I am Dudley Eirich. I have been doing astrophotography for a little less than two years. I own the SV550 80mm telescope and have been very happy with it but read great reviews about the 122mm version, especially the increased ability to gather light/data so I decided to give the 122mm telescope a try and compare the two telescopes. Finally, I bought an Sv550 122MM in October.
I was extremely pleased that it only took one week for it to arrive after I ordered it directly from SVBONY. It was packaged well and arrived in excellent shape. I couldn't be happier with a telescope. It is a little on the heavy side (14 lb/6.4 kg vs 12 lb/5.4 kg for the SCT) but it's not too much for a senior citizen like me to handle. It has a nice long dew shield that extends and retracts smoothly.
I use the manual focuser with a Bahtinov mask as a focus aid. It dials in smoothly and maintains focus once set. With the 1.0x field flattener, the stars are sharp and round points of light all across the field of view. In comparison with the 8" SCT with a 0.63x focal reducer, the quality of the images has improved greatly. In comparison with the SV550 80 mm telescope, it has over twice the light-gathering capability, so I am able to get more detail in my images during a single night of photography. The only downside is that it is pretty long, but that is to be expected with a refractor with a wide aperture. With the dew shield extended and my camera attached, it is 43 inches (109 cm) long, which means that I have to be much more careful as the telescope approaches the meridian. However, I have safety features set up to avoid collision with the tripod legs so it isn't a deal breaker.
With it, I was finally able to image the complete circle of the moon, the Andromeda galaxy, and a number of large nebulae. I use the SV405cc camera for imaging and typically use 120-second exposures and 120 gain. I do guiding with the 60 mm guide scope from SVBONY (SV106) with the SV305pro camera as the guide camera. I love this combination too. My guiding is excellent and I can get 10-minute exposures with no problem, but still use 2-minute ones routinely. The below pictures were completed by Sv550 122MM.
All in all, I am extremely happy with this telescope and expect to get many years of great images with it.