Stay above the dew point without overheating.

Estimate dew point, safety margin and first-order heater demand from local conditions and heater-band geometry.

Purpose and method

What this calculator does

How much dew-heater power do I need? Estimate dew point, optic margin and heater demand.

In words: First-order heater power offsets heat loss at the desired temperature margin.

The saved aperture supplies the optic diameter. Ambient conditions, heater-band width, efficiency and heat-loss assumptions must match the actual night and installation.

Working geometry

Dew-control geometry

A heater band raises the optic above dew point while heat is lost to the environment.

Inputs

Conditions and heater

Ambient temperature

Unit: °C

Relative humidity

Unit: %

Optic diameter

Unit: mm

Heater band width

Unit: mm

Margin above dew point

Unit: °C

Heat-loss coefficient

Unit: W/m²K

Heater efficiency

Unit: %

Supply voltage

Unit: V

Calculated now

Dew control estimate

Dew point: 8.43 °C
Ambient margin: 1.57 °C
Target optic temperature: 12.43 °C
Estimated heater power: 2.18 W
Estimated current: 0.18 A
Current risk: narrow margin

Equations

Magnus dew point

T_{d} = \frac{b γ}{a - γ}

First order heater power

P \approx \frac{h A ΔT}{η}

Power is a planning estimate. Wind, radiative cooling to the sky, insulation, cell mass, controller placement and sensor contact can materially change demand. Use closed-loop control and avoid warming optics more than necessary.

Optics & framing

Image quality

Acquisition

Mount & guiding

Sky & environment

Session planning

Formula

Where to find the inputs