andres Can you share your guiding parameter - do you use ASIAIR or PHD2 (or something else). I have a C8 edge and I cannot get the rest-135 to guide under 1".
With that large OTA, did you make sure to use a power supply between 15V and 16V?
B. J. Jeong (xuranus at Cloudy Nights, R&D manager at RainbowAstro/RainbowRobotics) had mentioned the RST-135 worked better at the higher end of the voltage range. I use a 15V buck/boost converter with my RST-135 even with just an FSQ-85 on the mount.
You cannot just use someone else's parameters. You need to fine tune for your own situation.
But the things to look out for are:
1) make sure you have at least 6 stars in multistar guiding. Make sure the guide camera is perfectly focused with a Bahtinov mask. If not, you are just guiding on measurement error, and not the error of the mount. Or worse.
2) guide with at least 2 FPS frame rate (that parameter is at the bottom left of Guide window). This means that you need to use an exposure time no longer than 0.5 seconds -- this is crucial for mounts like the RST-135 with huge periodic errors. With the ASIAIR's feeble processor, you also need to use 2x binning to achieve the 2 FPS fame rate. This is why you saw my earlier posts on what cameras are suitable and what cameras are not.
3) look for overshoots in the guide graph. E.g., a positive correction quickly turns into needing a negative correction and vice versa. If you see that, you are overcorrecting, and introducing guide errors yourself. Start with a low loop gain (on ASIAIR, an aggressiveness of 0.25 or less) and only increase it if you cannot keep up with the mount error (e.g., lots of correction pulses but mount still not correcting). With good guide parameters, you only need one or two correction pulse each time the mount deviates.
4) if you really cannot keep up, increase the max pulse duration. In general, 0.5x sidereal rate is good enough, but your situation could be different, and you might need a faster guide rate. 0.5x sidereal rate can already correct 1 arc second of error with a 0.5 second pulse. Keep in mind that ASIAIR uses 0.25 increments, while RainbowAstro uses 0.1 increments. If you select 0.25x sidereal rate, RainbowAstro will use 0.2x sidereal rate. If you select 0.75x on ASIAIR, RainbowAstro will use 0.8x. So I don't really recommend those guide rates. If you have the correct voltages and a small OTA, 500ms max pulse with 0.5x sidereal guide rate are sufficient. If not, bump the max pulse to 1 second.
Don't just ask for someone else's parameters. Every situation is different.
Keep in mind that the RainbowAstro will never give you good guide numbers. I get 0.35" RMS arc second by fine tuning everything to as close to ideal as possible (250mm focal length for reasonable guide scale, 2 FPS guiding by using 2x binning, IR-pass filter to reduce atmospheric turbulence, good focuser so I can critically focus the guide scope, etc). The RainbowAstro is expensive because it built to be extremely portable, not because it is a premium mount. You are paying for portability, not for tracking precision.
You will also need a counterweight with the large OTA. Just because the mount can swing a heavy OTA does not mean that it can move that OTA smoothly. This is also why even B. J. Jeong himself stated that the mount prefers the higher voltages.
Chen