DayStar ULF-90 – 90 mm Foldable Universal Solar Filter

DayStar ULF-90 – 90 mm Foldable Universal Solar Filter

Visit DayStar ULF-90 is a large, universal solar filter designed for telescopes, astronomical binoculars, spotting scopes, and certain large camera lenses with a compatible outer diameter.

It has an aperture of 90 mm and fits onto instruments with an outer diameter between 90 and 109 mm. It is particularly suitable for many telescopes and astronomical binoculars with a nominal aperture ranging from
80 and 90 mm.

Compatibility depends, however, on the actual outer diameter of the tube or steam barrier, and not just the aperture specified by the instrument's manufacturer.

Solar observation in white light

When properly assembled and securely mounted in front of the instrument's aperture, the ULF-90 allows you to observe or photograph the Sun with a tint orange, sharp, and high-contrast. It also lets you see the large spots
solar panels, if present.

This filter is suitable for observing solar eclipses and large structures visible on the photosphere. It is not a specialized H-alpha solar filter and does not allow you to observe prominences or details of the chromosphere as a dedicated H-alpha system would.

Thousand Oaks solar film, ND 5 density

The ULF-90 uses a solar film Thousand Oaks Optical, from a manufacturer listed by the American Astronomical Society as one of its recognized suppliers of solar filters.

The film has high optical density ND 5, corresponding to a rejection of 99.999 % of solar radiation. It meets the transmission requirements of the standard ISO 12312-2:2015 regarding filters intended for direct observation of the Sun.

Disclaimer Regarding the ISO Standard: The ISO 12312-2 standard applies to eyewear such as sunglasses. It was not designed to cover filters built into cameras, telescopes, or astronomical eyepieces,
binoculars or spotting scopes. At present, there is no recognized, consensus-based standard that specifically covers this entire product category.

The ULF-90 is therefore manufactured and packaged as a an optical accessory designed to be mounted in front of an instrument. It must never be used as a pair of glasses or held directly in front of the eyes.

Key features

• Effective opening: 90 mm
• Compatible outer diameter: 90 to 109 mm
• Suitable for many telescopes and binoculars with apertures ranging from 80 to 90 mm
• Compatible with certain high-end camera lenses and certain spotting scopes
• Thousand Oaks Optical Window Film: density ND 5
• Reduction of solar radiation: 99,999 %
• Double-layer thick cardboard structure
• Black interior surface that minimizes internal reflections
• Foldable tabs that hold the filter in place around the optical tube
• Lightweight, foldable design
• Delivered flat in a Stayflat rigid envelope
• Assembly required before use
• Made in the United States
• Bilingual packaging in English and Spanish

Recommended Compatibility

The ULF-90 is primarily intended for use with the following equipment:

• telescopes with 80- to 90-mm outer tubes that are compatible; ;
• 80- to 90-mm astronomical binoculars; ;
• certain large telescopes; ;
• certain telephoto lenses and large camera lenses; ;
• instruments with an outer diameter between 90 and 109 mm.

Important information: Measure the outer diameter of the tube and the steam baffle precisely
or the front part of the instrument. A telescope advertised with an aperture of 80 or 90 mm
may have a significantly larger outer diameter.

Essential Safety Guidelines

• Never look at the Sun without a specially designed solar filter.
• Never place the filter near the eyepiece: it must be installed in front of the instrument’s aperture.
• Do not use the filter if the film is torn, punctured, heavily scratched, or damaged.
• Never use the product when it is flat, unfolded, or partially assembled.
• Carefully inspect the film before each use.
• Make sure the filter completely covers the opening of the instrument.
• No part of the solar disk should be visible around the filter.
• Make sure the tabs hold the filter securely in place around the tube.
• Check that the filter is secure before tilting the telescope or lens downward.
• Never remove the filter while the instrument is pointed at the Sun.
• Handle the equipment with care to avoid moving or dropping the filter.
• If possible, add a non-destructive safety fastener to prevent accidental removal.
• Never leave a telescope pointed at the Sun unattended.
• Children must be supervised at all times by a responsible adult.
• Remove or cover the optical scanner if it does not have its own compatible front sunshade.
• This product is not a pair of eclipse glasses and should never be used directly in front of the eyes.

Reference: ULF-90