I have been looking for a fast wide-field astrophotography setup for fullframe DSLR imaging, as well as ASI CMOS imaging.
Actually, within a reasonabe price range there are not that many telescopes available on the market. I had some satisfying 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 dropped of the list. Also the Esprit 80mm F5 with 400mm focal length brings me too close to the Esprit 120mm F5.5 with 663mm focal length.
I took a gamble and ordered the Sharpstar 76EDPH after seeing one full frame result on Astrobin. The gamble is there because I could not at this time find 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.
Reasons to prefer the Sharpstar above the TecnoSky were the slightly shorter focal length, closer to my target, and the slightly faster F-ratio. I could test a specimen of the TecnoSky, and would be happy owning that instrument. However there is room for slight improvements in the corners of full frame image. These are by no means defects that would rule out using such an instrument, as a slight crop would solve everything. For APS or any format slightly smaller then full frame it does not matter at all.
I ordered the telescope with Teleskop Service (Germany) on Monday and on Friday the instrument arrived.
It was well packaged, with a double cardboard box, the box of the scope itself being inside a larger box that contained additionally the Bahtinov mask (ordered in addition) and the seperately packaged F4.5 reducer.
Inside the box was also an inspection checklist of Teleskop Service itself, checking a number of technical elements of this telescope including the collimation (which needs to be perfect for this F/ratio in order to have good stars in all FF corners). It was clear the box was not closed with the original tape. For a moment I feared that this speciment might have been a reject, sent back by a previous customer. I assume the inspection of TS explains the re-taping of the boxes.
When the instrument came out, it looked obvious that this material was all brand new, and not used in any way. The finishing is very elegant, the construction very solid. One is surprised by the weight of this little scope (almost 3kg).
I attached the finder shoe, and unboxed the heavy reducer, screwed it IN the focusser (the reducer fits inside the focusser for about 41mm). For that I needed to remove the 2″ to 1 1/4″ reduction ring, the M74 to 2″ adapter. The reducer/flattener has M48 threading to accept the camera connections.
I you want to use a 2″ M48 filter, also that is possible: the reducer can be split in two parts. The camera-side-part has internal M48 thread that accepts 2″ filters. I did not try that yet.
The reducer comes with two metal caps, nicely machined in aluminum, that serve as dust covers. One is M48 female, the other I guess M74 male.
Rotation of the camera can be done by a giant (in respect) 3″ rotator, that holds the complete rear-end assembly of focusser, reducer and camera. A tension knob allows you to unblock the rotator. Also the rotation friction can be adjusted using a few screws, however this is not recommanded. As small as this scope is, you can also slightly unscrew the scope collar itself and rotate the entire scope assembly.
When using a DSLR on this scope, the image you get is upright. That means it’s easy to use it also for bird imaging or other daylight applications.
The sky only briefly cleared that evening, still within twilight. It clouded out again completely by the time a partial penumbral eclips of the Moon set in, so I missed that.
I could capture a few frames with the Nikon D750, putting the scope on an EQ8, with a 8×50 finder attached, using an MGEN2 for guiding. I limited the exposure to 10 or 15 seconds to avoid any influence of bad tracking.
I could also snap some shots of the extremely bright Venus (all shots unprocessed, uncropped FF NEF files converted with View NX to high-quality JPG):
Venus centrally imaged
It’s too early to draw any final conslusions. i need a nice clear night without any Moon to make some wide-angle shots. Also with a CLS filter inserted or using the Nikon T-ring with the integrated Optolong L-Pro filter, this would allow me to check for reflections.
However, it can rightfully say that this instrument is properly collimated, and did not show evidence of obvious image defects in a FF corner. The star shape -especially of Venus – was not perfect but I can imagine that the extreme brightness of this object would bring out the worst.
Will keep you posted on next results!