explained z

Paul M posted some recent galaxy shots including M85. He got down to magnitude 19 and 20. And that let him tag a quasar in the background.

He shared this photo on all the usual favourite haunts, including the RASC astrophotographers group. But for the RASC Toronto Centre he didn't explain the technical value he noted, z. The red shift factor.

I sent an addendum to the group. For our new members. Or those not familiar with extremely deep objects...