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Sky Charts
 

Photography analysis  :
    1st case,  M51 FITS image from DSS
     
  • Image acquisition using Internet.

    • Click "Find" , select "Messier", then in "Cat. Id." enter 51, click "OK".
    Click "Field width" , drag cursor to "+0°30' ", click "OK".
    The chart will display a narrow field of view of M51.
    Click "Online Resources" , "Images", "ESO SkyCat DSS" or "Heasarc SkyView".
    The "Internet resource" window will display all the preselected parameters.
    If you want to keep this image for later use, change file name  $temp.fit to M51.fit.
    Click "Connect".
  • When transfer is complete click "OK" and the " Background Image"  window will display the image.
  • You can display the header by a right click on the file name "M51.FIT".
  • Notice the coordinates display at top of image. This indicates that the map superposition will be automatic.
  • You can now change the image appearance :
    • Change height or low threshold.
    • Select color table.
    • Select intensity table.
    • Zoom to a part of the image by drawing a rectangle with the mouse.

Click on image for full resolution
  • You can also preview the image at a larger dimension. Click "Full Size" and change the size with the "+" and "-" keys.
  • Click "OK". The image will display with the chart.
  • Click  to display the coordinate grid and "Labels" and "Options", change options to show name and  magnitude 

Click OK.

Click on image for full resolution

You must return to the image selection screen to be able to zoom. In this way the chart superposition is automatic.

You can also display only the photograph and the labels : click "Star appearance"  and check "Invisible" in the color box

Click on image for full resolution

  • Click  The chart will blink with the image.

    • To change the blink delay click Alt +  .
  • To identify all stars on the photograph you can extract data from the USNO-A catalog.

    • Click "Internet Resources " , "USNO-A", "ESO SkyCat USNO-A1.0" or "CDS VisieR USNO-A2.0".
    The "Internet resource" window will display all the preselected parameters.
    If you want to keep this data for later use, change file name  $temp.cat to M51.cat.
    Click "Connect".
  • When transfer is complete click "OK"

    • The chart will now show stars up magnitude 19 or 20.
  • To keep this chart as is, click "Saved charts" , then "Save chart". Enter file name i.e. M51 then click "Save". You can later reload this chart with the photograph in this exact state.