Here's how to spot Comet Nishimura before it's off for an over 400-year trip

SAN FRANCISCO — A fast-moving comet streaking through the predawn skies of the Northern Hemisphere will be gone by early Tuesday morning, but there is only a brief window of time when it'll be best spotted.

Discovered on Aug. 12 by Japanese amateur Hideo Nishimura, the comet's closest approach to Earth will be on Sept. 12; it will then carry on toward the sun.

Reaching perihelion on Sept. 17, it will never get closer than 78 million miles — too far away for it to be anything other than tough-to-spot but rewarding for astronomy enthusiasts.

The best chance to get a look at it will be during the 90 minutes before sunrise Monday morning.

The best sky charts to locate it Monday morning are available at skyandtelescope.com or astronomy.com. 

But those interested enough to search for a sky chart will know they are out of luck if they are not out in the country, under clear skies with an unobstructed view to the east-northeast, and before the colors of dawn begin to brighten the sky. 

Although, being away from the lights is not necessary. Generally, it's in Leo, and it will only be a few finger-widths above the horizon. 

It is a marginal naked-eye object, but binoculars will help in the endeavor to spot it. If you detect a greenish glow, that's a carbon signature.

After swinging around the sun — if it's not torn apart by the close encounter — it'll only be visible from the Southern Hemisphere later in the month.

So catch it while you can if you're a hardy soul. And if you have clear skies near the Bay Area far removed from city lights, don't forget to invite us all.

Or wait for the next time it comes around circa 2458. What an interesting world it will cast its glow upon then.