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Absolute beginner question.


Peter B
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As an absolute beginner I have a thousand questions to ask when I join my local astronomy society when they start meeting again, but for now there's one question which is bugging me.

 

I think I understand the difference between alt/azimuth and equatorial mounts and their respective uses but I don't understand why the Sky Watcher AZ GTi mount I have comes in both alt/az and EQ versions.

 

My AZ GTi mount has the telescope attachment on its left and its firmware is for alt/az use only.  The other version of this mount has the telescope attachment on its right and can be loaded with either alt/az firmware or EQ mode firmware.  I'm tempted to load the EQ firmware into my alt/az mount to see what happens.....but I'm not going to!

 

What I don't understand is why a mount which can be motored to track targets accurately in alt/az mode actually needs an EQ mode at all and I should be most grateful to have this point explained.

 

Thanks in advance for your patience with what is probably an obvious answer, but one which is lost on me.

 

 

 

 

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21 minutes ago, Peter B said:

Yes thanks, I've seen those, but why does it need a EQ mode when the mount will track targets perfectly well in Az-El mode?

Alt Azi doesn't track perfectly, thats the point.  You can not get long exposures.. with the right settings you can get PHD2 to guide pretty well apparently and therefore use it to get long exposures this way.

 

EQ mode, with very good PA should allow 3 min, maybe longer unguided exposures.

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Ah, OK, I didn't realize that, thanks.

 

On their firmware download page Sky Watcher state that their AZ GTi and GTe mounts are not designed for astrophotography, so you wonder why they have implemented a dual mode Az-El/EQ function for their motor drive firmware.  

 

Another puzzle is why the telescope must be mounted on the right side of the mount facing forwards for the EQ mode - but that's a different question I suppose.

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An alt az mount can track very well but the the image in the eyepiece will gradually appear to rotate. That limits it practical use for astrophotography to short exposures. Unless you use a wedge. 

 

You can use your mount with a wedge set to your latitude if the handcontroller allows you to point the scope below what it thinks is the horizon. If not then you can only point it at objects above the equatorial plane. And the goto may end up pointing the scope at the ground because it doesn't know the mount is on the wedge. 

 

Edited by paul
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Thanks Paul.  I hadn't considered the rotation aspect. but I see that that is going to be a limiting factor of exposure time with an Az-El mount.

 

I can't mount my reflector on the right side of my AZ GTi mount because it has a fixed mounting point and it would be upside down, but I could turn my reflector round in its tube rings and point it the other way on the right side of the mount.  However, I think I'll leave EQ mounts alone for a while until I gain some experience with Az-El and the planets and until my local astronomical society starts meeting again when I can pick some brains.

 

Thanks again for your help. 

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