What is the Baader 20nm H-alpha filter primarily used for?
This filter is designed to dramatically increase the contrast of emission nebulae (H-II regions) for both visual observing and astrophotography. It isolates the 656.3nm H-alpha wavelength, making objects like the North America Nebula (NGC 7000) or the Orion Nebula (M42) stand out, especially from light-polluted areas.
Why choose a 20nm bandpass for the Baader H-alpha filter instead of a narrower one like 7nm?
A 20nm bandpass offers a crucial balance. It's narrow enough to provide a major contrast enhancement by blocking light pollution, but wide enough to remain bright for visual observing. Narrower filters (like 7nm or 3nm) are excellent for imaging but are often too dim for the human eye to see through, especially with smaller telescopes.
How will the Baader 20nm H-alpha filter improve my images of the North America Nebula (NGC 7000) with a color camera?
When used with a color CMOS or CCD camera, this filter acts as an enhanced red filter. It isolates the rich H-alpha signal from the nebula while rejecting skyglow, moonlight, and other sources of light pollution. This results in a much stronger, more detailed signal from the nebula's structure, allowing you to capture impressive images even from a suburban backyard.
Can I use the Baader 20nm H-alpha filter with my f/5 Newtonian for visual observing?
Yes, absolutely. The filter is designed to perform well across all f-ratios, including faster systems like an f/5 Newtonian. The 20nm bandwidth ensures the view remains bright enough to be effective, providing a significant contrast boost on emission nebulae without dimming the image excessively.
Is the Baader 20nm H-alpha filter safe for viewing the sun?
NO. This is not a solar filter. You must never use this filter for any type of solar observation. Viewing the sun through this filter without a proper, full-aperture solar filter will cause immediate and permanent eye damage.
Which size of the Baader 20nm H-alpha filter fits my filter wheel and eyepieces?
Choose the size that matches your accessories. The 1.25" version is housed in a standard 1.25" cell with standard filter threads and threads directly into the barrel of any 1.25" eyepiece or into a standard 1.25" filter wheel. The 2" version is the right choice if your eyepieces, diagonal or filter wheel use the 2" format. Both sizes offer the same 20nm bandpass centered on 656.3nm.
