The 1.25" Baader 3.5/4nm f/3 Ultra-High-Speed Filter Set from Alpine Astronomical features three precision-grade filters recommended for extremely fast optical systems from f/3.4 to f/2.3. The set includes H-alpha, O-III, and S-II filters optimized for use with CMOS sensor cameras and suitable for CCD sensors.

3-Filter Set: H-alpha, O-III, and S-II    For f/3.4 to f/2.3 Optical Systems    CMOS-Optimized and Suitable for CCDs    Reflex-Blocker / Life-Coat    Blackened Edges

3.5/4nm half width (to harmonize exposure time of H-alpha with O-III / S-II), recommended for extremely fast optical systems from f/3.4 to f/1.8

Specially designed for filter requirements of highly opened optics, such as the Celestron RASA astrograph

Enables high contrast even with the strongest light pollution to minimize the size of stars and make nebula details accessible which is useful under a Bortle 9/8/7/(6) sky

Reflex-Blocker hard-coated and optically polished, with Life-Coat sealed coating edges

Blackened edges all around, with a filter front indicator in the form of a black outer edge on the front

Optimized for CMOS sensor cameras and suitable for CCD sensors

FWHM on each filter category is carefully designed to allow for 1:1:1 exposures, matched for typical CMOS quantum efficiency and s/n ratio

Identical filter thickness to existing standards, with attention given to parfocality in the design

Related Questions and Answers

Q: 1. Can you use this the same as a light pollution filter?

A: Light pollution filters and OIII filters pass different spectra and are used for different purposes. OIII are good for specific objects that emit in the OIII spectrum strongly, such as some nebula (veil, crab) and especially planetary nebula (dumbbell, ring). LPR filters are designed to filter light pollution - mostly sodium vapor light and are good for increasing contrast across a broader range of objects.

Q: 2. Can this lens be used alongside the hush kit for the HDX W20 Flex?

A: The Barco TLD+ 90° Ultra Short Throw (0.4:1) Lens is designed to be used with Barco UDX, HDX, and HDF series projectors. It will work for the Barco HDX-W20 FLEX.

Q: 3. Are these wheels compatible with Kupo High Roller Stand (14') BH #KUKS300112 MFR #KS300112?

A: The Kupo 8" Pneumatic Wheel with Square Speed Adapter (Set of 3) BH #KUKS941412 is suitable for use with the BH #KUKS300112.

Q: 4. What kind of modificatiom is required for Summicron 50mm? Also, does this work with Leica APO 2x teleconverter?

A: The Metabones Leica R-Mount Lens to L-Mount Speed Booster ULTRA 0.71x will work directly with the Leica Summicron R 50mm F/2 Lens and the Leica R APO 2X Teleconverter. Keep in mind this is designed for APS-C L-mount cameras.

Q: 5. Does this adapter can be use on Sony a77 and Sony a99 ii for Sigma 800mm F-mount with AF? If not what adapter do you suggest to be able to use this camera with AF?

A: No, the Metabones Nikon F-Mount Lens to Sony E-Mount Camera Speed Booster ULTRA will not work with the Sony A99 or the A77: https://bhpho.to/2dRc0U1

Q: 6. What kind of modification is needed for Summicron 50mm? Also, would this work with 2x APO Leica R teleconverter?

A: You would need to contact Leica for more information about modifications necessary to use the Summicron 50mm lens with the 2x APO Leica R teleconverter.

Q: 7. Does this adapter support autofocus on either SONY/Minolta's SSM af lenses or on the older SONY/Minolta screw drive af lenses?

A: Autofocus is not retained when using this adapter.

Q: 8. Does this adapter power the servo zoom thru the camera? Using an FS7 & Fujinon 20-120

A: No, It won't power anything thru the camera. It's just a passive adapter.

Q: 9. Will this fit and focus on a Celestron regal m2 100ed?

A: Yes the Pentax SMC XW 3.5mm Wide Angle Eyepiece (1.25") is compatible with the Celestron Regal series spotting scopes.

Q: 10. Hello, What are the exterior dimensions? Thank you.

A: The Triple Trek Messenger is 27cm tall, 37cm wide and 7cm deep at it's base.