- dew shield
Excellent images, Fast, Highly recommended!
First, as usual, kudos to OPT for Excellent service & fast shipping. This substantial and beautiful lens unit was packed well and delivered in perfect condition. I am using the Hyperstar V4 with a Celestron Edge 14 telescope and a Canon 6D full-frame sensor camera. V4 is the newest iteration of the Hyperstar and is designed for full-frame sensor cameras. Stars are sharp across the entire large and wide field of view, which spans almost 2x3 degrees in this configuration (Edge 14 + Hyperstar). The system is incredibly fast at f/2; in my suburban magnitude 5 skies I typically shoot subs at 10-30 seconds at ISO 3200. The short exposure time means that guiding is not required with my AP mount, which really simplifies the imaging process. I can take lots of short subs and most or all will be good ones. Focusing when shooting with a DSLR can be a challenge because the camera display is sticking way out of the correcter end of the OTA while the focus knob is 6 feet away at the other end, pretty much unreachable. One simple way around this, without a motorized focuser, is to connect the 6D camera to my phone via WiFi using Canon's Camera Connect app, which can display the camera's live view image on the phone's screen, then use a Bahtinov mask on the end of a dew shield. The shield supports the mask above the Hyperstar and camera, which stick out way above the corrector end of the telescope; the mask cannot be set on the end of the OTA as normal. Then trigger live view and watch the diffraction pattern on your phone to focus. Then engage the mirror locks. If the scope is moved very far, say to a target in another part of the sky, it's best to refocus as the mirror locks reduce but don't eliminate mirror flop / shift. One important note about pairing the 6D with the Hyperstar: there is significant vignetting, seen in a rectangular pattern, around the periphery of the field of view. I believe this is caused by obstruction in the camera of the reflex mirror and box assembly limiting what is probably a fairly steep ray path angle coming into the camera from the Hyperstar. The same size (full-frame) sensor in a purpose-built astro camera might not suffer the same problem. To use the 6D's full field of view in a final processed image requires careful and significant flat fielding. FYI if you use this combo. Great product, I would highly recommend it!