The Basic Image

Clear Image

Pixel Counts:

  1. Background: 425.228
  2. Brightest region of object: 2143.827
  3. Faintest observable region: 500.596
  4. Peak value of faintest stellar object: 495.868
  5. Peak value of brightest stellar object: 2591.034

Background noise level (measured along left edge of region 1 using profile) ~19 counts (in terms of base to peak of plot, minimum 409, max 428)

Faintest stellar magnitude detected:
Hubble Guide Star catalogue 2.2 gives a magnitude for the star in region 4 of 17.37 (red)

Brightest Stellar Magnitude detected:
Hubble Guide Star Catalogue 1.2 gives a magnitude of 13.59 for the star in region 5.

Image Scale ~ 73.18 pixels/arcmin
Image Size: ~7.11x7.00 (using base distance between bright star and fainter star of ~1')

Image Sharpness:
FWHM X= 5.85 (4.8")
FWHM Y= 5.37 (4.4")
The slight difference in FWHM means there is a slight tracking error in the X direction. The average FWHM is about 5.61 pixels, which equates to a resolution of 4.6".

 

Blue Image

Pixel Counts:

  1. Background: 9.739
  2. Faintest visible region of object: 9.087
  3. Brightest region of object: 63.682
  4. Peak value of faintest visible stellar object: 39.234
  5. Peak value of brightest stellar object: 95.112

Background Noise Level:
Measured same way as previous along left edge of region 1, ~6.7 counts

Faintest stellar magnitude detected:
The Hubble Guide Star Catalogue 2.2 gives a magnitude of 15.51 in the blue of the star in region 4.

Brightest Stellar magnitude detected:
Same star as previous, blue magnitude unknown, photographic magnitude 13.59

Image Scale: ~73.18 pixels/arcmin
Image Size: ~7.11x7.00

Image Sharpness:
FWHM X= 5.81 (4.8")
FWHM Y= 5.64 (4.6")
The tracking on this image is better than previous, although the FWHM is not as good. The tracking still seems to be slightly off in X. Average FWHM is about 5.73 pixels, which means resolution is about 4.7"

 

Image Comparison

STScI DSS POSS2/UKSTU Blue image 7'x7' My Clear Filter Image My Blue Filter Image
  1. Details seen/not seen: Adjusting the brightness and contrast of the DSS image revealed that while the image has better resolution, and the fainter aspects of the galaxy are much more visible, the nuclear region is washed out. It's counts are comparable throughout the region. On my images, the most of the fainter details of the disk and tangential spiral arms are not visible. The DSS image appears to have different scaling than the linear scaling of my images.
  2. Relative limiting magnitudes: The faintest object in the DSS image listed in the Hubble Guide Star Catlogue has a red magnitude of 17.79 and a blue magnitude of 19.30. Since this is a blue filter image the limiting magnitude of this image is 19.3, as compared to the 17.37 of the clear image and 15.51 of our blue image.
  3. Relative size of star diameters: The FWHM of the stars in the DSS image is about 3.5 pixels, which equates to about 3.5". Our images have FWHM of 4.6" for the clear image, and 4.7" for the blue image.
  4. Effect of detector wavelength on image detail: The DSS image seems to have much more detail than either of my two images. Among my images, the blue filter image seems better defined than the clear filter despite its noisiness. The clear filter image seems a little fuzzier than the blue image despite the fact that it's brighter and its FWHM is slightly better.
  5. Change/Evolution: From this image (and other images of the object) I can discern no change.

 

 

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Banner image is a slice of HST image by NASA/ESA