What happens if the power fails?

[Chocolate Elephant]

The usual bunch of premium geared mount junkies continue to denounce ASA DDMs (and direct drive mounts in general) by claiming attached instruments will be damaged or destroyed if the mount's power supply ever fails.

 

Can anyone tell me what failsafe systems are in place, if any?

 

Thanks.

[lukepower]

Hi Chocolate Elephant,

 

well, my experience is: If you set up everything right (that is, you balance your setup), then basically nothing will happen, the mount will just stop.

This changes if you didn't took the time to balance your scope: The mount has no gear, so any unbalance will result in a (possible) motion of the tube in any direction. Anyway, this is a problem you would also have when everything is powered off

 

As for the attached instruments, I could only imagine that they could hit something while the mount is moving without power... If a power failure would ruin attached instruments, this would apply to all mounts, I would guess

[nakbrooks]

Agreed.  There are no brakes (apart from manual locking screws) so when the power fails (or indeed if it is just switched off or the motors are powered down) then the axes are free to move without restraint.  This isn't a problem if you are well balanced.  As good balance is essential to the operation of the DDM mounts any residual imbalance is likely to be very small so any movement after power is turned off should be very slow and very unlikely to cause damage.

 

I'm lucky in having the XL pier (the Z-shaped one) so have full 360 degree movement in both axes without hitting anything so I can sleep easy at night!

 

Should only be an issue if the mount is left outside in a strong wind (and if it is outside I guess there shouldn't be anything to hit).

[lukepower]

I sign Nigel's comment about the bent pier, it has dramatically improved my use of the mount. Imaging through the meridian (and I do mean all the way) on both sides, and no problems with hitting anything (except my head or a closed roll-off roof) is a great plus now

[RamaSpaceShip]

Hi Chocolate Elephant,

 

A power failure can only be a problem if it occurs when you do a fast slew. As nothing will brake the mount, it will hit the mechanical stops violently, and this may cause some dammage.

 

To protect against this, there is a simple solution: use an UPS, for the PC and for the mount.

 

You also need to take care when you change your equipment as the balance is then broken and this may cause a quite fast movement, with the same result.

It is wise to set a lock in such a situation, in particular for RA.axis.

 

Of course a pier which avoids the meridian flip reduces the number of mechanical stops to those of the mount itself.

 

 

Best regards.

 

Bernard

[MarkS]

My mobile DDM60 set-up will run all night on a 38AH battery, so it's not an issue for me!

 

Mark

[Waldemar]

Hi Chocolate Elephant,

 

The people with geared mounts, also with the expensive ones, are used to "out-balance " the backlash,

so the mount is heavy to one side. If they would not have the gears to stop movement, they certainly would damage their instruments.

Not realizing or knowing the advantages of DD, they assume the same is necessary with the DDM mounts, which would result in crashed equipment when power fails. The only possible event may happen when power fails during a fast slew as is mentioned before.

I never tried this deliberately... but will when there is a possibility.

 

But as everybody here knows:  we do not have that kind of issues with our DDM's, so: don't worry, be happy :-)

 

Waldemar 

Edited February 8, 2014 by Waldemar

[Josch]

Hi.

I am running a remote observatory under pristine and clear skies.

At such a place power usage is an issue as the power is home (solar panel) made.

I usually sleep during observations and several times in nearly 3 y of operation power was cut, but so far nothing happened to the scope or mount neither PC.

I am pretty sure that also power was cut during slewing as my mount slews really a lot during the night (500-1000 times), so it is pretty high probability that during a slew the power was off.

The only problem after such a power failure is that the mount has lost its position and you need to do a manual homefind. Luckily after a while this is not really an issue using a webcam.

I am very happy with the DDM85 although there have been many problems, but for my work only a direct drive mount is able to perform.

 

Regards,

 

josch