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setup question on EQ-G

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#1 gonzosc1

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Posted 10 December 2012 - 05:20 PM

well of coarse I got the mount 4-5 days ago and clouds have parked over my house in SC.. but I'm just getting around to really playing with it and going through the setup.

I just got the polar scope redicle centered up on a street light about 100yds away. it adjusted easy enough. I then placed the street light in the polar circle and again turn the mount in RA and it tracks the light perfectly all the way around the circle.
now as I look throught scope and turn the mount in RA I see that the whole field of view moves even so slightly in an oval shape while the redicle is in perfect alignment with the street light.

does this mean that the polar scope itself is not aligned with the mount.
I noticed that there are four screws that look like they would be the ones to adjust but not sure..

#2 ourobouros2k2

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Posted 10 December 2012 - 09:20 PM

It means the polar scope's optical axis is not in line with the scope's mechanical RA axis.

When adjusting, only adjust half the distance you think you should, and you will find that you will not have to adjust as much as you think you will. Here is a good tutorial:

http://www.andysshot...nmentScope.html

#3 gonzosc1

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Posted 10 December 2012 - 09:41 PM

It means the polar scope's optical axis is not in line with the scope's mechanical RA axis.

When adjusting, only adjust half the distance you think you should, and you will find that you will not have to adjust as much as you think you will. Here is a good tutorial:

http://www.andysshot...nmentScope.html


Great site and thanks, but that is not the problem I have.
the reticle is not the problem. I got it aligned perfectly.

when I say that the field of view moves when the mount is turned in RA, I mean everything you see through the scope moves with it. the street light, buildings, everything. it all makes a small complete circle as you turn the RA while the reticle stays in perfect alignment.
or am I doing something wrong?

searching now on how to align the scope with the mount!

#4 gonzosc1

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Posted 10 December 2012 - 10:31 PM

OK got through to Orion on the service chat board. tech told me to first try another adjustment on a more distant target. and then told me how to align the polar scope itself with the mount if it needed it after that!

#5 ourobouros2k2

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Posted 11 December 2012 - 09:12 AM

Sorry, when you said scope, I assumed you meant polar scope. Let us know how it works out with selecting a more distant target.

#6 rmollise

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Posted 11 December 2012 - 11:20 AM

If the target (distant enough) stays centered in the polar scope as you rotate in RA, it is properly aligned. If the main scope itself is not precisely parallel to the RA axis, you might consider shimming it, but if this is not egregious, it is not a big deal, and doing a three-star alignment will generally eliminate the problems it will cause, which will be with go-to accuracy.

#7 andysea

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Posted 11 December 2012 - 12:01 PM

As a side note. When I had an EQ-G I found the plar alignment routine in Eqmod extremely useful. It's incredibly easy to use and it gets you reasonably aligned in minutes. At least close enough for guided imaging.

#8 rmollise

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Posted 11 December 2012 - 02:50 PM

As a side note. When I had an EQ-G I found the plar alignment routine in Eqmod extremely useful. It's incredibly easy to use and it gets you reasonably aligned in minutes. At least close enough for guided imaging.


Yep. That's exactly what I do when I go imaging. OTOH, the AllStar routine in the new Synscan HC firmware works good too... But I have had nothing but success with the EQMOD PA helper.

;)

#9 gonzosc1

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Posted 11 December 2012 - 04:40 PM

thanks for the tips. it is the polar scope itself that is not aligned with the RA. the reticle function is find.
the orion tech said it can be adjusted "if needed" with the 4 allen screws that surround the polar scope. but he did say that it can be a PITA to do. it does seem that I get more up and down travel then I do side to side when I turn it in RA

but I will see what happens when I aim it at a more distant target, but my thinking is that, if I see this much FOV movement at 100yd target it will only make a bigger pattern at a longer distance. anyway I'll post results when I can Xmas is knockin down the door and time is short at the moment..

#10 Phil Sherman

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Posted 11 December 2012 - 08:55 PM

The correct way to align the polarscope's reticle is to center the crosshairs on a target and rotate the mount on the RA axis. You'll need to point the mount at the target using the altitude and azimuth adjustment screws or by rotating the tripod and adjusting the leg lengths.

Now, as you rotate the RA axis, any movement of the crosshairs on the target means that the reticle needs to be centered a bit better. As Orion said, you use the adjustment screws on the polarscope. What Orion didn't tell you is that you can't adjust the reticle by tightening the screws. You need to loosen two or three adjacent screws before tightening the other or others. The screws press directly on the edge of the reticle and overtightening them can crack it. You really don't want to do this.

Your description of how things looked through the polarscope sounds like you have it perfectly aligned with the mount's axis. If objects viewed in the scope describe an oval, then you probably have cone error, caused by the scope's axis not matching the mount's. Orion's Vixen dovetail bar that the rings attach to has adjusting bolts where the rings are connected to correct cone error. You should use a target at least 500 yards (1000 or more is better) away when checking for OTA (Optical Tube Assembly) cone error. A scope with zero cone error has its optical axis perfectly aligned with the mount's RA axis.

A final thought - think about what happens when you collimate your scope. What happens to its optical path as you collimate? Could this introduce cone error? I'll leave it up to you to think about these things rather than spend more tome adding to this response.

Phil

#11 gonzosc1

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Posted 11 December 2012 - 10:58 PM

The correct way to align the polarscope's reticle is to center the crosshairs on a target and rotate the mount on the RA axis. You'll need to point the mount at the target using the altitude and azimuth adjustment screws or by rotating the tripod and adjusting the leg lengths.

Now, as you rotate the RA axis, any movement of the crosshairs on the target means that the reticle needs to be centered a bit better. As Orion said, you use the adjustment screws on the polarscope. What Orion didn't tell you is that you can't adjust the reticle by tightening the screws. You need to loosen two or three adjacent screws before tightening the other or others. The screws press directly on the edge of the reticle and overtightening them can crack it. You really don't want to do this.

Your description of how things looked through the polarscope sounds like you have it perfectly aligned with the mount's axis. If objects viewed in the scope describe an oval, then you probably have cone error, caused by the scope's axis not matching the mount's. Orion's Vixen dovetail bar that the rings attach to has adjusting bolts where the rings are connected to correct cone error. You should use a target at least 500 yards (1000 or more is better) away when checking for OTA (Optical Tube Assembly) cone error. A scope with zero cone error has its optical axis perfectly aligned with the mount's RA axis.

A final thought - think about what happens when you collimate your scope. What happens to its optical path as you collimate? Could this introduce cone error? I'll leave it up to you to think about these things rather than spend more tome adding to this response.

Phil


not talking about aligning the polar scope reticle. my reticle is in perfect alignment. its the "polar scope" itself that is not lined up with the RA axis. not looking through telescope..
example of what I'm talking about.
I aligned the reticle. I can place a street light in the polar circle of the reticle and turn the mount in RA in the street light tracks a perfect circle along the line thats in the reticle.
but,, as you turn the mount in RA and look through the polar scope everything you see is moving in a oval egg shape pattern in the field of view, buildings, street light, everything.
= the polar scope itself is not lined up with the mounts RA axis.

#12 rigel123

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Posted 12 December 2012 - 12:36 PM

I had the same experience as you. When I finally aligned it on a radio tower about a half mile away I could get that rotation you are seeing down to a minimum. This gets me close enough that I don't drift align after doing alignement with the PA and I can do 2 minute unguided and pretty much as long of an exposure that I want guided. I typically don't go over 15 minutes but could go longer guided.

So if you haven't tried this on something further away, try that first.

#13 gonzosc1

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Posted 12 December 2012 - 03:52 PM

I had the same experience as you. When I finally aligned it on a radio tower about a half mile away I could get that rotation you are seeing down to a minimum. This gets me close enough that I don't drift align after doing alignement with the PA and I can do 2 minute unguided and pretty much as long of an exposure that I want guided. I typically don't go over 15 minutes but could go longer guided.

So if you haven't tried this on something further away, try that first.


yes this is my next step, not going to turn any screws until I can try this first..






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