With your attic space that cold, you will spend a FORTUNE heating a tent, and end up heating the attic as well, making the roof frost-free if your building is not super well insulated.
You have no choice but to move it to another part of your house, or to build a framed room within your attic that is correctly insulated with foam-board or fibreglass batting, and heat THAT. It will come with other challenges like ventilating without cooling, and you may have to run a sealed room with CO2 up there. Search for user 'tranoble' for advice on that.