Astro-Physics Flat Surface Pier Adapter 1100/900 GTO

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  • Regular price $130.00
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Astro-Physics Flat Surface Pier Adapter 1100/900 GTO

Astro-Physics Flat Surface Pier Adapter 1100/900 GTO


In late 2012, the Astro-Physics Flat Surface Adapter (formerly part # 900FSA) was upgraded to include four additional thru-holes for more secure attachment to a flat plate with the larger 1100GTO and its payload in mind. It also includes "N" and "S" engraving to ensure that the base of your mount will be oriented in the correct direction when it is inserted.

The Astro-Physics Flat Surface Adapter bolts onto the flat surface on the top of your pier or tripod. Your pier's top plate should be a minimum of 7.75" in diameter. The 119FSA itself is 8.375" in diameter. It adds 1.265" to the height of your mount.

The bolt circle for attaching the 900 Flat Surface Adapter to your pier is 7.230Ÿ??????????? in diameter.

The holes for mounting the 119FSA to your flat surface are counter-bored to accept the head of standard ?????Ÿ??????????? socket head cap screws (13/32Ÿ??????????? or 0.406Ÿ??????????? diameter). This allows the 1100 base or 900 Pier Adapter to sit in the Flat Surface Adapter without interference. Because installations will vary, Astro-Physics does not provide the screws for mounting the Flat Surface Adapter to your pier or tripod.


The base of the 1100GTO slips directly into the 119FSA. There is no need for an extra pier adapter, as the 1100 incorporates the functionality of the Precision-Rotating Pier Adapter into its base. The extended latitude range of the 1100 also eliminates the need of a polar wedge.

900 (all versions)


Use this adapter for these applications:

  • Interface between the Precision-Adjust Rotating Pier Adapter (900RPA) and the flat plate on your custom-made pier or tripod.
  • Attach to the top of your 900 Hi-Lo Latitude Wedge (900WDG) if you wish to use the 900RPA.
  • Although the Standard Pier Adapter (900SPA) can bolt directly onto the flat plate of your pier or tripod, you can use this adapter to give a more finished appearance.

Additional Information

ManufacturerAstro Physics

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