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As no one had posted a blog entry since 2022 I thought I would but its probably nonsense!



I am just about recovering from my second bout with the Covid virus so I thought I would do something vaguely astronomical which wasn't cloud dependant.  We have had a lot of clouds in Lowestoft recently. I discovered a nearly completed low resolution transmission spectrometer with fixed slit in the shed which I was building some time ago for obtaining the spectrum of extended objects. Sounds very technical but as per my norm, very Valerie Singleton and Chad Valley.

Anyway somewhere in the past I read that it was possible to obtain a spectrum of sunlight by connecting a fibre optic cable to a spectrometer/camera set up and retiring immediately. No collimating and focussing lenses involved! Now I may have imagined this, probably the drugs! 

So being bored I finished off the spectrometer, fixed an audio fibre optic cable to the front end and my modded Canon 200d to the other end. When I pointed the end of the fibre optic cable at the sun I was able to snap away and collect some data which I promptly stacked. 

I then set about reducing the data to create a spectrum profile.  This is probably where I went wrong. First, how was I going to calibrate the profile which was all very lowercase squiggles? Well as the image encompassed the zero, first and second orders,  I could approximately identify one point 0 on the x axis. 

I then remembered that the temperature of the Sun roughly obeys Wien's law and as the internet could provide the visible wavelength at which the Sun delivers max flux I could obtain a second calibration point on the x axis for the highest y axis point on the flux curve. A linear calibration could then be performed. 

As I knew our Sun is a G2V star, I used this profile to correct my image profile for camera response. 

All very well but am I fooling myself? 

I remember being set an exercise by the legendary lighting Engineer, Joe Lines. It was 1969 and I was living a bohemian student life in Manchester. We had to create a lighting scheme and provide all the relevant calculations. I set about the task with much enthusiasm, a little knowledge and even less talent. A week later, project completed, I handed in my weighty treatise and awaited assessment by Joe. A further week later my flat mate Paul collected his and my now 'marked' submissions and left mine on my desk in my squalid room. Written on the bottom in red ink was "7/10  Stop fooling yourself Roberts". This came as something of a shock because Joe Lines was an extremely patient and kind man! What could this possibly mean?

What I only found out months afterwards, was that my friend Paul had added all the words after "7/10". I believe from that day onwards, I have suffered from what they now call 'imposters syndrome'.

I attach photos as supportive evidence of how wrong you can be!

George 'coughing' in an overcast Lowestoft




100linespermm spectrometer with fixed slit plus fibre optic cable.png

Sunlight corrected spectrumvery low resolution.png

Edited by Hawksmoor

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Your flatmate was mean but that's a great story.  That's a neat looking spectroscope; could you use a CFF lamp for calibration?


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44 minutes ago, saac said:

Your flatmate was mean but that's a great story.  That's a neat looking spectroscope; could you use a CFF lamp for calibration?


Hi Jim

Yes I guess I could have used a lamp with known output wavelength(s) for calibration. Didn't think of that at the time but Mrs H willing I might rerun the experiment using a lamp. I did make it clear I am a bit rubbish! As for Paul he was a bit of a character, could be difficult but always made me laugh! Thanks for taking the time to comment all help and advice is very welcome!

George in rainy Lowestoft next the sea.

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5 hours ago, Mr H in Yorkshire said:

Perhaps you could rig up a small neon light such as is found in mains switches as a reference source. Carefully!

You have seen the quality of my 'gung-ho' wiring skills before?

Thanks for your comment much appreciated!

George with sunlight streaming in the window in Lowestoft |Suffolk's lost town below the waves.

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