Eta Geminorum: a gem in Gemini

[Nik271]

Yesterday I had a brief window of clear sky between 8 and 9pm. The main goal was to try Eta Geminorum (Propus) with my Skymax 127. This is a rather close and unequal pair ( orange mag 3.5 primary and a bluish mag 6.2 secondary), which has become quite a bit easier with time. It was discovered by Burnham in 1881 and at the time he wrote that "it is difficult for telescopes of smaller than 12 inches in aperture".

Since then the gap has widened from 1'' to 1.7'' separation and of course telescopes have become better and now it must be within the abilities of a good 4 inch refractor in good seeing.

I started with my usual tests for seeing: Theta Aurigae, which was very steady at x120 (12mm EP) and Wasat (Delta Gem) which was also showing clearly.  I tried a few more of my favorites: Alnitak, Rigel, even Sigma Cass in the other side of the sky, all looking well.  So I was reasonably confident that Eta Gem is also possible. At x120 I can only see the orange primary. With a 9mm (x165) there was a hint of some disturbance in the first diffraction ring. Finally I went all in with 6mm (x250, about the maximum of the scope). The primary Airy pattern was not so clean and steady anymore but in moments of stability I  saw a bump on the  west side of the diffraction ring. Here is my sketch, the blue was more of a teal colour and more faint, I could not find the right colour on my sketchpad.

 

Afterwards a visit to the nearby M35 was a no brainer, I could just about fit it all in with the 24mm Hyperion at x65. The transparency was briefly excellent, I could spot the nearby NGC 2158 as a dim gray smudge. And then of course since I am in the neighbourhood I visited M1. It was showing very nicely (for my suburban sky), the elongated shape was obvious and I could see a hint of structure inside. Perhaps my eyes were well dark adapted by then, or maybe the approaching low clouds helped to block the light pollution.

Anyway, now is the season when Gemini is high in the sky, so give  Eta a try if you can!

 

Clear skies and thanks for reading,

 

Nik

 

Edited February 3 by Nik271

[JeremyS]

Super observation and a nice challenge 👍🏻

[chiltonstar]

Well reported - a lovely pair!

Chris