westmarch

Francis,

looks like the work of a craftsman. Good luck and as my old gaffer used to say, “measure twice, cut once”.

John

Dave,

Respect! Anyone who can put together a dob from raw materials deserves awe. Good Luck with your build, I look forward to following your progress.

John

Hi there,

no, that’s the beauty of it.  It is calibrated to turn an equatorial mount so it is already set. There is a standard adjustment knob so you can adjust it if you find your target drifting.

This seems to be the cheapest on sale at the moment:

https://www.rothervalleyoptics.co.uk/skywatcher-ra-single-axis-economy-motor-drive-eq1.html

John

Sounds like a malt whisky!

John

What a phenomenal piece of work this is.  A privilege and a pleasure to read.  Many thanks for posting.

John 

OK. Finally got out last night to test the platform with my 10” Dob.  I wanted to observe Jupiter and lined the platform up pointing roughly magnetic north and levelled using the iPhone app.   It was a revelation!  The platform averaged a 25 min cycle before hitting the stop and requiring resetting. The image initially drifted slightly to the left but a simple adjustment on the EQ1 motor dial had it holding Jupiter steady in a x2 Barlowed, 12.4 Plossl at mag x200 with Afov 14.6’.

Despite some initial high haze, I had some superb views of Jupiter, using a Meade #38A Dark Blue filter.    

N and S Equatorial zones distinct with whorls evident on both,  S Polar Region distinct from white S S Temperate Zone.   Narrow, dark, S Temperate Belt visible clearly against white of S Temperate and S Tropical Zone. 

Transit of Europa viewed. Shadow very distinct in the N Polar Region and following the moon's transit by a Jovian hemisphere.  The white disc of Europa only visible as it approached  the edge of the Jovian disc.

In all I got in nearly 2 hours of viewing - this is unprecedented for me on a single object. The old maxim of seeing additional detail the longer you looked is very true. A Dob, without the platform, was more an exercise in finding and identifying.  Keeping the object in the fov, loosing it and reacquiring were the next most pressing needs.   The platform  has added a whole new dimension to my observing.

John

4 minutes ago, pipnina said:

Being held down by gravity alone, I would be mortified at the thought of mine tipping over since we're at 51-56 degrees north in the uk!

You seem to have done a splendid job of it though. You'd think it was off-the-shelf by Meade, made specifically for that scope!

The recesses in the upper platform grip the feet of the Dob and even hefty pushing, at maximum tilt doesn’t shift it. It’s good for Yorkshire but Shetland might be a different story!

After good advice on equatorial platforms from Moonshane and reading his trial and error progress to mastery, I finally took the plunge.  

I lost the plot on how to work out the centre of gravity of my setup - see the last pic and you will understand why! - and assumed that the design would cope with common commercial 10” Dobs. (Don’t try this at home with a home build, bespoke Dob!)

I opted for Reiner Vogel’s  excellent design for a VNS (Vertical North Segment) platform, mainly because I lack the trigonometry to calculate my own curve for the bearing and he has templates for various latitudes.  The thin aluminium arc also worked for me since it only needed a hacksaw and I also lack the woodworking skills (and equipment) to cut the inclined woden arc required for a circular segment design.

Reiner’s general VNS guidance:

 http://www.reinervogel.net/index_e.html?/Plattform/plattform_VNS_e.html

Specific design for the smaller platform:  

http://www.reinervogel.net/Plattform/Vorlage Plattform 14 hoch.pdf

I dispensed with the need to have the upper platform as the Dob’s turntable base and just sat my Dob on it.

I couldn’t cope with the electronics and so am indebted to Nick Hill’s design for a motor - he just bought a direct drive EQ1 9v DC motor, widely available commercially from Celestron, Meade, etc. designed to move a telescope rig at equatorial speeds.

Some plywood and a saw had the bases constructed.  Four 18mm pillow bearings and a length of 18mm steel shaft, an aluminium plate for the curves, aluminium right angle brackets for the attachments and an aluminium block for the pivot bearing were all that was needed.  (Isn’t ebay a marvellous thing!) Oh, and various screws, nuts and bolts.

In all, it’s cost me £85 but you could save £15 on the motor if you got a standard EQ1 motor (they are all made in China and it looks identical but without the Meade/Celestron trade mark on it.)

Haven’t had a clear night since finishing it but the motor is moving the platform, the stops prevent it from coming off the bearings and the Dob azimuth brake is able to cope with maximum tilt.

Oh for a clear night to try it out! ?

John

Looking good Derek. Fascinating and inspiring work. 

John

Excellent post by acey - well deserved sticky.

This website has a night sky simulator that helps you to visualise how light pollution alters the night sky in different locations. Assuming you ever get a cloudless night!!

http://www.need-less.org.uk/#ukatnightsim

John

Dreek,

All hats off to you!  

I weep at the condition of this. Clearly this was someone's pride and joy, since lost to apathy and neglect. 

It takes someone with time and inspiration, like yourself, to pick up the baton. 

Sadly, not able to help with info but happy to donate any kit that would help. 

Good luck and let me know if any other help needed . 

John

What a superb piece of work.  Expansive in scope but elegant in explanation.  A privilege to read.

John

Some stunning dobs in this thread. This is my Meade Lightbridge 250 truss dob.

I've shrouded everything I can think of in my ongoing attempt to delay the inevitable dew/ice formation.  My original intention was to avoid the hassle of heaters, cables, power cells, etc. but..... still a work in progress.

John

Sorry, I've gone over to the dark side!

There is a nice little app. Called AstroAid that helps work out FOV, etc.  for different combinations. Handy if you are out of reach of a PC.