A compact, high-quality wide-field f/4.9 Petzval refracting telescope
I’ve been really interested in the William Optics RedCat51 scope since the announcement. A few web bloggers got ahold of early versions of this scope, and took some really fantastic wide field images with it. Once the scope finally released early reports from purchasers showed lots of issues. Poor coma and off axis issues were prevalent. I waited for the initial manufacturing run to go out of stock, and ordered when they started the second run hoping any issues would be cleared up and I would get one without problems.
The day finally arrived. I’ve only been able to get it out for a full night of Hydrogen Alpha imaging on the Elephant Trunk nebula. I paired it up with an older ASI 120MM-Mini guide camera that I had laying around, a ZWO Mini Guide Scope, and my existing ZWO ASI1600MM-Pro main camera, ZWO 8-slot filter wheel and Astrodon filters.
At first I couldn’t figure out how to focus. It turns out that the scope shipped with the lens hood flipped around covering the focus. I had to unscrew it and reattach the other direction. It makes the scope quite compact for traveling, and I intend to pair it with my Sky-Watcher Star Adventurer when I head out of town in the future. To set up for imaging, I had to reach the prescribed back focus distance, and I used one 16.5 adapter, the filter wheel and space to sensor to achieve 55mm of distance. William Optics also offers DSLR adapters that attach to the back of the scope where you can hook up your Canon or Nikon camera with no additional spacers.
Once set up to image, I placed it on my Celestron AVX mount, and loaded up EKOS to begin imaging for the evening. A quick Polar Alignment, and I was off imaging. I picked a target that would fully fit into this wide field of view, the entire Elephant Trunk nebula. Here’s the first image with around 37.8 hours of images. I calibrated and stacked the image with Astro Pixel Processor.
After about 6 nights of imaging, I had 37.8 total hours of integration. The above image is the final Elephant trunk nebula incorporating Hydrogen Alpha, Sulpher II, and Oxygen III filters.
I ran the final image through PixInsight’s FWHM/Eccentricity and image analysis tools. The final image shows very little issues with the scope. There is an interesting aberration with the largest stars, it looks a bit liked pinched optics. I have an e-mail out to William Optics to confirm and see if I can fix it by adjusting the screws around the lenses. There is very little coma in the final image. But it’s there.
Overall, i’m quite happy with the scope and look forward to imaging other large objects including the North American nebula (with the Pelican nebula), the SADR region, Andromeda, and more. UPDATE: I’ve now imaged the North American & Pelican Nebula, SADR Region, and the Veil Nebula.
Some more recent images taken with the RedCat 51
