Astronomy Filters

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.


Narrowband Optical Filters
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.

50mm dia. Hydrogen alpha

Wide Band Astronomy Filters

Description 1.25" dia. mounted 50mm dia. unmounted

50 x 50 mm square

RGB & Clear Filter Set




Luminance Filter (IR-blocked Clear)




Johnson/Cousins/Bessell Filters (UBVRI)

$175 per filter

$295 per filter

$500 per filter

Clear Filter for UBVRI



Neutral Density Filter (ND 2, 1.0%T)





Narrow Band Astronomy Filters


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




Red Continuum 640/10 nm




[O III] 500.7/ 8 nm (Oxygen)




Green Continuum 510/10 nm



Hydrogen Beta 486.1/10 nm



Blue Continuum 470/10 nm



[S II] 672.4/ 8 nm (Sulfur)




Methane 889/18 nm

Multiband: H-alpha, [OIII],  &  H-beta      

Spanner Tool for unmounting 1.25" filter


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Optics Cleaning Kit




* 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 656.3/4.5 nm* Hydrogen alpha graph

Hydrogen alpha 656.3/10 nm* Hydrogen alpha graph

Hydrogen beta 486.1/4.5 nm Hydrogen beta graph

[Oxygen III] 500.7/4.5 nm Oxygen III graph

[Sulphur II] 672.4/4.5 nm Sulphur II graph

Johnson/Cousins/Bessell Filter Set UBVRI filters graph

RGB Filter Set RGB filters graph

IR-blocked Clear (Luminance) IR blocked clear (luminance) graph

Neutral Density 2 Neutral Density filter graph

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

* For nighttime use only. NOT for solar viewing.

Hydrogen Beta Hydrogen beta filter

Narrowband Filters Various 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


Last Modified July 22nd, 2015