Losing power on a mount with no counterweights (Back driving)

What happens when you turn off the power on the Rainbow Astro RST-135 or RST-135E? Let's talk about back driving, what it is, what happens and how you can minimise the risk of it occurring.
RST-135E initial impressions video: • Harmonic Drive Mount R...
Timestamps:
0:00 Intro
1:10 What is back driving?
4:35 Using a counterweight
6:12 Back driving with heavy telescope
8:39 Can you stop/catch back driving?
10:18 Can it damage your equipment?
13:09 Conclusion
Patreon: / astrowithroro
Public Events: www.astrowithroro.com
Facebook: / astrowithroro
Instagram: / astrowithroro

[@georges3799]

The tripod looks so narrow when the Edge scope was mounted. It was making me anxious. ;)

[@golfbiker100]

It’s about getting out there and doing it, so glad you posted this, we can all relate.

[@rackmasterh]

Super informative and well presented!

[@prabhakarrao4922]

Thank you very relevant info for anyone considering purchasing one of these.

[@Barbaria_Sailing]

Thanks for the detailed video of this mount, good work 👍. Looking forward to see how it performs in the field, especially un-guided.

[@AstroWithRoRo]

No problem 👍 Fingers crossed for more clear skies!

[@deep_space_dave]

Interesting video! I have a HEM27EC and I recently loaded it up with a RASA 8 and now I notice it back drives even though it has a brake! It was scary at first but then I added a 5kg counterweight and no more back driving. I think that the weight overcomes the brake it will back drive and I think that lets you know if you have enough weight or not. I also learned that it is the vertical height of the OTA from the base that determines the distance of the counterweight. Also I forgot to mention, the strain wave gear has a stopping point so luckily my OTA never hit the pier before I realized this! Thanks for the video!

[@CuivTheLazyGeek]

Well that wasn't so bad - thanks for the video!

[@AstroWithRoRo]

Agreed! Definitely acceptable once you know about it or how to mitigate it (especially with lighter loads).

[@desmcmorrow2978]

Most informative video on back driving. Thanks. Looking forward to the next one on guiding. Definitely helping me make up my mind on whether to buy one or not.

[@AstroWithRoRo]

Glad it was helpful!

[@desmcmorrow2978]

@@AstroWithRoRo Quick question: does the mount back drive if the power is cut when it is in the home position ie pointing horizontally West?

[@AstroWithRoRo]

It will only back drive if you aren’t well balanced on your dec axis in the home position. If you change the home position to a traditional polar Parker position then it will be easier to balance.

[@johnhawk8624]

Great video as usual! One question - have you gotten around to shooting any deep sky with it yet? I'm thinking of getting one. Thanks!

[@hael8680]

Great review and demonstration. The big question is how well does it track under the stars??

[@dolph7656]

Would adding more counterweight be an option with a heavy rig?

[@MrWeesontan]

Hi, can the mount move to 0 degree latitude? I saw some videos said it can’t.

[@jdw715]

Peace Out!

[@lizards821]

I really appreciate the extremely informative video but I also have to say we need to meet up at a star party with our doggos because I also have a corgo.

[@AstroWithRoRo]

Corgies unite!!!

[@febsat]

Well that is quite the setup. It would have been interesting to see you disassemble that rig after the backdriving had put it into a very awkward position. Although you may be able to stop the backdrive with your hands, if you are there when it happens, you still need to either find another power source, which means letting it go while you search and connect that alternate power source or you need to shutdown for the night and pull the rig apart. Imagine that big scope swinging down with no counterweight... yipes! I can visualize some difficult moments, in the dark, when this is all taking place; especially if you are alone and both RA and DEC can backdrive independently. They need to implement a small backup battery (9v), which would engage a braking mechanism and perhaps turn on a flashing red LED. Electronically, it would know the difference between a slew command and a power failure. Everybody is looking for some peace of mind with their expensive gear investments.

[@AstroWithRoRo]

I wouldn't attempt to disassemble it in such an awkward position. Once thing I didn't show here is that you can reverse the back driving by lifting the telescope. If you're not able to get the power back on, you can lift the telescope back up to a neutral position where you can then remove it more safely. This is what I would recommend anyone does if they cannot get power back to the mount.

[@febsat]

@@AstroWithRoRo That makes sense. How much effort would be needed to lift the scope up to neutral position? Is this explained in the owner's manual? Thanks.

[@petef.4361]

I was thinking of getting that mount, would it be an upgrade from a CGEMii mount? How is the periodic error? Also wondering how long you can go unguided? Does it bother you at all, that this type of mount does not have clutches? Do you ever have problems with this mount not returning back to the proper home position, or has that been ok? Thanks.

[@AstroWithRoRo]

Great questions! I will be releasing a video going over the PE, guiding, power draw, unguided performance, etc shortly (just waiting on some more clear skies). It does take some getting used to no clutches, but so far I am not missing them. You just have to learn to do things differently. It always returns to the home position very easily and quickly, no issues there.

[@scottrk4930]

Very interesting , again ! I'm wondering if the "back-driving" produces any voltage from the motors back to the electronic circuits . Could be a bad thing . I think the Manufacturer would need to comment on that one . /SRK

[@AstroWithRoRo]

I agree I think we w3ould need to hear from Rainbow Astro on this. I will try and drop them a message to see if I can get an answer on it.

[@alandyer910]

I presume if back driving occurs the mount also loses any positional information it had? So you would have to re-align? It looks like you have to Park the mount with the scope oriented so no back-driving would occur when the power is turned off, if you want to power it up and not have to re-align the GoTo system. Thanks for the helpful video.

[@AstroWithRoRo]

Yes, back driving would cause the mount to lose knowledge of it's current pointing location. You would fix this by running the "homing" routine and then you would be good to go again.

[@tehkt86]

Sorry, i cant concentrate with the doggo behind u