Explore Scientific Rack and Pinion Focuser Extension Tube 1" Extension for our 2" Rack and Pinion focusers on our ED APO telescopes.
The thread is M68x0.75.
Here is some useful information from the manufacturer regarding these extension tubes:
The Explore Scientific doublets do NOT need, nor come with, extension tubes. The drawtubes are significantly longer, like more than twice as long, as the drawtubes on the triplets.
The Explore Scientific triplets that come with extension tubes are:
* ED80 CF
* FCE100-102 CF
* FCD100 127
* FCD100 127 CF
The appropriate size of 2 inch or 2.5" depends on the focuser type.
Note that the DISCONTINUED TED 152CF does ship with a single extension tube.
Any tube with an extendable dew shield also needs extension tubes.
These do NOT come with extension tubes:
* FLP53 115 CF
* FLP53 140 CF
* FLP53 ED165 CF
And, if the dew shield must be removed for storage, it does not need extension tubes.
The removable dew shield also carries over to the following statement: Complicating things is that some of the company’s original telescopes do not need extension tubes, while their more recent counterparts do. Knowing how to tell depends, as best I can tell, on looking at the visual back. If what looks like an extension piece is on the visual back, in front of the focuser, it does NOT need an extension tube.