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N0ZB

Celestron 8SE not tracking properly?

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Hello,

Super newbie here. Clearly I am doing something wrong and I am not sure what it is.

I have a new Celestron 8SE. I have been successful conducting the StarAlign. I then use one of the functions to go to Mars or a star in a constellation - the telescope slews over to the location, lands on it, stops....  then rapidly starts slewing away so the telescope ends up inverted. It comes all the way over the top, starts pointing the scope downward and then stops.

Help.

Scott

Edited by N0ZB

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I've not had this issue, but perhaps an upgrade might fix it?  Try:

http://www.nexstarsite.com/OddsNEnds/HCFirmwareUpgradeHowToVersion4.htm

The 'scope comes with a cable for the hand controller, but not the RS232-to-USB adaptor.

Doug.

Also - the adaptor/converter comes with a driver CD.

 

Edited by cloudsweeper

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That may well be power. Seems a bit of a feature when the power supply is inadaquate.

If you are using batteries use new ones and use the high power variety, worst aspect is to use a new set each time. A previously used set will likely be a little low the next time. The scopes will work at 12v but they get questionable at 11.5v, in effect 12v is the minimum. Many people run them just slightly higher, here quite a few Mains/DC supplys have a 13.2v option (mine does) and they use that. The slewing action take a high drain then there is just insufficent to maintain everything. I have/had a small Meade that did just about exactly the same.

Do not use rechargeables, they do not have the right voltage, so exactly the same problem.

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+1 for it being a power issue, I always use a 12v car battery or 12v mains adaptor to run my 8se.

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Yes I had trouble much as you described with my Nexstar 8SE mount when it was on batteries. Since I got a Baader power supply (https://www.firstlightoptics.com/power-accessories/baader-outdoor-telescope-power-supply-128v-15a.html) I've had no problem.

As final thoughts, when you set up your mount:

  1. Make sure it is on firm ground and as level as you can. Use a proper spirit level, not one of these buttons with a bubble in the centre which I've found to be hopelessly inaccurate.
  2. Enter your precise location.
  3. Enter you time as precisely as you can, say within 5s.
  4. Centre the star as closely as possible, starting at low magnification and finishing at a higher power.
  5. Use the same mount slew directions when centring all your alignment stars and chosen object.

Good luck with your new hobby.

Ian

Edited by The Admiral

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8 hours ago, The Admiral said:

Use the same mount slew directions when centering all your alignment stars and chosen object.

I've read this piece of advice before, but I am afraid I don't understand it. Does this mean I want my three objects to be in a straight line?

 

I have the Celestron Power Tank... it was charging last night, but is topped off and ready for use. I will be using that for power tonight.

- Additional Question: if I am using the Power Tank and have AA batteries in the base, does it default to the Power Tank?

 

Thank you very much for all the help! I really enjoyed seeing the Moon last night.

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I was able to figure out that the base will default to the external plug over the onboard AA batteries. Just by plugging in the Power Tank, I saw the brightness increase a bit on the hand control.

I did the StarAlign again tonight. First time, no problems. I used Mars and two stars to the right of Mars. When I slewed to the third "star", I saw rings! Alright! I used Saturn as the third object and the handheld said the align was good to go. I was just able to get my two little girls out to take a peak at Saturn before their bedtime. Where those some of Saturn's moons nearby or stars in the background?

The base seemed to be tracking Saturn without an issue. I started with the 32mm eyepiece. Then swapped it for the 25mm. Then the 13mm. The base was still tracking.

That was it for tonight. Hopefully we'll have clear skies this Friday and I can give the tracking another good test.

I'm still not exactly sure what "Use the same mount slew directions when centering all your alignment stars and chosen object." means. Mars, Saturn, and the third object I used tonight for the StarAlign formed a triangle and were pretty close together to the southwest of me.

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You can use three bright objects, or two named stars.  (And other methods - see handbook.)  I always used the two star method - quick and easy.  If you don't know the stars, just use a tablet app like Sky Map.  Better still, use Stellarium - and that will also tell you what you're looking at - moons, stars, etc..

Mount movements: it is recommended to align on an object in the same way as the mount slews to a target.  If it finishes with up and left, then do the same when you are aligning.  Some say it doesn't really matter much, and I agree.  I never bother with it, and GoTo always puts me very close to targets.  

Doug.

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As cloudsweeper says. The reason I think is that there is a certain amount of backlash in the drive mechanism, which in practice means that if you slew to a target in the opposite direction, then there is a period when the mount is stationary whilst the drive mechanism 'catches up'. In that time the target will drift off-centre. Not a major problem but could be an irritation. Similarly, if you align on an object the other way, the same will apply and the mount will 'think' it's in a slightly different position.

Ian

Edited by The Admiral

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