nytecam Posted September 12, 2013 Share Posted September 12, 2013 This is a field shot of M57 from last week with the Rainbow Optics grating before the CCD. It shows three emission lines eg the dominant OIII+OIII+H-beta blend in the centre, the H-alpha to left [longer wavelength] and right of OIII a feeble line in UV that Torsten Hensen also records here @ 382nm [=Hansen]- presumably Balmer 10->2 ? The 4th image to the right is the real [zero order] image of M57.I don't think I've recorded this far into near-UV before before on CCD and wonder if my change of CCD [sX_H9 mono cam] is responsible. M57 was near the zenith at the time so perhaps minimum atmospheric absorption comes into play.Have you recorded this UV emission line and extracted its wavelength Link to comment Share on other sites More sharing options...
NickK Posted September 13, 2013 Share Posted September 13, 2013 Love that view for spectra, far batter than looking at basic lines! How do you differentiate between the image (x,y) and the wavelength shifted image (x,y)? So if you pick a point in the image, how do you know only that part of the spectra for that specific (x,y) is sampled? Reason I ask is that it appears, with almost circular stars overlaid with the spectra image of the stars. Link to comment Share on other sites More sharing options...
nytecam Posted September 13, 2013 Author Share Posted September 13, 2013 Love that view for spectra, far batter than looking at basic lines! How do you differentiate between the image (x,y) and the wavelength shifted image (x,y)? So if you pick a point in the image, how do you know only that part of the spectra for that specific (x,y) is sampled? Reason I ask is that it appears, with almost circular stars overlaid with the spectra image of the stars.Nick - a transmission grating is partially transparent and records both the real [zero order] star and nebular images with their spectrum offset to one side - the separation defines their wavelength within the spectrum. Here I've ovelaid, as best I can, the spectrum of Altair with known lines mostly hydrogen Balmer lines for calibration. Ideally a slit is need for a difuse object. Link to comment Share on other sites More sharing options...
NickK Posted September 13, 2013 Share Posted September 13, 2013 Have you thought of using a beam splitter - then pulling the seperate paths into different CCDs? (a bit like a spectrum version od a multi CCD colour system) Link to comment Share on other sites More sharing options...
WaveSoarer Posted September 13, 2013 Share Posted September 13, 2013 Excellent work. Link to comment Share on other sites More sharing options...
nytecam Posted September 14, 2013 Author Share Posted September 14, 2013 Have you thought of using a beam splitter - then pulling the seperate paths into different CCDs? (a bit like a spectrum version od a multi CCD colour system)What separate paths?? Link to comment Share on other sites More sharing options...
NickK Posted September 15, 2013 Share Posted September 15, 2013 You can full bandwidth beam split, then use 50% on the spectrum and 50% on the image - so two CCDs one for spectrum and one for the image. Link to comment Share on other sites More sharing options...
Merlin66 Posted September 15, 2013 Share Posted September 15, 2013 Nick,Unfortunately a grating doesn't work that way.There will always be a "zero order" direct image of the FOV, this is superimposed on the spectral field. Link to comment Share on other sites More sharing options...
nytecam Posted September 16, 2013 Author Share Posted September 16, 2013 Nick,Unfortunately a grating doesn't work that way.There will always be a "zero order" direct image of the FOV, this is superimposed on the spectral field.Thanks Ken - saved me hurting my brain:-) Link to comment Share on other sites More sharing options...
robin_astro Posted September 16, 2013 Share Posted September 16, 2013 Nick - a transmission grating is partially transparent and records both the real [zero order] star and nebular images with their spectrum offset to one side - the separation defines their wavelength within the spectrum. Here I've ovelaid, as best I can, the spectrum of Altair with known lines mostly hydrogen Balmer lines for calibration. Ideally a slit is need for a difuse object. Here is M57 taken with a slit spectrograph (by Christian Buil using an Alpy 600 spectrograph) which I have found has very good performance into the UV (good grating efficiency and sharp focus.) I think the main feature you are seeing in the UV is perhaps the N[iII] forbidden line at http://www.astrosurf.com/buil/alpy600/data4/m57_3.pngfrom this pagehttp://www.astrosurf.com/buil/alpy600/performances.htmCheersRobin Link to comment Share on other sites More sharing options...
NickK Posted September 16, 2013 Share Posted September 16, 2013 http://www.shelyak.com/produit.php?ref=PF0036&id_rubrique=17Ouch .. I may have some birthday money left over after the move+pier.. Link to comment Share on other sites More sharing options...
nytecam Posted September 17, 2013 Author Share Posted September 17, 2013 Here is M57 taken with a slit spectrograph (by Christian Buil using an Alpy 600 spectrograph) which I have found has very good performance into the UV (good grating efficiency and sharp focus.) I think the main feature you are seeing in the UV is perhaps the N[iII] forbidden line at http://www.astrosurf.com/buil/alpy600/data4/m57_3.pngfrom this pagehttp://www.astrosurf.com/buil/alpy600/performances.htmCheers RobinThanks Robin - N[iII] in violet it is for my third emission line ! I presume the Alpy600 is a grism arrangement? Unusual for Christian he's named H-beta twice in his M57 spectrum ! Link to comment Share on other sites More sharing options...
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