STARTEST IMAGES GALLERY

 Refractor100_3

Type: Refractor (doublet)
Aperture: 100mm
Focal length: 1200 (f/12)

Images copyright
Markus Ludes (c) 2001

Picture

Inside Focus

Inside Focus

Outside Focus

Outside Focus

Eyepiece: 6 mm Zeiss Abbe ortho EP (617x magnification)

“This is a doublet airspaced ED Apochromat. We think it is some kind of SD or Fluorite design. From a set of four of these Apos this is the second best. The best was really outstanding and did show during a a Zygo test (632nm) an error of  1/11 wavefront p.t.v. and 99.1 % strehlratio. This lens show in my CCD images some additional colour, which are for human eye hardly visible, except when you are using very high magnifications on bright stars. And even than you will have to look twice to find any traces of violet. The images are looking quite good and are slightly misleading on the real quality of this instrument. The lenses are polished very smooth but high power Startesting shows an clear undercorrection with a bit of a turned edge. My impression on this lens is about 1/4~1/5 wavefront p.t.v. only , which can be seen only at higher power. The longer focallength of this scope is quite forgiving on such errors and makes them for most users invisible”

Markus Ludes (APM-Telescopes)
 

Picture

Testing was done on the green-channel of the leftmost image (inside focus). Due to a clear but minor pinching effect the simulation is less good on the inner-rings. The three outer-rings are simulated properly (spacing of the rings and height comparable to the original). This image is indeed rather close to a theoretically perfect image as the used LSA and HSA are rather small. Remarkable enough the instrument seems to be overcorrected. The total wavefront-error was estimated at 0.203 (1/5) PTV and the 0.052 (1/20) RMS.

Cor Berrevoets