RST-300 Prototype 2 is completed and tested. The main difference from Prototype 1 is that the DEC’s reducer is replaced with model number 25, which is the same as RA. The greater rigidity and power of the DEC axis makes it possible to mount larger and longer telescopes. The cost goes up and the mount’s weight increases a bit, but I think it’s a good option to increase the payload. As you can see in the picture, unlike the RST-135, all the ports are on the front. Since cable rotation is the minimum due to the rotation of the mount, cable management is more convenient. The weight of the mount is still around 8kg. 🙂

The goal is to be able to mount 30kg (14 inches) when the counterweight is not used and 16~17 inches (50kg) when using the counterweight. To test the photography performance (autoguiding performance) with 14 inches without counterweight, Celesteron EdgeHD 14-inch tube, 0.7x reducer, SBIG STL-11000M camera, QHY CCD OAG and QHY5III 174m are used. Total weight is about 30kg.

The autoguiding performance was very satisfactory. Because OAG is used for 14 inches of EdgeHD, the focal length of the guide scope is 2700mm and its aperture is 14 inches, so it is very influenced by seeing. In addition, the observatory is a three-story rooftop located in the city, with local bad seeing and vibrations. It’s amazing that Total RMS 0.86 seconds comes out in this environment. The stars in the guide ccd were so dark that I had to give at least three seconds of exposure. If I can shorten the exposure time with other settings, the result will be better.

Horsehead nebula at 10 minutes of exposure. I used a Ha filter with a transmission width of 3nm, the F number was 7.7 and the ha sensitivity of the STL-11K camera was so bad that it was too dark. Vignetting by light pollution and moonlight is also bad. It may seem worse because there is no hood on the tube. I took several 10-minute exposures and all the photos had almost the same star shape.

As a result, the guide performance of the RST-300 mount was quite satisfactory. With a few minor design modifications, the design of the production version can be finalized. Rainbow Astro is working hard to make great products. We will meet the expectations of those waiting for the RST-300. Thank you for your attention.