Image+Calibration

Please see the following for the original procedure:- http://www.tzecmaun2.org/wiki/index.php?title=Calibration_Using_MaxIm_DL Note: not all steps may apply. For example, if your images already have a dark frame applied when you download them, start with the Image Cleanup section.

Calibration
Calibration involves removing instrument noise from the images. Bias and Dark frames (calibration frames) are used by MaxIm DL to do this. Choose calibration frames with a date that is closest to the date your images were captured. If your light frame duration is different from the dark frame, the following process occurs when MaxIm DL applies the calibration frames to the light frames: The result is a dark frame where the bias remains the same, and the dark current has been scaled for duration of exposure. To calibrate your images in MaxIm DL, use the workflow below. You can find additional details on any of the opertions included in the MaxIm DL help file or manual.
 * Bias frame ** - records the number of electrons in each pixel at the start of the exposure. The temperature and bin mode must be identical to the light frame.
 * Dark frame ** - records the number of electrons in each pixel at the end of an exposure. The exposure is taken with the shutter closed. The electrons come from what is called //dark current,// electrons that migrate into pixels during the exposure. The temperature and bin mode must be identical to the light frame. The duration of the dark frame should be as close as is available to the light exposure duration.
 * The bias frame is subtracted from the dark frame. This count in each pixel now reflects the number of dark current electrons only. (Subtracting the bias removes the initial count.)
 * The count of dark current electrons is scaled for time. For example, if your exposure was four minutes and the dark was for five minutes, the values in each pixel of the adjusted dark frame are multipled by 0.8.
 * The bias is added back in
 * 1) Collect all of your images into a local folder on the computer with MaxIm DL. Put calibration frames into their own folder.
 * 2) Remove any old calibration groups (**//Process | Set Calibration//** menu option)
 * 3) Create calibration groups for your calibration frames
 * 4) Load your images into MaxIm DL
 * 5) Use **//Process | Calibrate All//** to apply your bias/dark frames
 * 6) Save your calibrated images with new filenames (don't overwrite your original data so you can go back if you made a mistake)

Image Cleanup
Once the images are calibrated, you may find that they still contain some problems. This might include hot pixels (bright pixels in the image), cold pixels (dark/dead pixels), or even whole or partial rows/columns that are unusually bright or dark. If the camera does not have anti-blooming circuits, you may also see vertical extensions on stars (blooming). The following steps will clean up the images, and should be done immediately after calibration and before any alignment or combining. I recommend that you save each image with a new filename after cleanup. This way, if you made a mistake, you don't have to start over with calibration again. For example, if you image was originally "myfile.fit," you could save it as "myfile_CAL.fit" after calibration, and as "myfile_CAL_CLEAN.fit" after cleanup. This will make it easy to keep track of what you are doing. code code code from the combine process. Otherwise, those problems will be incorporated into the final result! code
 * 1) To remove blooms, use the **//Process | Remove Bloom...//** menu option. If necessary, change the Saturation Level to match the brightness level of the blooms in your image. (To check saturation level: Open the Information window, set Aperture mode, and move the cursor over the bloom. Note the value for "Pixel" as you move the cursor around; set the saturation level a few thousand below the typical value for "Pixel.") Click the "Automatic" button and MaxIm DL identifies the bloomed stars. Click the OK button to clean up the bloomed stars.
 * 2) To clean up hot pixels, open the Kernel Filters Dialog (**//Filter | Kernel Filters//** menu option). Click on the "Hot Pixel" radio button. Set the Threshold value to a number between 5 and 30. For more aggressive hot pixel removal, use a **//low//** value. For less aggressive removal, use a higher value. If you use a low value (less than or equal to 15), look at the smallest stars in your image and make sure you haven't eroded them. If the stars become eroded during hot pixel removal, try a larger threshold value, and then run the filter a second time.
 * 3) To clean up cold pixels, open the Kernel Filters Dialog (**//Filter | Kernel Filters//** menu option). Click on the "Dead Pixel" radio button. Set the Threshold value to a number between 95 and 70. For more aggressive cold pixel removal, use a **//high//** value. For less aggressive removal, use a lower value. You will not have a star erosion problem with the Dead Pixel filter.
 * Note: ** If any images do not clean up well, are out of focus, show elongated stars, etc., they should be omitted

Align and Combine
Although you can align and combine images in separate steps, you will most often perform these steps together in MaxIm DL. code **Note:** For a list of descriptions of all of the Align options, please see [|MaxIm Align Options] code code For help with Manual - 2 star alignment, [|see this wiki page.] code Save the resulting file with an appropriate name. For example: "myfile_avg3.fit" if you want to remember how many files you aligned/combined, and that you used averaging as the combine method. This is the file you should open in Photoshop for processing. Note: if there are a lot of hot pixels, the automated alignment mode may not work. Make sure you do image cleanup before you try to align/combine. If you are creating master red, green, and blue images for an RGB color image, follow the above procedure for each of the images, and save a master image for each color channel. You can then use MaxIm DL or Photoshop to create the master RGB or LRGB image for processing in Photoshop.
 * 1) Open the images you want to align and combine in MaxIm DL. Only the images you wan to align and combine should be open.
 * 2) Use the **//Process | Combine//** menu option to open the Select Images dialog. Click the Add All button, the click OK.
 * 3) This opens the Combine Images dialog. Select the Align Mode from the drop-down list at the top of the dialog. For most cases, you will use "Auto - star matching." This uses the stars in the image to align. (If your image is full of nebuolosity or has few stars, or if the alignment simply fails, select the "Manual 2 stars" method instead. If rotation is not necessary to align the images, then you can also try "Auto - Correlation" instead.)
 * 4) "Bicubic Resample" should be unchecked. In many cases, checking this will make your stars slightly fatter. This setting is intended to increase the sub-pixel accuracy of the alignment, but if you have really sharp stars, you are better off without it.
 * 5) Output should be set to Average. (You can also use the more advanced output methods, but you'll need to read up about them in the MaxIm DL help/manual. The advanced methods require special settings, as well as a sufficient number of images to allow the underlying statistical functions to work correctly.)
 * 6) FITS Format should be set to 16-bit Int so that you can easily load images into Photoshop with a FITS plug-in (e.g., FITSPlug or FITS Liberator).
 * 7) Click OK to start the align/combine process.