I use a Simmons 42mm red dot on my scope,, once it is aligned it is quick and easy to place on the object and have it centered in the camera,, I find the field of view to be very good and do not notice any parallax issues,, if there is any it has to be extremely small as I also use the scope for some astronomy and when aligning on a star the image is dead center in the scopes eyepiece,,
I have attached a photo of one of my digascoping arrangements,, I also use a Nikon P5000 as well as the Oly E3 to shoot afocal through several of my TeleVue eyepieces,,
Derry