26.3.2020 Temperatures at focus of 6" f/10 H-alpha telescope.

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12:45 53/50F. I removed the complete PST etalon and filter stack to check the temperature at focus. I was using the outdoor capsule of my Indoor/Outdoor digital thermometers.

With only the Baader D-ERF in front of the 6" objective the temperature went right off the scale! Over 65C or 150F. I drew smoke from the white, plastic coated, external sensor! So much for a cool optical train after a Baader D-ERF! I'll try the thermal "gun" with a thin, metal target immediately after lunch.

14:00 I found a 130C spirit thermometer in my collection. With the bulb close against some Scotchbrite, maroon, abrasive fiber, I reached 122C before my arms became tired. I was unable to register a high temperature with the thermal pistol on a small piece of black painted metal.

So I used the fiber as a target and held the pistol "muzzle" close against the surface with the fiber at a slight angle to allow the gun a clear shot without casting a shadow. It registered over 130C! 

After adding the two protective filters in series with the D-ERF I registered 47C maximum at focus. [2" Baader 35nm H-alpha and a Beloptik KG3 about 230mm inside focus.]

I allowed the filters to "soak" in the telescope while it tracked the sun for a few minutes and then measured 18C on the back of the KG3.

Using the Scotchbrite as a target while facing the sun, inside the dome, I measured 35C. Which suggests the fiber is quite a reasonable thermal target. Having low thermal capacity but useful thermal absorption. Ambient temperature in the shade inside the dome was 57F with 51F in the shade out in the open behind the building.

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