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The Minor Planet Observer
and
Palmer Divide Observatory

2007 Shoemaker Grant Recipient

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Header Editor

 

Image Processing in Canopus

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The batch image processing form allows to process one or more images, creating a new image instead of overwriting the original.

 


Action

Description

Uses Image

Merge Dark

Subtracts the Dark frame from one or more images. Can also be used to subtract bias frame from one or more images.

Dark

(or Bias)

Merge Flat

Median combines the Flat frame with one or more images.

Flat

Merge Dark and Flat

Subtracts the Dark frame and then median combines the Flat frame with one or more images.

Dark & Flat

Average

Averages the pixel values at each X/Y position in all the selected images to create a single value placed in the new image. No registration is performed.

Good for making master darks and/or flats.

None

Median

Median combines the pixel values at each X/Y position in all the selected images to create a single value placed in the new image. No registration is performed.

Good for making master darks and flats.

None

Median Normalized

Finds average value of center region of first image to create a scaling factor. All images are multiplied by this factor so that the centers of all the images have approximately the same average. This accounts for fading/brightening sky when getting sky flats.

After scaling is done, then median combine as described above is performed. No registration is performed.

Good for making master darks and flats. Particularly good when making sky flats that have stars.

None

Add Operator

Adds the pixel value at X/Y in the operator image to the one at the same X/Y in each selected image. No registration is performed.

Operator

Subtract Operator

Subtracts the pixel value at X/Y in the operator image from the one at the same X/Y in each selected image. No registration is performed.

Operator

Multiply by Operator

Multiplies the pixel values at X/Y in the operator and selected image to create a new pixel value. No registration is performed.

Operator

Divide by Operator

Divides the pixel value at X/Y in the selected image by the value at the same X/Y in the operator image. No registration is performed.

Operator

Merge with Operator

Adds the pixel value at X/Y in the operator to that of the value in the selected image at the same X/Y. The value for each can be scaled, giving more weight to one image or the other. In video terms, a “partially dissolved” image is created. No registration is performed.

Operator

Stack (Average)

The same as Average except that all images are registered. Greatly increases SNR while cutting down noise. The Operator image is the reference image.

Canopus must be able to AutoMatch the images.

Operator

Stack (Average, Multi)

Stacks multiple images using average value as one group or in groups of a certain number, e.g., you can stack 100 images in sets of three.

Canopus must be able to AutoMatch the images.

None

Stack (Sum)

The same as Add except that all images are registered. Greatly increases SNR. Noise reduction is not as great and may actually increase. The Operator image is the reference image.

Canopus must be able to AutoMatch the images. Result images are converted to 32-bit integer to avoid reaching saturation.

Operator

Stack (Sum, Multi)

Stacks multiple images using summed value as one group or in groups of a certain number, e.g., you can stack 100 images in sets of three.

Canopus must be able to AutoMatch the images. Result images are converted to 32-bit integer to avoid reaching saturation.

None

Noise Reduction

Reduces noise in the image by performing a median comparison of pixels in a 3x3 region around each pixel. If the pixel value varies from the median by more than a user-set amount, the median value of the 9 pixels is assigned to the pixel being examined.

None

Fix Column

Same as Noise Reduction except that the operation is limited to a single column.

None

Resample

Resamples one or more selected images to 8x, 4x, 2x, 1/2x, 1/4x, or 1/8x original size (uses “Factor” setting).

None

Pixel Math (Add)

Adds a fixed value to each pixel in one or more selected images. Over and underflow checking is performed.

None

Pixel Math (Subtract)

Subtracts a fixed value from each pixel in one or more selected images. Over and underflow checking is performed.

None

Pixel Math (Multiply)

Multiplies each pixel value in one or more selected images by a fixed amount. Over and underflow checking is performed.

None

Pixel Math (Divide)

Divides each pixel value in one or more selected images by a fixed amount. Over and underflow checking is performed as well as divide by zero.

None

Convert to 16-bit

Converts one or more 8/32-bit integer or 32/64-bit floating point images to 16-bit integer. This is useful when working with other programs that cannot handle all of the FITS image formats.

None

Convert to 32-bit
integer

Converts one or more images to 32-bit integer format.

None

Convert to 32-bit
float

Converts one or more images to 32-bit floating point format.

None

Pad FITS to 2880

Pads the FITS header to a multiple of 2880 bytes filling with spaces (ASCII 32) and pads file to multiple of 2880 bytes, filling data beyond the image with ASCII 0.

None

Flop (left-right)

Reverses pixel positions left-right (rotate 180 about
Y-axis).

None

Flip (top-bottom)

Reversed pixel positions top-bottom (rotate 180 about X-axis).

None

AutoMatch (WCS)

AutoMatches one or more images and inserts WCS information into FITS header.

None

Crop

Crops images to reduce the number of rows and/or columns.

None

 

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This page was last updated on 01/19/11 15:52 -0700.
All contents copyright (c) 2005-2011, Brian D. Warner
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