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Viewing behind a scope when in EQ mode


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#1 tchemaly

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Posted 30 September 2015 - 06:47 AM

Hi

When one has a telescope on an equatorial mount how do you point the telescope to a star/planet that lies BEHIND the scope instead of in front it. On an ALT/AZ mount it is straight forward...just turn it on the AZ axis. However turning the scope on an EQ mount or wedge to point backwards seems impractical?

Thanks

TIm


Kind regards

Tim


#2 MistrBadgr

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Posted 30 September 2015 - 02:06 PM

Hi Tim,

When it looks like the scope is going to go up-side-down, you have to do the equatorial flip. You rotate the optical tube on the declination axis so that the open end is where there mirror end used to be and then rotate on the RA axis until you are in position to point the scope at the object. You will then be standing on the other side of the mount to look through the eyepiece. This takes a bit of getting used to!

An example of that is to assume you are looking at an object that is in the southeastern sky. The scope is pointed at the object and lets say you have a reflector. You will be standing to the south and west of the scope, looking through the eyepiece. As the earth rotates, you will rotate the scope toward the west to keep the object in view. About the time the object is directly South of you, the eyepiece will be level. If you go any farther, the eyepiece will start sloping downward. At that point, you rotate the optical tube in two directions. It really does not mater which comes first, but I will normally point the scope back toward the North, then rotate on the polar axis, over the top of the mount, until the scope is on the eastern side of the mount. Then point the scope at the object from that side. It will appear up-side-down in the viewing field compared to what you had before.

I hope got this right and it does not confuse you too much! :)

Bill Steen
Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#3 tchemaly

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Posted 30 September 2015 - 11:55 PM

Damn you confused me :) I wish there were some pics. I am using the Meade ETX on the tripod's builtin wedge. Not sure how to do the flip?


Kind regards

Tim


#4 MistrBadgr

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Posted 01 October 2015 - 07:20 PM

Hi Tim!

 

I did not think about that.

 

You should simply be able to tell the scope to go to the object and it will do what it needs to do to get you there.  If your handset is a 497 type or AudioStar, I think it may have that option. 

 

If doing it manually, there will be a place overhead to the North (Oops, for you South) where you would have to be under the scope to see through the eyepiece.  What I would do there is to rotate the scope around in the azimuth direction (now RA) so that the eyepiece is either on the east or west side to some degree.

 

I do not have the ETX 90, but do have an ETX 80.  My scope has a 494 handset, which is not as smart as a 497 or AudioStar, but I might take it out and play a little.  Mine does not have the ability to tilt to an equatorial position, so I would need to improvise somehow.

 

Anyway, it is an interesting question that I have not encountered before.

 

Bill Steen


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#5 MistrBadgr

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Posted 01 October 2015 - 07:23 PM

Tim,

 

What I was talking about in my first replay was related to what is known as a German Equatorial Mount, with counterweights and all that kind of stuff.  It is more akin to a single arm mount rather than a double arm like yours.

 

Bill


Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma




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