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Beulah

Dob build 16"

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I wanted to make my Skywatcher 400p more mobile, so tasked myself with the challenge of building a dob that can fit into a small car.

The wood was free - my workplace was getting rid of a load of pine wood shelving that had been there since the 70s...

Six months later,  this appears in my workshop...  :D

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Without the Little Black Dress...the brackets holding the secondary cage are rigid as...I had problems for ages trying to get the alt bearings to be smooth enough to move with a gentle push yet not let gravity take over. The magic formula was teflon bearings, ebonystar laminate and a couple of neoprene pads applied as the braking mechanism to the aluminium tear-shaped guides on the rocker box.

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The mirror cell. The holding screws were not needed as those hefty knobs holds the springs in place...

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Ready for a trip in the car...a bag will be made for the secondary cage and the alumium poles..

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The feet at the bottom are stabilisers if the dob is set up on uneven ground.

 

First light occured a couple of months ago and M42 was my target -  probably the most satisfying thing about this build is first light and when all the eyepieces come to focus.   :)

 

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Fabulous job Sam, great to see it all finished. Have you had first light with it yet?

Out of interest, what did you use to attach the poles to the rocker box and UTA? Specially bought connectors or something else? I'm planning on building a small 10" with a mirror set I've had for years!

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Very nice job Sam, well done 

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Thank you @Stu for your comments.

Yes, so far I have seen the Moon and M42 before going back into the workshop for more fettling. Both targets came into sharp focus and I was really pleased. I'm using the stock focuser at the moment as it was the first thing to hand whilst I was waiting for the Moonlite to arrive. I'll swap over once I know everything is stable.

The pole attachments I used are the following:

Aluminium angle (3mm thick), M6 furniture bolts cut to size with nyloc nuts for the aluminium truss poles (inspired by the dobmeister himself, Moonshane).

The secondary cage poles were a real doozy and held me up for a bit until I was able to obtain some star nuts... (with furniture bolts again)

Image result for star nut insert M6

I've just spent the last half an hour trying to dig up old invoices but can't for the life of me figure out where I bought them. Once they are hammered into the aluminium tubes, they won't budge!

 

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It looks very nice, and surely more portable that the original SW design. 

:thumbsup:

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Very nice indeed 👍

Its good to put some custom work to your scope, not just to make it a more effective package. But looks good to the eye also.

More dark site trips now 😀

 

 

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Thanks @Piero , I've yet to take it out. Not sure if this is the first time a SW conical mirror has ever been used in a self build. I had no frame of reference!

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Thanks Sam, very handy info.

Looking forward to a proper first light report :) 

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Well done Sam :)  It looks a lot like mine.

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Looks like a real winner to me. Very tidy job, congrats!

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Excellent conversion!   :icon_biggrin:

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Looks a grand piece of work, very nice indeed.

 

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Posted (edited)
19 hours ago, Beulah said:

Thank you @Stu for your comments.

Yes, so far I have seen the Moon and M42 before going back into the workshop for more fettling. Both targets came into sharp focus and I was really pleased. I'm using the stock focuser at the moment as it was the first thing to hand whilst I was waiting for the Moonlite to arrive. I'll swap over once I know everything is stable.

The pole attachments I used are the following:

Aluminium angle (3mm thick), M6 furniture bolts cut to size with nyloc nuts for the aluminium truss poles (inspired by the dobmeister himself, Moonshane).

The secondary cage poles were a real doozy and held me up for a bit until I was able to obtain some star nuts... (with furniture bolts again)

Image result for star nut insert M6

I've just spent the last half an hour trying to dig up old invoices but can't for the life of me figure out where I bought them. Once they are hammered into the aluminium tubes, they won't budge!

 

You can get those from bicycle shops, they're the star nut that the handle bar stem bolts into.  

https://www.tartybikes.co.uk/headset_spares/tartybikes_star_nut/c57p10541.html

Edited by CraigT82
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Posted (edited)

Great build by the way!

Where did you get the ebony star from??

Edit: Hurray 1000 posts!

Edited by CraigT82
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Great build. I love to see the design innovation, dedication & passion on projects like this.

Steve

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@CraigT82 @Stu,

I have just found out where I bought the star nuts (round spring threaded tube connector) - found the delivery note! It took a fair while to find some at a good price  ;)

https://www.vital-parts.co.uk/threaded-spring-inserts-396-c.asp?gclid=eaiaiqobchmiwsk7gefp2qivllhtch1u3gvdeaayasaaeglfe_d_bwe

With regard to the Ebony star laminte, I was able to grab a sample as didn't need that much....

Stu, I forgot to say that the truss poles are attached using male knurled knobs and wing nuts. Again, inpsired from Moonshane's design...

Another option are these as it's quicker and less chance of losing fixings when faffing around in the cold and dark: https://www.ebay.co.uk/p/Quick-Release-Bike-Seat-Post-Clamp-Skewer-Bolt-M6-M8-Bicycle-Silver-M8/1561770147

Employed thus (last image): http://www.reinervogel.net/index_e.html?/Planung/1_Intro_e.html

There is no finderscope on there as yet as I want that one to be light in weight - there is a shoe installed but I think I will go for a RDF.

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Posted (edited)

You've been planning this for a long time and it was worth the wait!...well done Sam ...I don't think the Dob mob needs to tell you where to go with that wonderful telescope...clear skies!

PS the best Dobs are black!!!

Edited by estwing
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Thank you for your kind words @estwing  :)

5 minutes ago, estwing said:

...I don't think the Dob mob needs to tell you where to go with that wonderful telescope...

 I'm already there, mate..   ;)

 

 

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That's great info Sam, thanks very much :) 

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On 12/03/2018 at 20:22, Beulah said:

Thank you @Stu for your comments.

Yes, so far I have seen the Moon and M42 before going back into the workshop for more fettling. Both targets came into sharp focus and I was really pleased.

Cracking result Beulah, you'll definitely  feel the benefit of it being more portable. I liked your comment about your pleasure in seeing that it focused correctly - I shared that feeling with my own build , it is such a relief when first light tested and the image come into focus, a huge amount of stress and worry just evaporates. Well done and good health in it's use. :) 

Jim 

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18 hours ago, saac said:

Cracking result Beulah, you'll definitely  feel the benefit of it being more portable. I liked your comment about your pleasure in seeing that it focused correctly - I shared that feeling with my own build , it is such a relief when first light tested and the image come into focus, a huge amount of stress and worry just evaporates. Well done and good health in it's use. :) 

Jim 

Thank you. I really love your interpretation of the truss telescope and hope you are getting good use out of it. :)

The main concerns with getting the telescope to focus is not just cutting the truss poles to size...it's making sure the primary and secondary box/cage aligns properly, too!

So many factors that can go wrong. Very, very similar to a handbuilt guitar singing for the first time. Quite heady stuff. :) I admire those who start further back with the ATM process, with mirror blanks and fabrication of their own cells/spider vanes; it must be very nerve wracking getting an ideal Ronchi test result...

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Great work there Sam. Was just catching up on SGL and noticed your build.

Glad you now have something more portable. Joined up truss tubes why didn't I do that :hello2:

Hope it's working well even though the weather tries to thwart every session.

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