This section takes you through the most basic procedures for taking CCD images with CCDOPS.  The only techniques employed are taking single exposures and taking dark frames.  Using only these techniques you can take very impressive CCD images of many objects.

Starting Simple

Once you have focused the telescope and centered your target, it is time to take an image.  Select the Expose tab in the MaxIm CCD window.

The appropriate exposure time will depend on the tracking accuracy of your mount and the focal length of your telescope.  Figure 30 to 60 seconds is a safe bet for starters.  In the Expose window, select an exposure time.  Choose the Clear filter from the pull-down menu if you are using a color wheel.

Above:  Typical exposure settings for a simple single exposure.

There is one additional step.  To keep things simple and to see an image right away, you will want to subtract a dark frame automatically from the image.  In the future it will be time saving to do this step in post-processing, but for now it will get you a prettier picture sooner to auto-calibrate.

Select the Settings tab from the MaxIm CCD window.  Choose Simple Auto-Dark under the Auto Calibration section.  This will automatically take and subtract a dark frame from the light frame.

Above:  Simple Auto-Dark in the Settings window.

To take the image, return to the Expose window.  Click Expose.  The window will display the progress of the image, beginning with the dark frame.

Above:  Exposing the dark frame.

Next, the image is read out.  In Version 3 of MaxIm DL a bar indicates the progress of the download.

Above:  An image being downloaded from the camera.

After the dark frame, the color wheel is moved to the clear filter and the light frame is exposed then downloaded.

Above:  Light frame being exposed.

Once downloaded, the final image--having been automatically dark-subtracted--is displayed.

Above:  Single, dark-subtracted exposure of M83.

The Next Step

After mastering the steps necessary for finding, focusing, and grabbing quick shots of objects, the next step is to take multiple exposures which can later be stacked to enhance the image.  See the Image Processing with MaxIm DL section for details on combining the images.  Also, more advanced techniques for using dark frames can be utilized to optimize images and to save time while imaging.

A good technique is to take longer and longer unguided exposures to determine how long your telescope can track before star trailing appears.  (If guiding the telescope, essentially the only limits to how long you can expose are light pollution and your patience!)  If you have determined that 60 seconds is the limit, start shooting a bunch of 60-second exposures.  (See also the next section on advanced techniques with MaxIm DL).

The process for imaging light frames is the same as outlined above, except that the Auto Calibration should be set to None in the Settings window.

To save time, shoot only the light frames, saving the darks for later.  If, for example, you take images of 8 objects using 20 exposures for each object, there is no need to take 160 dark frames!  In fact, a single dark frame would suffice as long as all the individual exposures are of equal length and the temperature setpoint remains the same.  In practice it is common to use at least three dark frames which are combined to reduce variations in noise from image to image.

Manual Dark Frames

Shooting a manual dark frame uses the same process as imaging a light frame except that the Dark button is highlighted in the Expose window.  The newest verson of MaxIm DL (version 4) automatically determines the right dark frames to use for a given image, so there is no critical need for a standard naming convention, but if you ever use the darks with another program or just want to keep track of what is what, it is good to name them with a theme.  For example, the name "dark30m8bin1" might indicate a dark frame that is 30 seconds long, taken at a temperature of minus 8 degrees, with a binning of 1x1.

Above:  A typical dark frame.  All the noise contained in this image will be subtracted from the light frames.

Next, Color Imaging Basics....

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