First light of Skywatcher 120ED refractor telescope - Moon and Saturn

Just received my new telescope - Skywatcher 120ED. With my old 10" dobsonian it was almost pointless to observe from the balcony - air turbulence was extremely severe and leaving no chances to catch even single clean frame. That's another reminder than bigger is not always better.



In 120ED I haven't noticed chromatic aberrations yet - FPL-53 glass did it's job. Very happy that I did not went for triplet apochromat - it would have been much more sensitive to misadjustment and temperature changes. Also, diffraction-limited apochromats are rare beasts despite their hefty price.

On interferometric test this 120ED shows quite decent results. One can only complain about slightly teared first diffraction ring, but overall quality is well above "diffraction-limited" criteria (Strehl ratio of 0.948 >> 0.8):


First of all, let's take a look at Saturn, even though it's very low over horizon (just 12°, which is not making image better).

From left to right: Saturn via my good old Sony 500mm F8 catadioptric lens, then 10" dobsonian and on the right - this 120ED. One can already see Cassini Division but there is still room for improvement:


Moon could be compared to my best shoot via remote telescope, for example on Copernicus crater (93km in diameter). 120ED on the left, remote photo on the right:


Whole moon photo (clickable):

My first impressions are very positive. Now I just need to figure out what to do with telescope mount, on photo tripod it is currently extremely flimsy. Also motorized focusing should make it much easier to work with.

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