Moderators: Dave Moll, Andrew Davie, Steve Anderson
Steve Anderson wrote:Harry, how are you planning to scan the image?
I've seen no mention of scanning discs or any other arrangement.
A PMT is not a camera tube per se, like a vidicon, plumbicon or other tube that usually require deflection (magnetic) yokes. Nor are they designed for that. A flying spot camera is a possibility I guess, but there's been no mention of that so far either.
Steve Anderson wrote:Remember that PMTs are generally blue sensitive rather than the red/I.R. of silicon. So whatever you plan plan to scan, bathe it in blue light...or bright daylight...forget tungsten...or fluorescent which have a really weird balance of output colours, but our eye/brain system seems to compensate quite well with that though. But maybe not PMTs. Our sun is considered a 'yellow dwarf', but it's output, sitting here at nearly 40C and 93 million miles away, is enough thank you! I'm glad I'm not on the surface of Venus right now!
Steve A.
Steve Anderson wrote:Harry, somehow I totally missed your posting on Thursday (the 7th)...and it's not exactly a small one!
Interesting bit of test gear, not seen anything quite like that before. Quite 'quirky' really. Its advantage over a monoscope is the interchangeable slides. A monoscope can only generate a single pattern and that's yer lot!
https://en.wikipedia.org/wiki/Monoscope
Today it simply would be stored in a memory and read out to generate the video signal. A 405-line version is here:-
http://www.thevalvepage.com/projects/te ... stcard.htm
For 525/625 use it would need a bit of rearranging for the different line and scan rates and a bit more memory. Ralph Taggart's ROM-scanner for NBTV/SSTV is based on the same principals. Doubtless a search through the BATC site would turn up others in all sorts of formats. I think Klaas has done one specifically for NBTV.
I think I may recognise those brown caps from the past! Good to see them put to use.
Harry Dalek wrote:....but i am itching to power up the PMT
Steve Anderson wrote:Harry Dalek wrote:....but i am itching to power up the PMT
Don't forget to keep it in the dark, PMTs do not like what you and I might call 'normal illumination'.
Steve A.
Klaas Robers wrote:For proximity focus in this arrangement:
- place the picture slide as close as possible to the CRT-screen,
- place a 90 degree mirror where you have now the screen.
- A glass mirror with the silver layer at its back may give ghost pictures due to internal reflections,
- so a surface silvered mirror is preferred,
- but difficult te get hold on.
- Place the PMT aside the other CRT,
- give it a light thight hood with a small viewing hole (pin hole).
- experiment with the size of the pinhole,
- the smaller, the better focus, sharper picture,
- but the less light.
Steve Anderson wrote:Likewise, not posted myself for a while, it's simply become too hot here to do anything, over 40 Celcius outside. Lethargic is the word..
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