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Hi folks: Quick report after a few nights testing.
1. If you have the SBIG OAG (the one designed for the STF) you cannot use it with this scope, even though you can get to focus with 5mm to spare on the focusser. The OAG causes a vertical diffraction spike in bright stars in the upper half of the image, and the prism shadow extends a significant way into the optical path; about 1/5th of the way on an STF8300. This has proven difficult to flat out.
2. Focussing the STi with the OAG in the optical train is also very difficult, especially as the OAG is not fitted with a helical focusser. The built in 0.7x reducer does not help. After finally getting it to the best focus I can, stars were still very ill defined. That said, perfect guiding was achieved.
3. Having removed the OAG, I mounted the STi with the lens kit. After two nights of trying, I cannot fix the differential flexure I am getting, despite all of the SBIG rhetoric about this lens kit. I believe the single dovetail mounting on the RH200 is the culprit, so I have a pair of rings on order. I am now testing guiding using the RCOS/STL11K. No results yet. Frankly, I still do not understand how you could get satisfactory images when your guider has an image scale of 30 arcseconds, and your imager has a resolution of 1.86.
4. So, if you have differential flexure in your system using this scope, and the SBIG OAG does not work great, then you have a problem. Solution? Dual CCD cameras. I cant speak for any other brand of camera/OAG solution, but I suspect the extremely steep focus zone of this f3 scope is going to be a problem for any OAG.
5. If you have any sort of tilt in your optical system whether it be a crap adapter or a sloppy filter wheel, it shows up like a sore thumb. The addition of the tip/tilt plate on the back of the scope is an excellent design feature, and why no other scope manufacturer has thought of it before is beyond me. Removing tilt by using this adapter is certainly possible, but man you need patience.
6. Focusmax - I have not yet successfully achieved a usable v-curve. In fact, the Focusmax vcurve tutorial speaks of how fast scopes will struggle in this regard. The approach to focus occurs extremely quickly as you get closer to focus - obviously, since the CFZ is extremely tight.
I have tried multiple step sizes and increments to no avail so far. When I quizzed John Gleason on this, he stated that he manually focusses having not succeeded with FM.
HTH
Martin
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