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The Mapstar 22" build


mapstar

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4 hours ago, Uplooker said:

 How did you attach the vanes to the central boss? Did you use the screws on the 100mm discs to secure "pillars" between the two and then utilise the 2 off holes in the vanes to fasten to those "pillars"?

Yes 2x M4 button head screws hold the vanes to the upright pillars. I think you can see one on the left ( bottom) and the rear ( through the top disc) vanes in the central boss pic.

Works o.k.  so  the next spider I make will be for a different scope :wink:

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The slip rings and new spider detailed on page 10 of the build were recently tested at the Peak Star party. 

They both worked without fault and I can highly recommend the slip ring mod to any dob owner especially if you don't have the space to fit a battery in the rocker box.

Here's a photo at the recent star party courtesy of Wookie1965 as I didn't take any. 

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The cable can be seen plugged into the base board. Good view of the new spider.

Here's another view of the scope (Courtesy of Swampthing) and shows the cable plugged in to the base board and also the one from the rocker to the mirror box. Probably the only part I will change for a coiled one.

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Good comparison with a 10" scope if you needed an Idea of the difference in size. When disassembled the 22" actually forms a smaller stack than the 10" 

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The mirror box weighs 31kg and is the heaviest part to answer the question I get asked quite a lot .

Enjoyed the build so onto the next.

Damian

Edited by mapstar
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  • 1 month later...

@mapstar

Damian, in doing yet more on going research about our potential Dob purchase, I happened upon this thread. I've been in awe reading the thread in it's entirety. It had me captivated to a point several cups of coffee went cold as I was so engrossed...

I'm envious of not only your scope but your talents. Truly stunning.

And there was me thinking stepping up to a 14" was a big step !!!

Simon

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On Fri May 19 2017 at 14:44, Racey said:

@mapstar

Damian, in doing yet more on going research about our potential Dob purchase, I happened upon this thread. I've been in awe reading the thread in it's entirety. It had me captivated to a point several cups of coffee went cold as I was so engrossed...

I'm envious of not only your scope but your talents. Truly stunning.

And there was me thinking stepping up to a 14" was a big step !!!

Simon

Thanks for reading through, enjoying it and for the compliment.

A 14" is a really good size in terms of aperture size and transportability. 

The views are a pleasure to share and don't hesitate to ask if we're ever at the same star party.

Damian 

 

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1 minute ago, mapstar said:

The views are a pleasure to share and don't hesitate to ask if we're ever at the same star party.

 

That'll be splendid... But after one of the comments you made in my "Paging the Dob Mob" thread, I'll ensure we form an orderly queue BEHIND you Sir !! ?

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  • 5 years later...

Hi Mapstar, what a beautiful build and it must give amazing views! One question though about your beautifully engineered slip ring system- why did you choose copper for the brushes rather than carbon/graphite? Have they worked out to be reliable or do you need to clean them regularly?

Mark

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Just reading through this again still amazed  by the workmanship truly a thing of beauty, what is sad is seeing all the posts by Gina who always had interesting things to say.

Hope your job is now sorted no more nerves about it and maybe one day soon I will get to look through it again.

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8 hours ago, markse68 said:

Hi Mapstar, what a beautiful build and it must give amazing views! One question though about your beautifully engineered slip ring system- why did you choose copper for the brushes rather than carbon/graphite? Have they worked out to be reliable or do you need to clean them regularly?

Mark

Hi Mark

Thank you for reading.

The choice of copper was easier to machine than carbon. I had to hand and they have been really reliable.

Carbon brushes for slip rings and large motors have a high percentage of copper content but these spin at high rpm. The scope probably does 20 rph so is fine. 

Damian

 

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Slightly out of sequence, I'm doing something similar with a 16" and looking at your mirror supports. The spherical bearing is just dropped and glued over the hole ? Or rebated in using a counter bore ? Albert T uses domed lock nuts drilled through but I dont see that gives enough freedom. 

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On 11/07/2022 at 08:16, skybadger said:

Slightly out of sequence, I'm doing something similar with a 16" and looking at your mirror supports. The spherical bearing is just dropped and glued over the hole ? Or rebated in using a counter bore ? Albert T uses domed lock nuts drilled through but I dont see that gives enough freedom. 

Think I wrote in a post on the thread somewhere that It was counter bored the outside diameter of the bearing. Think it was 14mm? The amount of movement is minute so various methods work. 

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