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Converted old CG-4 EQ mount to ALT/AZ! thanks CN!

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#1 lamplight

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Posted 11 January 2013 - 08:17 PM

Im soooo pleased. :jump: - was able to convert my CG-4 EQ mount to ALT/AZ. Particulaly with help from the CN archives. I was going to sell this CG-4 mount as I have the CG-5 for my refractor.. but i found myself not wanting to do alignment and powerup for visual. It's somewhat tedious to get the balance perfect in order to browse with the EQ mount I find, and I end up in weird positions or having to rotate the tube.. . More often than not im bringing out my SCT due to ease of setup without power. So i realized I need to start looking around for an ALT/AZ mount.

I came across DiscMounts which i promptly lusted after. sigh...

Then i saw something about converting an EQ mount and I thought a perfect project since Ive been too lazy to even sell my CG-4. I soon realized that it wasn't so easy to get the CG-4 to work as smoothly as the ALT/AZ motions of the unpowered SCT. Then I found this old archived thread on cloudynights outlining what needed to happen.

Astroview Modified to ALT/AZ. The thread went into detail about modifying the CG-4 for ALT/AZ as well. Only took about a half hour!

So happy and I can't wait to try it (its a Cloudy Night of course). the action is smoot, and the XLT 102 is light enough/the mount is heavy enough not to require counterweights! a super grab n' go setup. very smooth action I know its going to be a delight.. plus with the slow motion controls it should be sweet to run. I seem to think I had a cover for the polar alignment scope opening so there may be a few extra parts around the house somewhere.. :question:

I did go through the trouble of taking off all the motor drive components. I want to pass them on to someone who might use them, if anyone is interested send me a PM I just need postage, otherwise you can have it. seems all in great condition, but i really haven't used it (bought used).

Please take a look at my pics and let me know if I took off all the right parts for the motor drive? I wasnt quite sure as it came all attached to the mount.
CG-4 motor drive parts and finished CG-4 ALT/AZ mount

Posted Image

Posted Image

#2 Jon Isaacs

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Posted 12 January 2013 - 12:30 AM

Matt:

That's what folks used to do before mounts like the Vixen Portamount became available. You do have to be careful, in the photos, the scope is cantilevered out quite a distance, it actually looks like it's outside the tripod legs. This is risky because with the scope that far out, it is easier to tip over.

What I used to do was use the polar axis for the large rotations and the RA axis for the fine adjustments and keep the scope closer to the center so it was less likely to tip over. There maybe a peg that limits the rotation of the polar axis that needs some attention, sometimes they just unscrew.

I would keep the motor drives, you may decide to use this mount for a small refractor and do some astrophotography.

Jon

#3 mrvolt

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Posted 12 January 2013 - 02:35 AM

Hi Matt,
Very nice job on the conversion to alt/az. You will find it is very stable at high powers. I purchased almost the same setup last year for our family, a celestron 102ed on the cg-4 mount. We very soon converted it to alt/az, the slow motion controls work out great. In your pic you have it out past the legs, I tend to swing it back in over the center of tripod for a bit more stability inuse. I can't understand why more folks don't try this. The cg-4 is easily up to the task and very smooth with its dual ball bearings.
Again, congrats on the job. I think you will like it for qiuck looks.
All the best,
Tony

#4 lamplight

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Posted 12 January 2013 - 08:51 AM

What I used to do was use the polar axis for the large rotations and the RA axis for the fine adjustments and keep the scope closer to the center so it was less likely to tip over. There maybe a peg that limits the rotation of the polar axis that needs some attention
Jon


Not sure what you mean by this, but in the thread I linked to there was some lengthy discussion about the polar scope hole needing to be pointed UP (90*) for best results which is what I had to do. You make a good point and it is indeed not cantilevered out too far.. Feels very center weighted while rotation completely around 360 deg. (No degree symbol on iPad!!!). It's not out past the legs.. And they're not extended even. It is right at the edge when positioned between two legs. BUT I can get it even closer which brings up another question. I had mounted a little say 8" dovetail onto the 12" dovetail because I wanted to use the slots it had to take advantage of the little extra locking screw on the mount. I can def get rid of one of these dovetails.. I want to try the shorter one for said reason, I hope that is stable enough distance for the rings to be spread. Ill do that today which will get me an inch closer. It doesn't feel tippy at all even with pressure sideways to test it but ill still do what I can just in case.

Why I'm so excited Is not To have to spend more money. I have a cg-5 which I can use if I want eq mount and or tracking or pics. The Orion mount for the reflector. I do use the eq for refractor so infrequently I might even consider selling the cg-5 since I have the Orion mount.mhmm..

So that in mind, motors just sitting here.. And someone asked already so they're to be gone.

Thanks Jon!

#5 Eric63

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Posted 12 January 2013 - 09:08 AM

I did the same with my EQ3, however I also use the counterweight bar and one of the weights (especially if I have the 6" Newt mounted).

Eric

#6 Jon Isaacs

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Posted 12 January 2013 - 09:21 AM

Not sure what you mean by this, but in the thread I linked to there was some lengthy discussion about the polar scope hole needing to be pointed UP (90*) for best results which is what I had to do. You make a good point and it is indeed not cantilevered out too far.. Feels very center weighted while rotation completely around 360 deg.



The question is, what happens when it gets bumped at night, How far does it have to tip to become unstable.... I never liked having the scope so far away from the center.

Anyway, an EQ mount like the CG-4 has 4 axes. The RA, the DEC as well as a third axis which goes through the center of the hub. There is also the Altitude axis which is used to set the elevation of the mount, currently this is set to zero degrees. Finally there is the original Azimuth axis (I incorrectly called it the Polar axis) that is normally used to to align the mount so it is pointing due north.

In the current configuration, you now have two azimuth axes. If you use the original Azimuth axis for your course azimuth movements and the RA axis for the fine/slow motion controls, you can position the scope so that it is closer to the center of the tripod, a good thing in my experience.

Some mounts allow 360 degree rotation of the original azimuth axis, some do not but can be modified so that it can rotate 360 degrees.

Hope this makes sense now.

Jon

#7 lamplight

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Posted 12 January 2013 - 10:31 AM

Hi

No it's not clear at all. :confused:

I did just take off one of the dovetail bars and the shorter one got it closer by maybe 3/4" to the central axis of balance for the whole tripod. I can tip a leg up about 6" before it starts to tip. I will pay very close attention to this and use a counterweight (0r a weight on the eyepiece tray!) if it seems too flimsy. With this scope it feels solid.

I have the declination/altitude axis of the polar scope opening set at 90 degrees, not zero. That was specifically mentioned in the thread and in fact I found I had to do it that way vs 0 degrees. I have it the exact same way Dave does in his thread. I forget what the issue was but it had to be this way to get unobstructed balanced movement.

Regarding all the axes you mention I'm not following, but as it is now there is full 360 degree smooth movement left and right, and unobstructed horizon to zenith which is all I need. If there's something important you ink I'm not getting do you have pics? That would make it easier to understand. I did search and couldn't find any other cg-4 pics from after an alt/az conversion , except Dave's in that thread.

#8 CJK

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Posted 12 January 2013 - 10:36 AM

(No degree symbol on iPad!!!).


Actually, there is: press and hold the '0' (number zero) until you get a popup that allows you to choose '0' or '°'

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#9 lamplight

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Posted 12 January 2013 - 10:39 AM

Oh good. Tanks! °

#10 lamplight

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Posted 12 January 2013 - 10:43 AM

Adding the larger white counterweight above the eyepiece holder raised the tipping point to 7.5" roughly, took that off and the smaller counterweight added below the EP holder raised tipping point to 7". I haven't tried both but individually they create a slightly more stable center of gravity. Without appendages. ;)

#11 newtoskies

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Posted 12 January 2013 - 10:53 AM

Very cool Matt. I'm gonna have to try this with my mount.

#12 Jon Isaacs

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Posted 12 January 2013 - 10:54 AM

I have the declination/altitude axis of the polar scope opening set at 90 degrees, not zero.



You're right, 90 degrees, that's I have done it, I was trying to decide from your photos which it was, 0 or 90.

Anyway, here's a photo that hopefully will explain what I am trying to say, notice how the scope is over the center of the mount rather than cantilevered out near the edge. With a long scope like yours, you probably cannot bring it all the way in.

Jon

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#13 mrvolt

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Posted 12 January 2013 - 12:05 PM

Hi Matt,

Here is a quick pic of my setup. The only difference is that I run both slo-mo controls on one side. One short one long, makes it so easy to use them both without ever taking your eye away from the eyepiece. Tipping is not much of a problem.

Tony


I tried to post a picture from my ipad, but when i click on the choose file, on CN, i get no action or response. I'm new to all this:)

#14 newtoskies

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Posted 12 January 2013 - 12:27 PM

That pic helps a lot Jon. I'm gonna play around with mine today and see how this all works.

#15 lamplight

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Posted 12 January 2013 - 01:03 PM

Oh ok that makes sense. I just loosen a clutch to swing the scope around and it cantilevers moreover the center just like your picture... Just need to observe from a specific side of the tripod if i want it more centered point of gravity. Perfect! Plus the weights help too and would be more effective if lower but it seems good. Thanks again!

#16 KerryR

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Posted 12 January 2013 - 01:56 PM

I prefer alt-az mounts, but not if they're not simpler than an EQ mount.

I mean, If I'm going to carry an EQ head out the door, why not just use it in EQ mode, especially if I've gotta counterweight it anyway?

#17 CJK

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Posted 12 January 2013 - 03:00 PM

I tried to post a picture from my ipad, but when i click on the choose file, on CN, i get no action or response. I'm new to all this:)


Strangely, it works for me on my iPad 3 but not on my original iPad. I bet (but don't know for sure) it has to do with the difference in JavaScript versions between iOS 5 & iOS 6.

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#18 Jon Isaacs

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Posted 12 January 2013 - 03:00 PM

I prefer alt-az mounts, but not if they're not simpler than an EQ mount.

I mean, If I'm going to carry an EQ head out the door, why not just use it in EQ mode, especially if I've gotta counterweight it anyway?


A couple of thoughts:

- I prefer alt-az mounts, they are easier to point and generally more comfortable, no tube rotation, simple to use.

- For most mounts, most telescopes, there is no need for the counter weight when a GEM is used in the ALT-AZ mode. An EQ mount used alt-az is balanced, the pivot point goes through the center of gravity of the scope. The only possible purpose for the counter-weight is to keep the weight centered over the tripod but with the technique I discuss above, that is not necessary. These mounts are nimble as normal ALT-AZ mount.

Many of the smaller Gems, for example, the EQ-1 and EQ-2, the CG-2 and CG-3 can be used in the alt-az mode without any changes they work quite well. Two notable mounts are the Vixen Polaris and the Mizar mount of a similar size. Both these are high quality mounts, seemingly designed to be used either way, GEM or ALT-AZ.

(The photo is the Mizar GEM in the ALT-AZ mode)

Jon

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#19 lamplight

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Posted 12 January 2013 - 04:44 PM

I prefer alt-az mounts, but not if they're not simpler than an EQ mount.

I mean, If I'm going to carry an EQ head out the door, why not just use it in EQ mode, especially if I've gotta counterweight it anyway?


But I'm not "counter" weighting it at all. Just 7" added under the EP holder so Jon doesn't worry :roflmao:

#20 lamplight

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Posted 12 January 2013 - 04:50 PM

I can see how the mount design on that one makes for a more central point of balance over the tripod.. The cg-4 is a bit different.. But not a ton. I can't wait to use it this way.. I've been dragging my SCT out for manual alt/az browsing now ill only do that if I need a little more umph in light gathering and magnification. Thanks for the help guys. This is in a way. My first bargain in this hobby as far as I'm concerned ;) :grin:

#21 Jon Isaacs

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Posted 12 January 2013 - 05:09 PM

I can see how the mount design on that one makes for a more central point of balance over the tripod.. The cg-4 is a bit different.. But not a ton. I can't wait to use it this way.. I've been dragging my SCT out for manual alt/az browsing now ill only do that if I need a little more umph in light gathering and magnification. Thanks for the help guys. This is in a way. My first bargain in this hobby as far as I'm concerned ;) :grin:


Matt:

I have an EQ-3 which is essentially the same as the older CG-4, the Mizar mount is ideal for conversion, there is absolutely nothing to modify or change. But the CG-4 still can be used effectively as an ALT-AZ mount. You are chomping at the bit, ready to go, just waiting for some clear skies.

Jon

#22 Noisykids

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Posted 12 January 2013 - 06:00 PM

Seriously bemused here to find this thread. i tried converting the eq mount that my st-120 came with but couldn't get the head to go to 90 degrees. i wanted something i could grab and go and it wasn't really working out. i just took the whole head apart to locate the hard stop on the outside and it works. great. how do i explain to the war department the versa go that is supposed to be delivered monday? actually i don't care for the legs on this mount so i will probably keep the versa go. if i had found this thread two weeks ago i would be that much closer to the 8" edge hd.

eta 1/14--- the versa go is set up in the corner of the living room with an 80mm eon, an ra finder and a telrad. looks cool. my lovely wife took one look at it and remarked "is that the R2D2 model?" i kind of set her off when i brought the box in the house by asking if she noticed if the delivery guy dropped it. i shook it and it rattled. i said "this is a $6000 telescope." just had everything out looking at jupiter. it does what i want.

#23 lamplight

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Posted 12 January 2013 - 09:39 PM

Oh that's unfortunate timing. Depending on the vendor , can you just return it unopened and brand new? The war dept (ha!) won't have anything to say.

#24 Noisykids

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Posted 13 January 2013 - 01:02 PM

she wouldn't bustmy chops anyway. just looked at your moon photos. nice job. i seem to have trouble getting them to focus clearly. where exactly is west central ma? i describe my location at south central ma. i'm thinking millbury, brookfield,something around there, oxford, dudley,?

#25 newtoskies

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Posted 13 January 2013 - 01:07 PM

Too bad you guys aren't closer, would be great to hook up in the Spring for a small star party.






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