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I was out at a dark site this weekend - showed off a bunch of goodies to some friends & neighbors Thurs Nite but had superb sky to myself on Fri. After playing thru Sag & Scutum & Sagita & Delphinus, I realized that NA neb was winking naked eye. It looked fine thru my 11x56 broadband binocs. Pelican showed decent too. I sniffed pretty well at it thru the 30mm (40X) on the DOB. I added my dgm-npb filter to the 21mm and was able to track distinct variations throughout that nebulous region. I hadnt realized this narrowband could enhance the NA. Is this generally true? or only in dark skies? General emissions for NA=???
Steve

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Generally, the narrowband filters do wonders for the North America Nebula, although under some light pollution, the Oxygen III filters may yield somewhat higher contrast. It is important to use them at low to moderate powers (3.5x per inch to 9.9x per inch of aperture) and with an eye that is fully dark adapted. I find the filters actually work a bit *better* under dark sky conditions, so it is important to have them with you wherever you are observing. My favorite view of the North America comes in my 100mm f/6 refractor at 25x using either the NPB filter or the OIII filter. There is a good article on which filters might be useful for which nebulae on the web site of the Prairie Astronomy Club:

FILTER PERFORMANCE COMPARISONS FOR SOME COMMON NEBULAE

Clear skies to you.

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David W. Knisely
Hyde Memorial Observatory
http://www.hydeobservatory.info

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