Dew Guard

$26.46 ~~$42~~ In stock

Description

AstroSystems amazing Dew Guard secondary mirror heating system automatically senses the air temperature and the mirror temperature, then maintains the secondary at a preset (adjustable) temperature above the ambient air temperature. Gently warms the secondary at 2-4 watts when on full. The DG-1 has 4, The DG-2 has 6 and the DG-3 has 8 evenly spaced contact points for optimal thermal distribution. Uses any external 9-15 volt dc supply or you can run on a 9v battery mounted at the holder, eliminating the need for wires across the spider. Note: 9V rechargeable NiCd or NiMH batteries will not work, they are only 7.2-8.4V and have low capacity, rechargeable Lithium cells are 9V and will function properly. No more heat ropes! Three sizes to choose from.

DG-1 fits 1.3-2.1" Mirrors

DG-2 fits 2.6-3.1" Mirrors

DG-3 fits 3.5-6.0" Mirrors

Note: If your secondary is glued to a center post, the Dew Guard cannot be used. If your secondary is exposed and not inside a shroud the Dewguard will not be effective in controlling dew.

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Express Shipping: Handling (business days) 0–1; Transit (business days) 7–15.

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Standard Shipping · United States: $0.00

Express Shipping · United States: $3.99

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United States · Return window (days after delivery): 30. Return method: By mail. Return postage: Seller pays.

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Customer Reviews (4.8 / 5 · 5 reviews)

Steven Q. ★★★★★ Oct 20, 2026

Setup took all of five minutes, and the automatic temperature sensing has kept my secondary perfectly dew-free through three humid nights in a row. The preset adjustment is a nice touch—I set it once and haven't touched it since.

Isabella ★★★★★ Oct 19, 2026

I was a bit skeptical about how well it would regulate temperature, but after a few cold nights the secondary mirror stayed completely clear of dew. The adjustable preset is easy to dial in and the auto-sensing takes care of the rest.

David R. ★★★★★ Oct 18, 2026

The temperature sensing works perfectly—I haven't had any dew issues since installing it, and the adjustable preset is easy to dial in. It’s a simple setup that gives me real peace of mind during long observing sessions.