Product Details

• Description
• Specifications
• Included Items
• Reviews

• The Antlia SII 3.5 nm filter - Size 31 mm

  This SII filter is suitable for imaging of Sulfur II nebulas from observation sites with light pollution and from dark sites as well. It only allows 3.5 nm of bandwidth high transmission at a center wavelength of 671.6 nm. this extremely narrow bandwidth can effectively improve the contrast of the band at 671.6 nm, at the same time, it blocks interference of the light from other wave bands, especially artificial mercury and sodium lamps.

   

  Antlia narrowband filters are designed to enhance the contrast

  Contrast brings out faint features by reducing the background – the narrower the filter, the better. 

  Suitable for most emission nebulas, planetary nebulas, and supernova remnants, this filter can well highlight the details of SII contained in these imaging objects.

  Extremely narrow bandwidth

  The extremely narrow bandwidth results in a small amount of light. Antlia Filters recommends you to use a large-aperture telescope and long exposure time to collect enough signals to obtain the details of those faint objects with the SII ultra-narrow filter.

  Blocks other bands:

  The unwanted light from other wavelengths is cut-off, leaving only a width of 3.5 nm at the 671.6 nm wavelength (SII) center point, so that they get the highest contrast and the background is increased enormously. This results in an extremely dark background and minimized halos around bright stars.

   

  The Antlia Filters Production Process:

  In the production process, Antlia Filters uses very strict quality control standards. Each filter is individually tested and scanned to ensure that the product meets the parameters we need. In particular, starting from the selection of the substrate, they must control the tolerance of each substrate to a very high standard of +/-0.05 mm. As we all know, when light passes through optical materials, it will be refracted and the thickness of the glass will affect the length of light refraction. Antlia Filters allows their filters to achieve parfocal by minimizing this tolerance of +/-0.05 mm.

  All Antlia Narrowband filters edge are blackened. It is critical to minimize stray light for a filter that blocks most light except for the narrow bandpass. As edge blackening must be hand-made, it becomes very costly to them.

  Their cut-off rate has reached a very high technical data point. Many users will be very concerned about how high the filter transmission rate is and ignore the cut-off rate. It is a very important quality index. They keep the signal of 88%T at the 671.6 nm line. This makes it stable as the filter becomes spectrally narrower to ensure best Signal-to-noise Ratio, a cut-off rate of OD3 (0.1%) is required to reduce interference from other wavelengths. It is a very important quality index, and the accomplishment is very difficult, This process requires very high-end equipment, constantly thickens the layers of coating, add longer production times, and adds more cost to the completed product. 

  Wavelength Graph

  To see the graph, click on the Gallery thumbnail image to expand. Then use [CTRL]-scroll-up for an even closer look.

  Not Recommended:

  • Solar Observing and imaging.
  • Visual observation.
  • DO NOT LOOK AT THE SUN WITH ANTLIA FILTERS.
  • Serious eye damage will result if you fail to observe the warning.

  Technical Data:

  • Schott optical substrate.
  • 31 mm (2 mm+/-0.05 mm).
  • Surface Quality: 60/40 (Refer to MIL-O-13830).
  • 2 sides fine-optically polished to ensure accurate 1/4 wavefront.
  • 30 arcsec parallelism.
  • Center-Wavelength of Antlia SII 3.5 nm filter: 671.6 nm.
  • SII 671.6 nm T＞88%, (88% transmission at SII line 671.6 nm ＞OD3（0.1%）at 300 to 1100 nm).
  • 2 sides Multi-layers anti-reflection coating.
  • Single / Non-glued substrate.
  • Filter Ring: None, unmounted.
  • Laser Engraving No Fading..
  • Size: Unmounted, Dia 31 mm.

  Additionally:

  With an HSO-set (H-alpha, SII, and OIII) of filters (this is not the full set,) you are able to process your images like the ones from the Hubble Space Telescope.  See the blue Gallery tab for an example.  Click on the thumbnail image to enlarge.

   

• specifications

  Bandpass	3.5nm
  Filter Shape	Round
  Filter Size	31 mm
  Filter Thickness	2 mm
  Filter Type	SII
  Warranty	3 Year manufacturer's

• included items

  • Suitable for imaging SII (Singly Ionized Sulfur) emission nebulas, planetary nebulas, and supernova remnants.
  • This filter does not brighten deep-sky objects, it blocks unwanted light from other wavelengths and highlights the contrast of the SII band.
  • Ultra-narrow bandwidth of 3.5 nm, designed for astroimaging.
  • High transmission of typically 88% the filter gives you an enormous contrast boost.

   

  Not Recommended:

  • Solar Observing and imaging.
  • Visual observation.
  • DO NOT LOOK AT THE SUN WITH ANTLIA FILTERS.
  • Serious eye damage will result if you fail to observe the warning.