When your Alpha 100 handheld unit zooms out expectantly it is actually zooming out to try and show you where your dogs are.
Most of the time this happens when you don't use all of your collars and so your hand held is still trying to show you the last place it received the location of the TT10 Tracking collar. For example if you turned off your collars at your house, and the next day you just took one collar with you to a hunting spot 100 miles away and did not turn on your second collar, If AUTO ZOOM is enabled the unit will zoom out to 100 miles to try and show you that it "thinks" your dog is still at home.
These Units do not know the difference between the dog getting out of Range, or when the user turns off the collar. All it knows is it can not track your dog and it assumes you want to know where the last location it received was.
The most common problem is caused by Auto Zoom for the Dog tracking portion.
Change the Dog Tracking Auto Zoom setting to Off. To disable auto Zoom tracking of the dogs
Go to Setup>Map>Advanced setup> Auto Zoom > Off
The second issue that can cause this is the contact tracking or Tracking other Alpha Handhelds. If you have the Dog tracking Auto Zoom turned off and your unit is still zooming out. That is most likely caused by the Contact Tracking
Change the Auto Zoom Map to Contacts setting.
You'll need to go to Contacts>Menu> Zoom map to contacts "OFF"
These are two issues that most frequently cause your Alpha/Astro to zoom out on your map automatically. It can be very frustrating to say the least when it does this and you can not figure out what or how to change it.