DayStar Filters™

Overview of DayStar Filter Designs, and Function.

DayStar Hydrogen Alpha Filters

DayStar Calcium K-Line Filters

DayStar Double Peak Polarized and Custom Filters

DayStar Light Pollution Rejection Filters

Ultra-Precise Bandpass Filter Systems for Scientific Observing & Imaging

History: DayStar is a familiar name to professional and serious amateur observers of the Sun since February 1975 when Del Woods founded the DayStar Filter Company. DayStar developed several series of specialized filters for visual and imaging applications that would come to be found in most professional solar observatories. DayStar developed Hydrogen Alpha filter series which are engineered to be more affordable for those amateurs who seek a rewarding solar observing experience. DayStar also engineers custom filter solutions for other scientific applications. DayStar was the first to set the standards for reliable, high performance Hydrogen Alpha and Calcium K-Line solar filters and harness this technology rendering it attainable by many mere mortals.

Right: The Sun as imaged by a DayStar 0.5 Angstrom Bandpass Hydrogen-Alpha Filter (31,141 bytes). Image courtesy of NASA.

The hobby of astronomy os one of the few sciences where amateurs routinely make discoveries and meaningful contributions. Some hobbyists became retailers of astronomical equipment; some names of these retailers which came to "prominence" included the late Ken Hirsch whose regular advertisements in publications including "Sky & Telescope" featured spectacular prominence photos taken by DayStar customers. DayStar filters came to be employed not just on the ground but in space flight too where one sounding rocket crashed upon its return to Earth; among the few recognizable and working components where a DayStar filter. In the mid 1990's Del Woods hired someone whom he trained to replace him at DayStar, but this transition did not work out well for DayStar or the community. The mid 1990's became a turbulent time in the history of the company, with production numbers plummeting and wait lists for Hydrogen-Alpha filters growing to two or more years! Del's absence and later the passing of Ed Hirsh prompted a variety of fictitious rumors about the company. By 1999 Del Woods came back to work at DayStar, bringing his expertise and compassion back to the community until May 2005 when ill health forced Del to retire and sell the assets and knowledge to what became DayStar Filters Limited Liability Corporation.

Products: DayStar is best known for providing ultra narrow band optical interference filters primarily for solar observations. These filters transmit a single sub-angstrom bandwidth line from our Sun while rejecting the complete background radiation. However, DayStar has manufactured many custom filters over the years for many applications outside of those original markets targeted by DayStar. DayStar has the technical expertise to design a wide variety of filters and has since branched into other areas of astronomy including the manufacture of a high contrast nebular filter designed to reduce the effects of sky glow pollution from city lights.

There are a few points which we wish to emphasize:

1. The lead time for the fabrication and acceptance testing of a new DayStar Hydrogen Alpha filter averages between four to six months, maybe a bit less depending on the model desired. Company Seven does have some filter models in stock at times, but we suggest our customers not buy what we have unless it is specifically that model which they want.

2. In addition to being able to study the Sun on any clear day there are special events occurring every year somewhere on Earth including Solar Eclipses, Venus Transit, etc. As we approach another Solar Eclipse (March 2006 passing through North Africa and Turkey in particular) the demand for these filters does accelerate. We urge those who need filters for an event to place their orders six months or more in advance for the more complicated models, or a few months in advance for broader bandpass or simpler configurations.

3. Among the advantages of the DayStar system is that its design permits use of the Hydrogen-Alpha filter body with many differing apertures telescopes or lenses. This means one can operate the DayStar filter on a telescope with an aperture as small as .8 inches / 20mm, or up to 6.5 inches / 165mm aperture, or possibly even larger. The aperture selected will depending on the local "seeing" conditions, and which telescopes may be available.

In addition to the cost of the DayStar Hydrogen Alpha filter body, an optional Prefilter for your telescope would have to be employed. Each telescope requires this form of an energy rejection filter which is threaded onto or slip fit onto the front to lens in order to prevent damage to the telescope or to the Hydrogen-Alpha filter body. This "prefilter" is made by DayStar or can be custom made for our clients by Company Seven to a high specification. These glass filters usually appear as a deep red in color.

4. The DayStar Hydrogen Alpha filter systems are engineered to provide nominal performance when employed with a telescope or lens which is configured to provide an exit cone of light at about f/30. In order to obtain this f/30 beam with most telescopes we employ optional lenses to shape the beam; these include the TeleVue 2X or 4X Powermate 2 inch lens. These lenses resemble a Barlow lens in effect but also incorporate a beam shaping lens set to render the light rays more parallel as they exit the Powermate.

Company Seven: has become among the most experienced distributor of the DayStar filter systems. In fact it was one of our customers, Michael Olshausen who with little assistance from us developed the Questar Solar Observatory system incorporating the DayStar Hydrogen Alpha filter; this system has provided many amateurs and professionals a world wide "portable solar observatory". Other customers of Company Seven have published striking images on the Internet, or contribute images to or write the books on these subjects.

Company Seven has established a Solar Observing Program hosted at our showroom featuring our own DayStar University Series 0.3 Angstrom Hydrogen Alpha (115 v oven model), DayStar T-Scanner 0.5 Angstrom Hydrogen Alpha (a portable model that requires no power to operate), and DayStar 2.0 Angstrom Single Cavity Calcium K-Line filters among other "white light" filters which we offer.

The DayStar solar filters are engineered to function with an energy reduction "pre filter" or an aperture stop attached on to the front of almost any telescope, while the Hydrogen-Alpha filter body is installed onto the focuser of the telescope. The effective system aperture can be as large as the that of the telescope, so we at Company Seven have decided to equip our facility to study the Sun with our Astro-Physics and TeleVue refracting telescopes of up to 206mm aperture! Although for reasons of convenience and limits imposed by our local "seeing" conditions we routinely employ telescopes of only between 90mm to 130mm.

The reliable DayStar filter can be found in operation throughout the world's major educational and research institutions. Company Seven continues to sell and deliver the internationally acclaimed DayStar filters to amateurs, to professional observatories, and to research organizations. Most of these filters continue to provide uninterrupted service since delivered more than thirty years ago! Our filters have been been a component of some of the most exciting astronomical findings in history including the filtering system on board the Voyager space craft that detected the erupting volcanoes on Jupiter's moon Io. And of course these shock and vibration resistant systems have been flown on board the Space Shuttle. Most books and scientific papers about solar astronomy refer to the DayStar as an internationally acclaimed standard of excellence. To see amazing images and movies provided by these filters simply visit almost any major solar research facility web site, including that of the "Big Bear Solar Observatory" web site at "http://www.bbso.njit.edu" or search any number of NASA or university astronomy sites.