Home Astrophotography Accessories by Optec Optec-DSI 3.5-inch Telescope Extension Rings, Adapters and Retaining Rings
Optec-DSI 3.5-inch Telescope Extension Rings, Adapters and Retaining Rings
Optec-DSI 3.5-inch Telescope Extension Rings, Adapters and Retaining Rings
Optec-DSI 3.5-inch Telescope Extension Rings, Adapters and Retaining Rings
Optec-DSI 3.5-inch Telescope Extension Rings, Adapters and Retaining Rings
Optec-DSI 3.5-inch Telescope Extension Rings, Adapters and Retaining Rings
Optec-DSI 3.5-inch Telescope Extension Rings, Adapters and Retaining Rings
Optec-DSI 3.5-inch Telescope Extension Rings, Adapters and Retaining Rings
Optec-DSI 3.5-inch Telescope Extension Rings, Adapters and Retaining Rings
Optec-DSI 3.5-inch Telescope Extension Rings, Adapters and Retaining Rings

    Optec

    Optec-DSI 3.5-inch Telescope Extension Rings, Adapters and Retaining Rings

    $ 195.00
    $ 195.00

    This item is out of stock but you can place an order now and we’ll ship when it becomes available.

    Description

    Rich Simons of Deep Sky Instruments and Optec have jointly developed a new, larger diameter standard spacer for large aperture telescopes.  Like the Astro-Physics 2.7-inch spacer set, the Optec-DSI 3.5-inch spacers are available in a five different lengths.  

    The AP 2.7-inch thread has become an astronomy industry standard thanks to the tireless efforts of Roland and his team at Astro-Physics.  Optec has produced a complementary extension set and a few new adapters in an effort to extend this industry standard. However, there are times when the 2.5" clear aperture of the AP2.7 spacers will not allow enough light through clipping the edge rays. 

    Optec-DSI 3.5-inch extension tubes feature female threads on one end with male threads on the opposite end with knurled bases to help attach and detach these tubes.  The extensions can be combined and stacked. We believe our four and five piece sets will provide all the needed extension for fixed focal length telescopes with 1/4" (6.35mm) increments using a minimum number of pieces.  

    All extensions and mounts are made from high strength 6061 aluminum alloy and black anodized.  Anti-reflection threading and internal baffles on the largest extension tube help minimize internal reflections.  All internal surfaces are painted and baked with a non-reflecting ultra-flat black paint. 

    Specifications

    • Spacer Lengths Available: 1/2", 3/4", 1", 1-1/2", and 3"
    • Clear Aperture: 3.25" (82.5mm)
    • Back-focus Usage: Variable (see TABLE below)

    Extension Tube Sets

    Stock #19889
    DSI 3.5 Extension Tube Set, 4-piece set
    • Includes: 1/2", 3/4", 1", and 1-1/2"
    • Possible spacer combinations:
      0.5" through 3.25" with 1/4-inch increments plus 3.75" with all spacers combined.  (See Table below for combinations.)

    Stock #19890
    DSI 3.5 Extension Tube Set, 5-piece set
    • Includes:  1/2", 3/4", 1", 1-1/2", and 3"
    • Possible spacer combinations:  
      0.5" through 6.25" with 1/4-inch increments plus 6.75" with all spacers combined.  (See table below for combinations.)

    Individual Extension Tubes and Retainers

    Stock #19891
    DSI 3.5 Extension - 1/2" Length
    • Overall Height: 0.88"  (22.4mm)
    • Clear Aperture: 3.25" (82.5mm)
    • Weight: 1.0 oz. (30 g)
    • Back-focus Usage: 0.50" (12.7mm)

    Stock #19892
    DSI 3.5 Extension - 3/4" Length
    • Overall Height: 1.13" (28.7mm)
    • Clear Aperture: 3.25" (82.5mm)
    • Weight: 1.4 oz. (40 g)
    • Back-focus Usage: 0.75" (19.1mm)

    Stock #19893
    DSI 3.5 Extension - 1" Length
    • Overall Height: 1.38" (35.0mm)
    • Clear Aperture: 3.25" (82.5mm)
    • Weight: 1.8 oz. (55 g)
    • Back-focus Usage: 1.00" (25.4mm)

    Stock #19894
    DSI 3.5 Extension - 1-1/2" Length
    • Overall Height: 1.87"  (47.5mm)
    • Clear Aperture: 3.25" (82.5mm)
    • Weight: 2.4 oz. (70 g)
    • Back-focus Usage: 1.50" (38.1mm)

    Stock #19895
    DSI 3.5 Extension - 3" Length
    • Overall Height: 3.38" (85.8mm)
    • Clear Aperture: 3.25" (82.5mm)
    • Weight: 8.2 oz. (230 g)
    • Back-focus Usage: 3.00" (76.2mm)

    Stock #19896

    DSI 3.5x24tpi to AstroPhysics 2.7" female Adapter

     

    		 No Picture Available
    Stock #19897
    DSI 3.5 Retaining Ring
    • Overall Height: 0.14" (3.5mm)
    • Clear Aperture: 3.45" (87mm)
    • Weight: 0.4 oz. (15 g)
    • Back-focus Usage: 0.10" (2.5mm)
    • Anodize:  Gold

     

    Target Extension

    Spacers Required

    AP2.7 Spacer Stock Numbers

    DSI 3.5x24 Stock Numbers

    0.50”

    ½”

    19882

    19891

    0.75”

    ¾”

    19883

    19892

    1.00”

    1”

    19884

    19893

    1.25”

    ½” + ¾”

    19882, 19883

    19891, 19892

    1.50”

    1-½”

    19885

    19894

    1.75”

    1” + ¾”

    19884, 19883

    19893, 19892

    2.00”

    1-½” + ½”

    19885, 19882

    19894, 19891

    2.25”

    1-½” + ¾”

    19885, 19883

    19894, 19892

    2.50”

    1-½” + 1”

    19885, 19884

    19894, 19893

    2.75”

    1-½” + ¾” + ½”

    19885, 19883, 19882

    19894, 19892, 19891

    3.00”

    3”

    19886

    19895

    3.25”

    1-½” + 1” + ¾”

    19885, 19884, 19883

    19894, 19893, 19892

    3.50”

    3” + ½”

    19886, 19882

    19895, 19891

    3.75”

    3” + ¾”

    19886, 19883

    19895, 19892

    4.00”

    3” + 1”

    19886, 19884

    19895, 19893

    4.25”

    3” + ¾” + ½”

    19886, 19883, 19882

    19895, 19892, 19891

    4.50”

    3” + 1-½”

    19886, 19885

    19895, 19894

    4.75”

    3” + 1” + ¾”

    19886, 19884, 19883

    19895, 19893, 19892

    5.00”

    3” + 1-½” + ½”

    19886, 19885, 19882

    19895, 19894, 19891

    5.25”

    3” + 1” + ¾” + ½”  

    19886, 19885, 19883, 19882

    19895, 19893, 19892, 19891

    5.50”

    3” + 1-½” + 1”

    19886, 19885, 19884

    19895, 19894, 19893

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