An overview image of Gemini around Messier 35, the well know open Star Cluster. The open cluster is on the top left, with very cloise on it’s upper right, the smalle open cluster NGC2158. Near the lower centre, we see the red gas of the ancient supernova remnant IC443, and to the upper right the bright hydrogen nebula IC2175. There are some spots in the image that I cannot define, maybe it’s reflections.
Click on the image for a better view, not sure why it looks so unsharp in this format!
I have been looking for a fastwide-field astrophotography setup for fullframe DSLR imaging around FL 300mm, as well as ASI CMOS imaging.
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.