Welcome to http://hou.lbl.gov/~vhoette/Explorations/HOUtips/imagetips.html

Contents: * Creating bmp, jpg or gif * Improving Image Contrast * Resizing Images *
*Adjusting Negative Counts * Taking and Saving CCD Images for HOU *

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Create Other Formats, such as bmp, jpg or gif.

NOTE:   HOU-IP opens images that are saved in a 16 bit format as .fts from ccd cameras.   If images are saved as 8 bit or 32 bit, HOU will not open them.  PC versions of HOU will save as .bmp but you must choose that file type and rename the image with the .bmp extension.  You can also take screen shots of HOU screens with keyboard commands.

PC:  Save in HOU as bitmap (,bmp) then open in Accessories, Paint and Save As: JPG or GIF.

• PC:  Open .fts image in HOU-IP
• PC:  Save as a .bmp in HOU on a PC
  (Choose file type .bmp and type over the .fts with .bmp.)
• PC:  Open in Accessories, Paint.  Crop, label etc.  File, Save As: jpg or gif file.   (Or open in another type of graphics program and re-save.)

See Graphics for the PC: changing fts to bmp, jpg or gif.

PC:  Open in HOU and take screen shots. 

• PC: Open .fts image and use keyboard to take screen shots. 
  Print Scrn key, or Alt Print Scrn keys
• PC: Open Accessories, Paint.  File, New.  Edit, Paste.  Screen shot will appear. Crop if necessary.  File, Save as, choose type such as jpg or gif.

MAC: Open in HOU and take screen shots. 

•  MAC: Open .fts image and use keyboard to take screen shots.
  Apple, F, 3
• Go to MAC HD, Go to System folder, Look for Picture 1, Picture 2, etc.  These are the screen shots.  Open in Simple Text, or any graphics program.  In Graphics Programs Save as JPG or GIF.

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Improving Image Contrast for hard to see dim parts of image or for greater detail in brighter areas, such as galaxy centers.

Try cutting down the image by using Data Tools, Zoom Box.  Go to View, Reset min/max.  Then to Zoom on tool bar and change back to 1, press redraw or enter.  If you like what you see, then File, Save As and give a new name to the image.

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Resizing Out of focus or Too Fuzzy Images

If images are out of focus or too fuzzy, you can sometimes improve their display by resizing them.  Manipulaton, Resize, suggested amount: 0.5 on both axes.  Save in new window.  (If the files turns out with black centers for stars, then do Maniupulation, Divide, Divide Counts by 4, first. Then resize.)

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Adjusting Negative Counts

Note: FITS image standards have changed during the last decade.  HOU software does not comply with the current standard for use of signed and unsigned integers.  The result is that when images are taken with current ccd imaging systems, the files are saved in a format that is interpreted by HOU software in display counts that begin in a negative range.  We have adjusted most images in the HOU units and database.  However, if you should have images that are displayed with negative counts, you can use the following procedures to adjust the display range to be positive.

Images saved as fits and then opened in HOU-IP might display brightness counts from (negative)  -32768 to the highest counts recorded by the ccd up to 32767 counts.  (Range being 65535.)  These negative numbers are annoying and interfere with some of the Maniuplation routines.  To make all the counts positive, there are a couple of methods depending on the total range of counts in the image.  (You can check range under Data Tools, Histogram, Axes, to see the maximum counts.)  
    1.  Sometimes you can merely add 32678 to an image and the counts will become positive in the display min/max bar without any problem. But if the object is saturated or the range exceeds 32767, then parts of the image will  have black centers. 
    2.  If image has large range of counts or is saturated, then you will first have to divide the counts before adding.  Go to Manipulation, Divide, Divide Counts by 2.  Then go to Manipulation, Add, Add Counts: 16384..  (This time your total range is divided, so you add half of 32767 or 16384.)

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Taking and Saving Images for Hands-On Universe

Note:  This section is intended for those of you who have your own CCD cameras and are taking images. 

• Images should be saved as image.fts and the file type should be 16 bit fits.
• CCD Imaging computer's (not classroom computer) date and time should be set to Universal Time, Casablanca, Monrovia.  This time is five hours ahead of Central Daylight Time, six hours ahead of Central Standard Time.  The ccd cameras fts header date and time keywords assume Universal Time.
• Please put in the object name during imaging. 
• Please note the filter, if it is not automatically noted by the ccd system. 
• Please name images: object, filter, time, date, sequence. 
  For example: m57r60s010627c.fts, to mean m57, red filter, 60 seconds, 2001 June 27th, third image in sequence. 
  Note: However, the HOU database only allows 16 characters before the extension, .fts.  So, you may  have to   leave out information or be clever about abbreviations for long object names.  For Jupiter, use Jup.  For ngc3117 at 180 seconds, use ngc3117r3m010507.fts.  If you had a sequence of the same times for ngc3117 you might have to change ngc3117 to n3117, n3117r3m010507a.fts. 
• If you wish to contribute your images to the HOU database, contact Vivian Hoette or HOU Staff at addresses below.

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Questions, Comments, Suggestions: Email  houstaff@hou.lbl.gov or Vivian Hoette, vhoette@hale.yerkes.uchicago.edu.
Page Updated:  06/02/2001 

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