The DIY "poor man" long range LWIR spotter.... - Page 1
Forum section: electronics / general

author: Lambda
author_rank: Regular Contributor
timestamp: February 12, 2022, 04:58:14 pm
content: Hello.I wanted to share with you a quick attempt to improvise with cheap means a kind of long range LWIR spotter.The set-up is based on:- My DIY thermal camera based on a thermal core FLIR "Indigo mini A10".- A cheap and common Newton telescope: a 114/450 (F/D=4).The primary and secondary mirrors from this kind of scope is aluminized with a protective layer of SiO2 (transparent for Vis/Nir domain).Said layer seems to have nevertheless some reflectance capabilities in at least the domain of 8 um to 10 um, if i do not mistake myselfDesta, Feven & Buxton, Mike & Jansen, Jeroen. (2020).“Fusion of Mid-Wave Infrared and Long-Wave Infrared Reflectance Spectra for Quantitative Analysis of Minerals.” Sensors. 20. 1472. 10.3390/s20051472.https://www.researchgate.net/figure/The-mid-wave-infrared-MWIR-and-long-wave-infrared-LWIR-reflectance-spectra-of-a_fig2_339790155Therefore, i tried to couple in prime focus mode my camera to the scope and to try to do LWIR long range monitoring/spotting.... Do everything like big boys....Here is my "report".... hoping having not written too much silly things...As said, lot of room for improvement...Best regards.Stéphane

author: rpiloverbd
author_rank: Regular Contributor
timestamp: February 15, 2022, 01:06:53 pm
content: Thanks for sharing with us.

author: ArsenioDev
author_rank: Frequent Contributor
timestamp: February 15, 2022, 06:03:43 pm
content: This is very interesting, I've been lookin for a cheap reflector at thrift stores to pull the mirrors out of and re-sputter coat with gold, I have contacts that can pull that off.Currently working on mating a VGA core to my Dobsonian, need to lathe out an adapter ring for the M34 lens ring to the T mount and check focal plane distance.

author: Lambda
author_rank: Regular Contributor
timestamp: February 16, 2022, 08:55:15 am
content: Hello,Thank you guys for your feedback!I have also to investigate for spectrum matching mirrors like typically gold or silver ones to improve my system.I have also an old primary scope mirror F=800mm, D=200mm, and it could be a "simple" possibility to do (through a company) gold or silver coating directly on the original SiO2 protective layer ? It would perhaps minimize the cost of such operation (No need to remove the original coating and aluminure, before gold/silver coating step ?)....To be continued...Regards.Stéphane

author: Lambda
author_rank: Regular Contributor
timestamp: February 17, 2022, 11:36:59 am
content: Just as a simple post-it, for keeping easily reachable the infos comprised in this related discussion...https://www.eevblog.com/forum/thermal-imaging/catching-the-moon-in-lwir-before-it-can-be-caught-in-visnir/Regards.Stéphane

author: Lambda
author_rank: Regular Contributor
timestamp: February 17, 2022, 02:49:32 pm
content: Hello.I keep on with some additional attempts, with different "targets"!The "warm" sunny day was helpful, on a thermal point of view, for sure......Best regrads.Stéphane

author: Bill W
author_rank: Super Contributor
timestamp: February 18, 2022, 11:50:52 am
content: Might just be a (vertically) flat section reflecting the ambient land temperatures ?The other parts are angles so would reflect the skyBill

author: johnelot
author_rank: Contributor
timestamp: February 18, 2022, 07:08:12 pm
content: could it be a plume of different temperature air drifting across from an exhaust on the power station (or whatever the building is )?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 18, 2022, 07:48:21 pm
content: Given your sensor, the two things that dominate performance are collecting area (size of optics) and low F number which are both hard to get at low cost. I am really quite impressed with the results you have achieved so far.

author: Lambda
author_rank: Regular Contributor
timestamp: February 20, 2022, 04:56:53 pm
content: Quote from: Bill W on February 18, 2022, 11:50:52 amBill it may be possible indeed... Just that i have the impression the "panel" would be quite large, likely covering an angular field comprising the two huge curved pipes. It would be like a large glass panel? i do not "detect" it on the visible photo.I will do again this observation at my next sunny day, for checking carefully this "anomaly"....Quote from: johnelot on February 18, 2022, 07:08:12 pmJohnelot, it would be also a plausible ideas except that the "occulting" area gives to me really the impression to have a very "geometeric" shape, with at least horizonal straight and strict lines or edges. If it would be a plume or thermal air layer, i would expect some more blurry and randomized shape... But i can mistake myself of course...Quote from: CatalinaWOW on February 18, 2022, 07:48:21 pmThank you a lot CatalinaWOW for your encouraging words. The two limiting factors you mentioned are unfortunately a bit difficult to overcome for a simple hobbyist, but:- for the mirror, i have in a drawer a old classical Newtonian primary parabolic mirror (F= 800mm, D= 200mm, F/D=4) i am seriously consider to send to a company (french one) for doing a gold coating.http://www.mcm-optique.fr/http://www.mcm-optique.fr/traitement-optique-seine-et-marne-8They work a lot with amateur astronoms...In the evolution of this project, i would also use a better more recent sensor (320x240 at least, lower NETD) directly to the prime focal plane of this mirror, without using a secondary mirror like i do now.- 400 mm focal length, according my current little experiments, would be just fine for me. Therefore, my gold re-coated mirror (800/4) would be associated with a "focal reducer X0.5" i can already made with a germanium lens i own already (the nice 15mm/1.0 provided by Bill here:http://www.fire-tics.co.uk/spares.htm)I could find another similar one, or use perhaps also a decent ZnSe lens....Both of these measures would allow me, i hope to have a quite nice long range scope unit with a "LWIR optics: 400mm F/2"...in 2022, it may be, with saving budget on few months, reachable for a hobbyist, i hope so....Just a little reminder about a "old" thread i find very interesting:https://www.eevblog.com/forum/thermal-imaging/thermal-astrophotography/Best regards.Stéphane

author: Lambda
author_rank: Regular Contributor
timestamp: February 21, 2022, 12:14:27 pm
content: Hello.I did again a very short observation this morning of this thermal power plant with its curved pipes and vertical chimneys.This time, it was during the morning, at 7H00 A.M: with a partly cloudy and windy weather, around 5 °C.The top of the chimneys was clearly warmer than during the previous session (17/02/2022).The power plant was overall more active this time than the last time: plumes or vapors were also exhaled from the facility....It would be logical, early chilly morning in town would correspond to a higher energy request and domestic consumption from people.And this occulting structure was still present, identical to what was observed the last time. It tends to make me thinking that the theory from Bill is more and more probable..... Just to see where and what is the nature of this "reflecting flat section"...Best regards.Stéphane

author: Lambda
author_rank: Regular Contributor
timestamp: March 02, 2022, 02:37:35 pm
content: Hello!The "mystery" about this strange "occulting" element starts to vanish...Today was quite sunny and warm (around 15°C continuously since the morning...). I tried again to observe my thermal power plant with this improvised "long range spotter". The structure was warmed during the all day and quite well emitting in LWIR.Here is a photo extracted from a video i just made, with a light contrast enhancement under photo editor, in comparison with the normal reference photo you know already.Best regards.Stéphane

author: Lambda
author_rank: Regular Contributor
timestamp: March 02, 2022, 04:55:03 pm
content: Here is a last video wherein i try to compare (crudely, i have to admit....) this last observation with the previous one .Today gave to me better results, definitively. Which i attribute to the structures of the power plant having been warmer today than the 17/02/2022.Just a short copy of "notes" on my "logbook":"The fact that the structures from the power plant are likely to be warmer today than the 17/02/2022 allows to obtain better images.Taking into account the climatic/weather conditions experienced by the structures may give better chance to obtain better thermal images.Especially with a thermal system with modest/limited overall performances (like mine for instance)."Regards.Stéphane

author: bap2703
author_rank: Regular Contributor
timestamp: March 02, 2022, 08:43:27 pm
content: It's just surfaces that are not reflecting the cold (transparent) sky but the "warm" surroundings instead.

author: Vipitis
author_rank: Frequent Contributor
timestamp: March 03, 2022, 02:14:05 am
content: That's true for the metal pipes. They will reflect the cold sky and surrounding, but you can clearly see that the chimneys are hotter in the comparison video. They are less reflective and more emissive.

author: Lambda
author_rank: Regular Contributor
timestamp: March 03, 2022, 10:44:15 pm
content: Vipitis, bap2703, thank you fro your input. i record your remarks for my culture and future thermal observations.Here, a fresh session made this evening, with two good "catches". An airplane "relatively" close to me and a chopper passing close to my block...It really encourages me to investigate/invest in at least a better optics/mirror.... and a better thermal core!Best regards,Stéphane

author: Lambda
author_rank: Regular Contributor
timestamp: March 14, 2022, 08:58:52 pm
content: Hello.Tonight, i tried to film the sunset on the shore of the Nord Sea.I was hesitating, a bit concerned about the camera's safety, but after having done my "homeworks", i dared this experiment....Lot of room for improvement for sure, not the best video again for sure, but encouraging !...To be continued!

author: Lambda
author_rank: Regular Contributor
timestamp: March 17, 2022, 11:52:16 pm
content: Hello.Back again with a new attempt for filming the Sunset, in different conditions than the last time, and with a crude comparison in visible domain...Some "notes", memento in the description....Best regards.Stéphane

author: bap2703
author_rank: Regular Contributor
timestamp: March 18, 2022, 07:45:27 pm
content: Didn't you get a sunburn effect when you switched to high sensitivity?A bit after that you can see a dark ghost image of the sun superimposed on the image :/

author: Lambda
author_rank: Regular Contributor
timestamp: March 18, 2022, 10:41:18 pm
content: Yes it appeared, but, as i tried to describe in the description in this video, the ghost image was disappearing later in the same evening (few minutes later, for this session). No apparent damage.I used again this spotter today, without any traces of ghost images.Right now, i will do again one or two tries on the Moon.... I will just publish in the next post additional videos for the final checking.

author: Lambda
author_rank: Regular Contributor
timestamp: March 18, 2022, 11:58:19 pm
content: Here is a summary of my checking after the "sunset" session from the 17/03/2022 evening.Everything (despite the inherent defaults from this old second-hand core) are, prima facie, ok.I confirm: no gohst image from the Sun.I am quite happy, i start (especially when the telescope and camera's body are cold) to see some small variations on the Moon's surface.Regards.Stéphane

author: ikrase
author_rank: Regular Contributor
timestamp: April 07, 2022, 06:35:14 am
content: Is there a viable way to make this sort of thing work with a camera that has a lens on it, rather than prime focus?

author: Bill W
author_rank: Super Contributor
timestamp: April 07, 2022, 10:03:56 am
content: Possible, yes.Viable, maybe not. I would expect it to be easier to remove the lens from the camera.You place the same (or a similar) lens back to front in front of the camera lensThis creates a new focal plane out in free air.This is a thermal microscope, resolving at pixel pitch in the focal plane.You then put whatever lens you like in front, focused on the new focal plane.Downside is a lot of aberrations, more material in the way, and a pain to align the whole lot.Bill

author: Lambda
author_rank: Regular Contributor
timestamp: April 07, 2022, 12:59:03 pm
content: [ Specified attachment is not available ]Quote from: ikrase on April 07, 2022, 06:35:14 amYes, i indicated by Bill, with an additional LWIR lens, it would be doable.Keywords are typically: "afocal configuration", "shutter lens", "relay lens", "digiscopie".... often used in Vis Astronomie and long range spotting.Be careful also to the potential vignetting problem.But indeed, easier to implement in prime focus mode, and with potentially less aberrations and loss of signal.My English being what it is, a drawing would be clearer:Regards.Stéphane

author: Bill W
author_rank: Super Contributor
timestamp: April 07, 2022, 03:47:38 pm
content: Thanks for finding an image Stéphane.Modified version below - note use of additional L3 is reversed. Works for multi-element lenses and gives a flat focal plane.Bill

author: Lambda
author_rank: Regular Contributor
timestamp: April 07, 2022, 06:41:23 pm
content: Yes Bill, well mentioned!Thank you for this correction.Regards.Stéphane

author: cdev
author_rank: Super Contributor
timestamp: April 10, 2022, 01:44:34 pm
content: This is the exact moment when, if you are in California, looking west, of course, you might possibly see the famous "green flash" which only lasts a few seconds, and its quite vivid, when you see it. Unmistakeable, if you've been warned so you recognize it.Once I saw it twice during the same week. Other times its quite elusive.You probably can see it in many such situations as the terminator sweeps over your location.Quote from: Lambda on March 14, 2022, 08:58:52 pm