Mike do yourself a favour and go for a garden shed that rolls off the scope permanently mounted. Marking where the tripod goes seems a great idea but it is still frustrating to get a polar alignment, probably more so because you think you are close, and you are but close in astro photography means nothing. Dont worry if you cant see all the sky work with the area you get where to observatory is best placed. You can remove the mount head and place it on the tripod to get planets but for deep sky permanent position helps so much. You have not erected it pulled it down and again errected it yet .. in up down in out whatever it really takes away from the joy..save yourself that unpleasant experience and learn by others mistakes go for a secure shed that rolls away. Pay attention to insulation and fit a couple of fans working off a small solar panel so hot days are not a worry. My gear is only 8 feet away soon it will be in a little roll off shed. The advantages simply can not be ignored.You will get better photos. Trust me I have a hernia
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alex