Image Processing, Light and Dark Mono 2x2 Modes

1.Open all “light” images to be stacked in Maxim DL Essentials. Do this with the Open command in the File menu.

2.Click on one of the opened images, and select Dark Subtract from the Process menu. The averaged dark frame has now been subtracted from the selected “light” image. Repeat this process for all of the “light” images opened in Maxim DL Essentials.

3.Before these images are ready for stacking, they must be converted from raw format to color format. To do this, click on one of the opened images and select Covert Raw to Color from the Process menu. For convenience, there is a button on the toolbar that you can click instead of using the menu. Now, click the Reset Background Level and the Reset Scaling but- ton (scaling can be used to ﬁne-tune the color balance later on). Make sure the Anti-Alias Filter box is not selected. Click OK. Repeat this for all the open images.

You can save each image after dark frame subtraction and color conversion (using Save from the File menu), or you can just save the ﬁnal combined image once the individual images have been stacked using the Combine function.

Note that the Light Color 1x1 mode is really just for quick previewing how an image might look, and is generally not often used. For most astronomical imaging, the Light Raw 1x1 is the mode that should be used; this allows for Dark Raw 1x1 frame subtraction, with subsequent color conversion with the Convert Raw to Color command.

Light and Dark Mono 2x2 Modes

For added convenience and versatility, the SSDSI-II’s individual pixels (light- detecting sites) can be “binned” into units of two-by-two pixels (i.e. four indi- vidual pixels create one binned 2x2 pixel). This creates larger and more sensi- tive pixels, but with decreased resolution. This can be useful for some types of astronomical imaging, such as capturing faint nebulae. It can also be useful for quick-checking the aiming of the telescope or framing of objects within the ﬁeld of view of the camera before using the normal Light Raw 1x1 mode to actually capture images.

To use in “2x2” mode, select Light Mono 2x2 mode for capturing “light” images, and Dark Mono 2x2 mode to capture dark frames for averaging and subtracting. Images can be combined and processed in the same way as Light Raw 1x1 images, except the Convert Raw to Color command does not apply (as the 2x2 images are monochrome only).

Image Processing

After you have captured and combined individual images (with or without dark frame subtraction) into a single resultant image, you may want to perform some additional image processing to bring out subtle details or to make the image appear more pleasing overall. Maxim DL Essentials contains several functions which serve to do this. These can be found in the Process menu

Make Pixels Square

This command provides a one-step adjustment of the image aspect ratio. It uses the pixel aspect ratio determined by the ﬁle header and interpolates the image to make the aspect ratio 1:1. This generally has a very mild affect when applied to images. For best results, this function should be applied to individual images before stacking (for best image alignment), but can be used after stacking as well.

To use this function, simply select Make Pixels Square from the Process menu for any image currently opened in Maxim DL Essentials.

Filter

Filtering an image is an operation that emphasizes certain characteristics of an image while suppressing others. MaxIm DL Essentials supports two kinds of ﬁlters: Unsharp Mask and Gaussian Blur. In the Filter window (Image 14) select which one of these ﬁlter types you would like to apply

Unsharp Mask is a method of sharpening or high-pass ﬁltering an image. It amounts to subtracting a low-pass ﬁltered version of an image from itself. The low-pass ﬁltered version is called the mask. The Low-Pass Filter itself can be set to Mild or Strong for different effect. Use Mask Weight to control the strength of the mask applied to the image. The Mask Weight is in percent; the higher the number, the stronger the mask.

Gaussian Blur is a method of blurring an image. It can be used to suppress noise in an image at the expense of sharpness. The Radius setting controls the amount of blurring applied to the image. Increasing the radius increases the amount of blur applied.

For best results, turn on the Auto Full Screen preview button, and adjust the settings. This allows you to rapidly adjust the settings until you are satisﬁed with the results. Then, click OK to actually apply the ﬁlter settings to the image.

It is best to use a light touch with this command, to avoid over-processing the image. Over-processing can create artifacts; i.e. features in the image that are not real. It also ampliﬁes the noise in the image.