Some years ago, I performed a series of practical tests to determine the effectiveness of using a set of Celestron vibration suppression pads (VSP's) to:
i. better understand how they perform and;
ii. measure their contribution in suppressing vibrations for visual observing.
Cause a tennis ball, suspended on a fixed length of string, to strike the focuser under controlled conditions and estimate the amplitude of displacement caused by the mechanical strike and record the time to reduce any vibrations to zero amplitude.
I set up the test equipment in my garage to ensure that any breezes, or gusts of wind, did not pollute the experiment.
• Vixen GP-DX GEM.
• Vixen ED102S f9 refractor.
• 100mm focuser extension tube.
• Vixen GA-3 illuminated guider (built-in 3x Barlow, 6 concentric circles)
• Vixen 10mm Plossl.
• 3.9kg dec shaft weight.
• Orion Optics (UK) pier with adjustable feet. 1.1m long. Feet are terminated with metal plates that are slightly smaller than the VSP central pad.
• Dec shaft was horizontal.
• OTA was horizontal.
• Concrete floor.
Target Light Source:
• Red LED approx. 25 metres away.
Mechanical OTA Striker:
• Lawn tennis ball suspended on a piece of string 30 inches long. The ball was pushed back with my extended arm, to a fixed marker, then let go to strike the focuser tube with a single hit to produce a reasonably consistent and repeatable striking force.
• A kitchen LCD timer with press to stop/start button.
• A fixed red LED was observed in a Vixen ED 102mm f9 refractor field of view, using an illuminated reticule, (6 concentric circles), whilst a tennis ball suspended on a fixed length of string was made to strike the focuser under controlled conditions.
• The tennis ball was made to strike the focuser by releasing it from a measured, consistent height.
• The initial set up involved acquiring the red LED in the GA-3 illuminated guider, with a 10mm Plossl eyepiece, positioning he LED at the centre of the field of view of the telescope.
• The illuminated reticule has 6 concentric circles.
• The largest illuminated reticule circle (6) was visible just inside the edge of the field of view.
• When the focuser was struck by the tennis ball, the initial LED displacement was out to circle 5.
• The first measurement to be taken was when the LED's displacement amplitude decayed wholly to within circle 4.
• The second measurement to be taken was when the LED image ceased all movement.
Two measurements were taken for each tennis ball strike of the focuser.
• Measurement 1 - the time for the LED image to stabilise within circle 4 of the illuminated reticule was recorded.
• Measurement 2 - the time for the LED image to become completely stationary was recorded, i.e. nil displacement in the eyepiece field of view.
• Measurement 1 - Five separate strikes; LED image stabilized with circle 4, after 3 seconds had elapsed.
• Measurement 2 - Five further strikes; LED image came to rest after 6 seconds had elapsed.
With VSP's Fitted:
• Measurement 1 - Five separate strikes; LED image decayed to inside circle 4, after less than 1 second had elapsed.
• Measurement 2 - Five further strikes; LED image came to rest within 1 second, i.e. the LED returned to its stationery position in one second, without oscillating within circle 4 as previously.
• Based on 20 individual strikes, and within experimental error, the VSP's had no discernible effect on the amplitude of the displacement.
• However, the VSP's significantly reduced the dampening times.
• Timing measurements relied on hand/eye co-ordination to start/stop the timer.
Edited by Dennis_Oz, 06 August 2021 - 10:29 PM.