Re: ... and daytime polar alignment

Tyrel Smith

Joe, that makes sense. Thanks for clarifying.

Ty Smith

On Apr 21, 2019, at 15:51, 'Joseph Zeglinski' J.Zeglinski@... [ap-gto] <ap-gto@...> wrote:


Hi Tyrel,
    I agree with your comments.
In fact. as Rolando has said at times, you can even stand the mount on the side of a sloping hill, polar align on Polaris (with some added difficulty in such case), and you are no worse off than fidgeting with a level. One might use a bubble level for dusk time alignment, to prepare the mount for RAPID deployment. Your comments on RCAL are right on the mark, of course, but polar alignment is so much easier, if you are starting from an already, fairly accurately positioned platform. I don’t need “pencil marks” for either of my older mounts since the AP-900/1200 already has setting circles and their zero reference marks,  can be used for the same purpose, if desired. Only place I made  ink marker positions is on the counterweight bar, for various cwt positions if I change major scope accessories, and also ink markers on a “bandage taped to the D-Plate edge”, to shift the OTA in the plate,  in balancing the OTA when accessories (camera, guider, rotator, etc) are changed.
    Most of the time, in fact for years, I just use a small bubble level for a quick mount level “confidence check”.
    I use a bubble level on my fixed backyard setup, before each session, just to confirm the heavy scope hasn’t slipped its clutched positions in long intervening periods. It is also possible that in spite of being covered in a light nylon tarp, severe wind gusts could have caused an axis clutch slip as well. Having learned a severe lesson about mushroomed “clutch plugs” in the older series, I now follow the manual instructions NOT to tighten the clutches, beyond finger-tip tight.
    So, I use an inexpensive, but fairly good,  pocket-sized  bubble level (with its magnetic strip, longitudinal groove), just to confirm all is orthogonal with the celestial sphere.
****** Otherwise *******
    However, at the time (2016), when I came up with my “pipette bubble level”, I was investigating why the mount east & west sides were not giving identical pointing accuracies, and indeed different PEMPRO results, depending on which side of the sky it was performed. I needed a super accurate bubble, placed horizontally on the mount base plate, to see if the entire mount on its Losmandy HD tripod may be “tilting or wobbling”, perhaps due to the ground under the tripod feet’s buried concrete block support, shifting or giving way,  when switching sides. The nice foot-long bubble on the pipette, was a perfect “motion or disturbance indicator” as I performed a daytime Meridian Flip – and the bubble stayed in its position. The air bubble itself didn’t need to be at center, for that test. I only realized later, that the existing mm-markings meant for measuring lab fluids, was also bonus as an accurate millimetre “distance” scale for the bubble’s travel,  and indication of how rapidly the tilt was happening, It was important to know if there was a gradual sinking of a pier footing to one side, or if it were  a severe flip-flop each time. If the former, then it was soil related, if it were quick, then there might have been sloppiness in screws, machining tolerances (never !),  or clutch lock down.
    So,  no extra work required in adding a measurement recording scale for its use as a bubble level. In fact, I used a camera in movie mode to record any drift of the bubble moving in the log scale, for mechanical drift playback post-analysis.
    Once I proved to myself – thanks to the DYI Pipette Bubble Level -  that the mount and rugged tripod was sturdy and stood motionless under all “external” influences, I found other uses for the level on the OTA, etc. However, I was quite impressed in its use as an expensive, more precise, and accurate bubble level. So, I don’t use it regularly, per your comments, but it is nice to have it in my kit, if I ever require a “huge, accurate, easy to use” bubble level, that is temperature independent, doesn’t stick,  and doesn’t even require batteries.
Joe Z.

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