lumpy darkness

THURSDAY, JULY 18, 2019

simple Telrad heater

Built my own very simple dew heater for a Telrad using large resistors. A serendipitous discovery was that the large, heavy gauge leads of the resistors were strong enough to form a rigid frame for the entire heating element. It fits perfectly between the uprights, above the lens, and below the reflecting glass plate.

Commercial Telrad dew heaters: Kendrick Premier CDN $49; Kendrick FireFly CDN $37; Astrozap USD $35.

Of late, I have considered using the heater as a test unit; rather than using and possibly destroying a commercial dew heater wrap.

technical info:

• 2 resistors, 220 ohms each, are connected in parallel so to yield 110 ohms
• 0.11 amperes
• used the heavy, thick lead wires of the resistors to form a box frame that fits inside the Telrad uprights
• used 4 wire microphone cord
• used 2 wires for each channel

build costs:

• resistors, $1
• microphone cable, $5
• RCA plug, $1
• cable hooks, $2

research and build time:

• mock up testing, 1 hour
• final assembly, 1 hours
• testing, 1 hour

THURSDAY, JULY 18, 2019

bits and bobs

Parts for the dew controller build. Various sources including The-Store-Formerly-Known-As-RadioShack, Active Surplus, and Canadian Tire.

• 2 resistors, 2 watts, 220 ohms
• professional grade 4-wire microphone cable
• RCA male plug
• 2 cable hooks, self-adhesive

Tools, equipment, etc. used. You can do your own thing of course.

• testing
  • digital multi-meter
  • 12v SLA battery
  • alligator jumper cables, for jumping
• tools
  • soldering iron, adjustable
  • sponge
  • helping hands
  • alligator jumper cables, for heatsinking
  • side cutters
  • wire strippers, with small bolt cutters
  • heat gun (sister's)
  • pliers
  • small vice
  • needlenose pliers
• supplies
  • heat shrink tubing
  • solder
  • water

And a digital camera to photo-document things...

THURSDAY, JULY 18, 2019

blog links

Scattered through the blog proper are detailed reports and updates on the build with some posts showing photos.

• tested LED dimmer again, 18 Feb '19
• from the new deck in Union, 13 Jun '09
• sick and damp viewing in Union, 4 Apr '08
• catching up with Al, 29 Dec '06
• tested custom Telrad heater, 28 Dec '06
• found big resistors, 17 Dec '06
• gave Mom a Telrad, 25 Dec '04

links

		lumpy darkness sites:
		blog proper
		lists home
		telescopes:
		SP-C8 SCT
		GoToStar system
		Edmund 6" newt
		ETX90-RA MCT
		FirstScope 3" newt
		accessories
		life lists:
		planets, moons, etc.
		constellations
		notable stars
		double stars *
		Messier objects
		NGC objects
		other deep sky objects
		eclipses
		occultations
		photo gallery
		magnitude limit
		to do
		resources:
		SkyTools
		Stellarium
		TheSky
		NexStar 11
		Aladin quick query
		other lists:
		Greek alphabet in HTML
		judging angular size
		atlases, books, software
		what's up for the year
		meteor showers
		with just your eyes
		assessing darkness
		observing preparation
		presentations
		articles
		tips and tricks
		builds and hacks
		wx dashboards
		web site links:
		magazines
		sky conditions
		predicting aurora
		science and research
		space telescopes
		double stars sites
		retail stores
		clubs and associations
		DIY observatories
		miscellaneous