Dust cover up or down?

FWIW I have a VPI HW-40 and even though it has a hinged dust cover, I do not use the hinges. When I play, I simply take the cover off and set it aside. It goes back on after I am through. That is a lot better than dusting around the top of the table all the time. 

Mijo, I am trying to understand the structure of your Cosmos. Am I correct in thinking the cover hinges to the rear of the wood that forms the visible outer appearance of the TT? And you’re saying that the wood plus dust cover are isolated from the works by the spring suspension? If I’ve got it right, doesn’t the peripheral edge of the lucite also contact the wood, on at least 3 of 4 sides? Or is there a spacer that keeps them apart?

There doesn't seem to be much concern about the dust itself-- which is bad for your turntable-- it gets everywhere-- and bad for your records. It gets in the grooves, creates ticks and pops that are not always easily removed with cleanings. 

Some turntables should be used with the cover completely removed while others, like a SOTA Star Sapphire are designed to work with the cover on and closed. So like most things audio-- it just depends.

The least good thing to do is leave the cover on and up during playback.

I use a fine quality paintbrush to dust off the platter between plays, and the plinth every few days. Dust accumulation is bad for your gear. 

@lewm , the sub chassis, a 1" thick aluminum plate is hanging from 4 dampened springs that are attached to the underside of the plinth (Sota calls it the cover) top surface. The Three adjustable feet are threaded to posts that travel through holes in the sub chassis and also attach to the underside of the plinth upper surface. Nothing touches the sub chassis but the four springs, the main bearing and the tonearm board. The duct cover is hinged to the back surface of the plinth (cover). As supplied by Sota there were two rubber pads on the front upper surface of the plinth that the dust cover rested on. I did not like this arrangement as it left an open slot of about 1/16th inch all the way around the turntable. Fortunately, the dust cover hinges are adjustable. I removed the rubber pads and applied 1/4" wide, 1/16" thick heavy felt strips all the way around turntable and adjusted the hinges so that the dust cover sits flat on the felt completely closing off the upper chamber of the turntable. The sub chassis is further isolated from sound by the skirt that I made which closes off the bottom chamber of the table. There just happen to be two pictures of the table on my system page. The picture without the maple skirt shows the table as supplied by Sota with the two rubber pads at the front corners. The picture with the temporary maple skirt show the table with the felt gasket on the sides. The felt is brown so you have to look closely to see it. I had yet to install tthe felt along the front and back. 

When I get a chance I'll take a picture of the table as it is now. I'll also run another sine sweep with the microphone under the dust cover to see how much quieter it is. I just have to figure out how to get the mic's cable in there without breaking the seal. I'm hoping to get another 5 dB of attenuation, maybe more?  Whatever, the turntable sounds great.

I’ve found that since I’ve dramatically improved my room, it doesn’t matter if it’s up, down, or off.