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If we want to check a QSO's lyman alpha narrow band image, could a ground based telescope do that?

I mean under the circumstance that its lyman alpha shifts to 3300A.

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Are you asking what is the bluest commercially available filter, or the bluest ever commissioned by a professional observatory to make special observations? The former might be feasible to answer, but I cannot imagine that the latter will be, short of someone happening to know every single filter available to astronomers at every facility. I also don't quite understand the reason for your question. People are imaging ly-alpha sources and studying them spectrographically, so yes that is feasible. But why are you qualifying the question for ly-alpha sources red-shifted to 3000 Angstroms? –  Jeremy Apr 10 at 20:33
    
There are only certain windows of visibility for ly-alpha due to the atmosphere, requiring satellite/probe observations for frequencies outside those windows. –  Jeremy Apr 10 at 20:37
    
Just want to do a narrow band photometry. I find Gemini-N (gemini.edu/?q=node/10420) has a poor response at 3300A and the u-band filter is no longer available now.What is the bluest commercially available filter? As far as you know, what is the bluest ever commissioned by a professional observatory? –  questionhang Apr 11 at 1:26
    
Do you want to do photometry with your own equipment, or do you want to approach a facility to use theirs? Are you trying to source a filter for yourself (and if you find a place using a suitable filter, you will endeavour to also source one from where they did?) I think most U filters will be weak at 330nm. However, if you have special needs for a filter centred on 330nm, and you can fund it, I'm sure you could commission something... Who knows what others might have commissioned. –  Jeremy Apr 11 at 5:28
    
I find someone bought a suitable filter for their Keck observation. I know the absorption by the atmosphere at 3300A on the earth is large. If we want to get a 3300A narrow image,a space telescope,i.e. hst, is necessary? –  questionhang Apr 11 at 7:43

1 Answer 1

You probably will have difficulty imaging Ly$\alpha$ from a z=1.7 quasar at 330nm.

Says P. Veron: The lower limit [z=1.8] is set by the ultraviolet transmission of the atmosphere... between 3300 and 3600Å.

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Yes, the lowest redshift in their table 1 is 1.7. However their surveys are spectroscopic, a redshift lower than 1.7 is OK too.They can use other lines except lyman alpha. –  questionhang Apr 20 at 13:38
    
And isn't it ly-a you wanted to image? –  Jeremy Apr 20 at 20:17
    
Of course we talk about this problem under the premise that 3300A falls in the wavelength range. I should say larger than 1.7. 3300A low a response at a CCD's blue edge. It is marginal and maybe be not feasible. I do not know whether it is worth a try. I need to know how much feasibility is left. –  questionhang Apr 21 at 1:27
    
Why not use the T17 telescope at iTelescope.net using the U filter, and image a target of interest. See how it comes out, maybe post the result here in an answer. –  Jeremy Apr 21 at 7:34
    
I tried to register but failed. U band is too wide. I need a narrow band image. sigh, maybe hst is necessary. –  questionhang Apr 21 at 12:20

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