I find an easier, or, more accurate way to do focus for astro-pic's is to plug the 5D into the laptop. Then use live view on the laptop screen. It means I'm not bending my neck back and the image can be viewed larger. Sure, Jupiter works, but, Jupiter won't be around all year
As much as I want to do that it is not usually possible for me. I live in a city with pretty bright lights and the only way to do the astro is to get out of town and into the wilderness. There I struggle with setting everything up and am also hampered with Mosquitos and moths that get attracted by the light of the laptop.
5D3, 6D, 600D, RX100
16-35L, 24-70L II, 70-200L II, 100-400L, 50L, 85L II, 135L, 24TSE, 40, 100 macro, 18-55 II, 55-250 II, 600RT x 4
I come here to learn something new, not to learn how bad my gear is - I know that already ;-)!