New arrival: Sharpstar 76 EDPH F4.5

I have been looking for a fast wide-field astrophotography setup for fullframe DSLR imaging around FL 300mm, as well as ASI CMOS imaging.

Commercial range

Actually, within a reasonabe price range there are not that many telescopes available on the market meeting these criteria . I had some satisfying test results with the TecnoSky 70AG telescope a few weeks back. There is another alternative, with assumably very good image quality: the Esprit 80 F5 at a focal lenght of 400mm. And then you have this new model of the Sharpstar 61EDPH, the 76mm model.

The 300-350 focal range was important to me. Shorter focal lenghts would bring me too close to my regular DSLR telelenses of good quality (eg. the 180mm ED Nikkor F2.8). So Redcats and whitecats, with FL=250mm, dropped of the list for this reason. Also the Esprit 80mm F5 with 400mm focal length brings me already too close to the Esprit 120mm F5.5 with 663mm focal length.

High-end alternatives cost as much as 3 times more, like the Takahashi 85FSQ or the Vixen 100mm F3,8. That is more then I’m willing to spend on this instrument for these purposes. The Vixen gives a perfect image circle of 70mm, if you only use fullframe sensors what’s the point?

I took a small gamble and ordered the Sharpstar 76EDPH after seeing one full frame result on Astrobin. The gamble is that I could not find at this time any reviews or examples of uncropped full frame RAW frames.

There is one ED element in the triplet, it’s apparently not Lanthanum or FPL53. See here for a discussion on this topic. The Teleskop-Service website (where I purchased), mentions FPL-53, however the Shaprstar factory site does not mention it. It only discloses “ultra-low dispersion element’. In the discussion there is a mention that the 76EDPH does not use FPL-53 but glass with very similir properties. Anyhow, whatever the glass might be, color is very well corrected. I could not detect blue halo’s or fringes, even not in the very corners.

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Testing the TecnoSky AG70

On loan from a friend, I could spend some clear nights with this short-focus flat-field refractor. It has 70mm aperture and 350mm focal lenght, for an F/Ratio of F/4,9. It delivers a nice illuminated field and pinpoint stars almost to the corners of the frame. Some slight blue fringing is present near the corners. Focusing is very critical, and also very temperature-dependent. An autofocuser is almost indispensable to keep control over the focus.

Aldebaran non-cropped FF field without any filters (only stacked and stretched)
Aldebaran in B/W non-cropped fullframe with the Oprolong L-Pro (some fog or high clouds) only stacked and stretched
Cone & Christmas Tree nebulae, in B/W with the Nikon D750 (stitch line visible )
NGC2244 or Rosette Nebula mosaic 3+3 hrs Nikon D750 & TecnoSky 70AG