Dew Shields and Dew Heaters

Dew shields and dew heater systems are an essential telescope accessory for anyone operating a telescope where dew or frost regularly forms. Dew forms on a surface when its temperature falls beneath the dew point. This is a nightly occurrence from spring through fall for those of us in the northeast, your conditions may vary. Dew gives way to frost if the dew point falls below freezing. The formation of dew or frost on telescope optics can render them useless for the remainder of the night. Schmidt-Cassegrain telescopes are notorious for dew formation because of the large unprotected corrector plate at the front of the telescope. The best solution for dew on the optics is to stop it from forming in the first place.

A dew shield is a long extension to your telescope tube, which effectively insulates your front of your telescope. Dew shields work by maintaining a stationary column of air at the front of the telescope, trapping some of the heat within the telescope and slowing the arrival of new moisture, thereby slowing the formation of dew. Over time, the optics will still dip below a dew point, but passive dew shields for telescopes will sometimes work for several hours before dew begins to form on the optics. Typically, telescope dew shields are the less expensive option.

Situations involving longer observing sessions or heavy dew call for active or heated solutions. A dew heater is a specialized strip of resistive electrical wire that fits around the lens of a telescope. The wire is driven with dew heater controller, powered by a 12-volt DC battery, which then runs an electric current through the wire. The high resistance of the wire means it will heat up and directly transfer heat to the telescope, preventing it from dipping below the dew point. Normally a dew heater controller is used to set the desired amount of heat. Adding too much heat can lead to tube currents which will interfere with the image. Though they’re more effective, dew heaters tend to be more expensive. Since they require electricity to work, they also require more power in the field.

  • Astrozap Telrad Dew Heater
  • Astrozap Telrad Dew Heater

  • The Astrozap Telrad dew heater band is molded to wrap securely around the optical window of the Telrad Reflex Site. read more...
  • Our price: $35.00

  • Astrozap Dew Controller
  • Astrozap Dew Controller

  • The Astrozap Dew Controller uses pulse width modulation to regulate dew heaters from 5-95% of capacity. read more...
  • Our price: $105.00

  • Thousand Oaks Digital Dew Heater Controller
  • Thousand Oaks Digital Dew Heater Controller

  • Thousand Oaks Digital dew heater control unit provides individual control for up to four dew heater devices. read more...
  • Our price: $105.00

  • Astrozap Dew Heater Bands
  • Astrozap Dew Heater Bands

  • Astrozap Dew Heater Straps apply heat evenly across their length and are made with advanced materials right here in the USA. read more...
  • Starting from: $25.00

  • Thousand Oaks Dew Heater Bands
  • Thousand Oaks Dew Heater Bands

  • Thousand Oaks dew heater bands combat the formation of dew on the front element of refractors, Schmidt-Cassegrains, and Maksutov-Cassegrains. read more...
  • Starting from: $39.00

  • Astrozap Flexible Dew Shield for ETX 90 / C90
  • Astrozap Flexible Dew Shield for ETX 90 / C90

  • Astrozap AZ-103 flexible dew shields fit 90mm Maksutov-Cassegrains, such as the Celestron C90 spotting scope or Meade ETX90. read more...
  • Our price: $24.95

  • Astrozap Flexible Dew Shield for NexStar 4SE
  • Astrozap Flexible Dew Shield for NexStar 4SE

  • Astrozap AZ-104 flexible dew shield fits the Celestron NexStar 4SE, Orion Apex 102, and Meade ETX-105. read more...
  • Our price: $24.95

  • Astrozap Flexible Dew Shield for NexStar 5SE
  • Astrozap Flexible Dew Shield for NexStar 5SE

  • Astrozap AZ-117 flexible dew shield for Celestron NexStar 5SE has a notch cutout to accommodate the dovetail bar on the optical tube. read more...
  • Our price: $32.00

  • Astrozap Flexible Dew Shield for ETX 125 / C5
  • Astrozap Flexible Dew Shield for ETX 125 / C5

  • Astrozap AZ-105 fits Orion Apex 127 and older Meade EXT-125 and Celestron Nexstar 5 models where no dovetail notch is needed. read more...
  • Our price: $29.00

  • Astrozap Flexi-Heat Dew Shield for Nestar 5 SE
  • Astrozap Flexi-Heat Dew Shield for Nestar 5 SE

  • The Astrozap AZ-818 Flexi-Heat dew shield features a notch to accommodate a Vixen style dovetail bar as is used on a Celestron Nexstar 5 SE. read more...
  • Our price: $64.00

  • Astrozap Flexible Dew Shield for NexStar 6SE
  • Astrozap Flexible Dew Shield for NexStar 6SE

  • Astrozap AZ-116 flexible dew shield for Celestron NexStar 6SE has a notch cutout to accommodate the dovetail bar on the optical tube. read more...
  • Our price: $32.00

  • Astrozap Flexi-Heat Dew Shield for NexStar 6 SE
  • Astrozap Flexi-Heat Dew Shield for NexStar 6 SE

  • The Astrozap AZ-816 Flexi-Heat dew shield features a notch to accommodate a Vixen style dovetail bar as is used on a Celestron Nexstar 6 SE. read more...
  • Our price: $75.00

  • Astrozap Flexible Dew Shield for Meade LS 6 / LT6
  • Astrozap Flexible Dew Shield for Meade LS 6 / LT6

  • Astrozap AZ-120 flexible dew shields feature a very large notch (not shown) to accommodate the tube holder on Meade LS6 and LT6 telescopes. read more...
  • Our price: $34.00

  • Astrozap Flexible Dew Shield for 8-inch SCT
  • Astrozap Flexible Dew Shield for 8-inch SCT

  • Astrozap AZ-107 flexible dew shields fit 8-inch Schmidt-Cassegrains not fitted with full length dovetails bars, such as the Meade LX90. read more...
  • Our price: $34.50

  • Astrozap Flexible Dew Shield for 8-inch SCT Notched for Dovetail
  • Astrozap Flexible Dew Shield for 8-inch SCT Notched for Dovetail

  • Astrozap AZ-122 flexible dew shields for 8-inch Schmidt-Cassegrains notch cutout to accommodate the Losmandy style dovetail bar found on Celestron CGEM models. read more...
  • Our price: $39.00

  • Astrozap Flexible Dew Shield for NexStar 8 SE
  • Astrozap Flexible Dew Shield for NexStar 8 SE

  • Astrozap AZ-118 flexible dew shield for Celestron NexStar 8SE has a notch cutout to accommodate the dovetail bar on the optical tube. read more...
  • Our price: $36.00

  • Astrozap Flexi-Heat Dew Shield for 7' Maksutov / 8" SCT
  • Astrozap Flexi-Heat Dew Shield for 7' Maksutov / 8" SCT

  • The AZ-807 Flexi-Heat dew shield is intended for use with 8-inch SCTs that do not have a dovetail bar, such as the Celestron CPC or Meade LX90. read more...
  • Our price: $74.00

  • Astrozap Flexi-Heat Dew Shield for NexStar 8 SE
  • Astrozap Flexi-Heat Dew Shield for NexStar 8 SE

  • The Astrozap AZ-817 Flexi-Heat dew shield features a notch to accommodate a Vixen style dovetail bar as is used on a Celestron Nexstar 8 SE. read more...
  • Our price: $74.00

  • Astrozap Flexi-Heat Dew Shield for 8" Celestron - 1 Notch
  • Astrozap Flexi-Heat Dew Shield for 8" Celestron - 1 Notch

  • The Astrozap AZ-820-N-1 Flexi-Heat Dew Shield features a single notch wide enough to accommodate a Losmandy dovetail bar as is supplied on Celestron 8-inch CGEM, CGEM DX, and CGE Pro telescopes. read more...
  • Our price: $82.00

  • Astrozap Flexi-Heat Dew Shield for 8" Celestron - 2 Notches
  • Astrozap Flexi-Heat Dew Shield for 8" Celestron - 2 Notches

  • The Astrozap AZ-820-N-2 Flexi-Heat Dew Shield features two notches wide enough to accommodate a Losmandy dovetail bars mounted top and bottom. read more...
  • Our price: $92.00

  • Astrozap Flexible Dew Shield for Meade LS 8 / LT 8
  • Astrozap Flexible Dew Shield for Meade LS 8 / LT 8

  • Astrozap AZ-121 flexible dew shields feature a very large notch (not shown) to accommodate the tube holder on Meade LS8 and LT8 telescopes. read more...
  • Our price: $39.50

  • Astrozap Flexible Dew Shield for 9.25-inch SCT
  • Astrozap Flexible Dew Shield for 9.25-inch SCT

  • Astrozap AZ-109 flexible dew shields fit Celestron 9-1/4 inch Schmidt-Cassegrain telescopes without full length dovetail bars. read more...
  • Our price: $39.00

  • Astrozap Flexible Dew Shield for 9.25-inch Evolution
  • Astrozap Flexible Dew Shield for 9.25-inch Evolution

  • Astrozap AZ-132 flexible dew shields for 9-1/4 inch Schmidt-Cassegrain telescopes feature a notch to accommodate full length Vixen style dovetail bars. read more...
  • Our price: $41.00

  • Astrozap Flexible Dew Shield for 9.25-inch SCT Notched for Dovetail
  • Astrozap Flexible Dew Shield for 9.25-inch SCT Notched for Dovetail

  • Astrozap AZ-123 flexible dew shields for 9-1/4 inch Schmidt-Cassegrain telescopes feature a notch to accommodate full length Losmandy style dovetail bars. read more...
  • Our price: $41.00

  • Astrozap Flexi-Heat Dew Shield for 9.25" SCT
  • Astrozap Flexi-Heat Dew Shield for 9.25" SCT

  • The AZ-809 Flexi-Heat dew shield is intended for use with 9-1/4-inch SCTs that do not have a dovetail bar, such as the Celestron CPC. read more...
  • Our price: $86.00

  • Astrozap Flexi-Heat Dew Shield for 9.25" SCT Notched for Dovetail
  • Astrozap Flexi-Heat Dew Shield for 9.25" SCT Notched for Dovetail

  • Astrozap AZ-809-N-1 Flexi-Heat Dew Shield features a single notch wide enough to accommodate a Losmandy dovetail bar as supplied on most telescopes. read more...
  • Our price: $86.00

  • Astrozap Flexi-Heat Dew Shield for 9.25" Celestron - 2 Notches
  • Astrozap Flexi-Heat Dew Shield for 9.25" Celestron - 2 Notches

  • The Astrozap AZ-809-N-2 Flexi-Heat Dew Shield features two notches wide enough to accommodate a Losmandy dovetail bars mounted top and bottom. read more...
  • Our price: $96.00

  • Astrozap Flexible Dew Shield for 10-inch SCT
  • Astrozap Flexible Dew Shield for 10-inch SCT

  • Astrozap AZ-111 flexible dew shields fit 10" Schmidt-Cassegrains, including the Meade LX90, LX200, and LX600. read more...
  • Our price: $47.00

  • Astrozap Flexi-Heat Dew Shield for 10" SCT
  • Astrozap Flexi-Heat Dew Shield for 10" SCT

  • This Flexi-Heat dew shield is intended for use with 10-inch SCTs that do not have a dovetail bar, such as the Meade LX90 or LX200. read more...
  • Our price: $93.00

  • Astrozap Flexible Dew Shield for 11-inch SCT
  • Astrozap Flexible Dew Shield for 11-inch SCT

  • Astrozap AZ-112 flexible dew shields fit Celestron CPC 11 and other 11-inch Schmidt-Cassegrains without full length dovetail bars. read more...
  • Our price: $47.00

  • Astrozap Flexible Dew Shield for 11-inch SCT Notched for Dovetail
  • Astrozap Flexible Dew Shield for 11-inch SCT Notched for Dovetail

  • Astrozap AZ-126 flexible dew shields fit 11-inch Schmidt-Cassegrains and feature a single notch to accommodate a full length Losmandy style dovetail bar. read more...
  • Our price: $62.00

  • Astrozap Flexi-Heat Dew Shield for 11" SCT
  • Astrozap Flexi-Heat Dew Shield for 11" SCT

  • This Flexi-Heat dew shield is intended for use with 11-inch SCTs that do not have a dovetail bar, such as the Celestron CPC 1100. read more...
  • Our price: $125.00

  • Astrozap Flexi-Heat Dew Shield for 11" SCT Notched for Dovetail
  • Astrozap Flexi-Heat Dew Shield for 11" SCT Notched for Dovetail

  • Astrozap AZ-812-N-1 Flexi-Heat Dew Shields for 11-inch Schmidt-Cassegrains feature a single wide notch to accommodate full length Losmandy style dovetail bars. read more...
  • Our price: $120.00

  • Astrozap Flexi-Heat Dew Shield for 11" Celestron - 2 Notches
  • Astrozap Flexi-Heat Dew Shield for 11" Celestron - 2 Notches

  • The Astrozap AZ-812-N-2 Flexi-Heat Dew Shield features two notches wide enough to accommodate a Losmandy dovetail bars mounted top and bottom. read more...
  • Our price: $135.00

  • Astrozap Flexible Dew Shield for 12-inch SCT
  • Astrozap Flexible Dew Shield for 12-inch SCT

  • Astrozap AZ-113 flexible dew shields fit Meade 12-inch Schmidt-Cassegrain telescopes without full length dovetail bars, including LX90, LX200 and LX600. read more...
  • Our price: $64.00

  • Astrozap Flexi-Heat Dew Shield for 12" SCT
  • Astrozap Flexi-Heat Dew Shield for 12" SCT

  • This Flexi-Heat dew shield is intended for use with 12-inch SCTs that do not have a dovetail bar, such as the Meade LX90 or LX200. read more...
  • Our price: $135.00

  • Astrozap Flexible Dew Shield for 14-inch SCT
  • Astrozap Flexible Dew Shield for 14-inch SCT

  • Astrozap AZ-114 flexible dew shields fit 14-inch Schmidt-Cassegrain telescopes without full length dovetail bars. read more...
  • Our price: $88.00

  • Astrozap Flexi-Heat Dew Shield for 14" SCT
  • Astrozap Flexi-Heat Dew Shield for 14" SCT

  • The AZ-814 Flexi-Heat dew shield is intended for use with 14-inch SCTs that do not have a dovetail bar, such as the Meade LX200. read more...
  • Our price: $155.00

  • Astrozap Flexi-Heat Dew Shield for 14" SCT Notched for Dovetail
  • Astrozap Flexi-Heat Dew Shield for 14" SCT Notched for Dovetail

  • Astrozap AZ-814-N-1 Flexi-Heat Dew Shields for 14-inch Schmidt-Cassegrains feature a single wide notch to accommodate full length Losmandy style dovetail bars. read more...
  • Our price: $155.00

  • Astrozap Flexible Dew Shield for 16-inch SCT
  • Astrozap Flexible Dew Shield for 16-inch SCT

  • Astrozap AZ-115 flexible dew shields are fit 16-inch Meade LX200 and LX600 telescopes. read more...
  • Our price: $92.00

  • Thousand Oaks 20" Dew Heater Band HB-20
  • Thousand Oaks 20" Dew Heater Band HB-20

  • Dew heaters are used to prevent condensation on telescope objectives and eyepieces when high humidity and coolre temperatures combine. read more...
  • Our price: $49.00

Telescope Dew Shields & Telescope Dew Heaters

Anyone starting out in astronomy and observing the stars may notice the occasional formation of dew on the objective lens or corrector plate. This can make for a frustrating observing experience if you live anywhere that dew is common. That’s why dew shields and dew heater systems are an essential telescope accessory for anyone operating a telescope where dew or even frost regularly forms.

Dew and Your View

Dew forms on your telescope when the temperature of your scope’s objective lens or corrector plate falls below the “dew point,” causing moisture in the surrounding air to condense on optical surfaces. This is a nightly occurrence from spring through fall for those living in the northeast, primarily. 

Dew gives way to frost if the dew point falls below freezing. You might notice the same situation on a car’s windows in the early morning. However, telescopes are particularly susceptible to condensation because they point directly upward at space, radiating their heat more quickly due to their upturned position. Schmidt-Cassegrain telescopes are especially prone to dew because of the large, unprotected corrector plate at the front of the telescope.

When dew collects on your telescope lens, this essentially halts your viewing experience — the formation of dew or frost on telescope optics can render them useless for the remainder of the night. While you can try to heat your telescope up to get the lens back above the dew point using a hair dryer or other heating device, the best way to handle dew on optics is to prevent it from occurring in the first place. That’s where dew shields and telescope dew heaters come into play.

Get Dew Shields and Heaters

At Skies Unlimited, we offer a wide selection of dew control equipment, including dew , dew heaters and even heated dew shields. We also offer the advice you need to get the most out of your equipment. Since our founding in 2004 by amateur astronomers, we’ve dedicated ourselves to providing expertise to new amateur astronomers, making the field more accessible and easy. Whether you want to purchase a Celestron dew shield or are wondering which telescope dew control measures are right for you, we can help.

Call Skies Unlimited today or visit us at our store located in Pottstown, Pa., to get started shopping with us.

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