Sometimes the ADS doesn't scan like it should, so you have to do it again. Just cause you can see the object in front of you, doesn't mean the ship can, hence the honk. The DSS will only scan objects that it can see, and depending on the size of the object in question, you have to be in range of it. Small objects like most BH's and NS's you have to be within 5 LS to scan with the DSS (that's with an unmodified DSS), other large objects you can be up to 50k Ls, like large suns and what not. Most Gas Giants can start to scan upwards of 2k Ls away. When you first jump into a system, the main star and any large close objects will appear in your view screen, but the ship can't see them yet until the ADS honks. You have to put the ADS to a fire group in order for it to work, you can bind it to the primary fire key along side your weapons, while in supercruise, it will not activate the guns when you honk the system, only activates the Scanner. I use my AI to scan the systems when I jump in, I just say "scan" and it scans for 10 seconds and shuts down, enough to get a honk.