Mintron Dark-Frame Scaler

First produce a test data frame by stacking 10 data (image) frames. This will quickly produce a relatively smooth test frame to be used in the following procedure.

Produce a dark frame by stacking all of the dark-frames in Registax with no alignment.

Load the dark frame into the left hand pane of the program

Then load the test data frame into the right hand pane of the program.

Click on the slider handle which is on the left of the slider scale. 100 will appear in the numeric box at the top and the corrected image will appear in the right hand pane. It can be seen that the top left of the corrected image has been over compensated and is too dark. This is because 100% of the dark-frame has been used.

Just to see the effect, drag the slider over to the right hand side of the slide and the number will change to 0%. The image in the right hand pane shows the effect of using none of the dark-frame

i.e. an uncorrected image.

Now slowly drag the slider until the image is balanced as below, i.e. not corrected too much nor too little. The value in the numeric box shows the percentage of the original dark-frame that is being used. When you are satisfied that the dark-frame correction is right and the image is properly balanced, click on the save button and the corrected dark-frame will be saved. You can edit the filename to suit yourself. In this example, the scaled dark-frame is 75.294% the brightness of the original dark frame.

Use this scaled dark-frame in Deep-Sky-Stacker or Registax on the complete set of data frames to produce a stacked, dark-frame-corrected image that is available for further post processing.

Why do Mintron dark-frames need scaling?

With the majority of Mintrons, when you cover the front of the scope to produce dark-frame data, the camera automatically increases its sensitivity even if automatic gain control (AGC) is turned off (AGC is usually on for deep sky imaging). This results in dark frames that are brighter than they should be, with even brighter amp glow. If such a frame is used to correct the data (image) frames, it will over correct and one result is that the area of amp glow becomes too dark. Dark Frame Scaler solves this problem.

The function of Dark Frame Scaler is to produce a scaled dark frame that can then be used to dark-frame correct the image frames.