Vixen SD81S II apochromatic refractor with Flattener HD and Reducer HD kit

Kit composed by the Vixen SD81S II doublet apochromatic refractor, the SD Flattener HD field corrector and the SD Reducer HD focal reducer. With this kit you will get an high performance flat-field astrograph capable to cover the full-frame image format. Double focal length for maximum versatility!

Contact us for info about connecting your DSLR or your CCD / CMOS cameras.

The Vixen SD81S II apochromatic refractor is completely made in Japan and delivers an high quality SD doublet lens with 81 mm of aperture and 625 mm focal length (focal ratio F/7.7). You will find the best optical quality as usually delivered by Vixen along a sturdy yet ligh optical tube. Weight of the optical tube only is 2.3 Kg.

A new apochromatic refractor with high-performance Super ED Glass (=SD) made of leading-edge FPL53 glass reproduces extremely clear and sharp image by extraordinary eliminating color aberration.

The SD glass is designed to gather all g-ray (purple), C-ray (red), F-ray (blue), d-ray (yellow), and e- ray (green) around 0 value, which stands for an excellent lens material surprisingly reducing chromatic aberration over all colors. Using in combination with new optional SD Reducer HD Kit or SD Flattener HD Kit , it allows 44 mm image circle with full-format (D)SLR camera.

ED81SII, ED103S, ED115S were originally designed for both visual observation and photo visual users. SD Optical Tube Series optimized its position of "baffle" inside of draw tube in order to be compatible with full-size DSLR.

Features

• Optical Design: SD Apochromatic Refractor with S-FPL53 lens doublet (same optics as used in the former ED81S II)
• Aperture: 81 mm
• Focal Length: 625 mm
• Focal Ratio: F/7.7
• Coating: Multi Coating
• Resolving Power: 1.43 arc sec
• Limiting Magnitude: 11.3
• Light Gathering Power: 134x
• Back Focus (from rear edge of focuser body): 149.0 mm Back Focus
• Astrophotography: Prime Focus, Eyepiece Projection & Afocal Imaging
• Visual Back: 2" with compression Ring
• Optical Tube Length: 585 mm
• Optical Tube Diameter: 90 mm
• Outside Dew Shield Diameter: 100 mm
• Optical Tube Weight: 2.3 Kg (3.5 Kg with included accessories)
• Included Accessories: Tube Rings; Flip Mirror Diagonal; Dovetail Plate; Red Dot Finder; Carry Handle
• Made in Japan

Vixen SD Reducer HD Kit

The Vixen SD Reducer HD Kit includes the SD Flattener HD filed flattener, the SD Reducer HD aplanatic focal reducer, the EX Tube 66 extensione tube and the specific extensione tube to be used along the SD81S.

It is complete correcting and reducing lens system for Vixen SD81S, SD103S e SD115S optics designed to work with digital cameras or CCD/CMOS up to full-frame format (24x36 mm). Transforms Vixen SD optics into flat field astrographs with two differents focal ratio available. You can choose to use the HD field flattener only or in combination with the HD focal reducer.

You can use the SD Reducer HD only with flat field instruments such as the Vixen AX103S or the Vixen VC200L Visac.

On the Vixen SD optics you can use the SD Flattener HD only in order to get a corrected field with the highest edge illumination possibile. The field flattener enlarge focal length by 1.03x and 1.02x on Vixen SD81S and Vixen SD103S/SD115S respectively (focal ratio become F/7.9). With the SD Reducer HD the focal ratio goes down to ~ F/6.1

Vixen AS Coating

All the new high performance correctors by Vixen include the highly renowned Vixen AS Coating that ensures over 99.9% light transmission for each optical surface. It is the same coating used also in the Vixen flagship VSD 5-lens astrograph. This advanced coating cuts down to a negligible effect any possibile loss of light and any ghost or flare image.

SD Flattener HD specifications

SD Flattener HD + SD Reducer HD specifications

SD Reducer HD specifications

*1 : Over 60% is considered an acceptable value in photography. Field correction covers an imaging field of 44 mm so bigh enough to cover the full-frame APS format (24 x 36 mm) and much higher than APS-C format (28.8 mm).

*2 : Field correction covers a diameter 44 mm, but at the edge you will get a 47% illumination only. So we reccomend sensors up to 36 mm diameters, corresponding to the APS-H format.

Vixen SD Spot diagrams

Vixen SD103S spot diagrams at prime focus without correctors (F/7.7)

Vixen SD103S spot diagrams at prime focus with SD Flattener HD field flattener (F/7.9)

Vixen SD103S spot diagrams at prime focus with SD Flattener HD field flattener and SD Reducer HD focal reducer (F/6.1)

SD Reducer HD spot diagrams onto Vixen AX103S astrograph

The Vixen AX103S astrograph is natuvely corrected up to full-frame 24x36 mm format, but the former 0.7x reducer has been designed for sensor up to APS-C format. Now the new SD Reducer HD covers also the full-frame format, although reduction is a little bit lower (F/6.2 vs. F/5.6).

Vixen AX103S spot diagrams at prime focus (F/8)

Vixen AX103S spot diagrams at prime focus with SD Reducer HD reducer (F/6.2)

Vixen AX103S spot diagrams at prime focus with #VX-37228 0.7x designed for APS-C sensors (F/5.6)

SD Reducer HD spot diagrams onto Vixen VC200L "Visac" catadioptric

The Vixen VC200L Visac catadioptric is well known as a great imaging performer also on big sensors. Performances were good also with the former 0.71x focal reducer, expecially with sensors up to APS-C format, but now with the new SD Reducer HD focal reducer you can have an even better field correction over a 44 mm image circle, although we reccommend sensor up to 36 mm image circle because of vignetting at the edge. Field illumination at the edge of the 36 mm image circle is 60%, and only 47% at the edge of the 44 mm image circle.

Vixen VC200L spot diagrams at prime focus

Vixen VC200L spot diagrams at prime focus with SD Reducer HD installed (F/6.9)

Vixen VC200L spot diagrams at prime focus with #VX-37229 0.71x focal reducer installed (F/6.4)

Example images

The M3 globular cluster taken with Vixen SD103S and SD Flattener HD field flattener

The M31 galaxy taken with Vixen SD103S and SD Flattener HD field flattener + SD Reducer HD focal reducer

The M8 and M20 nebuale in Sagittarius taken with Vixen AX103S astrograph and SD Reducer HD

M101, the Pinwheel Galaxy, taken with Vixen VC200L Visac astrograph and SD Reducer HD focal reducer

System Chart