After several weeks of waiting for good weather, today I finally had the opportunity to try this telescope for the first time. I had high expectations after reading very good opinions about it, and also remembering the wonderful pictures I got with the recently purchased Royal Astro R-74 refractor. Unfortunately, what I saw turned out to be a huge disappointment.
Even at maximum sharpening, the image of Mars was dim and contained very distinct streaks radiating from the planet's small disc in three directions. After defocusing, the diffraction pattern looked exactly like case number 7 shown at https://www.telescop...aberrations.htm and resembled a triangular shield with rounded corners or a coat of arms field.
The description on this page says:
"7 - Pinched optics can produce various pattern deformations. The pattern shown - trefoil - would be caused by a support or retaining elements (clips) having near-perfect 3-sided symmetry (0.18λ and 0.36λ P-V)."
The description therefore suggests that the optics is pressed incorrectly in some way - probably in 3 points? The question is how is this possible, since the lens inside is pressed with a ring that acts evenly on it. Are there any collimation screws hidden somewhere that I don't know about? What do you think? Does anyone have any suggestions on what to do with it? In this state, the telescope can only play a decorative role, there is no reason to reach out to it for observation.
The temperature outside was quite low: -10 ° C (14 ° F), I gave the telescope 30-45 minutes to cool down.