I bought this Apogee refractor from another CN member last month. There is no label on the tube other than the name "Apogee".
It is very well made, thick tubing, integrated sliding dew-shield. Focuser flange seems to press-fitted into the tube. The objective cell can be unscrewed from the tube and also seems to be very well made.
However, I am not getting very good star images. Even at low magnification of 30x, one can see that defocussed image is not symmetrical.
The buyer sold it with the disclaimer that it needs collimation, so I was expecting to do some work to get it collimated. However I am finding that the objective is very different from any Achromat I have worked with.
First, the front Lens (crown) is 110mm aperture, but the rear lens (flint) is only 100mm.
Second, there are two metal rings between them to act as spacers. One ring close to the front lens is ~ 10mm thick, and the second ring is ~ 2 mm thick. (These are estimates I did not actually measure them). So overall the space between the two elements is ~ 12mm!
I don't think it is common achromat like Fraunhofer because of the different element diameters and the huge spacing between them.
I did not find any marking on the edges of the elements, but I pencilled in the "as-found" orientation.
I think the only adjustments possible to collimate it is to rotate the elements w.r.t each other, or rotate the spacers. In a Fraunhofer doublet, I can use Newton's rings to guide me how to rotate the elements or adjust the spacers. The large spacers preclude Newton's Rings method on this.
So anyone experienced with this before?
This picture below shows Top to Bottom:
100mm Flint
2mm Spacer
10mm Spacer
110mm Crown
Edited by sunrag, 05 April 2025 - 08:19 PM.