westmarch

Why would anyone laugh at this?

On 13/04/2024 at 10:27, AstralFields said:

Also to come back to the printable segments shared in this thread. They are incorrect for all the latitudes. Seems like Reiner has counted with a tilt degree for the segments of 15 degrees but in the plans it is 20 degrees. For some of the latitudes he did not apply the segment tilt at all, making the error bigger.

In practical terms this will induce some errors necessitating to change the speed of the motor during the tracking and some minor drift.

After I fixed it for my latitude, the difference between 15 degree tilt or 20 degree tilt is obvious

Sorry for the bad news to everybody who printed the segments for their platform. On the bright side, I guess they can be easily replaced. I may create a fixed version after I finish my platform for all latitudes as it is pretty easy using Libre Office - Draw

 

Another mistake I have noticed in this thread, people have printed the segments at the wrong scale. Somebody asked about this and someone else took a picture of a ruler over the segment. When you open them in Libre - Draw using the in-app rulers for the page, it is clear how big they should be. One can even draw a simple line and see exactly to mm how long the segment should be.

This is likely induced by the incorrect handling of PDR printing by the printer and some auto-scaling stuff going on due to printer margins.

To avoid, it is best to import the plans in Libre Office - Draw. Fix the segments there and print the segment directly from the app.

In order to perform the fix, one may need to temporarily increase the page size to 100x100cm as the ellipse creating the segments is that big.

The exact dimensions of the segments are very important because the distance in the plans is fixed at 244mm between them (meaning they should be at a specific size). Again all of this can be verified in Draw.

Not having them exact is again inducing minor errors in the system.

I think Peter has summed it up nicely. The platform is for visual not AP so slight drift is not a problem, particularly with wide field EPs. 

Hopefully the thread title keeps it clear that this is a low tech, inexpensive solution aimed at those with limited DIY skills.  Anything more really requires more outlay and/or knowledge and skills. 
 

John

well done, you make it all look so easy - unfortunately trig brings on my PTSD. 🤪  Stand by for the requests to compute segments for future builders. 😄

John

Ive always found the, “What to expect” section of @Qualia pinned guide to be one of the best ways to manage observational expectations.

John

Excellent build. Love the artwork. 😎

John

5 hours ago, Jimmy81 said:

So I’ve had a couple of nights to use my platform and have had mixed results. I get moments of tracking followed the dreaded drift. I have been tweaking the motor speed to try and eliminate this, but doesn’t seem to make much difference. I’m wondering that because I’m using a 6” Dob it’s not quite heavy enough and I’m getting slipping??

the only other difference to the design (from the original plans) is that I had to make the gap between the top platform and bottom platform 60mm because my motor drive had to mounted upside down due to the position of the driveshaft - would the bigger gap make any difference? My segments are still the correct curve for my location

I agree that the gap is unlikely to be the problem and battery or motor is worth checking. 
 

Another thing to check is that the grub screws on the flexible link collar are tight and not allowing the shaft to slip inside. 
 

John

2 hours ago, Orange Smartie said:

I have joined the club! I had to go slightly off-piste with my top board, as the feet on my Stella Lyra 10" must be a bit wider apart than those on the plan. So my top board is a little wider than the base board, but it still feels very stable. I need to do a few little mods; I'll probably chop the ends off the ellipses as they serve no useful purpose as far as I can see - on my wedge, one side hits the stop way before the thin end is reached.

It also needs to be painted or varnished.

I managed to get a quick test on Jupiter this evening, before clouds set in. This design really works! Thanks to the OP for sharing, I think it will revolutionise my viewing.

Please ignore Mrs Smartie's foot, which has phot-bombed my pic.

Great piece of work.  I agree with you and Peter, the sharp ends are a bit superfluous and  a hazard. 
 

John

3 hours ago, GasGiant said:

IT WORKS 🙂 

 

So, I get a very slight drift but I cant slow the motor down anymore.  

I have an idea what it is though. The two shafts instead of being 8mm are 15mm. I think the change in diameter has altered the 'gear' ratio.  If these shafts are smaller diameter then they will run slower on the wedge. I should then have more wiggle room with the speed controler.  I think 😁

I will whack em on the lathe and turn them down to 8MM

Hopefully shimming the shafts will sort it. The only other thing I can think of is that your design for wider arcs is distributing the weight of the rig more efficiently on the shafts and is leading to some slippage. 
 

John

Good Luck and hoping you get some clear skies. 👍

That looks like a fine piece of work!  You have the makings of a cottage industry there. 
 

Only one question, are those Velcro pads that you are using to hold the Dob in place?

John

Very impressive!  Love the Southern bearing - ingenious. 
 

You do know it’s going to be cloudy now til Easter. 
 

John

19 hours ago, GasGiant said:

This is a great thread, really useful.

Maybe I missed it, Can someone explain how you polar align please ?

Is it simply pointing the pointy end north as accurately as possible ? 

Also, im at 51 degrees. Should I use the 50 or 52 degree wedge ? 

The pointy end goes South - not North .  You should line up the platform so that the point of the A Frame base is pointing directly away from Polaris. As Peter says, near enough is good enough.🙂

John

On 02/07/2022 at 07:06, mdstuart said:

First light. That's odd the stars are going up with the motor on but drift to the left when the motor is off.

Top tip. The pointy end of the platform should be facing South NOT North!

So a 180 degree rotation of the platform and then point at Albeiro...super sharp view from the Orion dob as always. Turn on the motor....

WOW Albeiro just hangs their in the middle of the field of view. Called the wife who has a look and yes the double is still in the middle of the field of view.

So it all works perfectly. Next step is to add some paint to the platform.

 

 

 

 

 

It’s a mistake we’ve all made. 😁

Good luck with your next outing. 
 

John

Lovely piece of craftsmanship. Well done. 
 

John

Hi Sid,

a lovely piece of craftsmanship and a great web resource.  Thanks for sharing. 
 

John

It’s really not hard to build an EQ platform for a standard Dob setup. The52° profile will be fine for you. 

Good luck and let us know how you get on. 
 

John

What a loss!  Many thanks to Steve for his contribution to observational astronomy over the years. 
 

John

Like everyone else, “ticks and hums”. Sounds like you have a dud. 
 

John

Blimey!  What a job you undertook and hats off for attempting it. 

John

Thanks for the report. Good Luck with the next test. What sort of damage had you found and how did you try to fix it?

John

Great guide, as always.

John

Hi @hershey806,

There is an article here that explains the difference between the various Eq. platform types. https://britastro.org/section_information_/equipment-and-techniques-section-overview/telescope-making/equatorial-platforms-pt-1

As you can see, the Gee design is probably the most stable for lower latitudes with the northern and southern bearings angled.  On the upside, you are dealing with circles rather than complex ellipses for the segments. It does require some more involved woodworking skills to incline the segments at 39 ^o but nothing that needs more than a protractor.

Good Luck

John

Really enjoyed your post and can identify with everything you said about the joy of galaxy hunting.  There is nothing more satisfying than sitting alone in a dark sky environment while star hopping a truss dob towards an elusive bundle of archaic photons.   

May you have many more fruitful nights ahead.

John

Perhaps the problem is that AP tends to drift off into technical / software discussions that often hijack the thread?  

John

welcome back to the forum.

John