Astrodon 2nd Quality Filters

This individually serialized filter, Ic*_50R-200040, has been scored at 9.95 and has a 11.25% discount. Astrodon 2nd Quality filters are still covered by our warranty for longevity, but are otherwise sold “as is” and are not returnable.

Astrodon 2nd Quality Filters are sold at a discount. 2nd Quality Filters are individually evaluated and graded for edge chips, scratches, pinholes and inclusions according to the standards set below:

Edge Chips: Score 1 point for each edge chip. Score 1 additional point for each edge chip that extends into the filter more than 2mm from the edge.

Pin holes: Score 1 point for each pinhole. Score an additional point for each pinhole that is “large”.

Scratches: Score 1/2 point for each scratch.

Inclusions: Score 1/2 point for each inclusion.

Subtract the sum of the points from 100 and divide by 10. This is the filter score.

This individually serialized filter, UV*_50S-200041, has been scored at 9.9 and has a 12.50% discount. Astrodon 2nd Quality filters are still covered by our warranty for longevity, but are otherwise sold “as is” and are not returnable.

Astrodon 2nd Quality Filters are sold at a discount. 2nd Quality Filters are individually evaluated and graded for edge chips, scratches, pinholes and inclusions according to the standards set below:

Edge Chips: Score 1 point for each edge chip. Score 1 additional point for each edge chip that extends into the filter more than 2mm from the edge.

Pin holes: Score 1 point for each pinhole. Score an additional point for each pinhole that is “large”.

Scratches: Score 1/2 point for each scratch.

Inclusions: Score 1/2 point for each inclusion.

Subtract the sum of the points from 100 and divide by 10. This is the filter score.

This individually serialized filter, V*_50S-200047, has been scored at 9.975 and has a 11.88% discount. Astrodon 2nd Quality filters are still covered by our warranty for longevity, but are otherwise sold “as is” and are not returnable.

Astrodon 2nd Quality Filters are sold at a discount. 2nd Quality Filters are individually evaluated and graded for edge chips, scratches, pinholes and inclusions according to the standards set below:

Edge Chips: Score 1 point for each edge chip. Score 1 additional point for each edge chip that extends into the filter more than 2mm from the edge.

Pin holes: Score 1 point for each pinhole. Score an additional point for each pinhole that is “large”.

Scratches: Score 1/2 point for each scratch.

Inclusions: Score 1/2 point for each inclusion.

Subtract the sum of the points from 100 and divide by 10. This is the filter score.

This individually serialized filter, Ic*_50S-200042, has been scored at 9.975 and has a 10.63% discount. Astrodon 2nd Quality filters are still covered by our warranty for longevity, but are otherwise sold “as is” and are not returnable.

Astrodon 2nd Quality Filters are sold at a discount. 2nd Quality Filters are individually evaluated and graded for edge chips, scratches, pinholes and inclusions according to the standards set below:

Edge Chips: Score 1 point for each edge chip. Score 1 additional point for each edge chip that extends into the filter more than 2mm from the edge.

Pin holes: Score 1 point for each pinhole. Score an additional point for each pinhole that is “large”.

Scratches: Score 1/2 point for each scratch.

Inclusions: Score 1/2 point for each inclusion.

Subtract the sum of the points from 100 and divide by 10. This is the filter score.

This individually serialized filter, RedCon5_27R-200051, has been scored at 9.9 and has a 12.5% discount. Astrodon 2nd Quality filters are still covered by our warranty for longevity, but are otherwise sold “as is” and are not returnable.

Astrodon 2nd Quality Filters are sold at a discount. 2nd Quality Filters are individually evaluated and graded for edge chips, scratches, pinholes and inclusions according to the standards set below:

Edge Chips: Score 1 point for each edge chip. Score 1 additional point for each edge chip that extends into the filter more than 2mm from the edge.

Pin holes: Score 1 point for each pinhole. Score an additional point for each pinhole that is “large”.

Scratches: Score 1/2 point for each scratch.

Inclusions: Score 1/2 point for each inclusion.

Subtract the sum of the points from 100 and divide by 10. This is the filter score.

This individually serialized filter, NII3_50R-200049, has been scored at 9.95 and has a 11.25% discount. Astrodon 2nd Quality filters are still covered by our warranty for longevity, but are otherwise sold “as is” and are not returnable.

Astrodon 2nd Quality Filters are sold at a discount. 2nd Quality Filters are individually evaluated and graded for edge chips, scratches, pinholes and inclusions according to the standards set below:

Edge Chips: Score 1 point for each edge chip. Score 1 additional point for each edge chip that extends into the filter more than 2mm from the edge.

Pin holes: Score 1 point for each pinhole. Score an additional point for each pinhole that is “large”.

Scratches: Score 1/2 point for each scratch.

Inclusions: Score 1/2 point for each inclusion.

Subtract the sum of the points from 100 and divide by 10. This is the filter score.

NII Filter, 3nm, center bandwidth 658.4 nm

What about NII and H-a?
This is a bit complicated. It is not well known that most H-a filters pass both H-a and NII. H-a emits at 656.3 nm and NII emits most strongly at 658.4 nm (and weakly at 653.8 nm). These are very close together spectrally. Thus, most H-a filters are wide enough (e.g. 4.5 nm bandwidth and wider) to pass both emission lines as shown for the older Astrodon 6 nm filter above. Our 3 nm H-a begins to separate both emission lines and reduces the NII contribution significantly. In this example the 3nm filter only transmits 15% at the NII 658.4 nm wavelength, whereas the H-a remains unchanged. As mentioned earlier, some objects are enriched in NII, such as planetary nebula and Wolf-Rayet bubbles. The Dumbbell Nebula, M27, is a good example. The wispy clouds in the core of M27 are dominantly NII. A tricolor narrowband image is also shown below, mapping OIII to blue, H-a to green and NII to red to produce a beautiful color image. This information provides you with a choice based upon your light pollution, desire for more detail, or simply wanting all the photons you can get out
of your H-a filter.

Our NII filters have a center bandwidth of 658.4 nm.