Products > Thermal Imaging

Catching the Moon in LWIR before it can be caught in Vis/Nir...

(1/3) > >>

Lambda:
Hello.

Just an additional little experiment wherein i tried to "see" the Moon before it can be seen... :D :D

It is not spectacular, i have to find a better lens, among plenty of other things to improve

The description of the experiment is in the description of the video:

First video (part 1) wherein the Moon is not yet visible for the Vis/Nir camera, but only for the LWIR camera:


Second video (part 2) wherein the Moon become also visible for the Vis/Nir camera:


I will do better the next time, but it is encouraging... :-[ :) :)

Best regards.

Stéphane

Vipitis:
Aiming for the moon is something I want to achieve as well, I got my first signal but not a great image yet.

With the title here I wonder: does it not show up in visible due to the brighter sky? It surely isn't hidden hiding the planet and atmospherically lensed into place earlier in LWIR. We have about 92% moon illumination tonight, so the moon will be really bright, you should even see it during the day (it's not up during the day much). But this made me wonder - would you be able to see the new moon in LWIR any better than visible (using earthshine for example). And if one has the weather, time and effort for it. A side by side month long timelapse of a lunar day, seen from earth. I have a feeling the terminator line isn't as extreme as you see it in the visible since lunar regolith might be a tiny bit emissive as well (it's visual albedo is like .11). Or do you only see the moon against the coldness of deep space?

Is there any other object (past the sun and the moon), that is bright enough in the N-band (+/-2μm around 10.3) that might show up on a uncooled microbolometer? A question I have asked for years and haven't found any answers yet. Perhaps M42

Lambda:
Hello Vipiitis.

As long as the angular distance between the sun, during the day, and the Moon, is sufficient, the  brightness of the moon is not completely overwhelmed by the light coming from the sun. And in this condition, as long as its surfacic magnitude of the Moon is higher than the one of the sky, at the moment of the observation, the Moon stays visible during the day, as it is can be the case also for Venus, for instance.

Observing the new Moon in LWIR would be great and, it has be done, in a certain manner, by a french astronome, Thierry Midavaine. More precisely, it was during a lunar eclipse, which appears during the new Moon phase by principle.

https://fr-fr.facebook.com/cieletespace/videos/la-lune-en-infrarouge-film%C3%A9e-par-thierry-midavaine/10156244091440346/

But also by other people:

https://www.flir.eu/discover/rd-science/lunar-eclipse-when-viewed-in-thermal/

I guess, with the proper set-up, such experiment may be replicated during a normal new Moon, and by the way, during the whole set of phases of the Moon cycle.
It would be very interesting to see that!
What seems to be critical, in order to see some details, is to have access to an LWIR optics having sufficient focal length for giving a proper sampling for the image and reaching therefore a proper resolution, in accordance with the pixel size of the FPA of the thermal sensor (i humbly guess).



Ultrapurple:
Just to add a little to the conversation.

An inexpensive (<US$100) visible light reflector telescope can readily be adapted for LWIR use and is 'just good enough' to see a bright target like the Moon. As long as there are no lenses in the system you'll be just fine.

You'll need to use a 'bare' (no lens) thermal sensor. I used a Therm-App but there are many other suitable types.

Mount the sensor into the telescope focusing mechanism, point the telescope at the Moon. Adjust focus. Admire image.

The secret is that the mirrors in reflecting telescopes are very broad band - they'll usually work from high-GHz frequencies upwards - and although the efficiency may not be as good as in the visible range, when you're looking at something as bright (hot) as the Moon, that's not so much of a problem. Likewise the terrible effective aperture, which is probably f/6 or worse.

Lambda:
Indeed, it would be a very cheap appreciable alternative!  :-+

Just perhaps to be sure that the mirror is not coated by any protective layer like SiO2, which is currently the case  for now-day telescopes in the public market...
Or can we considered such coating sufficiently reflective in the range of [8um-14um] ?

I have a old mirror D=200mm, f/d=4, which would worth to be extracted from my junk box... :)

One possibility to render the effective aperture faster would be to use a conventional thermal lens as a focal reducer. for the mirror i have, and 15mm lens like the one i got from Bill, it should be doable to obtain an effective aperture around 2. Likewise what is currently done in standard astronomy in the visible domain.

Just thoughts for food.

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version