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Currently the segments are stuck to the top plate with double sided tape while I measure up heights, angles etc for the drive and idle shafts. I will also add a couple of safety blocks at the end of travel to prevent accidental overbalancing in either direction. These will probably incorporate cut-off switches to prevent the drive running but going nowhere (I have days like that!). I also need to disengage the drive shaft to re-set the platform - probably use a lift roller to accomplish that rather than a clutch... More thought required.

Equatorial Platform for my 10-inch GSO Dobsonian Having recently purchased my dob (end October 2018). While waiting for it to arrive I decided amongst other things to build an EQ Platform for it to save some nudging at the eyepiece whether just me observing or at some observing event etc. After searching the internet for a while and watching various videos of other people’s platforms I decided to build mine based around this web site: http://www.reinervogel.net/index_e.html?/Plattform/plattform_VNS_e.html the vertical north sector (VNS) version in particular, as it formed a more compact unit at my 52° north latitude. At this stage I hadn’t got a telescope to take physical measurements from so I relied on the details given on the TS website concerning sizes and weights, with a couple of emails to TS gave me other details not listed. https://www.teleskop-express.de/shop/product_info.php/info/p1192_GSO-10-inch-f-5-Dobsonian-Telescope-Deluxe-Version.html First. I needed to find a close approximation for the scopes centre of gravity. The only way I could do this was to take the physical sizes and weights for the base (rocker box) and the tube (OTA). These were given as 12.2 Kg and 15.5 Kg respectively. TS gave me 442mm as the spacing between the three feet under the ground-board. The only way I could do this was to make some close approximations for the rocker box panel sizes, the circular ground-board and azimuth base were given as 540mm OD, the panel height at 640mm. Front panel I guessed at based on the size in the photo in the TS advert relative to the 305mm OTA diameter (having the actual scope to measure is so much easier!). Armed with my known panel and base board sizes I calculated the surface area of the rocker box and given its assembled weight I found the weight per square cm (cm²) and multiplied this back to the individual components to give me their weights. I used Excel to calculate a string of weight x distance sums, coarsely at first and then refining the distance steps until I found a balance between the rocker box and OTA distance/weights numbers and used that for my centre of gravity height. This then allowed me to start using the information in the web site (above) to shape the vertical north segments for my 52° north latitude. The website gives templates for different latitudes around 50° north/south latitudes and a run time of about 1 hour. I was going for a run time of circa 45 mins to keep the segments shorter, so they didn’t stick outside the baseboard which in the dark I thought might be dangerous at ankle level. The segments are set at an angle (perpendicular to a line back to the pivot point). My reading of the website calculations: · From the intersection of the CoG line and latitude lines find the length of the perpendicular side of the triangle. · Multiply this length by Cos (latitude + small angle below top plate) Total 65° in my case. · This gives the half height of the ellipse · The 1/Cos (angle formed by the roller supports) gives a modification to the ellipse shape to compensate for the angled segments I used Photoshop to create a full-sized ellipse and the segments. I then printed off full scale, one of the segments on an A4 sheet and transferred that to the plywood. I purchased some 18mm birch plywood (1 piece: 1220 x 610mm (4ft x 2ft)) which let me layout and cut the ground board and top plate plus the two north segments with lots left over to cut bearing mounting blocks, various supports for the VNS’s and the pivot block assembly. After drawing out the components on the plywood I’ve used a jigsaw to cut out the main parts and glued the north segments together at a 25.2° angle so they form a single unit. I found a small 12 volt DC geared motor and further 40:1 reduction gear on ebay to power the platform. The motor is 2 rpm giving me an output with the reduction worm gear of 1 rev in 20 minutes. Given the circumference of the elliptical north segments I had a drive roller of 9.91 mm diameter to give me 1 rev in 24 hrs. The motor speed is controlled via PWM so a 10mm shaft is fine which will sit in ball races at each end. There are two shafts – one driven the other an idler responding to the motion of the driven one. I will mount the ball races in plywood blocks initially. The motor/gear assembly will sit between the platforms top plate and baseboard. Next stage will be making up the ball race and motor mounting blocks…

Absolutely incredible -brilliant - call it what you will - bravo to the pair of you, magic

Wiki DSS link no longer working

The only time I ever pressed a lap dry I used a fine dusting of acid washed talc over the mirror. That was OK but I usually pressed with a thin wash of CeO and taped the edges to stop it drying out

Failed for me tonight - predicted clear at all levels from 11-02am but I got about 15 mins - try again another night - looks good though

You can certainly get away without a driven mount but a tripod is a must. I've shot Orion with a 50mm lens and a series of 4 second exposures (about 70 I think) then stacked those in DSS - just rotate the camera a little west after about 20 frames to compensate for earths rotation. I've been playing with the iOptron Skytracker recently and have managed to image up to 600mm on it with resonable results - keeping exposures to about 1 min: http://stargazerslounge.com/topic/215837-ioptron-skytracker-v2-600mm-sigma-mirror-lens-m51/

That is just incredible, true dedication to: capture, processing, research and annotation

I'm sure things are fine but looking at the top phot the level looks to be sitting on a flat outer rim? its easy with deep curves to go down to the right depth in the centre only for the curve not to extend right to the edge. Hope I'm wrong.

You only need one and concrete threaded rods into your pier. Your mounting an EQ head they don't need to be completely level as you have adjustable axes to polar align with