Astronomik OIII Filter

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About this product

Astronomik OII visual filter designed for observation of gaseous and planetary nebulae.

The extremely narrow pass band of the two OIII lines brings a substantial contrast gain to these lines even under best observation conditions. On faint super nova remnants and faint planetary nebulae the Astronomik OIII filter will often make the difference as to whether the object can bee seen or not! 

The optimal aperture ratio for the use of the filter is 1:3 to 1:15 with apertures of more than 6" (150mm). Transmission losses and chromatic distortions, which arise with other filters, occur with Astronomik OIII filters only when extremely bright aperture ratios of 1:3 and more come into play. The Astronomik OIII filters thus can expand the view of dispersed objects, generally speaking, to the whole visual field of view of the eyepiece and are not limited to only the center of the eyepiece.

Main use

Since enough light must be available to make use of the OIII filter it is best to use this filter with apertures of more than 6" (150mm). Smaller instruments do not gather enough light for meaningful and satisfying astronomical work. However, please note: Many experienced Deep Sky observers, with apertures of more than 10" (250mm), prefer using the OIII filter instead of the more versatile UHC filter.

Due to the high optical quality of the Astronomik OIII filter substrate you will see the same needle-sharp stars as you would from your regular telescope.

Transmission Chart

• The horizontal axis is the Wavelength in Nanometers (nm). 400nm is deep blue, at 520nm the human eye senses green and at 600nm red. At 656nm is the famous "H-Alpha" emission line of hydrogen.
• The transmission in % is plotted on the vertical axis.
• The blue line shows the transmission of the filter.
• The most important emission lines from nebulas are shown in orange. The most important lines are from ionised Hydrogen (H-alpha and H-beta) and double ionised oxygen (OIII).

The major emission lines of artificial light pollution:
| Hg 435,8nm | Hg 546,1nm | Hg 577,0nm | Hg 578,1nm |
| Na 589,0nm | Na 589,6nm | Na 615,4nm | Na 616,1nm |

The major emission lines of nebulas:
H-β 486,1nm | OIII 495,9nm | OIII 500,7nm | H-α 656,3nm

Suitability

• Visual observation (dark skies): Very good, huge contrast enhancement at O III-emission nebulas
• Visual observation (urban skies): Very good, huge contrast enhancement at O III-emission nebulas
• Film photography: It depends, very long exposure time
• CCD photography: Good, when used with an additional IR-block-filter
• DSLR photography (original): Very good, huge contrast enhancement at O III-emission nebulas
• DSLR photography (astro modified): Very good, huge contrast enhancement at O III-emission nebulas
• DSLR photography (MC modified): Good, when used with an additional IR-block-filter
• Webcam / Video (Planets): Unsuitable
• Webcam / Video (Deep Sky): Reasonable, if light pollution is a big problem and OIII Objects are beeing observed​

Technical Data

• Transmission of nearly 100% of both OIII lines
• Complete blocking of all disturbing wavelength coverages
• The ideal filter for telescopes 10 " (25cm) and larger
• Main operational use: Planetary nebulas & super nova remnants
• Scratch-resistant!
• Excellent carrier material. The optical performance of your telescope is not reduced by the filter in any way.
• Parfocal with other Astronomik filters
• Glass thickness: 1mm
• Completely resistant against high humidity, scratches and ageing effects
• Diffraction limited, the filter will not reduce the optical performance of your telescope!
• Astronomik filters are delivered in a high-quality, long lasting, filter box
• 12nm Pass Width

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