Elimination of scattered light is crucial to imaging low-contrast objects such as the solar photosphere and planetary surface features.

In practice, scattered light elimination amounts to performing three tasks wherever possible throughout the optical train:

• Darken all lens edges with a black Sharpie pen (or equivalent).
• Paint all structural surfaces (tubes, etc.) with Krylon ultra-flat black. Note that the paint will outgas for a couple of days, so it's best to leave painted surfaces away from valuable optics while the paint cures.
• Cover critical surfaces with skid-guard (which is an anti-slip mineral abrasive with an adhesive backing — commonly used for skid-guarding steps). Be sure to paint the skid-guard with ultra-flat black paint, then let it cure for a day or two, before applying it to telescope tubes and parts.

I cannot emphasize enough how important it is to be utterly, obsessively anal about applying the above three tasks to the entire optical train. It is also very enlightening (no pun intended!) to assemble your optical components in a dark room and shine a bright flashlight in one end while viewing the opposite end. (An LED flashlight is ideal.) Any rings or areas of brightness not associated with the central bright spot are due to scattered light. They must be reduced or eliminated. NOTE: even very expensive optics with scattered light mitigation (flat black paint, light-scattering grooves, etc.) will almost always have a completely unacceptable amount of scattered light and will require fixing (at least for solar, lunar, and planetary imaging).

Here are a few photos of the kinds of places that needed fixing in my optical components (click on the thumbnails for larger views):

Skid-guard applied to the interior of the telescope dew shield.

Here you can see skid-guard applied to the inside of the telescope tube. The un-skid-guarded surfaces have all been painted ultra-flat black. Also, though it is hard to see in this photo, the achromat objective lens edges have been colored black with a Sharpie pen.

This is a 1.25 inch to C adapter for attaching my video camera. Note that the skid-guard has been applied to the inner lip, which was a terribly good reflector of scattered light.

Here is the other end of the 1.25-inch to C adapter.

Here is the view in one end of the 2-inch Herschel wedge. All interior surfaces have been covered with skid-guard. This required careful disassembly and reassembly of the wedge housing.

This is a view through the other end of the Herschel wedge.

This is an interior shot of the TeleVue 2× barlow. Note the skid-guard. The interior of this tube was another distressingly efficient reflector of light.

This is a shot of the TeleVue 4× PowerMate. After blackening the lens edges, I found it necessary to replace the very reflective retaining ring with a baffle made of skid-guard material.

Application of anti-scattering techniques were unsuccessful on this highly-sensitive night-vision component.

This over-exposed view shows the remaining scattered light in a train consisting of Herschel wedge, 2× barlow, 4× PowerMate, and 1.25-inch to C adapter (see next photo). The scattered light sources are labeled. Despite appearances, this is actually very, very good; there is only a tiny fraction of the original amount of scattered light.

This is an outside view of the optical train used in the above photo. This is my current setup for high-resolution white-light solar observing.