Antares – Alpha Scorpii – It Can Be Difficult To See The Companion, But Easy When Using A UHC Nebula Filter?

Antares:  Magnitudes 1.0/5.4 with a separation of 3.2 arc seconds.  

Notes from July 6th, 7th and 13th 1995:  “10-inch reflector; seeing good.  Tried all eyepiece combinations, but could not see the companion.”   

The glare of the bright primary makes this a difficult pair to split, despite good seeing and a well-collimated 10-inch reflector.

July 1995:  While browsing through some back issues of Sky & Telescope, I found an interesting article by Walter Scott Houston (December 1991 issue, p. 685) concerning the use of a UHC nebula filter to show the companion to Antares, as reported by Richard Miller.  

The article stated that the companion was barely visible using a 10-inch reflector at 230x, but that the filter showed the fainter star easily through a 6-inch at 96x.  

“The filtered view through the 10-inch showed two crisp disk with a band of sky between them.  Furthermore, the filter’s selective transmission causes the pair to appear deep red and apple green.”

Would the UHC filter work for me?  

I set out to try this for myself on the night of July 14th 1995.  All of my previous efforts to view the companion to Antares through my 10-inch reflector had failed.  

However, when I used an Orion Ultrablock nebula filter with my 10-inch at 240x, there it was…..the companion was clearly visible.  

Because of the filter….both stars appeared greenish, but were only visible for a short period.  The conditions, which were good for double stars earlier, quickly deteriorated as a hot breeze began to stir.    

I’m hoping to attempt the companion with my 6-inch reflector, using a UHC filter.  Would it be possible using a 4-inch refractor?   

Roger Ivester  

 

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