Astro-Tech #38A Dark blue 1.25" color filter


Availability: In stock

If you have a big scope (10" in aperture and larger), this #38A dark blue Astro-Tech 1.25" eyepiece filter can be useful when observing Jupiter's belts and features on Mars during periods of violet clearing . . .
Our Product #: ATCF38

Product Description

This #38A dark blue Astro-Tech 1.25" eyepiece filter is a distinct help when observing surface and atmospheric features on Mars during periods of violet clearing with telescopes 8" in aperture and larger . . .

Recommended applications for this filter:
Moon - Somewhat useful for improving contrast between lunar features in scopes 8" and larger. Mercury - May improve observations of rarely visible dusky surface features at twilight, when the planet is near the horizon. Venus - Increases contrast of occasional faint dark shadings in upper Venusian clouds. Mars - Useful for enhancing the visibility of surface features and localized dust storms, clouds, and ice fogs with 8" or larger scopes, particularly during the still-unexplained phenomenon of violet clearing (when the Martian atmosphere - normally a bright, featureless disc in violet light due to the scattering of short wavelengths of light by the thin atmosphere - becomes transparent through a violet or blue filter, revealing large dark surface features). Jupiter - Primarily used for enhancing the boundaries between the reddish belts and adjacent bright zones in the upper atmosphere. Helpful in defining the Great Red Spot and festoons in the belts. Saturn - Enhances low-contrast features between the belts and zones in the planetary disc. Comets - Brings out the best definition in comet gas tails. Useful with 10" and larger scopes for observing orange Sodium D lines in gas tails when combined with #21 filter.
17% transmission

Tech Details

Color 38A - Dark Blue
Weight 1 oz.
Warranty 1 year


Review by:
Astro-Tech Filters are a great value! This is a fraction of what you'd pay elsewhere and works just as well.
This filter works well on Jupiter. (Posted on 1/11/2019)
How do you rate this product? *