I would like to hook my satellite box to my oppo udp-205 for two channel audio

With a long cable I would personally start with the digital coax. More generally, however, inputs are often a scarce resource, so if cable length is not an issue I would use the coax for the source with the highest sound quality (e.g. BD player) and optical for e.g. the television.

The cable box only has optical out
Using HDMI for the TV
I will get a cheap optical and try that

Thanks

Good idea.

An even better idea.
See here for such issues on the usb side: http://archimago.blogspot.nl/2015/05/measurements-corning-usb-3-optical.html