The Blue Snowball

NGC 7662, a planetary nebula in Andromeda

A star like our Sun at the end of its life, puffing its outer layers into space. Its exposed core makes the gas glow; the blue-green is oxygen. The Sun will do this in about 5 billion years.

What you are looking at

The Blue Snowball, with its parts named, a scale bar and north marked

Swipe sideways to see the rest. Tap the picture for full size.

Distance: Roughly 5,700 light-years (not well known)
The shell is: About 0.8 light-years across: 50,000 times the Earth to Sun distance
The light left: Before the pyramids were built
Honest note: Taken before the telescope was refocused, so it is soft

For photographers

The first deep-sky target of the night, shot before the focus was fixed.

Exposures: 25 x 6 s at ISO 1600: 2.5 minutes
Frames: 25 taken, all kept
Sampling: 0.194 arcsec per pixel: the sensor's 0.388 enlarged 2 x by Lanczos. Stars are rings 7 arcsec across: out of focus
Field: 5.0 x 3.3 arcmin, cropped from one sensor frame
When: 3 October 2026, late evening. 84 degrees up, no Moon
Field rotation: 0.5 degrees in 10 minutes, corrected in registration
Calibration: None beyond a fitted sky. No flat, no darks
Stacking: RAW colour planes (no demosaic), hot pixels by 3 x 3 median, registered on stars with rotation, sigma-clipped mean: noise 4.8 times lower than one frame
Finish: Black 26 and white 194 of 255, S-curve 0.2. Saturation x 1.4; dark sky shown without colour and smoothed
Telescope: Celestron 8SE Schmidt-Cassegrain with dew shield: 203 mm aperture, 2,084 mm focal length (measured by plate solve), f/10.3
Camera: Sony a6000, stock, at prime focus: APS-C 23.5 x 15.6 mm, 6000 x 4000, 3.9 micron pixels, RAW
Mount: Sky-Watcher EQ6-R, unguided. Set down 27 degrees off the pole; both axes driven from a pointing model fitted to plate solves. Residual drift about 0.1 arcsec per second

© 2026 Brad Gessler · Celestron 8SE (8 inch, 2,080 mm) and Sony a6000 on an EQ6-R · San Francisco Bay Area · 4 October 2026
Capture and mount: Observatory (Elixir on a Raspberry Pi 3). Stacking: numpy, OpenCV, rawpy. Plate solving: astrometry.net. Stacked from the camera's RAW frames. Nothing generated.