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Starthrotch Analyser Mk1




When I was a ten year old kid I used my pocket money to buy job lots of old broken clocks from Maidstone Market.  I would take them home and spend hours in my Mum and Dad’s cellar taking them apart ostensibly to get them working again. They never did but hey I never let failure deter me.

Nowadays, being happily retired (and no gloating intended), I have many an hour to while away in my shed.  Nothing that I can get away with, gives me greater pleasure than recycling old bits of metal, plastic, wood and abandoned technology - for astronomical functions. Sometimes they work and sometimes they don’t – so no change there then!

My latest project, to construct a thermometer for taking the temperature of stars or as it might be described a ‘Chad Valley Spectrometer’, is well under way.  It remains to be tested but what with the transit of Mercury and the sudden outbreak of rain which followed, I await a clear night with mounting excitement. 

The ‘Starthrotch Analyser’, catchy name ehh, has been constructed from a vandalised Logitech E3500 webcam, a section of chromed tubing, some aluminium plate left over from a DIY yard gully, 3 BRE hardwood samples from my late and great mate Barry Shulver, a piece of galvanised mesh, half a dozen screws, some pieces of black felt, Gorilla glue and lots of Evostik impact adhesive.  I did have to purchase from ‘Edulab Scientific Supplies’ for about £10 - 3 slide mounted 100 lines/mm transmission gratings.  All in all and if it works, quite a‘thrifty’ piece of kit!

My daughter, Rachel, was quite impressed. She thought the general appearance of the ‘Starthrotch Analyser’ was very ‘1960s Star Trek’, my partner Toot believes it would not have looked out of place in ‘Blake’s 7-the cardboard years’. Praise indeed!

I will let you know in a future post whether it works or not, although my best guess is it probably won’t! 

I wonder if I could make an operational ‘photon torpedo’ from a second hand Halfords top box and an obsolete Tom Tom - SATNAV?  Anything is possible in a shed.

Starthrotch 1.png

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Yep, that should work in principle, attached to the telescope in place of the eyepiece,  for bright stars.  I began my jouney in to astronomical spectroscopy and the development of the Star Analyser


 in much the same way back in 2002


(first light)

You will need to remove the webcam lens and space the grating around 25-30mm away from the camera sensor to give a decent length spectrum and to explore into the IR, remove the IR block filter

Good Luck!



Edited by robin_astro
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Thanks for your kind comment Robin. I had removed the lens and infra red filter. Was not sure whether an IR pass filter was required as for unblurred planetary capture? More by trial and error I set up the camera at the right distance from the grating. Have not had much free time in the last week but did manage to try it out on my 66mm. Altair Astro Starwave refractor. Just on a photo tripod managed blurry zero and first order spectra of Jupiter on the small chip. Used Jupiter as brightest thing in the sky. Given the time and a clear night I will try it out on a bright star and with my equatorial mounted 127mm.apo.

I have visited your threehills internet site, a great resource and extremely Inspirational to beginners like me. 

I hope you were not offended by my nonsense name for my DIY device. It does have some unintended similarity to the name of a proper piece of professional kit. Please accept my apologies.

 I have always had a weakness for self mockery and the 'throtch' concept is a family joke developed in my undergraduate days at Manchester University in the late 1960s.  It is a made up collective noun for technically difficult and poorly understood methodologies and technologies.  You have probably guessed I have arts rather than scientific qualifications.

Best regards George


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