Antares – Alpha Scorpii – Very Difficult To See The Companion, But Easy When Using A UHC Nebula Filter and a 10-Inch Reflector

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 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. 

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 approximately 30 minutes.  The conditions, which were good for double stars earlier, quickly deteriorated as a hot breeze began to stir.    Roger Ivester

 

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