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  #1  
Old 27-12-2017, 04:30 PM
g3n1u5 (Tony)
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Talking Analogue Computer and Spectrosocpy

Good Afternoon,

I have noticed a resurgence in Analogue computing, and there seems to be strong ties with Spectroscopy. I have a Star Analyser 100, and a bunch of different pass through filters, etc.

I am interested in communicating with other people who are interested in breaking down the light into meaningful data.

Regards
Tony Nolan
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  #2  
Old 27-12-2017, 05:01 PM
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Merlin66 (Ken)
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Tony,
I’ve been actively involved in most aspects of spectroscopy for over ten years - even published a few books on the subject....
I’m not sure what you have come across Re Analogue computing but would certainly be interested in following up.
Using a Star Analyser is a great starting point - I call it “Spectroscopy 101”.
We have developed many very effective processing processing software solutions which have had a significant impact on the amateur community.
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  #3  
Old 28-12-2017, 09:29 AM
g3n1u5 (Tony)
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Thanks

Good Morning Ken,

Thanks for your reply.

There is starting to be a move away from binary coputing ie 0 & 1, to analogue computing like fuzzy logic 0 - .99 for example. There are some interesting ways to use cameras, and break down the light into its RGB components, and then assign a number of digital fingerprint to that specific combination. Then you can do soem interesting maths with them, in optical calculations, etc.

I am interested in how I can get readings from the stars, and see the differences between them. I am interested in seeing if you can identift a star from its spectrum, rather than its position ?

Regards
Tony
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  #4  
Old 28-12-2017, 09:42 AM
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Merlin66 (Ken)
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Tony,
I think I understand...
Using filters - RGB, Photometric or Narrowband to separate different sections of the star spectrum is not uncommon, and can be used determine stellar magnitudes.
Unfortunately to positively identify a unique star is almost impossible even from a high resolution spectrum. The best we could probably do would be to say it's a G2v type star......and there are thousands of those ;-)
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  #5  
Old 28-12-2017, 09:49 AM
rally
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Hi Tony,

Can you provide some links to this information so we can read about it please.

Thanks

Rally
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  #6  
Old 28-12-2017, 01:45 PM
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trent_julie
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Ken,
Not to hijack the thread but could you please link to your books. As I built a few spectrometers of differing designs recently. It would be good to see a “been there, done that perspective”
Kind Regards,

Trent
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  #7  
Old 28-12-2017, 02:08 PM
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Merlin66 (Ken)
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Trent,
"Astronomical Spectroscopy for Amateurs"
https://www.amazon.com.au/Astronomic...+spectroscopes
Covers some history, spectroscope design, commercial spectrographs and software as well as construction details for a DIY instruments.

"Grating Spectroscopes - How to use"
https://www.amazon.com.au/Grating-Sp...+spectroscopes

Primarily for users of the Star Analyser/ Rainbow Optics gratings. How to set them up and process/ analyse the spectra.

"Imaging Sunlight - Using a digital spectroheliograph"
https://www.amazon.com.au/Imaging-Su...aging+sunlight

Background history and details of solar phenomena - photosphere and chromosphere. Solar filter design and commercial solar filters. Applying hi resolution spectroscopes to obtain AVI files of the solar spectrum, converting these to a very narrowband solar image. Examples of many SHG built around the world.

Hope this helps,
Ken
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  #8  
Old 28-12-2017, 03:14 PM
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Thank you.
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  #9  
Old 28-12-2017, 03:29 PM
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Merlin66 (Ken)
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Trent,
On our webpage you will find some great links - I must give honorable mention to Christian Buil's excellent resource material....well worth the visit.
http://www.astronomicalspectroscopy.com/reference.html
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  #10  
Old 28-12-2017, 03:47 PM
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sheeny (Al)
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Having used real analogue computers at uni, you had me intrigued...

FWIW I don't think fuzzy logic in a digital computer qualifies as "analog". I don't mean to crash your thread, so I'm just offering the following FYI so everyone is on the same page. I was expecting Op amps and feed back and feed forward loops, etc .

https://en.wikipedia.org/wiki/Analog_computer

That's OK, fuzzy logic is cool too.

Having done a bit of spectroscopy, I'd be interested to see how fuzzy logic applies. The existing digital processing tools seem pretty adequate to me, so you've got me intrigued how fuzzy logic would add something to the mix.

Pass the pop corn...

Al.
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  #11  
Old 29-12-2017, 03:04 AM
robin_astro
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Machine learning techniques have been applied quite extensively to the automation of classification of astronomical objects from their spectra eg
https://arxiv.org/pdf/1609.03147.pdf

Robin
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  #12  
Old 29-12-2017, 08:16 AM
g3n1u5 (Tony)
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Analogue websites

Hi Rally,

there are a few articles on the web, and in the IEEE mags. I will be making a webpage with a list of them very soon.

Regards
Tony
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  #13  
Old 29-12-2017, 08:39 AM
g3n1u5 (Tony)
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fuzzy (Analogue) vs crisp (binary)

The group / focus I come from, believe that digital computing is dead, and was a cheap and easy branch of technology, but now its showing it cant cope with what is required.

Jack Ma, the guy that owns Alibaba has been saying for a while now, that almost all artificial intelligence work is down the wrong track, and that platforms could be to blame.

So when you apply fuzzy logic and digital hashes to optical calculations using light, in a single 10th of a second photon pulse, you can transmit a number between 0 and 16.7m. A practical application, is to have 3 analogue sensors which produce a colour, which is transmitted to a sensor that breaks down the colour and controls a systemic response. So lets say for example, you have a humidly, temp, and wind speed. The combination of them produces one of 16.7m different colours, and the reciever is programed to turn on and off watering systems when a range of colours appear. And this process is at the speed of under a second, etc

By applying fuzzy to a value, rather than 1s and 0s, speeds up the whole operation.

The app, i have in final stages of development, can read light transmissions, do calculations between 0 and 240 trillion, map sound and motion patterns. Especially with horse or muscle memory, and it can encrypt messages in jpgs, that can be transmitted.

So i can write a computer program in english, transform it into colour using my hash, and then send that jpg to some one, and they can decode it, save the program, and it will run.

But that is just where we are at now, and there is more play time ahead.

But I am really interested in the Spectroscopy side of it, which is what took me down this inventing path in the first place. But i do have to confess, I am not only interested in stars, but also in the viewing of objects in normal sun light also. So i have turned my lens/filter onto trees, metals, buildings, people, etc.... to try and better understand the variations.

But now I want to focus on stars, and better understand how to use it. Im on ASNSW, and i heard there was a special interest group in this, but i tried to make contact several times, but never ever got any replies. So here i am, hoping that others might have an interest like mine.
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  #14  
Old 29-12-2017, 08:58 AM
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Executive summary of the 17 page paper referenced by Robin:

Spectra of 100,000 stars was used to train a computer to recognise the spectral classes (OBAFGKM etc) using three different algorithms (PNN, SVN and K-means).
These algorithms were then used to identify a batch of 300,000 spectra.

It was necessary to use 700 data points on the spectrum between 3850 and 8900A.
These algorithms have been able to correctly classify approximately 80% of the data set.
It took between 23 and 29hr computing time to do the analysis.
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  #15  
Old 29-12-2017, 09:39 AM
g3n1u5 (Tony)
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one link

https://spectrum.ieee.org/computing/...m_medium=email
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  #16  
Old 30-12-2017, 07:49 AM
g3n1u5 (Tony)
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Software

Good Morning,

Is there software, that can be used with a cam and filter please?

Regards
Tony
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  #17  
Old 30-12-2017, 08:03 AM
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Merlin66 (Ken)
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I've detailed most of the available software on the website.
I use and recommend BASS Project.
http://www.astronomicalspectroscopy.com/process.html
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  #18  
Old 19-02-2018, 09:49 PM
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I'm by no means trying to poo-poo anyone's ideas, the analogue computing thing as described sounds interesting, and the overarching point of looking for different platform paradigms to enable new insights or cast off unconsciously accepted shackles has solid historical precedent.

but.

light transmission of any kind is affected by the medium through which it travels. optical fibres (which trump air by huge scale factors for efficiency) induce wavelength shifts and pulse broadening with heavy transmission length dependence, and dictate careful signal control to fit what is transmitted into broad "bins" that can be reliably differentiated by a receiver. If you look at a research-grade R=80000 spectrogram of an M dwarf star and think "there are ~10k spectral features I could use to fingerprint that star at (sometimes) 0.07 angstrom resolution, therefore, I could get 64k "bits" out of that single spectrum with a simple binary intensity threshold for each spectral element..." you have to remember that only that instrument, that time sees that spectrum. The corrections necessary for even a low res spectrum to account for eg. which side of the earth's orbit we were on (doppler shift), what the sky was contributing (telescope elevation = atmospheric dispersion) time of night (OH glow) are substantial, and require knowledge external to the signal.

OK, so transmitting a single flash of colour and interpreting it doesn't have to be done to the 200th of a nanometer, you could use a more coarse spectrum. But existing, binary, laser diode/PiN detector technology can put 40 gigabits/s down the 1550nm transmission sweetspot of fused silica *already* in a "single" colour. Wavelength division multiplexing can usually manage 20ish simultaneous channels within that transmission sweetspot (effectively what you're talking about: multiple colours simultaneously) in the lab, though the telco people talk about ~300 channels. The problem is signal to noise, if you want to split a pulse of light into multiple colour bins with an optical system that sends different energy photons to spatially different detectors (eg pixels on a camera sensor), you're trying to detect a very small energy spike above each detector's background level, and your error rate skyrockets, so you can't use that same 0.05ns photodiode rise time available for brighter pulses that enables you to detect your laser's maximum reliable rep rate (or lack within a given data frame).

There is promising research in photonic circuits, which might be related to what Tony describes. In such devices direct photonic (and sometimes photon-moderated eg optoacoustic or surface physics) interactions are used to "gate" a signal so you get, or don't, light out a particular waveguide depending on what's going in another one, but not that output's actual source. These interactions obviously have a wavelength dependence (e.g can gate green with green, but not with red) and the waveguide geometry on the chip can be used to sort out or combine particular wavelengths as desired. It is hoped that electronics-style miniturisation/manufacturing tech improvements will lead to a several-orders-of-magnitude improvement in processing capacity (above all with very little waste heat, the perennial bugbear of electronics). I'm talking about gates and this implies "still binary" (albeit multichannel), but theoretically the door is open to "less binary" computation... but even the binary processing, and even over very tightly controlled and short (of order 1cm) transmission distances are in their infancy.
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