|
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
didymium - sodium light buster + other filters
I've posted at http://home.freeuk.com/m.gavin/grism2.htm
some colour spectra via a digital camera showing the transmission of various filters like... TT RGB interference set showing red leak Hoya CMY didymium -sodium light buster TV monitor, fluorescent, neon and energy saving lamps [emission lines] and spectrum of daylight all via a simple but effective homemade spectroscope. I'd appreciate feedback. Maurice Gavin - WPO - UK |
#2
|
|||
|
|||
didymium - sodium light buster + other filters
Robin Leadbeater wrote:
"Maurice Gavin" wrote in message ... I've posted at http://home.freeuk.com/m.gavin/grism2.htm some colour spectra via a digital camera showing the transmission of various filters like... TT RGB interference set showing red leak Hoya CMY didymium -sodium light buster TV monitor, fluorescent, neon and energy saving lamps [emission lines] and spectrum of daylight all via a simple but effective homemade spectroscope. I'd appreciate feedback. Maurice Gavin - WPO - UK Hi Maurice, Good to see someone else checking up on those filter claims ;-) I have been thinking about getting a prism to improve my similar spectroscope. See http://www.leadbeaterhome.fsnet.co.u...er_spectra.htm Where did you get you prism from? Regards Robin I have one (possibly two, will have to check) old prisms from an old pair of wrecked binocularss if anyone wants it (them ?) Nice work on both sites BTW ! DH Telford |
#3
|
|||
|
|||
didymium - sodium light buster + other filters
Robin Leadbeater wrote:
"Maurice Gavin" wrote in message ... I've posted at http://home.freeuk.com/m.gavin/grism2.htm some colour spectra via a digital camera showing the transmission of various filters like... TT RGB interference set showing red leak Hoya CMY didymium -sodium light buster TV monitor, fluorescent, neon and energy saving lamps [emission lines] and spectrum of daylight all via a simple but effective homemade spectroscope. I'd appreciate feedback. Maurice Gavin - WPO - UK Hi Maurice, Good to see someone else checking up on those filter claims ;-) I have been thinking about getting a prism to improve my similar spectroscope. See http://www.leadbeaterhome.fsnet.co.u...er_spectra.htm Where did you get you prism from? Regards Robin I have one (possibly two, will have to check) old prisms from an old pair of wrecked binocularss if anyone wants it (them ?) Nice work on both sites BTW ! DH Telford |
#4
|
|||
|
|||
didymium - sodium light buster + other filters
On Sat, 12 Jul 2003 11:50:37 +0100, "Robin Leadbeater"
wrote: "Maurice Gavin" wrote in message ... I've posted at http://home.freeuk.com/m.gavin/grism2.htm some colour spectra via a digital camera showing the transmission of various filters like... TT RGB interference set showing red leak Hoya CMY didymium -sodium light buster TV monitor, fluorescent, neon and energy saving lamps [emission lines] and spectrum of daylight all via a simple but effective homemade spectroscope. I'd appreciate feedback. Maurice Gavin - WPO - UK Hi Maurice, Good to see someone else checking up on those filter claims ;-) I have been thinking about getting a prism to improve my similar spectroscope. See http://www.leadbeaterhome.fsnet.co.u...er_spectra.htm Where did you get you prism from? Regards Robin Nice site Robin - I should visit uk.sci.astronomy more ofteng. Grism eg combined weak prism + trans grating on one surface to give a 'straight-through' view been in the junk box for years source unkown but probably from a 1890's prom scope. Without the prism the spectrum from the grating is angled to the side so either the slit or tube carrying it must be offset slightly - but you knew thatg. Maurice |
#5
|
|||
|
|||
didymium - sodium light buster + other filters
On Sat, 12 Jul 2003 11:50:37 +0100, "Robin Leadbeater"
wrote: "Maurice Gavin" wrote in message ... I've posted at http://home.freeuk.com/m.gavin/grism2.htm some colour spectra via a digital camera showing the transmission of various filters like... TT RGB interference set showing red leak Hoya CMY didymium -sodium light buster TV monitor, fluorescent, neon and energy saving lamps [emission lines] and spectrum of daylight all via a simple but effective homemade spectroscope. I'd appreciate feedback. Maurice Gavin - WPO - UK Hi Maurice, Good to see someone else checking up on those filter claims ;-) I have been thinking about getting a prism to improve my similar spectroscope. See http://www.leadbeaterhome.fsnet.co.u...er_spectra.htm Where did you get you prism from? Regards Robin Nice site Robin - I should visit uk.sci.astronomy more ofteng. Grism eg combined weak prism + trans grating on one surface to give a 'straight-through' view been in the junk box for years source unkown but probably from a 1890's prom scope. Without the prism the spectrum from the grating is angled to the side so either the slit or tube carrying it must be offset slightly - but you knew thatg. Maurice |
#6
|
|||
|
|||
didymium - sodium light buster + other filters
On Sat, 12 Jul 2003 11:22:16 +0100, "Kev"
wrote: "Maurice Gavin" wrote in message ... I've posted at http://home.freeuk.com/m.gavin/grism2.htm some colour spectra via a digital camera showing the transmission of various filters all via a simple but effective homemade spectroscope. I'd appreciate feedback. FWIW I think that if you could get hold of various filters and publish them on a page like this - from various friends and local society members then you could be very popular with amateur astronomers and very unpopular with some brands of filter makers ! regards, Kev Kev - yes something for the autumn when societies return from the summer break. I'm sure makers will be interested in the independent 'truth' - the TT IF don't seem to pass yellow so if you have LP sodium skyglow it should be noticeably suppressed via TT RGB imaging. Maurice |
#7
|
|||
|
|||
didymium - sodium light buster + other filters
On Sat, 12 Jul 2003 11:22:16 +0100, "Kev"
wrote: "Maurice Gavin" wrote in message ... I've posted at http://home.freeuk.com/m.gavin/grism2.htm some colour spectra via a digital camera showing the transmission of various filters all via a simple but effective homemade spectroscope. I'd appreciate feedback. FWIW I think that if you could get hold of various filters and publish them on a page like this - from various friends and local society members then you could be very popular with amateur astronomers and very unpopular with some brands of filter makers ! regards, Kev Kev - yes something for the autumn when societies return from the summer break. I'm sure makers will be interested in the independent 'truth' - the TT IF don't seem to pass yellow so if you have LP sodium skyglow it should be noticeably suppressed via TT RGB imaging. Maurice |
#8
|
|||
|
|||
didymium - sodium light buster + other filters
In message , Maurice Gavin
writes I've posted at http://home.freeuk.com/m.gavin/grism2.htm some colour spectra via a digital camera showing the transmission of various filters like... TT RGB interference set showing red leak Hoya CMY didymium -sodium light buster TV monitor, fluorescent, neon and energy saving lamps [emission lines] and spectrum of daylight all via a simple but effective homemade spectroscope. I'd appreciate feedback. That's a very nice way to display higher resolution spectra. How did you get the colour spectrum to be a decent rendition in colour? My digicams (and colour films for that matter) baulk at giving an accurate coloured representation of the monochromatic light at different wavelengths in a spectrum. I should declare an interest here, since I sell a neodymium doped glass filter, Nonad, as a sideline. Info and low resolution spectra at: http://www.nezumi.demon.co.uk/nonad/nonad.htm The didymium filter you used looks to be less dense than Nonad. Was it a Baader or one of the other possible commercial didymium glasses? For completeness you might consider also doing one of the standard US broadband LPRs (optimised for mercury light) and the Orion UK sodium light filter which is about as good as you can get visually for mixed HPS and LPS lighting environments. If more people could see independent assessments of these filters they might buy the right ones. If any filter deserves to be called the sodium light buster it is Orion UKs. Didymium or neodymium glass like Nonad is only effective against the nearly monochromatic orange-yellow low pressure sodium lights. Then it works well, but the effect is still quite subtle visually. Look at the spectral absorbtion lines and you will see why. It is most effective photographically when it delays the onset of sky fog and keeps it a more neutral black for considerably longer exposures in suburban environments. I found the spectrum of the near IR leak on TTs R+B a bit confusing at first, but to be fair to TT you should perhaps give some indication of how much longer the exposure has to be for that image compared to the others. The leak isn't obvious on the normal spectral exposures. I presume TT R+B is a much longer exposure? Another light source that has a very interesting detail spectrum is an HPS lamp - self absorbed on the sodium D-lines and an odd turquoise emission line smack bang in the middle of the OIII narrow line filter passband. Even the humble low pressure sodium lamp has some other faint spectral emission lines that should show nicely in your setup. Regards, -- Martin Brown |
#9
|
|||
|
|||
didymium - sodium light buster + other filters
In message , Maurice Gavin
writes I've posted at http://home.freeuk.com/m.gavin/grism2.htm some colour spectra via a digital camera showing the transmission of various filters like... TT RGB interference set showing red leak Hoya CMY didymium -sodium light buster TV monitor, fluorescent, neon and energy saving lamps [emission lines] and spectrum of daylight all via a simple but effective homemade spectroscope. I'd appreciate feedback. That's a very nice way to display higher resolution spectra. How did you get the colour spectrum to be a decent rendition in colour? My digicams (and colour films for that matter) baulk at giving an accurate coloured representation of the monochromatic light at different wavelengths in a spectrum. I should declare an interest here, since I sell a neodymium doped glass filter, Nonad, as a sideline. Info and low resolution spectra at: http://www.nezumi.demon.co.uk/nonad/nonad.htm The didymium filter you used looks to be less dense than Nonad. Was it a Baader or one of the other possible commercial didymium glasses? For completeness you might consider also doing one of the standard US broadband LPRs (optimised for mercury light) and the Orion UK sodium light filter which is about as good as you can get visually for mixed HPS and LPS lighting environments. If more people could see independent assessments of these filters they might buy the right ones. If any filter deserves to be called the sodium light buster it is Orion UKs. Didymium or neodymium glass like Nonad is only effective against the nearly monochromatic orange-yellow low pressure sodium lights. Then it works well, but the effect is still quite subtle visually. Look at the spectral absorbtion lines and you will see why. It is most effective photographically when it delays the onset of sky fog and keeps it a more neutral black for considerably longer exposures in suburban environments. I found the spectrum of the near IR leak on TTs R+B a bit confusing at first, but to be fair to TT you should perhaps give some indication of how much longer the exposure has to be for that image compared to the others. The leak isn't obvious on the normal spectral exposures. I presume TT R+B is a much longer exposure? Another light source that has a very interesting detail spectrum is an HPS lamp - self absorbed on the sodium D-lines and an odd turquoise emission line smack bang in the middle of the OIII narrow line filter passband. Even the humble low pressure sodium lamp has some other faint spectral emission lines that should show nicely in your setup. Regards, -- Martin Brown |
#10
|
|||
|
|||
didymium - sodium light buster + other filters
On Tue, 15 Jul 2003 09:09:32 +0100, Martin Brown
wrote: In message , Maurice Gavin writes I've posted at http://home.freeuk.com/m.gavin/grism2.htm some colour spectra via a digital camera showing the transmission of various filters like... TT RGB interference set showing red leak Hoya CMY didymium -sodium light buster TV monitor, fluorescent, neon and energy saving lamps [emission lines] and spectrum of daylight all via a simple but effective homemade spectroscope. I'd appreciate feedback. Ahhhhhhh - Kev judge this subject matter well !!! That's a very nice way to display higher resolution spectra. How did you get the colour spectrum to be a decent rendition in colour? My digicams (and colour films for that matter) baulk at giving an accurate coloured representation of the monochromatic light at different wavelengths in a spectrum. Never had problems with colour spectra - been doing it for some years. I should declare an interest here, since I sell a neodymium doped glass filter, Nonad, as a sideline. Info and low resolution spectra at: http://www.nezumi.demon.co.uk/nonad/nonad.htm The didymium filter you used looks to be less dense than Nonad. Was it a Baader or one of the other possible commercial didymium glasses? No - it was a sample from an ophthalmatist used, so I understand, in some prescription glasses For completeness you might consider also doing one of the standard US broadband LPRs (optimised for mercury light) and the Orion UK sodium light filter which is about as good as you can get visually for mixed HPS and LPS lighting environments. If more people could see independent assessments of these filters they might buy the right ones. Agreed. Will be pleased to receive samples including Nonad for testingg. If any filter deserves to be called the sodium light buster it is Orion UKs. Didymium or neodymium glass like Nonad is only effective against the nearly monochromatic orange-yellow low pressure sodium lights. Then it works well, but the effect is still quite subtle visually. Look at the spectral absorbtion lines and you will see why. It is most effective photographically when it delays the onset of sky fog and keeps it a more neutral black for considerably longer exposures in suburban environments. I found the spectrum of the near IR leak on TTs R+B a bit confusing at first, but to be fair to TT you should perhaps give some indication of how much longer the exposure has to be for that image compared to the others. The leak isn't obvious on the normal spectral exposures. I presume TT R+B is a much longer exposure? Somewhat longer but not excessively so - the unfiltered sample of daylight is at the top - the filter only covers the lower half of the slit in a single exposure. The red leak is at~7000A and an IR block filter suppresses it and longer wavelengths remembering that some [non Starlight Xpress - Sony camcorder chips] CCDs typically peak ~7000A. Another light source that has a very interesting detail spectrum is an HPS lamp - self absorbed on the sodium D-lines and an odd turquoise emission line smack bang in the middle of the OIII narrow line filter passband. Even the humble low pressure sodium lamp has some other faint spectral emission lines that should show nicely in your setup. Yes - I've done LPS [its outside my house!] and will post shortly and maybe HP sodium too although luckily none are nearby. Just feel a little conspicuous aiming my devise at street lampsg. Maurice Gavin Regards, -- Martin Brown |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
"Tired" light | Marcel Luttgens | Astronomy Misc | 107 | December 21st 04 07:20 AM |
Nebula Filters? | Dave Grist | Amateur Astronomy | 14 | December 29th 03 10:48 PM |
Filter Question | Doink | Amateur Astronomy | 7 | October 29th 03 03:13 PM |
Wesley Clark Support Warp Drive, Time Travel | Mark R. Whittington | Policy | 97 | October 17th 03 03:10 AM |
Filter Help!!!! | Jon Yardley | Misc | 2 | July 26th 03 05:01 PM |