Arp 316 at 2500 mm

[Nocturnal]

Using an OAG isn't easy and in fact I lost half a night on this target when the rather dim guide star I was able to find was lost. In Cartes du Ciel I have two circles around my imaging rectangle to indicate the approximate range my OAG can reach. I also turn the camera do the narrow side is facing the imaging camera. That way it sweeps the most space.

http://www.carpephoton.com/index.php?option=com_content&view=article&id=29:oaghd11&catid=3:equipment&Itemid=3

For long exposure long FL imaging you need an OAG. It's what separates the men from the boys