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Motor-drive problems: not tracking!


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I have the Astromaster 130EQ-MD and i feel I am now in tune with the CG3 mount. I have treated myself to the Celestron eyepiece kit and so very keen to start using everything. The problem i am still having is the configuring of the motor drive. To date, i have managed to successfully track Jupiter ONCE. I have tried to repeat this a number of times and i keep failing. Anything i place in my FOV just keeps drifting out. I believe i am being accurate when polar aligning and my tripod is level. Once aligned, i am keeping latitude and azimuth stationary for the whole observing session and only using RA and Dec to move around the sky (Firstly, is this correct? once polar aligned DO NOT use move azimuth or latitude?) Then i am locating a nice bright object and i try to get the motor speed correct. This is the part which i find most difficult. Because the speed is variable, i am finding it hard to accurately match the speed of the rotation of the earth. I don't even know if it's going too fast or too slow.

Does anybody have any advice for me?  :)

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Something in what you say doesn't either make sense or is not clear.

Problem is I cannot work out what or where.

It is an EQ mount.

So set the Latitude to something like 52.

if there is a polar scope or a hole for a polar scope then get Polaris in the centre (forget full alignment).

After that as best I know the thing will track, and should track at the default rate of sidereal to follow stars etc.

The minor hiccup is that the axis that the unit rotates around has to be aimed North, just wondering if you have the mount bit aimed North but that can mean the axis is (could be) aimed South. In which case the mount is the wrong way round and things will disapper out fast.

It is easy to get the 2 bits mixed up. I often do this as "normal" .

Next question is: Is there an otpion to disable the tracking?

And is tracking disabled?

Finally when doing whatever it does wrong it is still doiing something so the motors appear to be operating, meaning I suspect a error on plonking it on the ground and pointing the right bit in the right direction. I have 2 EQ mounts and they make close to no sense at times.

Remember it is NOT the scope that is being aligned but the mount. May be an idea to keep the scope off, put mount on ground, get it level, and then set latitude and then point the axis North ( polarscope or just polarscope hole) then put the scope on. It removes the possibility of using the scope and less bits while setting it up.

Edited by ronin
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its a CG3 there is no polar scope or even polar scope hole. 

What I did with mine when I had it, was point one leg of the tripod north as near as I could get using a compass,  set the  lat  ring to roughly 52 degrees,  centre the object I wanted to view in the eyepiece, using Dec and RA controls, then started the motor, adjusting speed as needed,

I just ended up giving up on that mount and bought myself an SW AZ Goto

Leigh


 

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When I was first looking for a scope/mount I read something along these lines.

If when roughly aligned a star drifts to the West then the motor is too slow, if it drifts to the East then the motor is too fast, ignore DEC drift because that is not controlled by the motor.

Unfortunately that's about it IIRC, you have to set it on a hit n miss basis and will be slightly different between solar system and DSO.

I didn't buy it due to this vagueness so don't have hands on experience.

I would think that you will obtain better results by deciding what it is you want to observe at the beginning of a session and then try to set the motor accordingly rather than joggling between planets and DSO.

Best of luck,

Rich

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It could be that you're using too high a magnification or that your polar alignment is off. Also possible that you're not using the correct rate. Or any of the stuff mentioned above. If you would like someone to look over it then drop in for a free session with East Midlands Stargazers - very friendly crowd and we'll have the problem either identified or sorted in no time at all. (See social groups section for details of meetings). :)

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Thanks for your responses guys. I had better luck last night. I think the problem was that the mount was not level. In fact it was far from level. Last night i didnt even both with the motor, i just used the RA slow motion control which worked fine. But as soon as i turn on the motor i couldn't seem to get the object to stay in the centre of my eyepiece. It is rather audible and so i can hear how fast it is going. It seems to be more precise when the thing is barely turning (well, sounds very slow). is that usually the case? for the planets, is the speed setting very slow?

thanks guys

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Having used the same 'scope for some years, I think I feel your pain :grin: :grin: !!

When setting the 'scope up, polar alignment is normally the most important thing of all. There is no polar 'scope to use so you have to do it manually. The tripod does not need to be level, but the mount should point directly at the North Celestial Pole in order for the RA to track properly.

I've found that the best approach is to set the OTA for a declination of +90° ( pointing straight along the mount ) and then use the latitude adjustment bolts and the bolt under the tripod head so that I can see Polaris dead centre in the eyepiece without moving the OTA relative to the mount. I then tweak this just a little to reposition on the NCP. I normally use a 26mm eyepiece for this as I am familiar with the pattern of stars around Polaris in this eyepiece.

A word of warning though, do not trust the DEC setting circle to point you at exactly 90°!! On this mount they are notoriously inaccurate, so you may find that setting the mount up in daylight and using your Mk1 eyeball to find out what the scale reads when you are convinced that the OTA is in line with the mount is the best way of finding out what you should set it to.

Once you have your polar alignment correct then it should be a simple matter to get any object ( other than the Moon as it does not move at sidereal rate ) in the eyepiece and then adjust the motor speed so that you can track it.

The only other thing I would point out is that the motor uses a simple control circuit that is affected by its drive voltage - PP3 batteries don't tend to like the cold and their output voltage can drop quite considerably, so use a new battery if at all possible. I have to say that I got fed up with the motor drive so I designed and built a new one, documented here http://stargazerslounge.com/topic/162657-a-low-cost-ra-stepper-for-small-telescopes/ .

Hope this helps,

Alan

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have a EQ1 with cheapy motor drive. 

only ONE AXIS is moved when tracking 24/7 this is the RA axis

the dec AXIS is set to gain object in center of the eyepiece. 

first off i set my scope to 52 degrees lattitude ( in truth its about 51 and a gnats hair lol)

next i line up the mount to polaris ( for me its a rough guess using compass and technology)

now if i want to view orion and it is in the WEST side of the sky my telescope is on the EAST side of the mount ( remember mount points north,

 and the same if Orion was in the east sky my scope needs to be on the west side of the mount)

so i pop the scope on the east side, now i adjust dec so i am the right hight for orion and slew the RA to bring it to view. 

NOW YOU LOCK DOWN the mounts clutches and engage the motor drive.

if the motor drive is turning TO slowly you will notice the object starts to drift out of the view , if your polaralignment is fairly good

this movement will be in one PLANE only ie up/down - left right. 

if you find you have to keep tweeking the DEC this means your mount is not polaraligned very well and could do with a little adjustment.

The DRIFT method alignment helps with polaraligning and also getting the best alignment for tracking.

here you will lock onto a star and start tracking it, as it moves and starts to drift you can work out if you need to adjust

the mount lattitude wise or north alignment wise. 

Edited by Mr TamiyaCowboy
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that's really helpful Alan and MrTamiya :) Yes i found myself having to adjust Dec a little bit now and again. So, i need to polar align more accurately which is difficult without a polar scope or a hole through my mount. Oh well, practice n all...

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OK problem solved.. Either i have the MD on incorrectly, or the drive has been made wrong. It works fine when i flip the switch to SOUTH :/

Arghhhh!! I'd completely forgotten about this as I got rid of the motor some time ago. You're right, the bracket and slo-mo controls mean that the motor has to be placed on the other side of the mount, so you have to use southern hemisphere tracking instead of northern hemisphere.

The motor can be ( and probably was originally designed to be ) used with other mounts where it sits on the correct side for its design.

Glad you've got it sorted,

Alan

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