Astronomy Filters

Narrowband Optical Filters 50mm dia. Hydrogen alpha

Our business began in 1990 as research astronomers came to us to obtain high-performance, high-precision  telescope filters and optics. This was driven in part by the emergence of CCD imaging. At that time it was only large research institutions that could afford the $200,000 + costs associated with custom-building of such large format, digital cameras. Over many years, we perfected our skills and techniques in designing and manufacturing filters that are optimized to function with CCD cameras.

In the mid and late 1990's, as the costs of off-the-shelf CCD cameras dramatically declined so that amateur astronomers could own them, too, we found that those amateur astronomers were also coming to us to obtain high quality filters, just as their researcher "cousins" did. In response to that, we developed and stocked a series of commonly used filters. Although such filters when built for a research astronomer could cost thousands of dollars, by mass production techniques and minor changes in design we were able to lower prices often by more than half.


All of our astronomical filters have IR blocking "built-in" so IR light does not contaminate today's sensitive CCD detectors. When you use filters from Custom Scientific, you do not need any additional IR blocker filters. One exception is in the thickness-matched Clear filters which transmit all wavelengths from the UV to the far IR; they are clear, high-precision, optical windows designed to transmit all wavelengths of light without having to refocus when switching back to a color filter.

The filters offered below are the most commonly-used filters by research astronomers on a limited budget, by astronomy teachers, and by serious amateur astronomers. We also routinely make custom optical filters in other sizes and wavelengths, some of which can be seen on our research astronomy page.  We also do custom filters tuned for fast (low focal ratio) telescopes and Doppler shifted emission lines.  Please contact us to request a quote.

Wide Band Astronomy Filters
Description 1.25" dia. mounted 50mm dia. unmounted 50 x 50 mm square
RGB & Clear Filter Set $495 $810 $900
Luminance Filter (IR-blocked Clear) $95 $150 $195
Bessell Filters (Johnson/Cousins) (UBVRI) $175 per filter $295 per filter $500 per filter
Clear Filter for UBVRI $90 $225 $350
Neutral Density Filter (ND 2, 1.0%T) $150 $225



Narrow Band Astronomy Filters
Description 1.25" dia. mounted 50 mm dia. unmounted 50 x 50 mm square
Hydrogen Alpha* 656.3/4.5 nm Contact us for price. Contact us for price. $800
Hydrogen Alpha* 656.3/8 nm $330 $500 $500
Red Continuum 640/10 nm $400 $600  
[O III] 500.7/ 8 nm (Oxygen) $330 $500 $500
Green Continuum 510/10 nm $400 $720  
Hydrogen Beta 486.1/10 nm $400 $600  
Blue Continuum 470/10 nm $400 $600  
[S II] 672.4/ 8 nm (Sulfur) $330 $500 $500
Methane 889/18 nm $450    
Multiband: H-alpha, [OIII],  &  H-beta      
Spanner Tool for unmounting 1.25" filter $10 - -
Optics Cleaning Kit $99 - -

* For nighttime use only. NOT for solar viewing.

  •  Contact us for pricing on other sizes, including custom sizes.
  • All filters have anti-reflection (A/R) coatings.
  • Narrowband filters are also useful for capturing high resolution images in cities and other areas with high contamination by unwanted light. Thus, they are effective light-pollution filters.

Typical filter spectra

Hydrogen-alpha/10 spectrum<

Hydrogen alpha 656.3/10 nm*
(NOT for solar viewing.)

Hydrogen alpha spectrum

Hydrogen alpha 656.3/4.5 nm*
(NOT for solar viewing.)

Hydrogen beta spectrum

Hydrogen beta 486.1/4.5 nm

[Oxygen III] 500.7/4.5 nm

[Oxygen III] 500.7/4.5 nm

[Sulphur II] 672.4/4.5 nm

[Sulphur II] 672.4/4.5 nm

UBVRI filters spectrum

Johnson/Cousins/Bessell Filter Set

RGB Filter Set

RGB Filter Set

IR-blocked Clear (Luminance)

IR-blocked Clear (Luminance)

Neutral Density filter spectrum

Neutral Density 2

Multi-Band Hα filter spectrum

Multi-Band Hα (656.3nm), [O III] (500.7nm), and Hβ (486.1nm)- One filter, 3 emission lines.

Hydrogen Beta filter

Hydrogen Beta

Various Narrowband Filters

Narrowband Filters

Please check out our Optics Cleaning Kit.

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Custom Scientific, Inc.
3852 North 15th Avenue
Phoenix, Arizona 85015 USA
Phone: 602-200-9200
Fax: 602-200-9206