Hi Arif, what is the scope you are imaging through? All we know is its an 80mm f/5 refractor. I used the 300D extensively on the Orion 80mm f/7.5. It definitely benefited from a flattener (and reducer). I did a review ages ago that may still be relevant
http://www.iceinspace.com.au/93-458-0-0-1-0.html
Since then I've used the WO 72FD f/6 and it also needed a field flattener to illuminate the chip evenly. Its not uncommon to need one.
The other thing you might find is not only is the chip tilted to the objective, but it could also be offset from poorly operating brass compression rings in your focuser.