there should not be a conflicting interpretation. Either way, it is probably preferable to tag them as separate areas, because it is unlikely that the whole of a campsite will be a good observation site, and it takes the burden off of parsers if you tag them separately.

Future Work

Some work is needed to come up with a tagging scheme that includes Dark Sky Parks. That could be done here, but it seems more reasonable to have that as a separate proposal.

Rendering

This should be rendered using a telescope icon which could not easily be confused with the observatory icon.

Please comment on the discussion page.