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Old 10-09-2018, 02:42 PM
boz_m (Alexander)
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Join Date: Jun 2018
Location: Sydney, Australia
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Aligning Mount

Hi all,

I have a Celestron 8” EdgeHD, with a 0.7x reducer, and an AVX mounts.
I am just interested in the steps others take when getting their scope out of the shed.

To date I have really just taken it out, done the 2 star alignment plus the 4 calibration stars, then done the polar alignment that is given in the mount. I know there are better methods to get polar aligned but I don’t really know where to start (drift align in PHD2?).

If anyone has a similar setup can they let me know the steps they take to get up and running for the night.
Cheers
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Old 11-09-2018, 10:17 AM
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sil (Steve)
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I have the 11" CGEM dx model. WHat I did was to align during the day.
Mine has the mount unit separate from tripod which has a "stop" on it so I could put the mount on, swivel against the stop then tighten it, this gave me a guarenteed relative position between mount and tripod.If your does too this mine work for you.

My steps:
1 pick a spot to set up outside where i will always use the rig (so good sky view and away from tripping hazard). On a paved area. mark roughly on the ground a point directly under the mount.
2 solar noon align a north south line on the ground. i used a thin white crayon to distinctly draw it so it would remain for a while. I set up my tripod and mount over the first mark i made (where the mount would go), set the mount to its fixed "home" position, I'll assume you've got markers on your rotation axes to park it in a home position. at this point your dovetail should be roughly over the north south line.
3 with the parked home position of the rig all relatively aligned in a repeatable way (especially in the dark) now you try to get the dovetail as accurately aligned to the north south line as you can. You could use a laser level to draw a vertical plane perfectly through the ns line on the ground and move the whole rig until the laser line runs down the center perfectly of the dove tail. Now mark carefully on the ground where the points of the tripod feed touch.
4 with a masonry drill i made divots in the pavers for the tripod feet to sit in, just the tip of a wide drill bit was needed, not drill in a hole. I had to redrill each slightly and place the tripod in them until they seated positively with no rocking. This now gave me a fixed relative piosition to align the rig to the ground easily, in the dark. I hit the holes with a little white spray paint so they were easy to find in the dark for me.
5 Now place the tripod into position without the mount. using a digital level on the top "plane" seat of the tripod where the mount sits I then adjusted the legs (i did a rough align earlier sorry with legs at full position) to get the seat perfectly horizontal. one by one I put my level on top parallel to one leg and adjusted that leg until level was at zero, then turned level to next leg and repeated, repeat for third. now test with level in many directions it should always stay zero. Otherwise start again and take it carefully to be perfect. Double check the tripod is still seated in the divots firmly with no rocking and the top level. take the tripod away and put it back into place again and triple check. adjust divots and legs as required to ensure a repeatable process of placing the tripod gives you a level seat every time.
6 now you have a tripod you need to leave standing but can take inside and put outside in a repeatable accurate position. I stopped at this point and came back in the next few evenings to quadruple check everything remained perfect with temperature changes etc.
7 set up the tripod and put the mount on in its fixed position. I would now microadjust one clutch to get a new home position marked where the dovetail would be perfectly aligned north south via the solar noon line you created, not a phone compas.
8 using your latitude as a target angle, place a digital level meter on your dovetail and adjust until the dovetail is pointed up in the south direction at that exact angle. lock and mark all adjusters at this point. Anything you dont need to move during a session you should lock down as best you can and the clutches mark a new home position and they should probably be the only moving parts.
9 you are now south celestial pole aligned. the process goes from a rough setup position in the correct direction with good line of sight (move until its good) and everything in expected positionsprobably roughly aligned. then you incrementally lock off each part relative to each other and eventually to a true north south line for your location. then microadjust and lock and mark positions from the ground up.

at the end you are left with three divots in the ground and inside an open tripod you can take out any time and accurately place north south aligned. A mount you can then place on top and lock into position so its again north south aligned in its parked home position. Lastly attach your OTA and you should at night be able to see the SCP in the fov of the eyepiece, if youve done everything carefully. I periodly checked with just dslr mounted to the rig and the stars showed scp in the fov every time. by locking off the parts I could the assembly could be done in the dark and works every time.

You dont mention what your problem actually is though. you should balance your rig in roughly the position/diurection of the target you want to slew to. I would still multistar align though and my target would be dead center every time when properly balanced for that direction. without knowing your problem , phd2 may solve or may not. anyway the above will get you polar aligned.
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Old 11-09-2018, 05:09 PM
Karlzburg (Karl)
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Awesome Sil, I'll have to try that. Just need a patch of concrete now, 100 acres and no concrete.
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Old 11-09-2018, 08:52 PM
RyanJones
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Great write up Sil. Thank you
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