Contains:  Solar system body or event
THERMAL imaging of celestial bodies (experimental stage : earth's moon), 



    
        

            Wanni

THERMAL imaging of celestial bodies (experimental stage : earth's moon)

Technical card

Imaging telescopes or lenses: Skywatcher collapsible Dobson 12" GoTo

Imaging cameras: SeeK thermal compact


Date:March 27, 2020

Time: 18:30

Frames: 2

Focal length: 1500


Resolution: 674x589

Locations: Home Observatory, Syke, Niedersachsen, Germany

Data source: Backyard

Description

THERMAL imaging of celestial bodies : It's not about pretty pictures... (not yet !)
This is my first attempt to attach a thermal imaging camera to a telescope !

Way before the current circumstances I bought a thermal imaging camera which can be
attached to a smartphone. (iPhone in my case)

The "SeeK thermal" compact has 206 * 156 pixels (yes PIXEL, not MEGA PIXEL !)
Field of view : 36°
Thermal temperature measurement range is -40° C to 330° C (-40° F to 626° F).

My immediate idea was to try to capture celestial objects:
What is the temperature of the moon ?

We need to differentiate infrared imaging from thermal imaging :

CCD / CMOS cam near infrared imaging might range from 700 to 1200 nm wavelength.

At thermal imaging we are talking 3000nm to mm range wavelength.
In this frequency range, standard optical components like lenses, filter, corrector plates etc. will block thermal wavelengths. ( This excludes telescope types like Catadioptric, Achromat)

But a Newton type telescope might work, because mirrors are reflecting light on metallic surfaces, including the thermal wavelengths.

I used my 12" Dobson and mounted the thermal cam on the opening to the secondary mirror.
Note : Stray ambient light does not play a role at all in this case!

The first results are better than expected : The waxing, gibbous moon drifted through the telescope FOV from top to bottom . ( two snapshots :see final)

I am limited by the existing DOBSON optical train and the fixed FOV of the thermal camera
The secondary mirror support structures and spiders are emitting ambient thermal
energy and are clearly visible in the images.

To get a proper full size image I would need a special thermal wavelength adaption lens,
but thermal lenses are quite expensive and made of special material :
Germanium, Silcon, Zinc sulfide e.t.c. .

Anyway, I quite enjoyed my first results.
Of course I did not expect to see craters on the moon with the meager resolution of this cam.

Maybe this could be the next stage of Amateur-Astronomy ....

cheers
Wanni

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wanni60
Wanni
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  • THERMAL imaging of celestial bodies (experimental stage : earth's moon), 



    
        

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  • THERMAL imaging of celestial bodies (experimental stage : earth's moon), 



    
        

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  • Final
    THERMAL imaging of celestial bodies (experimental stage : earth's moon), 



    
        

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Description: Seek thermal cam mounted on secondary mirror opening

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Description: moon image using Dobson / iPhone internal CAM minutes later

E

Description: moon drifting from top through the telescope opening

Histogram

THERMAL imaging of celestial bodies (experimental stage : earth's moon), 



    
        

            Wanni