Nebula Filter Suggestions
A few years ago I created an observing list for myself to highlight some interesting sky objects sorted by the month of the year. It included all the Messier objects and a variety of other items that I had found through internet searches. These objects were selected for their variety and often based upon the enthusiasm of the internet author for the object itself. If the object was one of their favorites, maybe I would like it too!
With a little more research, I added a list of nebula filters to the appropriate objects as listed below. These filters provide additional viewing contrast, by blocking specific light wavelengths (sky glow for example) and passing the wavelengths of interest to help the object to stand out in the EP. The filter type is listed with the best performing filter listed first.
|M8, M16, M27, M42, M57, NGC7000, NGC7009, NGC281, NGC3242||UHC / OIII|
|M17, M76, M97, NGC6888, NGC7293, NGC7023, NGC2392, NGC2244, NGC2246, NGC6543, NGC6210||OIII / UHC|
|M20||UHC / H-Beta|
|M1||UHC / Deep Sky|
UHC - Ultra High Contrast; Narrow band pass filter (24nm) isolates the two doubly ionized oxygen lines (496 and 501nm) and the hydrogen-beta line (486nm) emitted by planetary and most emission nebulae.
OIII - Oxygen III; Narrow band pass filter (11nm) isolates just the two doubly ionized oxygen lines (496nm and 501nm) emitted by planetary and extremely faint nebulae.
H-Beta - Hydrogen Beta; Extremely narrow band-pass filter isolating the hydrogen-beta line alone (486nm).
Deep Sky - Intended for viewing nebulae from light-polluted skies. Blocks all mercury vapor and high & low pressure sodium vapor lamp light, neon lights and airglow, while transmitting the rest of the visible spectrum. Can be used for astrophotography.Published in the August 2007 issue of the NightTimes