The starglow effect is an easy way to enhance selected stars in a constellation or asterism.

Above:  Comparison of original image of the Hyades star cluster and image using the starglow effect to enhance certain stars.

Selecting Stars

The first step is to select the stars you wish to enhance.  The easiest way to do this is to select them manually using the Elliptical Marquee tool.

Above:  The Elliptical Marquee tool on the toolbar

Select the Elliptical Marquee tool and a menu bar will appear at the top of the screen.  For Style select Fixed Size from the pulldown menu.  You will have to experiment to see which size works best, but for this example (using a 6 megapixel image) a size of 30x30 pixels was used for most all of the stars expect one (see below).

Above:  Choosing a Fixed Size of 30x30 pixels in the menu bar

Begin by selecting one of the stars by clicking to the upper left of the star.  Knowing where the circular selection will end up takes a little practice.  Continue selecting the stars you wish to enhance by holding the Shift key when clicking.  30x30 pixels was sufficient for all the stars in this example except Aldebaran, the bright orange star.  For this, the size was changed to 60x60.

Above:  The selected stars in the Hyades image

Duplicating and Blurring the Stars

Once all the stars are selected, they need to be duplicated to a second layer.  Do this simply by pressing Ctrl-J.

Be sure the Layers window is visible by selected in Window > Layers, or by pressing F7.

Above:  Stars copied to a new Layer

To produce the starglow effect, apply a Gaussian Blur to the duplicated star layer.  Select Filter > Blur > Gaussian Blur.  The radius of the blur will depend on the size of the image and desired effect.  For this image, a 4-pixel radius was used.

Above:  Applying a Gaussian Blur to the duplicated stars

Changing the Blend Mode

The stars are now blurred but do not look quite right because they have lost their bright centers.  To fix this, change the blending mode of the layer.  In the pulldown menu in the Layers window, change the blending mode from Normal to Screen.  Now the original stars show through but have soft glows surrounding them.

Above:  Changing the blending mode to Screen

Finally, if necessary, you can adjust the intensity of the effect using the Opacity slider in the Layers window.  For this example, the effect was toned down slightly by setting the Opacity to 80%.

Once finished, flatten the image by selecting Flatten Image from the Layers window flyout menu (at the upper right corner of the Layers window) or by pressing Ctrl-E.

Final Image

Above:  Final starglow effect.  Image of the Hyades and NGC1647 in Taurus by Larry Moore using a Canon EOS 10D, 75-300mm IS lens, 5 minute exposure.

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