[Windston (Dan)]

Like the title states, I've recently been having a bunch of trouble taking flats with my Newtonian. At night time, the is pretty much 0 light entering the system from the primary cell or the focuser, it's pretty much only from the sky. However during the day when trying to take flats, light is obviously entering the system through the primary mirror cell, as the primary mirror back is basically completely exposed, and the gaps from the focuser fit to the tube isn't perfect.

My question is, how the hell do I combat this? I've done in the past a pure black t-shirt doubles over the primary cell and held on with a rubber band (over the back of the tube), and another black t-shirt over the focuser, but I don't think it's perfect and it's a lot of dicking around, is there a better way?

Cheers
Dan