DayStar Filters are designed to be mounted at the rear, eyepiece end of the telescope. This application allows flexibility to use the filter on many different kinds and sizes of telescopes. You are not aperture limited when using a DayStar Filter. Many DayStar owners use thier filters with apertures of 150mm or greater with great success. The important idea to remember when using a DayStar Filter is that light entering the filter must be as close to parallel as possible. That is to say that your focal ratio should be approximately F/30. Lower F/ratios allow light to enter the filter at different angles, affecting performance. The following diagram demonstrates how owners can adapt different telescopes to the F/30 required by either introducing a barlow (negative lense) or by masking the objective and reducing the aperture.

The result of using a telescope at a faster focal ratio is a wider transmission of the filter. A 0.5Å filter will transmit a wider spectrum at shorter f/ratios, and it's bandwidth increase at F/8 or F/5 to more than 1Å.

For Calcium Filters, it is not necessary to use F/30, as these filters are 10Å, 5Å and 2ÅThey can be operated on telescopes at F/20. This also provides a brighter image, which is often necessary for viewing in Calcium.

Barlow (negative lense) introduced before Filter	Aperture Reduction Mask and Energy Rejection Filter

DayStar Filters LLC • 149 Northwest OO Highway • Warrensburg, MO 64093 - USA
Telephone: 660-747-2100 • jen@DayStarFilters.com • FAX: 1-866-791-0448