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Filters for double stars?

Started by raolson, 06/20/2005 05:25PM
Posted 06/20/2005 05:25PM Opening Post
OK now I am feeling comfortable looking for and finding multiple and double stars. Are there any good filters out there that dim the primary star without blocking the smaller secondary stars? I have an OIII and an UltraBlock. The UltraBlock helps some. I was just wondering if anything else is available.
Posted 06/20/2005 06:45PM #1
I don't believe so in general.

However, if you have a scope with a lot of false color you may benefit from a minus violet filter. Or just about any colored filter. Then you will only get two spots of light, instead of a smear of the two lights. Of course, you will sacrifice some of the light.

And as far as other filters, they work by cutting out all but a specific color of light. If the two stars you are looking at have the same color light--and they pretty much do--they would both be affected equally by the filter rejecting the light.

Posted 06/21/2005 12:00AM #2
It's not so well known that Antares is a visual binary star. It's not easy to split, since the companion is quite a bit fainter and quite close. Many people (myself included) have thought that the companion looks green. As such, I have found that splitting Antares is much easier using a nebula filter but cutting out the light from Antares much more than for its companion. This is the only case I know of where a nebula filter will help split a binary. As mentioned before, such a filter can help reduce chromatic aberration, caused by a refractor lens or by the atmosphere. If a binary is low in your sky, atmospheric dispersion can make it harder to split. If it's bright enough, a nebula filter can help to sharpen the view.

Mike Connelley