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Weight Positions

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#1 Gregory2012

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Posted 13 June 2018 - 11:55 AM

I hope that some of you can provide feedback about the locations of two of my weights. Image below. I don't like it when the scope is not fully seated in the saddle. I also was having a hard time balancing the tube until I put these two weights on the front of the OTA. The two weights fit perfectly. The two weights are loacted at the top of the OTA.

 

Thanks,

Gregory Gig Harbor, WA.

 

LX200 and Weights.jpg



#2 baron555

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Posted 13 June 2018 - 12:05 PM

Get a longer dovetail.

 

Maybe another weight attached under the front of the dovetail.



#3 gnowellsct

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Posted 13 June 2018 - 12:32 PM

Get a longer dovetail.

 

Maybe another weight attached under the front of the dovetail.

No, he needs a longer saddle.  The dovetail goes the whole length of the tube, which is plenty.  

 

We have a whole thread going on this topic including pics already.  Lemme go look.



#4 gnowellsct

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Posted 13 June 2018 - 12:34 PM

Here it is.  

 

https://www.cloudyni...8/#entry8638282



#5 Gregory2012

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Posted 13 June 2018 - 12:48 PM

No, he needs a longer saddle.  The dovetail goes the whole length of the tube, which is plenty.  

 

We have a whole thread going on this topic including pics already.  Lemme go look.

 

No, he needs a longer saddle.  The dovetail goes the whole length of the tube, which is plenty.  

 

We have a whole thread going on this topic including pics already.  Lemme go look.

I found a 10in saddle from Astro-Physics for $190, that's about twice the length of the current saddle in use.

Gregory Gig Harbor, WA.



#6 gnowellsct

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Posted 13 June 2018 - 12:51 PM

Go to astro-physics and get this (DOVELM162) part and look at the instructions--you don't want to use this with just any Celestron dovetail (really you should switch to Losmandy--you're in the domain of not wanting to screw around).  

 

I can't directly link to the part due to the way AP runs its website.  

 

Greg N



#7 Gregory2012

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Posted 13 June 2018 - 12:52 PM

Get a longer dovetail.

 

Maybe another weight attached under the front of the dovetail.

One of the issues is the location of the weights on the weight bar. I can add another weight, but these have nothing to do with balancing the OTA. The additional weights provided the ability to bring the OTA into balance.

 

Gregory Gig Harbor, WA.



#8 gnowellsct

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Posted 13 June 2018 - 12:55 PM

If you get the sixteen inch you won't regret it.  Remember that your SCT is basically cantilevered out from the center of the Dec head.  You have *paid* for that long dovetail to stabilze your system.  To get *value* for that long dovetail, put a longer saddle on. 

 

By the way if you get a long refractor you can leave it mounted offset.  You just turn it around so the dovetail points down/south.  That centers the clamp over the axis of rotation.  Works fine for 5 inch apos I've never had a six inch.  Point is you don't need to remove and re-screw the saddle.  Refractors tend to be equally balanced between front and center and so they "prefer" a classic "T" distribution of the tube over the dec axis.

 

Greg N



#9 gnowellsct

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Posted 13 June 2018 - 12:58 PM

One of the issues is the location of the weights on the weight bar. I can add another weight, but these have nothing to do with balancing the OTA. The additional weights provided the ability to bring the OTA into balance.

 

Gregory Gig Harbor, WA.

You're talking about RA balance versus Dec balance.  The Dec balance requires the longer SADDLE.  The RA balance requires the proper counterweights.  The general rule is that more weight higher is better than less weight lower.  That is, when you have the counterweights all the way out there's a kind of bendiness (you won't see it, but in theory it's there) between those weights and the optical tube which adds to instability.  You gain in stability by moving the weights higher up, but you lose leverage, so you need an extra weight.

 

This is not so much of an issue with Astro-physics which has a counterweight shaft that must be two inches in diameter.  But it's something to consider on a G11.  If you're not doing astrophotography it probably doesn't matter much.

 

Greg N



#10 Gregory2012

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Posted 13 June 2018 - 01:03 PM

If you get the sixteen inch you won't regret it.  Remember that your SCT is basically cantilevered out from the center of the Dec head.  You have *paid* for that long dovetail to stabilze your system.  To get *value* for that long dovetail, put a longer saddle on. 

 

By the way if you get a long refractor you can leave it mounted offset.  You just turn it around so the dovetail points down/south.  That centers the clamp over the axis of rotation.  Works fine for 5 inch apos I've never had a six inch.  Point is you don't need to remove and re-screw the saddle.  Refractors tend to be equally balanced between front and center and so they "prefer" a classic "T" distribution of the tube over the dec axis.

 

Greg N

I actually owned some AP equipment including the 16in dovetail. They are fantastic. I got rid of mine, because I sold my Mach One (mistake) and gave the dovetail to the new owner. I was going to keep it, but I started feeling bad about that, so I sent it with the Mach One (mistake)

 

Also 16in dovetail was the only mount I could fine that worked with my Tak MT160. Their mountings are wide and most dovetails don't fit. The one from AP fit like a glove. It's much wider than most other dovetails.

 

Does offset have to do with balance or something else.

 

Thanks,

Gregory Gig Harbor, WA.



#11 macdonjh

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Posted 13 June 2018 - 01:03 PM

Maybe talk with the guys at ADM.  They used to make a saddle that fits G11s, but I don't see it on their website anymore.



#12 gnowellsct

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Posted 13 June 2018 - 01:23 PM

Maybe talk with the guys at ADM.  They used to make a saddle that fits G11s, but I don't see it on their website anymore.

Yes I looked there too.  But I don't think you save a great deal over using the Astro-physics, and Astro-physics is good quality.  That said, I have quite a bit of ADM stuff.  My C8 has a Losmandy rail on the bottom and an ADM one on the top. 

 

If you have to use U.S. gear you can get a screw sizer and keep it around for when needed, I must confess that were I living somewhere overseas I might be tempted to buy a mount from a European manufacturer.  I don't know those brands well enough to comment.  I know they are there, I have seen them at NEAF.  

 

But I would talk to these guys about any such problems, seems like they are sellling *mostly* U.S. mounts.

 

Greg N



#13 macdonjh

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Posted 13 June 2018 - 01:34 PM

Yes I looked there too.  But I don't think you save a great deal over using the Astro-physics, and Astro-physics is good quality.  That said, I have quite a bit of ADM stuff.  My C8 has a Losmandy rail on the bottom and an ADM one on the top. 

 

If you have to use U.S. gear you can get a screw sizer and keep it around for when needed, I must confess that were I living somewhere overseas I might be tempted to buy a mount from a European manufacturer.  I don't know those brands well enough to comment.  I know they are there, I have seen them at NEAF.  

 

But I would talk to these guys about any such problems, seems like they are sellling *mostly* U.S. mounts.

 

Greg N

I looked to ADM because I have one of their dual saddles on one of my G11s and like it.  My initial reaction to anything AstroPhysics is, "expensive", so I recommended ADM.  As we discovered, we can't make a price comparison because a G11 saddle isn't shown on the ADM website anymore.  Not that this is relevant, but my other G11 has a Cassady saddle, which is also nice.



#14 Gregory2012

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Posted 13 June 2018 - 01:47 PM

Maybe talk with the guys at ADM.  They used to make a saddle that fits G11s, but I don't see it on their website anymore.

I too had ADM equipment, but I stopped using the stuff. I have a Losmandy Dovetail to Vixen mounting saddle from ADM. I put a brand new OTA on the thing, double checked the mounting. All of sudden the scope just popped off and crashed into a tripod. The scope still works, but it's collimation is way off._grin

 

There are also numerous dents. It was a cheap scope, a Bressor 8in Newt, that I wanted to practice using a Newt and learn how to collimate a scope like that, as a learning tool.

 

The scope came with Vixen dovetail, so I don't think the weight of the scope had anything to do with accident. I have now had two different scopes fall off of a Vixen saddle. I stopped using the stuff.

 

Oh well.

Gregory Gig Harbor, WA.



#15 gnowellsct

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Posted 13 June 2018 - 02:12 PM

Big thumbs up for the old Cassady line.  

 

I haven't had these issues with "Vixen saddles" of which there are many variations.  Many not made by Vixen.  Losmandy tops are now dual capacity Losmandy/Vixen.  My Geoptik refractor mounts use Vixen dovetails and I've entrusted them with my refractors.  

 

But for mounting a big OTA, yes, my preference would be for Losmandy dovetail and saddle.  I haven't had problems with ADM gear and have bought a lot of it but when you side by side it with Losmandy there does seem to be a little something extra on the Losmandy side.

 

I have an ADM dual saddle too but I'm very cautious about using it.

 

Greg N



#16 Gregory2012

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Posted 14 June 2018 - 02:27 PM

So to finalize, longer saddle plates can play a large role in balancing the dec axis more effectively than the short saddles?

 

I wonder why Losmandy doesn't build larger saddles?

 

Thanks to everyone that responded, all of it now makes sense. I needed extra weight on front of the OTA because of the load on the back of the OTA. I was unable to move the scope forward on the saddle any further (due to the short saddle length) and had to add the front weights to compensate for the lack of good balance in the dec axis.

 

I hope that's all right.

Gregory Gig Harbor, WA.



#17 gnowellsct

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Posted 14 June 2018 - 04:23 PM

So to finalize, longer saddle plates can play a large role in balancing the dec axis more effectively than the short saddles?

 

I wonder why Losmandy doesn't build larger saddles?

 

Thanks to everyone that responded, all of it now makes sense. I needed extra weight on front of the OTA because of the load on the back of the OTA. I was unable to move the scope forward on the saddle any further (due to the short saddle length) and had to add the front weights to compensate for the lack of good balance in the dec axis.

 

I hope that's all right.

Gregory Gig Harbor, WA.

That's not right.  You don't need extra weight.  You need the entire system moved forward.  The longer saddle plate lets you do that.  I don't know why Scott doesn't make a long saddle plate.  Partly the reason is, I imagine, that he doesn't get many requests because other people are already providing it.  My Losmandy stock saddle plate is in a drawer in the basement.  If you haven't looked at the pics in the link I provided in post #4, then this isn't going to make much sense to you.

 

Greg N


Edited by gnowellsct, 14 June 2018 - 04:23 PM.


#18 Gregory2012

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Posted 15 June 2018 - 10:08 AM

That's not right.  You don't need extra weight.  You need the entire system moved forward.  The longer saddle plate lets you do that.  I don't know why Scott doesn't make a long saddle plate.  Partly the reason is, I imagine, that he doesn't get many requests because other people are already providing it.  My Losmandy stock saddle plate is in a drawer in the basement.  If you haven't looked at the pics in the link I provided in post #4, then this isn't going to make much sense to you.

 

Greg N

I think there was some confusion. I understand I do not need the extra weights, if I have a long enough saddle to allow the scope to slide forward or backward allowing the OTA to balance in Dec. The only reason I am using the weights in their configuration is to compensate for a really short saddle. Correct?

Gregory




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