Variable Star IY Dra Spectrum
In the above image
star IY Dra round spectral order zero is in the upper left corner and it's first order blazed grating spectrum is located on the top to the right side. The processed spectrum band is below the blazed grating spectrum.
Spectrum image was taken by the below
- In the above image processed spectrum bands have been added below the spectrum images.
- Variable infrared star IY Dra spectrum is on the left.
- Quasar KUV18217+6419 spectrum is on the right.
- The above cropped image shows the rectangle selection area that was used for the spectrum 3-D surface plot, the spectrum band and the spectrum chart below.
- The selection area is 6 rows by 428 columns.
- The short spectrum wavelengths are on the left in the selection area.
- The long spectrum wavelengths are on the right in the selection area.
- The black pixel in the zero mode is the centroid location.
Spectrum 3-D Surface Plot
- This is a spectrum 3-D surface plot of the selection area.
- The short wavelengths are on the left and the long wavelengths are on the right.
- The average of the rows is used to generate the spectrum band and the spectrum chart below.
- The average of the vertical column of pixels in the selection area is used to generate the spectrum band below.
- The spectrum band is three times the original horizontal size so that it matches the below spectrum chart width.
- Short wavelengths are on the left and long wavelengths are on the right.
- The spectrum band is linearly scaled between the intensity 20 to 230 to better see the spectrum details. (Black = 0 and white = 255)
- Spectrum band starts at 2999.9559 angstroms
- Spectrum band ends at 10692.2873 angstroms
- No sharpening or other image processing was done on the spectrum band.
- The above chart is the average of the vertical pixels in the selection area of the spectrum.
- Spectrum Plot Selection Start: 2999.9559 angstroms
- Spectrum Plot Selection End: 10692.2873 angstroms
- Spectrum Plot Average: 17.9727 angstroms/CCD pixel
- The vertical axis is the intensity values (average of the vertical pixels in the selection) of the spectrum image.
- Three reference yellow line markers were added.
- Vega H-alpha absorption line was used to calibrate the x axis in
angstroms by measuring the distance of the grating to CCD.
- Vega H-alpha absorption line distance was measured from the centroid of the spectral order zero.
- The below table shows the four images used and the calculated grating distance between the grating and the CCD.
- The grating distance mean is 18.3272 mm with a standard deviation of 0.01414 mm.
- The first angstrom calibration equation is Å =SIN (ATAN (0.0000068* pixel distance /.01832719265135))*0.000005*10000000000
- Å is light wavelength measured in angstroms.
- 0.0000068 m is QSI532ws pixel size (6.8 microns).
- Pixel distance is the horizontal pixel distance from the centroid of spectral order zero.
- .01832719265135 is the distance of the grating to CCD (18.3272 mm).
- 0.000005 m is the distance between the Rainbow Optics grating filter lines (200 lines/mm grating).
- 10000000000 converts the wavelength from meters to angstroms.
- See the second column Angstroms in
- The second angstrom calibration equation is a linear x=Ay+B to align the H-delta angstrom value and H-alpha angstrom value to the absorption lines of image vega08062010-01605s. See the third column Angstroms Adjust in
Signal to Noise Ratio
The background measurements are of the above yellow selection box.
- The image extreme stretch is used to check for faint stars or spectrum that could affect the below measurements.
- Background Mean: 358.0155
- Background Minimum: 355.4602
- Background Maximum: 360.6219
- Background Standard Deviation: 0.8454
- Background Mean/Standard Deviation: 423.4909
- Spectrum Maximum: 379.3303
- (Spectrum Maximum Signal - Background Mean)/(Background Standard Deviation) = Spectrum to Noise Ratio: 25.2130
ImageJ Macro Spectrum Log
The following test pattern is to help you adjust your monitor to best view the CCD astro images.
The test pattern is used for adjusting monitor brightness, and contrast.
Adjust monitor brightness and contrast to see all 16 gray scale levels.
The most important adjustment when viewing astro images is to see the differences in all of the black bands.
© 1998-2010 David Haworth