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My Favorite Winter Binocular Variables

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SET's picture
Joined: 2010-07-23

Hello Visual Observers,

I'd like to take a few moments to share with you some of my favorite Winter binocular stars. I have followed these for years and they are a treat when this time of season returns.

BU Tau in the Pleiades. 5.0-5.3 though the range may be a bit more in visual. You couldn't ask for a prettier star field.

W Ori- 5.5-6.9 SR star. This star gets very red at or near maximum light. Use out of focus or quick glance methods.

CK Ori- my own experience gives it a visual range of 6.0-6.4

W CMa- 6.2-7.0 SR. Nice star in the Milky Way. If you are still using the OLD chart from 10 or more years ago, make a new one from the VSP. The old chart had terrible comp stars and I questioned if a few of them applied to the correct comp star.

U Mon- 5.5-7.7. This is in a nice geometric star pattern.

Don't forget a few naked eye stars like Betelguese and Eta Gem.

Have fun with these. I think you will agree that these are nice, easy stars to observe.

Good Observing.

Chris Stephan   SET

Robert Clyde Observatory

Sebring, Florida

Some comments on your winter (my summer) bino stars
Sebastian Otero's picture
Sebastian Otero
Joined: 2010-09-19

Hi, Chris,
All those stars are in my observing program (excepting CK Ori) and I observe them every clear night I'm out. Interesting stars.
Some remarks.

BU Tau.
Everything is blue here so there are no color problems but the huge problem is the proximity of Atlas, a 3.6 mag. star only 5' away. This makes Pleione look fainter than it actually is when compared with the best comp star that is HD 23985 (V= 5.25). Pleione varies with a periodic pattern over 34-35 years. It slowly rises in brightness over the years until it undergoes a sudden half a magnitude drop (approx. 4.9 to 5.4) and then the cycle starts again. This is probably due to a binary companion.

W Ori.
A very red star, it is i the new AAVSO Binocular program and we have made a new sequence for it. We can try the Binocular Chart option in VSP to get the proper comparison stars.

CK Ori.
I used to observe it and noticed very few activity. Then I realized it was a constant star with V= 6.21. So the 6.0-6.4 range means your obervational scatter is +/-0.2.

W CMa.
It is also in the Binocular Program with a new chart so I second your advice.

U Mon underwent a very deep fading last season, it surprised me.

And eta Gem is a little difficult, its range has been very small lately, only between 3.1 and 3.4.

Good observing!


Whilst you're up around eta
pox's picture
Joined: 2010-08-12

Whilst you're up around eta Gem, remember there are several good binocular variables here - TU, TV, BU, WY and SS Gem, this last an RV Tau star, though possibly a bit faint if you suffer from light pollution. I honestly don't see much point in stars like CK Ori though, because of the small amplitude. BL Ori is a nice red star on the border with Gemini, and BQ Ori which isn't too far away has a decent range in magnitude.

CK Ori is not variable
Sebastian Otero's picture
Sebastian Otero
Joined: 2010-09-19

Hi, Mike,

CK Ori doesn't have a small amplitude, it is just constant:


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