Mohsen Bahremand

Thanks a ton Complete and satisfactory answer!

Hello everyone I have a Sky-watcher heritage 150p with 750mm focal length. When i use a 4 mm eyepiece which gives 188x magnification, i can still see the details on moon very clearly without any blurriness. This makes me think that there's still room for using a 2 or 2.5 barlow although it passes the max 300x magnification. Do you think that it might work? Can it make any problem with focusing? For instance should i put them so close to the secondary mirror that it doesn't fit the tube?