Question 1 ~ Data Reduction

A) Image Data

The following is a list of the data and the processing performed on it:

File

Date

Time (CST)

Exposure (s)

Filter

CCD Temp (C)

Processing Steps

Bias
b1-50-0-015 9/14/2004 10:02:05 0 ~ -50

1) Images imported as a stack
2) overscan region measured and mean value subtracted from each image.
3) Images cropped from 512x512 pixels to 504x512 pixels
4) Images combined by average intensity to create MASTER BIAS.
b2-50-0-016 9/14/2004 10:03:44 0 ~ -50
b3-50-0-017 9/14/2004 10:04:12 0 ~ -50
b4-50-0-018 9/14/2004 10:04:35 0 ~ -50
b5-50-0-019 9/14/2004 10:05:07 0 ~ -50
b6-50-0-020 9/14/2004 10:05:32 0 ~ -50
b7-50-0-021 9/14/2004 10:05:54 0 ~ -50
b8-50-0-022 9/14/2004 10:06:20 0 ~ -50
b9-50-0-023 9/14/2004 10:06:45 0 ~ -50
b10-50-0-024 9/14/2004 10:07:07 0 ~ -50
b11-50-0-025 9/14/2004 10:07:32 0 ~ -50
b12-50-0-026 9/14/2004 10:09:35 0 ~ -50
b13-50-0-027 9/14/2004 10:10:03 0 ~ -50
b14-50-0-028 9/14/2004 10:10:33 0 ~ -50
b15-50-0-029 9/14/2004 10:10:57 0 ~ -50
Darks
d1-50-300-001 9/14/2004 8:12:22 300 ~ -50

Steps 1-3 from Bias frames repeated
4) Master Bias subracted from each image
5) Images combined by average intensity to create MASTER DARK.

d2-50-300-002 9/14/2004 8:20:35 300 ~ -50
d3-50-300-003 9/14/2004 8:26:13 300 ~ -50
d4-50-300-004 9/14/2004 8:32:41 300 ~ -50
d5-50-300-005 9/14/2004 8:38:09 300 ~ -50
Flats
sc1-50-300-001 9/14/2004 10:12:02 300 clear -50

Steps 1-3 from Bias repeated
4) Master Dark subtracted from each image
5) Master Bias subtracted from each image
6) Background Extractor plugin used to normalize each frame by its mean and combine using medians to create MASTER FLAT.

sc1-50-300-002 9/14/2004 10:20:19 300 clear -50
sc1-50-300-003 9/14/2004 10:26:31 300 clear -50
sc1-50-300-004 9/14/2004 10:32:08 300 clear -50
sc1-50-300-005 9/14/2004 10:37:54 300 clear -50
sc1-50-300-006 9/14/2004 10:43:35 300 clear -50
Target
ic239c1-50-300-006 9/14/2004 8:43:51 300 clear -50

Steps 1-5 from Flats repeated
6) Images divided by Master Flat
7) Image -006 deleted from stack due to star trails
8) Image -009 and image -010 deleted from stack due to large offset compared to the other images
9) Stackreg (rigid body) used to align the images
10) Images combined by average intensity to give AVERAGE IMAGE.
ic239c2-50-300-007 9/14/2004 8:54:26 300 clear -50
ic239c3-50-300-008 9/14/2004 9:03:16 300 clear -50
ic239c4-50-300-009 9/14/2004 9:16:59 300 clear -50
ic239c5-50-300-010 9/14/2004 9:22:46 300 clear -50
ic239c6-50-300-011 9/14/2004 9:30:38 300 clear -50
ic239c7-50-300-012 9/14/2004 9:36:05 300 clear -50
ic239c8-50-300-013 9/14/2004 9:43:09 300 clear -50
ic239c9-50-300-014 9/14/2004 9:50:33 300 clear -50
ic239c10-50-300-015 9/14/2004 9:56:04 300 clear -50

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B) Images

The following are the master calibration frames, created as described previously. The numbers below the links represent min/max values of the linear transformation function applied to each to show each image to its best:

MASTER BIAS MASTER DARK

MASTER FLAT

-38.4/28.59 16.85/243.79 0.91/1.08

And these are the changes, from raw images to final average, images except for final average displayed North down and east left, due to ImageJ's penchant for flipping FITS files:

 

AVERAGE IMAGE

Raw Images
Overscan Subtracted and Cropped
Dark Subtracted
Bias Subtracted
Flat Divided
 
 

North up, East left
Brightness/contrast adjusted linearly: range 4226.01 - 5326.17

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C) Critique

The calibration frames did do an adequate job at getting rid of the noise due to the CCD and the optics, but processing would have been more effective if there had been a way of correcting for the light interference from the stars in the image; the really bright star south of the galaxy in particular. One problem was that once the master flat frame was divided out, each image seemed to develop black spots, two of which were around (174, 396) and (254, 280). However, since these were on fixed pixel locations on each image, and there was slight offset from image to image, averaging the image took care of them.
If we were to attempt to collect this data, I think we could improve the overall quality of the image by attempting to keep the galaxy more or less centred in the image, like in frames -009 and -010, which would minimize the effect of the bright star somewhat. There wouldn't be as much overflow anyway.

 

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