Can't stop Telescope wobble :(

[Cath]

Hi

I'm trying to find out what I can do to keep my NexStar 6Se stable, but I can't see what the problem is.

Their is no wind to blow it about, but I always get double stars and small wobblerly traily bits (random trails).

Here's a short video from the EOS 500D camera at prime focus, you'll see it moving about very slightly. The still images shows the setup, the scope legs are as short as possible and is mounted on a solid concrete base.

The telescope tracking is turned off (motors aren't moving) and it's pointing at a roof top about 60 feet away.

Any suggestions?

http://www.youtube.com/watch?v=gTQrjhi0fNo

[Rustmonkey]

Firstly.....how stable is that slab that the scopes sat on. You may be getting small movements with you stood on it too. Also.....having watched the video....some of it is thermal movement. I.e. atmospherics. You will always get that unless it's a really stable night. Obviously the video is taken during the daylight so heat will be radiating off objects which will cause the shimmering.

Make sure the scope is on a stable base....preferably one that you don't have to stand on as well. Remember also that a magnified image will exaggerate even the slightest movement. You may not think its windy but your scope will pick up even the slightest breeze.

[Cornelius Varley]

Concrete doesnt make a good base for tripods. Vibration is easily transmitted through the concrete to the tripod legs. having you tried standing the mount on grass which has better dampening qualities.

Peter

[Cath]

Thank you RustMonkey.

The slab is a solid block of concrete, probably weighs 1/2 a tone. But I've also tried it on another solid concrete area with the same results, the other concrete area probably weighs many tons.

[Cath]

I wasn't walking on the concrete when I took the video (just as the sun was setting), I was inside recording the video on my main PC. The scope had been their for about an hour and I hadn't gone outside to the scope for probably 30mins before taking the video.

I haven't tried it on the grass because it's normally quite water logged, it's quite squishy today.

[Rustmonkey]

You'll be surprised how much these things don't like even the faintest of movement . My SW150pl is like a windsock.

This is why the big fish swear by the NEQ6's and other very expensive mounts. For us mere mortals we just have to get on with it and hope for the best.

[Photosbykev]

The trackng maybe turned off but are the motors still trying to maintain their current position which might cause the movement you are seeing? If the motors are steppers they will be working, so turning the mount off completely and then checking you might see a difference.

[Jiggy 67]

I agree with the concrete theory, I've had mine on concrete and grass and grass is better, if you notice the legs have spikes to push into the ground, this must add to stability

[jonathan]

I would agree, that doesn't look like it is caused by anything other than the environment, or certainly not a fault with the mount. You may even be getting vibration from a nearby road or strong sound source.

You could try vibration suppression pads First Light Optics - Celestron Vibration Suppression Pads

Or... you could try three small flag stones on the grass instead of the concrete area.

Here's mine:

I put sand/ash underneath the flags to make them sit flat, but that's probably not necessary on grass as long as it's flat enough already.

One last thing to consider is your mount - it is a single arm mount which is more susceptible to vibration than a fork or EQ style mount (I have the same Goto mount for my 8SE). The added weight of a camera at one end will exaggerate vibrations even more, and may give a pendulum effect. I've added so much to my 8SE (focuser, finder scope, dew shield, heavy eyepieces...) that the original Goto mount can no longer cope, I have gone straight to an NEQ6 which handles it with ease.

[Cath]

OK, thank you guys for replying.

I'd really love an NEQ6, and I would if I could afford one, but unless I won the lottery it'll never happen.

Brought it all back indoors now, total cloud cover now that it's dark - typical as I wanted to have a go at collimating it.

I'll check it out again tomorrow if the weather is OK.

[jonathan]

OK, thank you guys for replying.

I'd really love an NEQ6, and I would if I could afford one, but unless I won the lottery it'll never happen.

Brought it all back indoors now, total cloud cover now that it's dark - typical as I wanted to have a go at collimating it.

I'll check it out again tomorrow if the weather is OK.

You may not need go as far as an NEQ6 for the 6SE. Check the combined weight of your scope and typical attachments, and see what mount can handle it. Also, make sure it is correctly balanced along the dovetail.