Description
ions. This helps to maintain image brightness and color balance. In addition, particular wavelengths associated with emission nebulae, such as H- (656nm), H- (486nm), OIII (496nm and 501nm), and SII (672nm), are highly transmitted, ensuring minimal loss of image brightness for those objects.
H-alpha H-beta OIII (H-H-OIII) Imaging Filter The specialized H-H-OIII Imaging Filter, also known as the Nebula Filter, is a narrowband filter that allows very high transmission of select wavelengths of light from emission nebulae while blocking the rest of the spectrum. You’ll immediately notice much higher contrast in your images, even from your light-polluted backyard! And since the transmission at the critical wavelengths is so high, the nebulae are not dimmedonly the background is made blacker.
The H-H-OIII Imaging Filter is perfect for imaging emission nebulae like the North America Nebula (NGC 7000), Lagoon Nebula (M8), Orion Nebula (M42), and the Carina Nebula (NGC 3372). The transmission spectrum for the H-H-OIII Imaging Filter is 85% or greater at key wavelengths (486nm, 496nm/501nm, 656nm) and less than 0.5% transmission elsewhere. And while other nebula filters can’t keep up with RASA’s fast optics and end up blocking some of the the wrong wavelengths, this filter is engineered to pair perfectly with this ultra-fast f/2 system.
Both the Light Pollution Filter and the H-H-OIII Imaging Filter are custom-engineered to work with RASA 8, so they won’t block any of the “good” wavelengths, specifically targeting light pollution and other undesired wavelengths. The filters fit directly into the internal filter mount in RASA 8’s front lens cell, where the optical window normally mounts. To use a filter, you first remove and replace the clear window with the desired filter. Since you are not introducing new layers of glass into the system when you swap out the window with the filter, you maintain RASA’s exacting performance.
Each filter has a plastic storage case to safely store the filter or the optical window that came with your RASA when not in use. You will also receive a spectral transmission graph unique to each individual filter, verifying its performance.
| Camera | Compatible with RASA 8? | Adapter required |
|---|---|---|
| Astronomical CMOS/CCD camera with C-mount | Yes | C-mount adapter (included) |
| Astronomical CMOS/CCD camera with M42-thread mount | Yes | M42 adapter (included) with M42 extension tubes (not included) |
| Astronomical CMOS/CCD camera with other mount | Yes | Custom camera adapter |
| Canon mirrorless with APS-C sensor | Yes |
Canon mirrorless adapter (sold separately) |
| Sony mirrorless with APS-C sensor | Yes |
Sony mirrorless adapter (sold separately) |
| Canon mirrorless with full frame (42mm) sensor | Yes, but not optimized across the full sensor |
Canon mirrorless adapter (sold separately) |
| Sony mirrorless with full frame (42mm) sensor | Yes, but not optimized across the full sensor |
Sony mirrorless adapter (sold separately) |
| DSLR | No | — |
Tech Details:
| Aperture | 8″ |
|---|---|
| Focal Length | 400mm |
| Focal Ratio | f/2 |
| Heaviest Single Component | 17 pounds |
| Motorized Controls | n/a |
| Weight | 17 pounds |
| Optical Coatings | Starbright XLT |
| Resolution | .68 arc seconds |
| Supplied Eyepiece | n/a |
| Telescope Type | Schmidt-Cassegrain |
| Warranty | 2 years |
| Back Focus | 25mm |
Supplied Accessories:
M42 camera adapter, C-thread camera adapter, fan battery pack
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