Winter Observing

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Winter Observing

• Nov 2, 2007

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The Winter Sky
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Humidity

• Relative Humidity
• Current Water Content at Current Temp relative to
  Max Content (as )
• Warm Air Holds More Moisture than cold
• Humidity rises as evening cools
• Dewpoint
• Temp where Saturation (100) is Reached

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Dew

• Condensation on a surface that is Dew Point
• Still air aids dew formation

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Where is Dew Likely to Form?
Secondary Mirror
telerad
Eyepieces
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Preventing Dew

• Prevent air circulation
• Cover
• Heat

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Prevent Air Circulation
No evidence that a baggie (oops a shroud) helps a
Dob
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Cover items not in use

• Keep the finder caps on
• Put an eyepiece cap over the eyepieces

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Active Heating

• Ultimately the only solution that will lengthen
  your night
• Wraps
• Builtin
• Hair Dryer

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Wraps
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Built-in Heaters

• Some High Quality secondaries offer builtin
  heater
• Newer, high end SCTs

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When all else fails
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The rest of the stuff

• Keep your cars closed
• Protect Laptop and papers

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Keeping Warm

• You need to dress at least 10 colder
• Protection from wind and wet
• Hot drinks snacks will help
• Different people use different strategies
• War Surplus is cheap way to buy warm

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40s
Lightweight head gear
Fleece Jacket
Old CC Ski boot
Windpants
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30s and below
Thermal Underwear
Bib or insulated pants
Heavy headgear
Insulated coat
Gloves
Insulated boots (e.g. Sorels)
Warm Sweater
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Other Winter Challenges

• Be careful of Black Ice
• Dont use for car battery for dew control
• Use www.sjaa.net/weather

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Where to Go?

• Coyote
• Hard surface, easy drive
• Low gets valley fog
• Coe
• High
• Nasty road, SJ Lights, gravel surface
• Fremont Peak is closed except to FPOA
• Check with TAC (www.observers.org)