Here is how I solved the weight problem as the TAL 200K is close to (or exceeds) the photographic weight limit for a HEQ5 mount.
http://www.iceinspace.com.au/forum/s...ad.php?t=14071
To obtain a flat field for a full frame some modification has to be made for most telescopes. For the TAL I used a Hutech focal reducer (7887) to obtain a flat field.
The Orion 100ED was modified to take an Astro Physics 2.7" focuser with a AP focal reducer. The field was then flat for a full frame.
See here for some pics
http://www.iceinspace.com.au/forum/s...ad.php?t=15883
Below is another taken with the TAL. 1.2MB
http://users.bigpond.net.au/avandonk/CAR_lt.jpg
The Hutech FR had not been quite optimised when this image was collected. This FR is adjustable with spacers between the element pairs. It can accomodate 500 to 800mm refractors and also works very well for the Tal.
There is no correct answer only the best compromise.
Bert