I have the STS80 and love it, but, if you are going to use it for backpacking then I would get the 65mm model. As far as it goes towards getting a straight or angled, I would ask myself how I would be using it. As stated above, its nice to have the straight if putting on a window mount and viewing from the car. I previously had an angled version and also loved it. When I would be hunting and looking in the area where the sun was rising the angled worked out so much better. You look down into the scope and the sun will not effect your view by you having to squint, and, if wearing a ball cap, it will help block the sun while looking thru it. I believe if you take digital camera images thru it I think the straight would be better. But for my purposes I wish I had bought the ATS65 instead of the STS80. My 2 cents. Kerry