WEGA Samyang adapter. Not impressed.

[ollypenrice]

This product comprises a 3D printed set of tube rings with holder for the ZWO focus motor, a 3D printed dovetail and finder-guider bracket and a pulley system to drive the lens focus barrel. The concept is fine but the execution is lamentable.

1) The wing nuts for the finder guider are regular hex nuts onto which printed wings have been placed. They fall off and will always fall off.

2) The tube rings have clearly proved to be fragile so the manufacturer includes washers which prevent them from being over tightened. They also prevent the rings from holding the lens firmly. If you fit the washers and tighten the clamps, you can slide the lens up and down in the rings or rotate it easily.

3) The pulley for the lens is split to let it slip over the focus barrel. Its two ends are held together by a minute plastic press-in clip of such fragility and bad design that it broke of its own accord overnight. And, even before breaking, it allowed the focus pulley to turn on the lens barrel anyway. Useless.

4) There are no instructions.

5) This tat sells for £139.00. (One hundred and thirty nine pounds.)

 

Having got this far with the wretched thing I'm going to continue. I'm not using the finder shoe anyway. I have put thin double sided tape around the focus barrel, slipped the pulley over that, threaded some copper wire through the holes for the silly clip and twisted the ends together before putting a drop of solder on them. With luck the pulley will now turn the focus barrel.

I'll stick with the washers which prevent the tube rings from holding the lens but put the same double sided tape round the lens to see if it will hold still.

I don't know who Wega are but they need to go back to school.

Olly

Edited December 5, 2022 by ollypenrice
typo

[Alien 13]

Doesn't sound good Olly and gives 3D printed parts a bad reputation, if designed correctly with appropriate use of metal inserts/parts etc they can be very strong. If you want to modify any parts with metal strengthening etc the normal type superglue is a good bonding agent for use on PLA.

Alan

[PeterCPC]

That's not good. I got the Astrodymium system and am quite impressed with it - no slippage. https://astrodymium.com/

[ollypenrice]

13 minutes ago, PeterCPC said:

That's not good. I got the Astrodymium system and am quite impressed with it - no slippage. https://astrodymium.com/

That one looks much better. Who sells these?

Olly

[PeterCPC]

1 minute ago, ollypenrice said:

That one looks much better. Who sells these?

Olly

I got mine direct from Astrodymium - they are in Canada.

[Chris-h]

FLO sells them as well. I have had 3 other 3D sets for the 135, and they all failed in some way. The Astrodymium system just works, and is rock solid!

https://www.firstlightoptics.com/adapters/astrodymium-ring-system-with-zwo-eaf-asiair-mount-for-samyang-rokinon-135mm-f2-lens.html

[pipnina]

This is quite unfortunate to hear. I have two WEGA printed mounts for my ZWO EAF (for the TS 2" crayford, and the TS3" R&P) both of which cost more than 40 quid each! I have to say I had an easier time with them than you, though far from perfect

In my case, the crayford bracket was a rather clever design using a friction fit, as the focuser has a gentle taper on it, so the circular smoothed-out plastic could grip the focuser quite snugly and the connection to the focusing shaft kept it in place. Even then however, I found I had to file the inside gently to get it to go over the focuser at all! Which wasn't great, and there was a useless little wing that was meant to go under the focus motor area, held on by a tiny little M2 or M3 sized screw, which promptly stripped the threads in the PLA material with barely any effort. Thankfully that wasn't a functional piece!

The one for the TS3" R&P was better, although it was a single piece and didn't rely on friction anywhere.

I feel like us amateur astronomers have more use cause than most people to own our own 3D printing equipment, a lot of us would probably save money on the 200 quid investment after a few months or years!

[Tomatobro]

The focus barrel on the Samyang is 2mm pitch so a toothed belt will drive it ok so I don't understand the need for the extra drive pulley. it almost looks like the designers did it this way for toothed belt focusing.

Edited December 5, 2022 by Tomatobro
picture added

[tomato]

Agreed, why use a toothed clamp on ring when there is a suitable tooth belt drive already on the lens?

[geeklee]

1 hour ago, Tomatobro said:

Samyang is 2mm pitch so a toothed belt will drive it ok

@tomato @Tomatobro What does the engagement look like on that?  I have to admit I didn't think it seemed very good on mine so designed and printed a pully like a lot of the 3rd party solutions.  Its belt engagement is perfect with the 2GT.  My Samyang ring (Canon fit) doesn't seem like it would be the same.

Edited December 5, 2022 by geeklee

[Tomatobro]

Even with a "slack" belt it works fine. On one of my lenses the tension on the pulled side of the belt pulls the optical train out of alignment so i always instruct the focuser to reverse a couple of stepper motor pulses to centre the optical train and even out the belt tension but I see this only one one of my Samyangs.

For this reason I do not tighten the belt over the lens but just enough to prevent the belt from riding out. Even with level of tension slippage of the belt does not occur. Perhaps one reason for fitting a separate drive pulley close to one end is to apply the offset load of the belt closer to the focus support mechanism.

 

[Tomatobro]

1 hour ago, geeklee said:

What does the engagement look like

Its not perfect over the full span but the discrepancy is so small that about 10 teeth engage before it starts to ride out. Give that 10 teeth are more than enough to drive the focuser even with minimal tension I settled for that. After all its not a Cosworth DFV!

[ollypenrice]

3 hours ago, Chris-h said:

FLO sells them as well. I have had 3 other 3D sets for the 135, and they all failed in some way. The Astrodymium system just works, and is rock solid!

https://www.firstlightoptics.com/adapters/astrodymium-ring-system-with-zwo-eaf-asiair-mount-for-samyang-rokinon-135mm-f2-lens.html

I honestly can't remember, but I probably saw this and discounted it because of the '30 to 40 working days' stock estimate - to which I have to add the best part of a fortnight while the delivery companies waste my time, energy and faith in human decency.

Regarding the Christmas cracker Wega tat, I'll add that I put two heavy cable ties around the lens-camera system so that a failure of the tube rings will not send £2,500 pounds' worth of optics and cameras heading towards a well-made six tonne concrete floor.

Olly

[ollypenrice]

It seems that Wega also stand accused of industrial plagiarism: https://www.facebook.com/deepskydad/posts/theft-alertwega-telescopes-from-germany-has-copied-our-design-for-wo-redcat-auto/842992756438285/

Olly

[Adreneline]

19 hours ago, Tomatobro said:

Even with a "slack" belt it works fine. On one of my lenses the tension on the pulled side of the belt pulls the optical train out of alignment so i always instruct the focuser to reverse a couple of stepper motor pulses to centre the optical train and even out the belt tension but I see this only one one of my Samyangs.

For this reason I do not tighten the belt over the lens but just enough to prevent the belt from riding out. Even with level of tension slippage of the belt does not occur. Perhaps one reason for fitting a separate drive pulley close to one end is to apply the offset load of the belt closer to the focus support mechanism.

 

I don't doubt that it works but I do have doubts about using that arrangement based purely on my experience. I found that despite the level of tension in the belt the belt would precess on the focus ring and so I found there were issues with repeatability over time. This problem was exacerbated for me because I was using Astronimik 2" Ha and SII filters and a Baader 2" OIII filter; the Astronomik filters are 1mm thick whereas the Baader is 2mm. This difference in thickness required very different focus positions (~500 on the EAF) and over time the belt would 'walk' around the focus ring so although the relative difference for Ha/SII and OIII remained the same the absolute positions on the EAF changed. In the end I adopted the same approach as @geeklee and installed a toothed ring which works perfectly.

With regard to mounting the EAF @ollypenrice I have tried under, over and at the side. The under-lens mounting I didn't like because it sets the lens high and the guide scope even higher above the Vixen bar and flexing problems start to surface. Mounting the EAF above the lens screws up any chance of mounting the guide scope. In the end I have settled for 'at the side' mounting of the EAF leaving the top bracket clear for the guide scope. The downside with 'at the side' mounting is it throws out the whole issue of DEC balancing which is partially resolved by rotating the EFW but even this requires the addition of a 100g laboratory weight to achieve perfect balance on my CEM25. Rotating the EFW however does allow space to fit the guide scope so it all seems to be a win-win in the end.

I am a 100% fan of using the WO mounting ring and buying the WO handle to mount the guide scope. I also use the ZWO camera support ring to ensure I don't get any misalignment of the camera-lens combination - no droop! Even though I use the Astrojolo M42 replacement end mount for the lens I was still getting a tiny amount of droop - the ZWO support fixes the problem completely and provides a very rigid mounting platform.

All personal experience over the last three years of tinkering and messing around - exactly what you do on cloudy nights!

Adrian

[Adreneline]

As an aside the gear ring allowed me to establish accurately the backlash in the system:

Photo dates from when the EAF was above the lens.

[Tomatobro]

I need to mention that I use geared stepper motors and build and program my own design focus controllers so my experience is limited to my own hardware and not commercial equipment. It starts to get expensive where dual rigs are involved and could not justify two commercial focus controllers which is why I did everything to keep costs to  a minimum. I think each focus unit cost around £5 for the stepper motor, £3 for the drive belt, £6 for the toothed pulley and about £20 for the components to make the focus controller.

Edited December 6, 2022 by Tomatobro
picture and cost ammended