Astrodon Near IR Luminance Filter - 31mm Round Unmounted
Astrodon Near IR-Luminance Filter - 31 mm
Professional astronomers use expensive CCD detectors made of different materials for NIR measurements that extend beyond the Si range. For example, J- and K-band images are taken at 1250 and 2200 nm, respectively. The 2MASS survey carried out 30 years ago was done in the NIR. The "2" in 2MASS means 2 microns (2000 nm). The readily available photometric I filter covers the NIR region, also shown in the figure below. NIR commonly refers to the region from 700 to 2800 nm and infrared (IR) for longer wavelengths. Tri-color images are typically made by placing red (R), green (G) and blue (B) filters between the telescope and the monochrome CCD camera. They are combined in software to form the RGB color image. The color images are generally taken at lower resolution by grouping (binning) pixels in the CCD camera, thereby permitting shorter exposures. The lower resolution RGB image is then used to colorize the deeper, higher resolution (unbinned) luminance image. This forms a high resolution LRGB image.
There are two types of luminance filters; NIR-blocked (L) and unblocked (C = Clear). L is designed to match the spectral coverage of the RGB filters. One school of thought is that this is the best combination for color images because of the spectral matching. The other school of thought is that one wants all the photons possible. C adds about 40% more signal from the NIR (using the Kodak KAF3200ME detector, for example) to produce a deeper luminance image. The question is how the additional NIR signal relates to the RGB image that will colorize it. This is still debated. Lastly, narrowband filters bring out detail in nebula and supernova remnants from the emissions of hydrogen (H-alpha or H-a) at 656 nm, oxygen (OIII) at 497 and 501 nm, sulfur (SII) at 672 nm, and others. It is common to add H-a into the RGB of an emission nebula to enhance structural detail. All of these colors and emission lines lie within the VIS spectrum.
More on Astrodon Near-Infrared Tricolor Filters
Some of the goals of Astrodon Near-Infrared Filters are to produce tri-color images entirely in the NIR. Color combine weights for NIR1, 2, 3 are ~ 1:1:1.2. Now you can examine objects highly obscured by dust in the plane of the Milky Way, such as the IC342/ Maffei group, that are difficult to image at VIS wavelengths. The Astrodon NIR filters permit you to explore faint, extended red emission (ERE) nebula. Uncover stars and other details in nebula that are obscured by bright VIS emissions from H-a, SII, OIII or other elements! What's more, you can mix NIR with RGB of globular clusters to enhance the appearance of cooler stars and minimize terrestrial light pollution from sodium and mercury street lamps and oxygen skyglow for imagers living in suburban or city locations. Use the NIR luminance (no visible light) to explore galaxy structure in comparison to VIS luminance data.
Astrodon Near-Infrared Tricolor Filters Features
- 1.25-inch unmounted, 31 mm diameter
- 3+/-0.05 mm thickness
- Parfocal with other Astrodon LRGB and Narrowband filters*
- NIR Luminance (>700 nm)
- NIR123 (700 to 800, 800 to 900, >850 nm)
- NIR Luminance sold separately
- ~1:1:1 for KAF3200ME and similar detectors
OPT Product Number: AN-NIRL-31R
|Accessory Type||IR Pass & Luminance|
|Warranty||5 Year Warranty|