Mirror Temperature Monitor

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Piet Le Roux South Africa
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Mirror Temperature Monitor

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Post by Piet Le Roux »


"Seeing" conditions has a huge effect on how well your reflector telescope preforms, Much of the "atmospheric seeing" problem, however, arises surprisingly close to the telescope, the 'boundary layer' of warm air directly in front of the primary mirror is the chief culprit. Having a 15" Dobsonian with a lovely 2" thick mirror does have its downside because it is not easy to get to the ambient air temperature. Gary Seronik in his "Beat the Heat: Conquering Newtonian Reflector Thermals — Part 2" article :
https://garyseronik.com/beat-the-heat-c ... ls-part-2/
supply some nice graphs to show the difference in cooling a 1" and 2" mirror. A handy tool to monitor this process is a duel temperature monitor, these are sold in automotive accessory stores to monitor the inside and outside temperature of your vehicle. It has a "inside" and "outside" temperature display : the "outside" is measured by a remote sensor, I removed the remote sensor from its plastic housing and covered it in thermal conducting grease, the type used to mount computer CPU's. I mounted the sensor on the top side of my mirror, near its surface, with double sided tape, placing a piece of aluminium baking foil on top of the double sided tape to thermally isolate it better. According to Gary the mirror has to be within 5½°F (3°C) of the ambient air temperature to overcome thermal problems.
20190624_050456.jpg
The photo shows the bottom of my Obsession's mirror and fan housing with the monitor above that.
Main Equipment : Tele Vue 27mm Panoptic, 7&13mm Nagler, Big Barlow : 8" Meade LX90ACF with Meade 2.0" Enhanced Diagonal : Camera Fuji XT100
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Piet Le Roux South Africa
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Location: Bloemfontein, South Africa
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TSS Photo of the Day

Re: Mirror Temperature Monitor

#2

Post by Piet Le Roux »


Just to clarify the sensor placement.....
mirror_image_for_seeing_m.jpg
mirror_image_for_seeing_m.jpg (17.28 KiB) Viewed 2909 times
Main Equipment : Tele Vue 27mm Panoptic, 7&13mm Nagler, Big Barlow : 8" Meade LX90ACF with Meade 2.0" Enhanced Diagonal : Camera Fuji XT100
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