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You are caught in no man’s land between not enough outward travel without diagonal and too much with.
I just tried my ED80 with Andrews 2x 2” diagonal (similar to GSO but Saxon looks to have a longer barrel) and without diagonal I needed to add a 3” extension tube. The diagonal is adding about 4” but in any case you should omit it for photography.
Try racking out fully and then also pulling the Barlow out (with camera attached) until you get focus. (Try on a distant tree). You will then see how much extension you need.
I also tried Barlow + diagonal + camera and couldn’t rack inward far enough. I then tried diagonal + Barlow + camera and was able to get focus with 10mm to spare (inward limit).
Your Barlow seems to have a longer barrel and this may be contributing to you not having enough travel. A 3” extension should be all you need without diagonal in place. It is handy to have both 2” and 3” extensions in one’s kit for things like this especially if you have multiple telescopes or you add a focal reducer/flattened which then changes things again.
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