Buford7

12 minutes ago, Mr Spock said:

That looks really nice 👍

Thank you! 

Well—here are some pics of the finished product from this month’s build!  I’m very happy with how it’s turned out.

Many thanks to the great information, instructions and modification ideas on this thread.  
 

I’ve added a removable jig for a green laser pointer that can stay in place temporarily via magnets so I can more accurately polar align the platform to Polaris through the polar axis of the mount (54° angle for my latitude).  

Everything seems to be working in theory. Now waiting to get some clear skies to try it all out for real!  😊

@PeterStudzYes makes sense!  I have been reading up since I posted and that was what I was imagining it needed to look like. Very helpful—Thank you for confirming.  Now to just wait for the parts to arrive. 
 

Cheers!

Graeme 

@PeterStudzAh beautiful!  I can see where that would work nicely. Thank you so much. I shall hunt this down!

Peter, I can also see some value in the little micro switch that you set up to stop the motor when it gets to the end of its range. Would you mind explaining how to wire that switch into the battery/dc converter and motor set up that you have? I can see that I might want to give that set up a try as well. 

I thought I should post the same question to the group as a whole that I posed to Peter yesterday—but is anyone able to check what the shaft size under the Speed Control dial is on the EQ drives you are using for your vns platforms?  Everyone seems to be using the same basic one (Celestron 93514 or equivalent) and I’d like to put a larger dial on there to make it easier to adjust in the dark. Just need to know a shaft size so I can order something from AliExpress. Thanks!

On 04/08/2022 at 05:42, PeterStudz said:

Almost there. I lost some time due to holiday but once you’ve cut out the boards and aluminium arcs the whole thing quickly goes together. My Dob has a rather “solid” DIY base with large feet and I haven’t quite worked out how to secure it. But as soon as I had something that worked I could not resist giving it a go, the Dob just carefully plonked on-top. Didn’t have much time before the forecast clouds came in so I homed in on Saturn. Even at 300x (far too much for a sharp view) I could keep the planet centred. Went in to make a coffee and even after 4-5 mins Saturn (some drift of course) was still in the eyepiece. I could even make out 4 moons (a first for me), the advantage of having more time to observe before having to nudge. Now, just need to finish it off!

Nothing that different from the excellent instructions. And I have to say that @westmarch should get some sort of prize for this thread.  I know he’s taking ideas and inspiration from others but this platform is minimalistic, simple and straightforward to make that just about anyone can give it a go. All in the tradition style of the Dob. The only tools I used were a handsaw, hacksaw, electric drill, file, and some screwdrivers.

I did break a drill bit when drilling the fixing holes for the aluminium block, the end of the bit stuck fast. Cheesed off I went down the shed to see if I could find something as a substitute. In the end I used a scrap plywood block, a couple of penny washers to form a recess and a dome nut to sit on top of an M12 bolt. The dome nut is 18mm diameter which is similar to an M20 bolt with the threads filed off . Seems to work well with a smooth rotation.

I’m a veteran of the EQ1 motor drive. I had one for an EQ1 (my first telescope) and it was the best £28 I’ve spent in astronomy. It transforms the EQ1 into something useable. Although I did try and improve it by replacing the 9v battery with something with more beef and that’s rechargeable. I did find that I was going though 9v batteries far too quick and that this small battery didn’t do that well in the cold. For this I used a cheap 12v sealed lead acid battery (the type used in alarms) knocked down to 9v with an equally cheap converter. This pushes out a steady 9v almost whatever the temp and lasts an age before needing a recharge. I also added a little voltmeter over the motor terminals - the idea here (I know it’s not quite as simple) is that I could quickly dial back a motor speed that worked. Oh, also a proper size “knob” on the potentiometer. I’ll change the wiring around somewhat  but it’ll basically stay the same with a battery box on the lower board. I was also going to use a micro switch for a motor stop but playing around I felt that for security it does need some sort of physical stop. For that I just added a couple of wooden blocks and I might still add a micro switch on top of one of these.

PS - my drill can take a 25mm bit. I was wrong there! 

Hi Peter!  Love your setup here. I am doing some similar work in the next few weeks. Your upgrade knob for the potentiometer—would you let me know where you got it, or what size is needed to replace to stock knob. Love that mod and want to do the same when my EQ drive shows up. 
 

Thank you! 
Graeme

4 hours ago, westmarch said:

I average about 40 mins tracking on my platform. It actually lasts longer because I have it switched off while I am star hopping to my target and only switch it on when I am in the acquisition region.   I have not had balance issues and the recessed feet in the platform gives additional stability. On the basis that most commercial 10 inch Dobs are mechanically fairly similar, I think that it should work.

BTW Peter found a great app which cheaply does away with the star hopping bit and turns the Dob into a GoTo scope.

John

 

 

That’s all great feedback John—I appreciate hearing more of your experience.   Tracking is going to be a wonderful addition

And great idea about the app—I will check it out for sure. 
 

Thank you again for starting this thread a few years back. It has stimulated a great deal of help for DIY astronomers. 

2 hours ago, AstralFields said:

I think the bigger platform will be better in all regards. 10cm is a very minor difference and I wouldn't worry about it at all. If anything it should improve the balance of the whole thing.

I have the same feet distance on my 8" and I had a width of 500mm and it fit very nicely.. So you can basically settle on a width between 490mm and 600mm and take it from there.

Yes I would agree—in fact I plotted out my scope on the larger Vogel template last night and looks like a great fit and alignment!  So between that template and John’s (original poster) excellent instructions here I am using a calculated COG of my whole setup to adjust the South pivot point which I’m hoping will enhance tracking accuracy (Sketch attached) I believe I shall proceed with this. Thank you for your thoughts!

@westmarch/PeterStudz-I hadn’t though of moving the feet, so will consider that too. 
 

Are you guys getting 90min or so of tracking on this design now that you’ve had it awhile?  

With not getting into the whole COG calculations that the Vogels original plans called for—you’ve been happy with the results and not having balance issues or tracking time issues on 10” units?

@AstralFieldsThe issue with feet distance is that only bottom of the board is 490mm, once you cut out the 20° angle it is now less than 490 where the Dob feet need to rest. 
 

I though about building Vogels larger one as well, or just widening the base of the 10” plan to fit my Dob better—just not sure how modifying the template affects balance, tracking time etc. 

Hi everyone—I’m late to the party on this thread, but I see that it is still active.  Great work by all, and I’ve enjoyed learning what you have been trying.

I’ve been hard at work on trying to make the plan from the OP work for my Apertura 10” Dob.  Sadly, my base is slightly too large for the original plans posted here and my groundboard feet sit about 2cm centimeters outside the template on the north axis.  I’ve been scouring also through the www.reinervogel.net website referenced in the beginning, to try and work out how to make this project fit for my Dob, and trying to figure in Centre of Gravity (COG) calculations and his original measurements to see how to “stretch” this template to fit and be accurate and stable.

When designing according to Vogel’s original instructions, I am getting my South axis calculated to be underneath my Dob groundboard.  Knowing my groundboard is larger, and guessing my COG is lower than the OP template—perhaps this makes sense.  But I have not seen anyone else here with this issue and am not certain how this would affect balance and tracking.

I have thought of 3 options overall:

1)Extend the North axis base by several centimeters on both ends and build the rest of the template according to the OP plans.  Again—no idea how this would affect balance and tracking

2)Use my calculations from Vogel’s original plans that puts my South axis underneath my Dob and hope that works.  Also—no idea if this is safe or effective.

3)Reach out to the community here and get help.   I believe this will be my best bet.  I am hopeful that someone will be able to provide further direction before I put saw to wood.  Below I am including some of the parameters and measurements that I have been gathering, and I hope that will be enough to give someone who is experienced what they need to point me in the right direction.

Measurements:

• Outer distance from one groundboard foot to a second groundboard foot:  465mm
• Optical Tube Centre of Gravity to ground:  600mm (assumes this is from centre of the altitude axis pivots)
• Rocker Box Centre of Gravity to ground: 150mm
• Optical Tube weight:  18.63kg
• Rocker Box weight:  13.63kg
• Distance from azimuth bearing to outer side of groundboard foot:  267mm
• Calculated COG of assembled telescope:  388mm to ground
• Height of ground feet: 22mm
• My latitude is 53.5 degrees, in Sherwood Park, Alberta, Canada

Many thanks to anyone who can provide me with direction and support!

Thanks,

Graeme LaRue