What is the Difference Between 1D Spectra and 2D Spectra?

[randa177]

Hi,
I am wondering what is the difference between 1D spectra and 2D spectra? I see many documents talking about one of these 2, but I couldn't find any clear definition...

 

[AstroRoyale]

2-d spectra are what you have on the CCD after taking an exposure with the spectrograph. The object that you are taking a spectrum of, say a star, typically extends over several pixels wide on the ccd chip. To get a 1-d spectrum, you sum up all the counts in the pixels in the 2-d profile in each row or column depending on how the chip is oriented, and subtract off any unwanted backgrounds at the same time. The end result is a 1-dimensional vector of total counts vs pixel number. For a quick and dirty 1-d spectrum, you can just plot across one of the rows/columns in the spectrum (again depending on the orientation of the ccd).

The gory details can be found in the link below. . .


http://iraf.noao.edu/iraf/ftp/iraf/docs/spect.ps.Z

 

[randa177]

2-d spectra are what you have on the CCD after taking an exposure with the spectrograph. The object that you are taking a spectrum of, say a star, typically extends over several pixels wide on the ccd chip. To get a 1-d spectrum, you sum up all the counts in the pixels in the 2-d profile in each row or column depending on how the chip is oriented, and subtract off any unwanted backgrounds at the same time. The end result is a 1-dimensional vector of total counts vs pixel number. For a quick and dirty 1-d spectrum, you can just plot across one of the rows/columns in the spectrum (again depending on the orientation of the ccd).

The gory details can be found in the link below. . .


http://iraf.noao.edu/iraf/ftp/iraf/docs/spect.ps.Z

Thank you, that was helpful, however, unfortunately I wasn't able to open the document with the details, that you mentioned,,, :-(

 

[AstroRoyale]

Why were you not able to open the file, works for me at least. Try this one instead perhaps. . .

http://iraf.net/irafdocs/spect.pdf

 

[randa177]

Why were you not able to open the file, works for me at least. Try this one instead perhaps. . .

http://iraf.net/irafdocs/spect.pdf

Yea, Thanks, i was able to open that one, I think my computer doesn't read the .ps.Z files, do you know how can I fix that?

 

[mgb_phys]

I think my computer doesn't read the .ps.Z files, do you know how can I fix that?

To read .ps (postscript) you need a free program called ghostview and ghostscript, they are available for just about all platforms.
The .Z is a compressed file (rather like .Zip but more common on unix) I think newer versions of ghostview can read them automatically - otherwise something like 7zip will uncompress them.

There are other types of 2d spectra, an Echelle puts multiple orders of the same spectra in different parts of the image, so the same line can appear many times - they are a little more complex to process. There are also multi-object spectrographs that produce spectra of many different objects in the same field at the same time

 

[randa177]

To read .ps (postscript) you need a free program called ghostview and ghostscript, they are available for just about all platforms.
The .Z is a compressed file (rather like .Zip but more common on unix) I think newer versions of ghostview can read them automatically - otherwise something like 7zip will uncompress them.

There are other types of 2d spectra, an Echelle puts multiple orders of the same spectra in different parts of the image, so the same line can appear many times - they are a little more complex to process. There are also multi-object spectrographs that produce spectra of many different objects in the same field at the same time

thanks a lot. my question this time may sound really stupid, but I am new to unix, and I don't know who to run ghostview on Unix, is there a command to do it?
Thanks

 

[mgb_phys]

If you installed from a package then it should have been put on one of the application menus, or double clicking on the .ps file should start it.
Otherwise 'gv' from the command line.

 

[randa177]

If you installed from a package then it should have been put on one of the application menus, or double clicking on the .ps file should start it.
Otherwise 'gv' from the command line.

is it just typing the 2 letters gv in the command line? I did that but it didn't work :(

 

[mgb_phys]

Do you have ghostview installed?
You can either install it from here (http://pages.cs.wisc.edu/~ghost/)
Or use the package manager in your Linux distribution.

You might also have evince installed - it's a combined pdf/ps viewer, again there should be a link on one of the menus or you can start it with "evince"

On unix you can also do "man -k postscript" to search for all the manual pages that mention postscript