Star clusters and asteroids

 Yesterday interstellar comet 3I/ATLAS made its closest approach to Earth ("close" being relative: it was 168 million miles away).  I obtained seven images over the span of about ten minutes and was surprised that its motion was very evident.  It is moving at about 140,000 miles per hour, more than twice Earth's orbital speed.  Here is an animation produced from the seven images obtained with a 135mm lens.  Some of the fainter stars twinkle in and out because the exposures were not all equal.

Motion of comet 3I/ATLAS over ten minutes.

 

 New Moon also occurred on 19 Dec, so it was a good opportunity to do some more lens testing before the sky gets any brighter.  Last night the measured brightness was 19.68 mpsas. I set up the Canon FD 300mm f/4 L lens on a ZWO AM3 harmonic-drive mount to look at some star clusters in the eastern sky.  

Collinder 69 (Cr69) in Orion

 Collinder 69 is a loose open cluster in the head of Orion.

Cluster M35 and asteroid (10) Hygiea (circled)

 M35 is a nice open cluster in the constellation Gemini.  Asteroid (10) Hygiea was discovered in 1849 and is the 4th largest asteroid, after Ceres, Vesta, and Pallas.  Last night it was shining at magnitude 10.4.

M38 and M37 are open clusters in the constellation Auriga.  M38 is also known as the "Starfish Cluster".

M38 (above center) in Auriga

M37 in Auriga

 

NGC 2264, the "Christmas Tree Cluster"

The open cluster NGC 2264 in the constellation Monoceros is also known as the "Christmas Tree Cluster".  It is embedded in a larger nebulous region that is too faint to show up in this short 30 sec exposure (just a hint is visible near the bright star).

 

Open cluster NGC 1647 in Taurus (upper right) and asteroid (16) Psyche (circled)

The open cluster NGC 1647 is close to the much larger Hyades star cluster in Taurus.  Asteroid (16) Psyche was discovered in 1852.  It was once listed as the 16th largest asteroid, but new size measurements have moved it farther down the list.  It is the 11th most massive asteroid.  Last night it was shining at magnitude 10.