Newbie needs help with accurate reliable tracking. [Deep Sky] Acquisition techniques · Tony Carro · ... · 28 · 886 · 1

I own the sirius eqg which is heq5pro twin. It seems like 300s exposures on a 120mm refractor might be pushingthe limits of the hardware. Its state max 15lbs for astrophotography. Im guessing you are over that. Try lower exposure times, but ultimately that  mount is not going to guide well with 20lbs of gear.

Tony Carro:
The mount is listed as a 30lb capacity, I am well under that with the Askar V (light weight).  The Evostar and gear approaches around 18 pounds but didn’t weigh it.    It should hold this stuff up as the mount itself is heavy with the extension tube.  Considering putting the belt mod as was suggested in the thread.
Waiting for some clear skies now because it’s all moot if I can’t observe.

I guess I misunderstood your question, I thought you were looking at guiding performance not visual. I have always (possibly incorrectly) read that Astrophotography performance with guiding basically cuts the mount capacity in half. Visual is way more forgiving. 

I have considered the belt mod before, I dont think it increases load, but have heard it improves guiding numbers. To be honest when I watch the howto videos it scares me off, I could see me wrecking the mount as I am not super mechanical.  That belt mod does seem to be a good upgrade, if I could get the guts to do it. 

I dont have exact numbers/weighs to share but can tell you on a clear still night last summer, I was guiding a 72mm refractor with a small 40mm guide scope, asiair, autofocuser, asi camera etc, and was getting 0.25 numbers for guiding, then I got ambitious and changed to an 8 inch sct on the same night, this increased my weight to 20lbs. My guide numbers were always above 1.0. The only difference was the weight, however it could be argued that I wasnt perfect at balancing, or that I dont really know what I am doing. Which could be true...