19 replies to this topic

[wapfunz1]

Evolution 8.

Just wondering what protection is there just in case murphy's law strikes and the scope hits or bottoms out on the tripod.

Yes you can stop the motion by pressing the hand controller if you catch it in time - but what if...

Is there a hard stop shut off?????????????

[emflocater]

Great question. Wondering if my Skywatcher NEQ6 has a hard stop as well. Looking forward to the answers by experts out there!

Cheers

Don

[Nemo51]

I don’t think so. Don’t ask. 

[jimr2]

Nope, not on Celestrons--don't know about Skywatchers....

[Northernguy]

No stop other than your equipment acting as a doorstop. 

Best would be to make sure you have a short OTA that doesn't reach that far down. Or babysit

[wapfunz1]

Dam shame that, no failsafe.

[Notdarkenough]

There is a Cordwrap feature to save your power cord, but it needs to be adjusted each session, individually. As for mount strikes? I found the power switch to be the fastest. The Evo handles the C8 weight well, and if using for visual, I did find a happy place where the OTA was far enough forward to allow the diagonal to not strike when pointing directly up. With a camera, maybe with an uncooled cam. It really does depend on your OTA/accessories weight and your usage. I was concerned about mount strikes as well, so I purchased a CEM70 with a mini-pier. Now it impossible to have a mount strike.

[Mac163]

On the 8 and 6SE handsets you can set Slew Limits so that the OTA will not travel past the point it will hit the mount. It will give you a message on the handset that the target is beyond your slew limit. Then you just press the back button to go to another target.  The mount won't slew unless you give it the ok.   Page 135 of Michael Swanson's book explains how to do this in detail.

 

You can also press any of the direction control arrows on the handset when the mount is slewing and it will immediately stop.

[mlord]

Is it true that the slew limits are NOT respected until AFTER alignment is completed?

[Mac163]

Is it true that the slew limits are NOT respected until AFTER alignment is completed?

I can only speak for 8 and 6SE setups.  I set up my slew limits before aligning and it works just fine.  You have to have the OTA level at its index points.  Turn off the mount and turn it back on and go slew to the highest position you want the OTA to travel. Go to the Get Axis Postn in Utilities. Read the Alt position from there, then enter that number in Scope Setup menu Slew limits Max.  Leave the Minimum setting at 0.

 

This setting remains with my mount until I change it.  Even using the ASIAIR Plus for EAA last night, the mount refused to go above my set limits.  The NexStar User's Guide 2 by Swanson goes into detail on how to do this.  Hopefully my description makes some sense.

[Mac163]

Is it true that the slew limits are NOT respected until AFTER alignment is completed?

After rereading your question, I don’t know if it would go beyond the slew limit during the alignment phase, but since directing the mount manually at that point it probably would. I don’t generally align with objects that are that high in the sky so haven’t tested that yet!

[speedster]

Does it matter?  My only experience is an unattended night when the computer lost control of the mount (CGX-L) before the meridian flip.  When I woke up the next morning, camera (or whatever) was firmly against the pier and the mount had continued to drive it into the pier for hours.  Did not go quite far enough to hit the hard stops.  No damage other than my mental state for a few minutes. 

[InfiniteMort]

Is it true that the slew limits are NOT respected until AFTER alignment is completed?

Yes this is my experience. I have also read several others experiencing the same thing.

 

I used to do alignments without a camera attached, to avoid damaging the equipment and screwing up alignment, when auto align wanted to align something high in the sky.

Now I have a star diagonal attached for photography and the optical tube moved far forward so it doesn't strike the mount, during alignment.

[whizbang]

I have a newer EVO mount.  I experimented with the Slew Limits setting one day.

 

I set the limit in the hand control using the hand control menu.  I did a fake indoor alignment on "Polaris".  Using SkySafari, I slewed to several objects.  By just eyeballing it, the slews looked approximately correct.  Next I tried selecting and slewing to objects near zenith, and above the slew limits.  Nope.  Nada.  The mount simply ignored the command.  It didn't budge. 

 

Next, I connected to SkySafari using a BlueTooth connection.  Operation was identical.  Perfect slews to objects below the limit setting and no movement whatsoever to objects near zenith above the limit setting.

 

Lastly, I selected a couple objects NEAR my slew limits.  The mount slewed fine as usual.  From there I was able to manually use the direction arrows to move the mount near zenith above the slew limit setting.

 

I liked the way the slew limit operated.  It will protect your OTA from hitting the mount accidentally.  And, if you want to manually, carefully slew near zenith, you have that option.

 

Two thumbs way up!!

Edited by whizbang, 27 May 2023 - 03:25 PM.

[Tulloch]

After a number of years of being very careful with my mount and controlling the length of my imaging train behind the visual back, I stupidly slewed to something high in elevation without moving my C9.25" SCT forward enough on my Evo mount a week or so ago.

 

The camera hit the base of the mount and it stopped moving. I turned it off, turned it back on again and moved it down so I could get the camera out. I thought I might have done some terrible damage to the back of the OTA, the camera, something ... it hadn't even affected my collimation, it was still bang on. So while I'll make sure not to do it again, it doesn't seem like it's the end of the world if you do...

 

Andrew

Edited by Tulloch, 27 May 2023 - 07:38 PM.

[wapfunz1]

Now that is nice to hear and reassuring because I did something similar

[mlord]

There is no sensor or anything to detect the OTA hitting the mount.  So if it does do that, the motor controller will continue pushing hard on it, until either the gears slip (bad) enough for the optical encoder to think it has reached the destination position, or the clutch similarly slips (okay), or until the LM293DD chip overheats and stops working (bad).

 

I wonder if that's why 2/4 of the "dead" Evolution main boards I had simply needed new LM293DD chips?

[rcooley]

shouldn’t be a problem unless you’re slewing at warp 7

[ButterFly]

Evolution 8.

Just wondering what protection is there just in case murphy's law strikes and the scope hits or bottoms out on the tripod.

Yes you can stop the motion by pressing the hand controller if you catch it in time - but what if...

Is there a hard stop shut off?????????????

There is no torque limiter, current detector, or anything of the sort.

 

When my 120mm refractor on my AVX strikes the tripod leg, the motors impart enough force that the scope slips in RA in its slip clutch.  I need to goto an object, the physically center it in the eyepiece while unclutched to avoid redoing an alignment.

 

Slipping in the clutch is not a safety feature, and doing so is bad for the motors.  Avoid it.  The regions of the sky it happens in is consistent, but remember that it can pass through the region on its way to another region.  For a long refractor on an EQ mount, the answer is a pier.  Too bad Celestron doesn't make one for the AVX.

 

Your mount with an SCT should be okay.  With a long refractor, yes, be careful.

 

 

shouldn’t be a problem unless you’re slewing at warp 7

One can also track right into a tripod leg.

[MikeB 2]

Maybe check your slew limits settings.