Inside Focus

Inside Focus

Outside Focus

Outside Focus

Eyepiece: 6 mm Zeiss Abbe ortho EP (282x magnification)

“This is an 4-lens design Petzval Fluorite Apo. I bought this scope as an demoscope for my
showroom and selected it from 4 samples as the best I could find. The colorcorrection on this one is very good. But as the images confirm this lens suffers from a turned down edge: inside focus you can see more diffraction rings, than you should see, too much energy is pulled out of the airy-disc. Startesting at lower power would again mislead the real quality, at  higher power (250x or more) the startest will show the clear diffrences between inside and outside focuse image . my impression on this lens is more towards 1/4 wavefront than higher”

Markus Ludes (APM-Telescopes)

Once more a test that was easily run, The original image (green channel) is the same as the leftmost in the above inside->outside focus images. To make the test more appropriate the image was reduced less than in the above row. The test shows that this instrument has -0.16 LSA and -0.2 HSA and probably a minor central zone (reddotted line slightly above expected simulation). The total wavefront is estimated at 0.279 (1/4) PTV and 0.06 (1/17) RMS. Both are in agreement with the estimate Markus gave.

Cor Berrevoets