Zenith Tech Summary

About Zenith

This is a real time view of the stars above you right now. The stars move faster than you’ve seen before because the view is zoomed in. Zooming in not only makes things look bigger, it also makes motion appear faster. This is not time lapse, or sped up. The motion you see is only due to the earth’s rotation.

If you’ve ever tracked something moving on a map, like a delivery, you may have zoomed in to get detail of its motion.

(h/t Max Harms for the uber map idea)

Zooming in gives more detail and faster motion, but shows less surrounding context.

Photography and computer displays use the term “zoom”. With telescopes it’s “Field of View” or “magnification”. It’s the same concept. Tiny field of view = higher magnification = zoomed in. The magnification is about 180x

The goal of this project: zoom in enough so that the amount a star moves in 30 seconds would span the screen, this would make the turning of the earth visible. Therefore I defined the field of view as the amount the sky turns in 30 seconds.

That Field of view turns out to be a patch of sky the size of a grain of rice, held at arm’s length.

Q : If objects under high magnification move due to the Earth’s rotation, then how do Astronomers look at stars without them wandering out of view?

A : Those telescopes have a precise motorized system, called an Equatorial Mount which turns the telescope in the opposite direction to the earth’s rotation, to counteract that apparent motion, maintaining the position of objects in the field of view.

A View from space (click to explore a 3D model)

This animation demonstrates earth’s rotation and your zenith point sweeping a path across the celestial sphere.

Q : Why did the website request to know my location, and what do you do with that information?

A : It asks in order to show the sky over your particular location. That information never leaves your computer. We (smorgasb.org) never see it. You can decline, and it will default to showing the the view overhead Stonehenge. Depending on your device’s settings, the location request itself may be suppressed - ie, your browser may not offer the option of sharing your location.

Q : What are the grid lines?

A : They are the coordinate grid on the “Celestial Globe” (see the interactive model above), and are 0.5 arcminutes per side. Just like latitude & longitude on earth, the RA lines (longitude) get closer, the farther north you go, and the Declination lines (latitude) have a constant height.

About Your Personal Ribbon

ZenithTrack shows a strip of the sky, a thin ribbon, one rice-grain tall, about 2,500 rice-grains long. It repeats every sidereal day, (23 hours 56 minutes). It repeats exactly, and doesn’t change with the seasons. You share this view with everyone else on earth at your exact latitude. People due east or west of you get the same movie, but starting at a different time.

This viewport is so slim that it is completely different for someone just 5 miles north or south of you. They get a completely different ribbon.

People north/south of you : different movie

People due east/west of you : same movie, different times

What are the images?

Zenith displays images taken by the Pan-STARRS telescope in Hawaii. We use image from the Pan-STARRS1 data set, collected from 2010 - 2014. This remains the most current astronomical survey which fulfills our requirements of coverage and resolution.

The images are hosted at the MAST archive at Space Telescope Science Institute(STScI). Your device connects directly to STScI to receive images. They are not hosted on this site.

Space Telescope Science Institute

Special thanks to the STScI help desk at for their superb and prompt support!

Why that particular telescope and survey?

Making earth’s rotation visible requires a field of view on the order of arcminutes. For a browser window ~1k pixels wide, PanSTARRS meets this critical need with a resolution of 0.26 arcseconds/pixel.

1000px x 0.26”/px = 260” = 4.33’

PanSTARRS makes this observatory feasible with the necessary:

resolution

broad sky coverage

of visible light

That said, it’s not the ideal image set for our purpose. While it has the resolution and coverage, PanSTARRs’ primary mission was moving object detection (near-earth asteroids, etc.) and deep field sensitivity, not providing presentable images of known stars. Hence one tradeoff is frequent oversaturation. Any major star blows out the sensor and shows color distortions. See below.

Object names: SIMBAD database

https://simbad.cds.unistra.fr/simbad/

The SIMBAD astronomical database provides basic data, cross-identifications, bibliography and measurements for astronomical objects outside the solar system.

We query SIMBAD for objects based on the current field of view. Zoomed in this deep, it’s all obscure. Getting the Horsehead Nebula will be like winning the lottery.

Tiling & Overlays - leaflet.js.

Leaflet is typically used for interactive (Earth)...