Moonfish® 1.25" Parfocalizing Ring
These extremely practical parfocalizing rings are used for several purposes:
If you would like to make your non-parfocal eyepiece set parfocal you can put one of these rings on each eyepiece and adjust the height so that all eyepieces are at the same focus point. Now, when you swap eyepieces, you won't need to refocus every time!
They are also extremely useful when used with a flip mirror (like the one built into the ETX) for photography.
To use a parfocalizing ring with a flip mirror you would first use the telescope focus knob to put your attached camera in perfect focus, now slide a ring over the eyepiece of choice and raise and lower the eyepiece in the holder until it is perfectly in focus. Once you find the focus point that is perfectly matched to the camera slip the ring down and lock it in place using the included wrench. Now you can focus using the eyepiece (much easier than a dim focus screen) and just flip the mirror and take a picture! Leave the ring in place on the eyepiece and you can always quickly and easily pop it back in for photography.