Timer Astable with NE555 not getting +V
If you have a load attached to the NE555 (perhaps something like 1K from the output to ground) that is about right. 

If you have no load, the output should be closer to 11.5V. 

If the 555 is the CMOS type, the output will swing to almost 12V with no load. 

The bipolar type output section looks like this: 



For a very light load and output 'high', it looks like 6.2K to Vcc in series with the base-emitter junction of Q27, in series with 3.9K. In other words, there is a diode drop in there. 

If you remove whatever load is on there (!), and add a pullup resistor such as 10K to Vcc to the output you should get very close to a 0-12V swing.