Description
Ready for taking great photos of deep-sky objects!
The SD flattener HD kit is designed for a flat focal plane to produce a crisp image of stars with the SD series of APO refractors. It consists of a high-performance flattener lens and a connecting tube ring.
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The SD flattener HD lens improves off-axis image quality greatly with a minimum charge of the focal length. It covers a 44mm photographic field in diameter that is sufficient for the full-frame DSLR cameras.

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Ultimate light transmission AS coatings for extremely high contrast images.
The same anti-reflection AS coatings that are used for our high-end VSD100F3.8 renowned for extremely high light transmission (99.9% per surface) are provided on each of the lens surfaces of the SD flattener HD. Also, matte-finish is elaborate to eliminate internal reflections and loss of light completely.

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Optional HD focal reducer.
If combined with a Reducer HD sold optionally, the focal length will be reduced by 0.79 times (F.7.7 to F6.1) without diminishing the image circle of 44mm. A result is a sharp image throughout the photographic field of view.


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An example is taken with an SD103S using the SD Flattener HD: M3 Globular Cluster.

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Setup diagram.

Specifications
SD Flattener HD Kit
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ConstructionSD Flattener HD: 2 elements in 1 group
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CoatingsAS coatings (Over 99.9% light transmission every single surface)
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Size/WeightSD Flattener HD: 58mm x 34mm long /111g
Spacer ring SD81: 57.5mm x 22.5mm long /18g
EX Tube 66: 68mm x 76mm long /89g -
Others52mm filters are usable with the SD Flattener HD.
Use with SD81S
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SD Flattener HDFocal length: 644mm (F7.9)
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Image circle *144mm
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Illuminated field of view0.89
Use with SD103S
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SD Flattener HDFocal length: 811mm (F7.9)
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Image circle *144mm
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Illuminated field of view0.83
Use with SD115S
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SD Flattener HDFocal length: 908mm (F7.9)
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Image circle *144mm
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Illuminated field of view0.8
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*1:Imaging range of good-shaped stars and more than 60% of illuminated field of view. A 44mm in diameter covers an image sensor of full-frame DSLR cameras and a 28.8mm in diameter covers an image sensor of APS-C digital cameras.
Configuration
- SD Flattener HD
- Spacer Ring for SD81
- EX Tube 66





