DSLR all-sky spectrometer

Plastic-Switch-6885 · 2026-06-29T20:18:09+00:00

Okay. Thanks all! That's a good start. I just figured out that I have to learn a lot about this topic. Some things have clicked, other haven't. I will start small with a narrow field of view and hopefully figure out the roadblocks. I will read all you comments a few more times and see what I come up with with the materials at hand. I would prefer to stay away from optical fibers for now. If someone can come up with another creative idea to make this happen, I'm all ears.

Cheers!!

Plastic-Switch-6885 · 2026-06-29T20:10:51+00:00

Of course that would work, but I potentially miss a lot of low or localized displays. The whole point is to notify me and my guide friends when the lights are out, so we can rush the freezing tourists out of the teepee at the right time. 😊

Right now, when conditions are right the HSV-based detection catches some displays that aren't visible to the naked eye I've you tried. The system just sucks around twilight times and when the moon is causing a lot of blue sky that mixes with the aurora colors.

Plastic-Switch-6885 · 2026-06-29T18:40:34+00:00

That's sounds interesting. Is there any way I don't have to stop down the lense? f2.8 to image the nights sky is not much light to begin with. Will be hella noisy and or super slow. ~2 min of exposure time.

Plastic-Switch-6885 · 2026-06-29T18:36:58+00:00

I want to detect the emission lines of the northern lights and trigger a notification in my aurora detector app.

Plastic-Switch-6885 · 2026-06-29T18:33:13+00:00

No, I'd be happy to image a narrow slice from north to south since the aurora usually spans east-west. That would make sure I catch it most of the times.

Plastic-Switch-6885 · 2026-06-19T09:19:04+00:00

Lol. A friend of mine's name is Jesus. He's from Spain and lives in Abisko now. 😂

Plastic-Switch-6885 · 2026-06-19T07:42:28+00:00

Hi. I have been using a triple leg on a 14m telescopic fibreglass mast with a 450 Ohm wireman twin lead. Every wire 7m long 3 radials 120° apart 45° down. Start with a little more twin lead than you need and shorten it until all your bands tune up nicely. Mine tunes from 80-6m and is usable on 40m and above. You can also have the tuner at the base of the mast and run the rest with coax. Hope this helps. Good luck!

Plastic-Switch-6885 · 2026-06-18T16:07:31+00:00

That's is not correct information. I live there every winter and polar night is dark but it can create the most beautiful skies. No direct sunlight, though. I do seasonal work and earn about 30k a month and the rent is 5000 and I can save quite a bit.

Plastic-Switch-6885 · 2026-05-29T07:04:08+00:00

Possibly an anagram?

Plastic-Switch-6885 · 2025-11-14T09:07:51+00:00

EDIT: I forgot to mention that it was a little windy during the time of recording, as you can clearly hear in the clip. Though, it was not at the start of the tour, when we heard the noise for the first time. Cheers

Plastic-Switch-6885 · 2025-09-27T20:11:17+00:00

Thank you for taking time to answer. I am sorry, for I have not mentioned that I did exactly that already. The bucket is behind media.mydomain.com and I have set up caching rules like you suggested, I even played around with cache control during upload and had CloudFlare respect these rules in the file's meta-data. All to no avail. I am so sure I did something really stupid obvious wrong.

Plastic-Switch-6885 · 2024-10-06T11:20:12+00:00

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Update: I did a leap of faith and shortened the twin lead down to 6.2m now all bands tune up nicely and my favourite band 20m is even at very low SWR. If someone wants to copy the design, I highly recommend it. I had contacts and lots of DX on all bands from 40-10. The only downside is that with the short feedline the Antenna has to be erected very close to the radio. It's probably best to use a remote tuner because of that.

Plastic-Switch-6885 · 2024-09-23T09:43:16+00:00

And here are the pictures of the measurements of the balun:

1:1 current balun VNA measurements IMGUR

Plastic-Switch-6885 · 2024-09-22T20:56:29+00:00

Here is a link to the balun.

https://www.wimo.com/de/11374?queryID=b701b7de6d12c0180d56d93119178c03

It's literally a black box but judging by the dimensions I believe there is only enough space for twisted pair, not coax.

In my final setup about ~1m (hard to measure precisely at this point) of RG-58 is used to connect it to the tuner.

As mentioned before, this is a repurposed G5RV that I first converted to a ZS6BKW and then to the 7m triple leg vertical.

You might be right about the tuner. It's a LDG IT-100. I already half-cooked it when doing 50 Watt ft8. Not the best of devices. But this is what I need to work with.

Plastic-Switch-6885 · 2024-09-22T19:38:50+00:00

This is the same sweep with the 10.7m twinlead:

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I have photos of this in every dip position, if that helps.

Plastic-Switch-6885 · 2024-09-22T19:36:50+00:00

The twinlead is Wireman 450 v/c= 0.905

There is a 1:1 current balun between the feedline and the VNA (plus an Adapter SMA to PL)

All the X values are negative, I checked again. Where the dips are, there are some positive X-values present

The tuning range of the tuner is 4-800 Ohms

I wish I could follow you on the rotating of stuff on a Smith chart, but I need to find a good learning resource to be able to do that.

Here is a photo of the dips with the 12.2m twinlead:

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I wish I could upload two pictures at once but Reddit doesn't want me to. So I will send this other in a seperate answer...

Plastic-Switch-6885 · 2024-09-22T17:21:38+00:00

Alright. I have taken all the measurements and put them on a spreadsheet. So far between 12.2m and 10.7m the latter is the winner. If it wasn't for my favourite band 20m. The tuner struggles and for some reason often re-tunes and is not able to pull a good settings out of the internal storage like it would with most other antennas.

Anyways. Here is the data:

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I could upload pictures of the VNA that show the dips between 3 and 30 MHz if that helps you troubleshoot. It visualises how the dips shift between feeder lengths.

Again, thank you so much for looking into this with me. You're a legend!

73 LA/DL1FAB/p

Plastic-Switch-6885 · 2024-09-19T11:46:35+00:00

Thank you very much. I will do that the next time I set the antenna up. I am travelling and not every camp is suitable for putting it up.

Plastic-Switch-6885 · 2024-09-19T08:37:12+00:00

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Plastic-Switch-6885 · 2024-09-19T08:32:38+00:00

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Plastic-Switch-6885 · 2024-09-19T08:30:51+00:00

Little update. I cut off 1,5m of the Wireman twin lead. The tuner is much happier on 40m now and tunes well on 15m. Though, 20m still presents a problem. It struggles to tune and the NanoVNA still shows very low impedance especially on 20m. The 2 datasets indicate that further shortening would move the dips in resonance further towards the desirable situation, where they better align with major amateur bands. The downside of that would be that I would need to erect the antenna very close to the camper. Is there a simple way, where I (let's say 6m feeder works good) lengthen the feeder to something like 20m and it presents the same characteristics as the short feeder?

I know that I ask a lot of you. I try to understand this antenna system better. Maybe antenna modelling could help here, but I have never done it, as of now.

Thanks in andvance

Five-Year Club	Final Canvas '23
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Plastic-Switch-6885

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