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EQ3-2 mount question


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Ok this will probably be a stupid question but here goes!

There seems to be 2 declination pointers on the EQ3-2 mount. One on the right side (if your looking through the scope straight ahead) which is a black pointer on a metal background, the other on the left is pure white and is raised out a little from the mount. Which is which?

If I was looking for something with a positive declination (for example andromeda galaxy +41 deg 16' 9") I'm guessing that I should be setting it according to the black pointer on the metal to the right, and if looking for something with a negative declination I should be using the white pointer on the left...?

To be honest I've not had any problems so far finding things just using the constellations and star hopping but there should be something about it in the manual for thicko's like me! ;)

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And in terms of the RA settings - as far as I understand it I should find a star for whose co-ordinates I know then set these co-ordinates on the RA axis and lock it using the screw. Is this right? Then everything is kind of all matched up, right? But then how does it if the earth is constantly rotating?

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Hi Steve,

I noticed the same thing with my EQ3-2 and to be honest I have no answer. At least with my mount, the arrows don't match up in the setting circles. If you set the nice clear black printed arrow to 90°, the arrow cast into the metal on the other side of the mount is indicating about 82°.

I used the black arrow and set it to 90° when I aligned the mount, then marked the footprints on the floor so I can respot the mount without re-aligning each time, and I have not had any major problems finding (big) things using the setting circles.

Like you, I usually star hop, but I tried it a couple of times with the setting circles just to learn how.

Rik

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And in terms of the RA settings - as far as I understand it I should find a star for whose co-ordinates I know then set these co-ordinates on the RA axis and lock it using the screw. Is this right? Then everything is kind of all matched up, right? But then how does it if the earth is constantly rotating?

If you have a clock drive and you lock the RA circle on an object, the object stays in the eyepiece and the drive keeps pace with the Earth's rotation so the locked RA circle is always in the right place.

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Actually they work fine without the motor drives so long as you polar align the mount reasonable closely. If you line up on an object where you know the RA, if you then lock the RA circle it remains the right setting only so long as the object you lined up on is in the eyepiece, so you keep tweaking the fine controls. Or, you could just adjust the DEC control to shift to another (fainter perhaps) object at the same RA as the object you lined up on, but then you would have to keep that new object in the eyepiece for the RA setting to stay valid.

The other thing to do is to line up on a known bright object, set the RA circle to the right setting but don't lock it. Then you can you can move the mount to the right RA and DEC settings for a fainter object you want to find, and it should appear in the eyepiece.

The DEC motor for the EQ3-2 bolt on directly over the black arrow, so actually it is harder to use the setting circles when you have the drives installed. It is nor a great design.

Rik

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I think I understand it now, thanks, but let me see if I've got it right...

So, if I want to find something whose RA and DEC I know but is very dim and hard to find I would first find a star which is easy to find and whose co-ordinates we also know (like sirius for example) then change the RA setting circle to show the correct co-ordinates of Sirius. Then i can keep the RA setting circle unlocked and turn the RA knobs to show the correct RA of the star I want to find and wahey it will be in the viewfinder. Thats what I thought.

But to take the above example of Sirius - Sirius (or rather we) will move over time and everything will become unmatched again. I gather that we would need to re-find Sirius and reset the RA setting circle accordingly and then everything will again match (for a limited period of time). We basically need to repeat the process every time we want to find something new.

And if I just want to track an object after finding it I would lock the RA setting circle and just use the RA slow motion control to keep it in view.

This has been bugging me for a wee while now! It would be great to finally nail it!

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Based on my own experience with the 3.2 mount and other members advice I'd have to say the setting circles are pretty hopeless and too small to be used with any degree of accuracy.

That could probably be said of most modern mounts especially compared to the mounts from years ago which had much larger and easier to read circles.

Nowadays it's probably more of a styling exercise than a means of navigation.

I think an affordable mount with integral digital circles would prove popular as I'm sure there are many like me who might not want full goto but need a helping hand in our less than dark skies.

Or does one already exist ?

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I've never used my setting circles, but then I only nominally polar align my scope. I just like the EQ mount because I find it easy to follow star hopping directions (N, E, S, W are all independent).

Andrew

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The asy way to use setting circle - if you use them at all is (assuming you are polar aligned). Set the declination (which doesnt change for any given star) and then swepp through the RA looking for the object.

With that said even the HEQ5 and EQ6 have terribly duff and inaccurate circles. Maybe if GoTO hadnt been invented the manufacturers would have put some effort into the setting circles ;)

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I know they are pretty useless in practice but I hate having something that I don't know how to use at least in theory ;)

But I think I've got it now except for 1 thing - how to set the declination on this thing! Do I use only one or both of these pointers and is right side for + dec and left side for - ?

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Truthfully to set the dec circle you need to zero the mount so that an object in view stays in position when you swing the scope from one side of the mount to the other.

Once that is correct you need to loosen the locking screw on the dec circle, turn it until zero lines up to the arrow and then lock it up and it should never need adjusting again.

Sorry if that doesn't make sense, I can't think how to describe it any better.

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Yeah, I agree, pretty useless for actually finding anything small and faint.

I tried it a couple of times just to get it straight in my head how it worked. I lined up on Castor and then shifted to find M35 then down to M67. (big challenge ;) ). It worked but it was such a faff that I haven't bothered since and just star hop to find things.

Rik

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I don't think it matters so use whichever one you prefer, just set it to 90° when you polar align. I used the black one but now I have the drive motor installed, I can't see it unless I stand on my head.

Rik

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The black pointer is thinner and possibly easier to use accurately.

Am I right in thinking you can ensure your Dec axis is square to your RA axis by aiming at an object and swinging the scope from one side of the dec axis to the other and adjusting the mount until the object remains central throughout the range of movement then adjusting the dec circle with the locking screw if the pointer isn't on 90 degrees.

Does that sound right ?

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Sorry guys I have yet another declination question!

There are 2 sets of 90 degree markers on the mount and 2 sets of 0 degrees - fine got that. Right side one for positive declinations and left one for negative declinations (is this correct!?)

BUT why are there 4 of everything else - eg 4 sets of 10 degrees, 4 sets of 20 degrees etc etc

Again I know in practice I will never use them but it would be nice to know at least in theory whats going on...

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Steve,

relative to the "zero" marker you select, the other degree divisions are + and - ie +10 North on one side of the 0 and -10 degree South on the other, repeated for each "zero" position.....

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Hmmm..I'm still not getting it to be honest. If I turn the pointer 90 degrees to the left (-) of the 0 marker and then 90 degrees to the right (+) I'm only covering 1/2 of the sky so what about objects located on the other half (the half behind me)?

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If the mount is set up (roughly) so that the polar axis is pointing towards the pole star - the dec should read "90" - this is +90 degree north.

If you swing the axis round to read "0" this is the Equator - so all objects with a + dec are between the pole star and the equator.

If you continue to swing further the new reading -10, -20 etc are declinations south and if you kept going ( the telescope would be upside down!) you eventually point to the south pole.

Here in the UK the pole star is about 51 dec altitude, so the equator will look (90-51=49 degree) 49 degree altitude and you could view objects say as far south as 30--35 degrees.

Sounds like you are reading only the + degrees ie 0 to +90 to 0. Try it again and see if it makes sense.

Ken

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By God I think I've got it! The penny has finally dropped!

So if my scope is polar aligned....

+1 would actually be almost directly LEFT, +90 is dead ahead, -89 is fractionally to the right and -1 almost directly to the RIGHT. Going beyond these and the telescope starts to point more and more towards the ground and the south pole.

Cheers mate you have made my day!

Jings, its actually quite easy.

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