Guest devil74 Posted June 4, 2013 Share Posted June 4, 2013 Last weekend i got the scope out for 2 nights running..the first night i was up on the slabs with the scope and the second i was down the grass. James pointed out that it should be better on the grass due to the heat being stored and released in the slabs what with the hot weather. I know it could have been atmospherics etc but when i was up on the slabs Friday night the view through the EP was kind of ripply (not extreme though) but on the second night the view was noticeably clearer/crisp and less ripply. Noticed it most on something easy like Saturn. Anyone got any thoughts? Link to comment Share on other sites More sharing options...
Brantuk Posted June 4, 2013 Share Posted June 4, 2013 It was probably the difference in "seeing" between the two nights. But if you'd been LE imaging whilst walking round the scope I dare say you'd have got more vibration on the slabs than on the grass and it would have shown in your pics. You may also have been looking through nearby rising heat sources if you're in the garden with houses all round (as well as atmospheric effects). Link to comment Share on other sites More sharing options...
philjay Posted June 5, 2013 Share Posted June 5, 2013 Concrete, hardcore, hardstanding will store heat and slowly release the heat over a period, therefore immediate atmospherics will be affected and if your scope is on it then yes the image will be degraded. Setting up on grass is always preferrable because of this. Also bare in mind that the lower your scope (closer to the ground) the more it will be affected by ground heat, e.g dobs sat direct on the ground will be more affected than say an f15 on full height tripod where the f15s lens is about 6 or 7 foot above the ground and well away from heat sources Link to comment Share on other sites More sharing options...
Guest xanthic Posted June 5, 2013 Share Posted June 5, 2013 If viable, you could cover the slabs with a white sheet during the day, so that they don't absorb so much heat. Link to comment Share on other sites More sharing options...
Guest devil74 Posted June 5, 2013 Share Posted June 5, 2013 I have my dob base on another base (homemade) which lifts the focuser to eye height so I think I have a fair bit of height. Link to comment Share on other sites More sharing options...
philjay Posted June 5, 2013 Share Posted June 5, 2013 Thats ok for comfy observing but think of where the mirror is, still close tobthe ground in all that nice warm air coming off the slabs. Its always best to observe off grass if possible. Link to comment Share on other sites More sharing options...
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