Alignment trouble (sort of)

[Fusion]

Hi folks. I've been lurking here for a while now and really love the place. I am not totally new to this little hobby but still far from the expert level.

I just recently acquired a Celestron Nexstar 8SE SCT and am very pleased with it. My problem is the computerized goto feature. I can do the three star alignment and I get a confirmed alignment from the scope.

Now the problem. Everything I go to with the scope doesn't end in the field of view. I can manually center a known object in the field of view and hit the identify button on the handset and it tells me that I'm about 1 degree off (was told this is about 2 moons wide). I have confirmed that the problem isn't a time or location error by using 2 identical scopes sitting 10 feet apart with identical settings and same alignment stars. The other scope gets the selected object at least in the field of view 100% of the time. My score is 0%.

I have contacted Celestron and am waiting to hear from them.

Any ideas? Hints? Tips?

Thanks in advance for your ideas and suggestions.

[Gary Beal]

Hi Fusion
welcome aboard, it is a nice forum isn't it.
I am sorry to hear of the hiccups with goto, but have little knowledge on the Celestron system. I am sure that someone here will have though, and that your answer will appear soon.
From my own experiences with both goto (Takahashi Temma) and push to (Argo Navis) I have found that if it isn't 100% I can then "synch" on that object and it will make that area of the sky more accurate. Are you able to do this.
Good luck,
Gary

[Fusion]

Originally Posted by Gary Beal

From my own experiences with both goto (Takahashi Temma) and push to (Argo Navis) I have found that if it isn't 100% I can then "synch" on that object and it will make that area of the sky more accurate. Are you able to do this.
Good luck,
Gary

Hi Gary

I can sync my scope but it doesn't help with the goto. It is still off on the next object. I have found out that the goto is off the same on each object. It doesn't "jump around" all of my goto selections are off by the same amount. Meaning I can find the object because I know where to look but that defeats the purpose of a goto.

[Gary Beal]

Originally Posted by Fusion

Hi Gary

I can sync my scope but it doesn't help with the goto. It is still off on the next object. I have found out that the goto is off the same on each object. It doesn't "jump around" all of my goto selections are off by the same amount. Meaning I can find the object because I know where to look but that defeats the purpose of a goto.

Hmmm, then I am beat. But if it is repeatable like that then I would suggest it won't be too hard to rectify. Chase Celestron, or the dealer who sold it to you.
Good luck,
Gary

[Jim Fusco]

Hi Gary,

I was thinking. I think he should change the batteries and also change the slew rate to the slowest "1" when alignment is being done. What happens some time at high speed the encoders can lose count. Another factor is a piece of plastics or something could be blocking a few holes on the one of the encoder wheel. The CPU will not see this as error so is somethin to look into.

Jim Fusco


http://tech.groups.yahoo.com/group/SkySensor2000/
http://www.geocities.com/jgfusco3/CI-700Hercules.html

[Fusion]

Thanks for the replies. After much trial and error I was able to figure out the culprit.

The bubble level that the dealer sent with the scope.

I used my own level and it is repeatedly dead on. I releveled with the other and it's 1 degree off.

Whew!!

[Gary Beal]

Originally Posted by Fusion

Thanks for the replies. After much trial and error I was able to figure out the culprit.

The bubble level that the dealer sent with the scope.

I used my own level and it is repeatedly dead on. I releveled with the other and it's 1 degree off.

Whew!!

Great news, but have you tried it at night? Is leveling that critical???
Great if you fixed it though.
Gary

[Jim Fusco]

Fusion,

A few more ideas. Try land mode, save 3 fixed objects, like a wide "V" " to determine which axes. Go back to them if the nexstar has not centered them, this may be a software problem and not a encoder. You may want to reset the controller and check for a updated.
The other is after the land objects are stored turn off and then on. Goto your first object and align, go to your second and align, now see if it goes to the third. If it over shoots the encoder is missing count and may need a cleaning. Keep in mind the encoder wheel is very thin and has very small holes so air should be used.
Also look at the connections because a spotty cord could cause issues. So the other Nexstar, use that controller and cord and switch around to help trouble shoot if the controller, cord or encoder may be the issue.
As you said with the level, I think the controller will adjust for not being level, to what degree I don't know, and that 1 degree may be border line.
Look at everything.

Jim Fusco

[Fusion]

Hi guys. I have rechecked everything. I have the scope set up on a concrete drive that has a 3" slope across a 30' area. This is to allow water to drain off of it but isn't noticeable without a level. If I don't level the scope at all I get alignment failed everytime. If I use the provided level I'm 1 degree off. If I use (my) level it is now hitting everytime; hitting 20 out of 20 objects selected. Not all were dead center but all were in the FOV when the scope stopped.

I didn't think leveling was that critical but after leveling and aligning 12-14 times I have learned differently; at least with my scope. A friend of mine has the older model Celestron 8I that he has had about 2 months. He hasn't had any trouble with it whatsoever. We put them togeather and he leveled his with the level that I received with my scope and his was the same 1 degree off.

Thanks for the tip Jim. I'll give that a try just to check.

Thanks again guys.

[BradH]

One more thing that will help is us a Illuminated Reticle 10mm will work fine. This will help you get your alignment star dead center.

Brad