The web-browser version of Google Sky has gone live. It’s announced on the official Google Blog, where we learn that it is the the labor of love of Google’s Latin America Code Jam finalist and winter intern Diego Gavinowich, and on on Google Lat-Long Blog, where we find a run-down of the features.

The Good:

Much of Google Sky (web) involves applying the well-honed technology of Google Maps to a new data set: Instead of Map/Satellite/Terrain we get a base dataset plus Infrared/Microwave/Historical, though it comes with a big big new feature that Maps doesn’t have: Opacity sliders! While this isn’t a first (Yahoo Maps came out with layer opacity sliders last September) it makes absolute sense when playing with wavelengths.

You can blend microwave and infrared imagery over the light layer to your heart’s content… but what about X-ray and ultraviolet wavelengths? These are part of another new feature: a strip along the bottom of the screen that contains collections, “showcases” of smaller, detailed overlays of objects (as opposed to the whole-sky layers for microwave and infrared). These collections roughly correspond to the default layers available as overlays in Google Sky (app), but what’s really nice is that each object gets a little preview image that is good enough for you to recognize and choose favorites. Just as with the standalone application, the web version lets you change the opacity here too (where applicable.)

In fact, the web version’s ability to show infrared data by default improves on the standalone application, where you’ll need to add infrared data through a network link developed independently by Robert Simpson at Orbiting Frog. Oops, in fact Google Sky (app) now shows this layer, and also a layer called Sky Community, where user-contributed placemarks are visible.

Finally, just as with Google Maps, you can paste a subset of KML files into the search text box, and display the file. There isn’t much eligible KLM out there yet, so feel free to use this outline I made in Google Sky (app) of a recently created constellation and saved as a KMZ… Ah, the wonders of user-generated content.

The Bad:

Unlike Google Maps, where labels are part of an image tile, Google Sky (web) only places icons n the viewer. All text is found in popups. This becomes a bit awkward when you turn on the constellation collection and get balloons that serve as labels for constellations — you have to click on a balloon to see its name in a popup, which is much less useful than just giving us the name.

By the same token, there is no layer showing constellation boundaries or a layer for grid lines — without these, I have trouble placing myself in the sky, both in terms of orientation and scale. I don’t know why such layers are not available, but I’ll hazard a guess: In the standalone Google Sky, these grid lines are vectors; on the web these would have to become image overlays (much as the labels overlay in Google Maps), and with the addition of several new opacity layers, I suspect it becomes a technical limitation.

The Ugly:

Another technical limitation inherited from Google Maps: No sky near the poles! Instead, you get “sky substitute”:-)

There is another new feature in Google Sky (web): A collection of podcasts about the sky from Earth & Sky. They are indeed entertaining, but they are embedded in popups that are referenced to random coordinates in the sky. In that case, I’d rather just listen to them in a non sky-referenced manner — especially as you’ll break off the podcast mid-sentence if you start panning the sky while listening. That’s a usability no-no.

(And another peeve: The sky imagery on the web is watermarked, which it isn’t in the standalone app. When meditating on the immensity of the universe while staring at the Sombrero Galaxy, it jars a little, even though I know why the watermarking is necessary.)

In Sum:

Of course, now I’m feeling ungenerous, critiquing a programming tour de force that is completely free. Still, we need to compare it to Microsoft’s free Worldwide Telescope, the Windows standalone app due out by the (northern) summer (and also to Sky-Map.org, the incumbent web-based sky imagery viewer.)

Pros:

• Platform agnostic — a true universal sky browser usable on billions of browsers (is it billions yet?) (same for Sky-Map.org)
• Unlike Worldwide Telescope, it is available now, not later (same for Sky-Map.org)
• Easy to add user generated content via KML (unlike Sky-Map.org)
• Permalinked URLs for Sky locations (same for Sky-Map.org)

Cons:

• No smooth zooming (same for Sky-Map.org)
• No touring feature (same for Sky-Map.org — Google Sky (app) has a rudimentary touring feature)
• No polar content (unlike Sky-Map.org)
• Difficult to orient (WWT has a little mini map that indicates what constellation you’re in). (unlike Sky-Map.org, which also has constellation boundaries)

As a result, I think all these sky viewer competitors inhabit slightly different spaces. For Google Sky (web), it’s most convincing feature is its universal accessibility, the permalinkability of specific views and the ease with which you can browse to objects using the gallery strip at the bottom of the screen — if that tool’s learning curve were any flatter, it would be going downhill.