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Equipment Discussions >> Eyepieces

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karstenkoch
sage


Reged: 04/21/12

Loc: GMT+9
Eyepieces of similar weight ... what's your range?
      #5952878 - 07/03/13 10:48 AM

Hey all,

If you want to grab few eyepieces and head out to observe without the need to rebalance your scope, what range of eyepiece weights do you use as your rule of thumb? About 100 grams is my range. If all the EPs I'm using in a session fall within the same 100g range, I don't need to rebalance between EPs and use very little clutch friction or knob tightenting. How big or small is your range?


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Mark9473
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Reged: 07/21/05

Loc: 51N 4E
Re: Eyepieces of similar weight ... what's your range? new [Re: karstenkoch]
      #5952918 - 07/03/13 11:15 AM

If this is a problem for you, try a DM6 mount. I have little or no problem going from a 22mm Nagler to an 18mm ortho (other than the shock of the huge AFOV jump).

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Sarkikos
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Eyepieces of similar weight ... what's your range? new [Re: karstenkoch]
      #5953060 - 07/03/13 12:45 PM

For grab-n-go, I use a Baader Zoom, Nagler Zoom and maybe some small light-weight single focal-length eyepieces. I don't select them according to any exact range of weight, but just use common sense.

For my 10" f/4.8 Dob, which does not have altitude detention, I've already preset the balance for my heaviest eyepiece. When I want to put in a lighter eyepiece, I attach a magnetic weight on the OTA beside the focuser to make up the difference.

Mike


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spencerj
Pooh-Bah
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Reged: 11/17/04

Loc: Londonderry, NH
Re: Eyepieces of similar weight ... what's your range? new [Re: Sarkikos]
      #5953181 - 07/03/13 01:59 PM

I use the Televue equalizer when I use my Unistar. It allows me to use heavy 2" eyepieces and lighter 1.25" eyepieces without issue at the same balance point.

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Sarkikos
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Eyepieces of similar weight ... what's your range? new [Re: spencerj]
      #5953217 - 07/03/13 02:15 PM

I have a TV Equalizer. I've used it in the past but don't use it much any more. Its additional weight does not make up for the difference between my heaviest and lightest eyepieces. I would still need to attach a magnetic weight to the OTA near the focuser to compensate. The Equalizer also has a set screw and brass ring to hold the eyepiece. It'd like it better with a twist-lock holder.

Mike


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Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: Eyepieces of similar weight ... what's your range? new [Re: Sarkikos]
      #5953229 - 07/03/13 02:19 PM

My range is 20 ounces of weight difference. Only a counterweight can handle that unless you have a scope you can slide back and forth in a cradle.
Even if the mount can be tightened, that much weight difference would make the scope jerky at some point.


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cjc
sage


Reged: 10/15/10

Loc: Derbyshire, England
Re: Eyepieces of similar weight ... what's your range? new [Re: Starman1]
      #5953342 - 07/03/13 03:22 PM

My main set goes from 6 to 14 ounces which cause no problems with balancing on any of my scopes. There is also little issue accommodating the orthos which go down to 3 ounce. Weight was a factor in my getting a Hyperion Aspheric 36mm rather than some other 2".

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Sorny
professor emeritus


Reged: 03/15/12

Loc: Southern MN
Re: Eyepieces of similar weight ... what's your range? new [Re: cjc]
      #5953354 - 07/03/13 03:29 PM

On my CPC I don't worry. It's balanced "even" with no eyepiece in the diagonal, and just slightly back heavy with my heaviest 2" eyepiece. I'll re-check once my Binotron & D21 pair show up, but thus far I have no issues. It did take a lot of weight to get the scope balanced like this though...

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karstenkoch
sage


Reged: 04/21/12

Loc: GMT+9
Re: Eyepieces of similar weight ... what's your range? new [Re: Sarkikos]
      #5953356 - 07/03/13 03:34 PM

Mike,

That's an elegant idea ... magentic weights. A lot of fine tuning ability there: size, number, placement on OTA. I'm going to give this idea some thought!


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Eyepieces of similar weight ... what's your range? new [Re: karstenkoch]
      #5953517 - 07/03/13 05:24 PM

I setup my scopes so they handle my heaviest eyepiece, the 20mm Type 2 Nagler as well as no eyepiece. With small mounts, that generally means slow motion controls for high magnification observations.. with larger scopes, it's not an issue.

Jon


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Sarkikos
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Eyepieces of similar weight ... what's your range? new [Re: karstenkoch]
      #5953728 - 07/03/13 08:05 PM

Karsten,

Quote:

That's an elegant idea ... magentic weights. A lot of fine tuning ability there: size, number, placement on OTA. I'm going to give this idea some thought!




Here are the magnetic weights I use:

Magnetic Weights for Steel Tube Scopes

You might be able to find them less expensively elsewhere, but these are readily available and ScopeStuff ships fast.

The top and bottom of these weights are padded with felt. The weights might slide down the tube if you observe in a dewy location. But it's easy enough to attach a square of Velcro - the ribbed side - onto the OTA near the focuser. The weights will stay put on the Velcro, even in very dewy conditions.

Mike


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Arizona-Ken
Pooh-Bah


Reged: 08/31/08

Loc: Scottsdale, Arizona
Re: Eyepieces of similar weight ... what's your range? new [Re: Sarkikos]
      #5953819 - 07/03/13 09:01 PM

When I'm in mono vision on my CPC1100, I keep all eyepieces at about 16 oz max.

Arizona Ken


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karstenkoch
sage


Reged: 04/21/12

Loc: GMT+9
Re: Eyepieces of similar weight ... what's your range? new [Re: Sarkikos]
      #5953822 - 07/03/13 09:03 PM

Hmmm, this is going to sound really cheesy, but I was thinking about hanging some kind of simple sling under my refractor focuser and then adding glass marbles to it until I achieved balance with the eyepiece I'm using. Might help in going from my UWA 24mm to my ES82 4.7mm. But I can also see the sling breaking, marbles bouncing everywhere, and my refractor flipping forward smashing the side of the objective on something hard. Let's see where I stand after this brainstorm clears up...

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Sarkikos
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Reged: 12/18/07

Loc: Suburban Maryland, USA
Re: Eyepieces of similar weight ... what's your range? new [Re: Arizona-Ken]
      #5954613 - 07/04/13 11:21 AM

Quote:

When I'm in mono vision on my CPC1100, I keep all eyepieces at about 16 oz max.

Arizona Ken




I use whatever eyepiece I want to, regardless of weight. This is possible if you balance the telescope for the heaviest eyepiece, and then use a compensatory weight if necessary near the focuser when switching to a lighter eyepiece.

I've even set up my 5" f/5 Dob this way. I can observe with an ES 82 30 and Paracorr in that telescope with no balancing problems.

Mike


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Wade J
sage


Reged: 05/27/07

Loc: south dakota
Re: Eyepieces of similar weight ... what's your range? new [Re: Sarkikos]
      #5954655 - 07/04/13 11:52 AM

My main eyepiece set is between 6 to 8 ounces. I have no problems changing eyepieces. The set I use is 24 and 19mm Panoptic, 13, 11, 9 and 7 mm Nagler T6 and a 3 to 6mm Televue Zoom.

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Arizona-Ken
Pooh-Bah


Reged: 08/31/08

Loc: Scottsdale, Arizona
Re: Eyepieces of similar weight ... what's your range? new [Re: Sarkikos]
      #5954685 - 07/04/13 12:30 PM

Quote:

Quote:

When I'm in mono vision on my CPC1100, I keep all eyepieces at about 16 oz max.

Arizona Ken




I use whatever eyepiece I want to, regardless of weight. This is possible if you balance the telescope for the heaviest eyepiece, and then use a compensatory weight if necessary near the focuser when switching to a lighter eyepiece.

I've even set up my 5" f/5 Dob this way. I can observe with an ES 82 30 and Paracorr in that telescope with no balancing problems.

Mike




Mike:

In working out the balance on my main telescope (CPC1100), I found that even substituting a 6 oz eyepiece for a 16 oz eyepiece puts the scope out of balance. For visual use, I have found that balance is not extremely critical; get it close and you're OK. GOTOs and tracking are quite acceptable. I balance my telescope so that it is slightly heavier on the back end.

Now with my ES127 on my GT5 tripod mount with a pier extension, the mount is working near its limits due to a combination of weight and the moment arm of the telescope. However, due to the type of observations I do (double star and planetary), the weight range of eyepieces is only about 6 oz.

If you have a Dob, or your rig is near the weight limit of your mount, it is another story. You may need to use a "compensatory weight" as you put it, for large differences in eyepiece weights.

Arizona Ken


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McUH
member


Reged: 05/29/13

Re: Eyepieces of similar weight ... what's your range? new [Re: Arizona-Ken]
      #5954805 - 07/04/13 01:51 PM

I don't want to fiddle with any balancing mechanisms, so I just try to have all EP's below 400g, then all is fine and difference between "eyepiece" and "nothing" in diagonal is Ok. And it is not only ballancing but also lifting 1kg eyepieces all the time is not much fun for me .

Yes, it limits me to 70 in 2" and 82 in 1.25" but that is acceptable compromise for comfort.


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Eyepieces of similar weight ... what's your range? new [Re: McUH]
      #5955198 - 07/04/13 07:41 PM

Balance is about the mount... Some mounts tolerate imbalances of a couple of pounds without much difficulty, some are finicky. Myself, I do not tolerate mounts that are finicky about balance.

Jon


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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: Eyepieces of similar weight ... what's your range? new [Re: Jon Isaacs]
      #5955212 - 07/04/13 07:56 PM

Quote:

Balance is about the mount... Some mounts tolerate imbalances of a couple of pounds without much difficulty, some are finicky. Myself, I do not tolerate mounts that are finicky about balance.

Jon



Could you switch from a 13 Nagler T6 (6 ounces) to a 21 Ethos (36 ounces) in your 10" without a balance difficulty? If it was that hard to move, it wouldn't be much pleasure to use it. I think it matters more what percentage of the overall scope weight is represented by the eyepiece.
That 30 ounce difference would be about 2-1/2% of the weight of my 12.5", but a much smaller percentage of the weight of your 25". If you pulled a 21 Ethos out of the 25's focuser, chances are likely the scope would stay put.
If I do that on my 12.5, or you on the 10", depending on where the scope is pointed, the scope would head for the zenith if it was balanced at the altitude where the eyepiece was being used.


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Eyepieces of similar weight ... what's your range? new [Re: Starman1]
      #5955255 - 07/04/13 08:46 PM

Quote:

Quote:

Balance is about the mount... Some mounts tolerate imbalances of a couple of pounds without much difficulty, some are finicky. Myself, I do not tolerate mounts that are finicky about balance.

Jon



Could you switch from a 13 Nagler T6 (6 ounces) to a 21 Ethos (36 ounces) in your 10" without a balance difficulty? If it was that hard to move, it wouldn't be much pleasure to use it. I think it matters more what percentage of the overall scope weight is represented by the eyepiece.
That 30 ounce difference would be about 2-1/2% of the weight of my 12.5", but a much smaller percentage of the weight of your 25". If you pulled a 21 Ethos out of the 25's focuser, chances are likely the scope would stay put.
If I do that on my 12.5, or you on the 10", depending on where the scope is pointed, the scope would head for the zenith if it was balanced at the altitude where the eyepiece was being used.




Don

The entire equation involves more factors than just the weight of the OTA. The size of the bearings, the position of the pads, the diameter and length of of the OTA as well as the initial balance all enter into the equation. The stiffness of the structure is also relevant.

My 10 inch is a stock scope and is top heavy to begin with. My 12. 5 inch has adjustable height altitude bearings, large diameter bearings, a short focal length. The bearings are smooth and free from"sticktion" so it tracks nicely and yet does not suffer balance issues even with the 20 mm Type viewing Omega Centauri. The action probably requires more force than some 12.5 inch scopes but in my experience it's not the force that makes for smooth tracking but the freedom from "sticktion," The action is certainly lighter than the 25 inch.

People praise the large altitude bearings without always realizing that their primary effect is to increase the tracking forces.

With small scopes like my NP-101, it is also possible to setup an alt-az mount so there are no balance issues. Slow motion controls are very helpful because it means tracking at high powers can be done accurately without relying on the action of the mount. Friction that is easily adjusted is helpful too. I have my Portamount setup so i can swap eyepieces like the 20 mm type 2 without a problem.

Jon


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Ebbisham
super member


Reged: 10/02/10

Loc: Surrey, Uk
Re: Eyepieces of similar weight ... what's your range? new [Re: Jon Isaacs]
      #5956628 - 07/05/13 07:37 PM

The closest i could find is my Pentax XL 40 and my Leica ASPH 17.8-8.9 zoom.
The XL 40 is pleasant but surely not the best out there. Unfortunately everything with good reviews in the 30-40mm range seems to weight a ton so i might stick with what i have until i find a mount that tolerates different eyepieces weights better than my Ayo AOK and my Gibraltar.


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iluxo
sage


Reged: 09/23/08

Re: Eyepieces of similar weight ... what's your range? new [Re: karstenkoch]
      #5956763 - 07/05/13 09:29 PM

Rebalancing was one of the factors leading to my decision to buy a set of vixen LVW's - all roughly the same weight from 5 to 42mm and 2" barrels - no swapping adapters either. Weights here http://www.vixenoptics.com/acc/lvw_eyepieces.html

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JustaBoy
Carpal Tunnel


Reged: 06/19/12

Re: Eyepieces of similar weight ... what's your range? new [Re: iluxo]
      #5956778 - 07/05/13 09:41 PM

Hi,

Those are not the actual eyepiece weights for the Vixen LVWs.

For the actual weights of each EP please see this site:

http://agenaastro.com/eyepieces.html?ca_ep_series_bucket=176&camptype=hom...

Vixen has a very poor home page and poor marketing to go along with it.

Such very fine eyepieces, and yet few have ever tried any of them:-(

Clear Skies!

-Chuck


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McUH
member


Reged: 05/29/13

Re: Eyepieces of similar weight ... what's your range? new [Re: Jon Isaacs]
      #5957771 - 07/06/13 03:53 PM

Quote:

Balance is about the mount...




I kind of disagree. Balance is about gravity. If you have well balanced system, adding 1kg anywhere outside centre of gravity will unbalance it. Longer the scope - bigger the imbalance (lever). Lighter the setup, the bigger the imbalance.

Of course you can fight it with stiff bearings (with slow motion controls), with heavy setups. But it is there.

Best solution is to observe from space, no gravity, no problem with balance, and as a bonus no fear of dropping heavy expensive equipment .


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Jon Isaacs
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Eyepieces of similar weight ... what's your range? new [Re: McUH]
      #5957919 - 07/06/13 05:32 PM

Quote:


I kind of disagree. Balance is about gravity. If you have well balanced system, adding 1kg anywhere outside centre of gravity will unbalance it. Longer the scope - bigger the imbalance (lever). Lighter the setup, the bigger the imbalance.




If imbalance is a force or moment, then the weight of the scope has does not directly enter into the equation, the imbalance force is proportional to the length of the lever.

How the scope reacts to the imbalance depends on a number of factors, in a Dob, the diameter of the altitude bearings and the friction are the relevant factors. The weight and coefficient of friction enter into the equation as they affect the friction...

I think it really does come down to balance but not the simple balance one thinks of, rather balancing the forces and the friction... low friction is easily achieved, but not desirable. Some friction is desirable and necessary.

Jon


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McUH
member


Reged: 05/29/13

Re: Eyepieces of similar weight ... what's your range? new [Re: Jon Isaacs]
      #5958066 - 07/06/13 07:20 PM

Quote:

Quote:


I kind of disagree. Balance is about gravity. If you have well balanced system, adding 1kg anywhere outside centre of gravity will unbalance it. Longer the scope - bigger the imbalance (lever). Lighter the setup, the bigger the imbalance.




If imbalance is a force or moment, then the weight of the scope has does not directly enter into the equation, the imbalance force is proportional to the length of the lever.

How the scope reacts to the imbalance depends on a number of factors, in a Dob, the diameter of the altitude bearings and the friction are the relevant factors. The weight and coefficient of friction enter into the equation as they affect the friction...

I think it really does come down to balance but not the simple balance one thinks of, rather balancing the forces and the friction... low friction is easily achieved, but not desirable. Some friction is desirable and necessary.

Jon




Yes, balance itself is just sum of forces, which will be mostly gravity, perhaps some wind too. Aside from balance alone, it is important how the resulting force affects the system (will it slide?). And here mount, weight etc. comes into account. Big friction can render the resulting force incapable of moving scope, but it also makes it harder to move manually (compromise). To move heavier object, you need bigger force, or more precisely, the same force will move heavier object slower. So heavy setup will be more resistant to unbalancing and more precise to track manually despite big friction. And so on.

To cut it short, I prefer lighter setup (for comfort) without too much friction (to make high power manual tracking easier), so for me eyepiece weight matters more.
And I need some good reason why not to spend big money on these 100-120 eyepieces, which are heavy .


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karstenkoch
sage


Reged: 04/21/12

Loc: GMT+9
Re: Eyepieces of similar weight ... what's your range? new [Re: McUH]
      #5958129 - 07/06/13 08:19 PM

Funny! I just used the heavier weight of the ES100 14mm to justify it's acquisition! Previously, my Meade UWA 24mm was the only thing I had above 500 grams. It was way up there all by itself at 825g. Didn't play well with all my other EPs. Recently, I saw the ES100 14 weighs in at 836g. Having been very interested in getting into the 100 degree experience, that was all it took. Now, I'll soon have two nicely complementary EPs that I can use without any rebalancing or tightening so I can get that smooth pan across the cosmos feeling! The 800g range will be my "wide" set. Got another set in the 400g range that is my long eye relief set. Clear skies,

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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Eyepieces of similar weight ... what's your range? new [Re: McUH]
      #5958207 - 07/06/13 09:53 PM

Quote:

And here mount, weight etc. comes into account. Big friction can render the resulting force incapable of moving scope, but it also makes it harder to move manually (compromise). To move heavier object, you need bigger force, or more precisely, the same force will move heavier object slower. So heavy setup will be more resistant to unbalancing and more precise to track manually despite big friction. And so on.




I think the issue here is friction, to move the scope, you are overcoming the friction of the bearings, the "weight" or more properly the moment of inertia, is probably a small factor. This is similar to pushing a car. On flat ground, the reason a car is hard to push is not it's weight but rather the frictional forces that result from the weight.

The weight increases the friction of the bearings in a Dob design but the bearings could be designed so there would be essentially zero force required to move the scope. Decreasing the diameter of the bearing reduces the force required to move the scope. The fact that premium Dobsonians all use very large diameter bearings should be an indication that small forces are not desirable because those large bearings increase the force required to move the scope.

Myself, I set my scopes up so they balance with all my eyepieces as well as with no eyepiece, that means 0 lbs to 2.3lbs. The motion probably requires more force than some might like but force is not a major issue, it's only a couple of pounds and in any event I am able to track at magnifications in the 500x-800x range with what I find to be acceptable precision.

Jon


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dennilfloss
sage


Reged: 01/06/13

Loc: Ottawa, Canada
Re: Eyepieces of similar weight ... what's your range? new [Re: Jon Isaacs]
      #5958399 - 07/07/13 01:56 AM

I only have two eyepieces: the 24-8mm zoom listed at 370g and the 36mm listed at 415g. Hopefully I won't need to rebalance until I add the 2" Luminos barlow (312g).

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McUH
member


Reged: 05/29/13

Re: Eyepieces of similar weight ... what's your range? new [Re: Jon Isaacs]
      #5958701 - 07/07/13 10:43 AM

Quote:

Quote:

And here mount, weight etc. comes into account. Big friction can render the resulting force incapable of moving scope, but it also makes it harder to move manually (compromise). To move heavier object, you need bigger force, or more precisely, the same force will move heavier object slower. So heavy setup will be more resistant to unbalancing and more precise to track manually despite big friction. And so on.




I think the issue here is friction, to move the scope, you are overcoming the friction of the bearings, the "weight" or more properly the moment of inertia, is probably a small factor. This is similar to pushing a car. On flat ground, the reason a car is hard to push is not it's weight but rather the frictional forces that result from the weight.




Long time since I had any physics class, but I think weight (more precisely mass) plays considerable role, and not only in increasing friction. True, with zero friction you can move car, truck, even a train applying small force. But how fast it moves (how much unbalance you perceive) depends on mass. That is why Earth does not move much when I jump and apply force to it .

To be resistant to 0-1kg difference, it must be resistant also to your force to move it. You need to apply bigger push, which is more unbalancing on light system if you push too much. But all in all I think we are talking about the same thing.


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Jon Isaacs
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Re: Eyepieces of similar weight ... what's your range? new [Re: McUH]
      #5958923 - 07/07/13 01:06 PM

Quote:


Long time since I had any physics class, but I think weight (more precisely mass) plays considerable role, and not only in increasing friction. True, with zero friction you can move car, truck, even a train applying small force. But how fast it moves (how much unbalance you perceive) depends on mass.




It has also been a while since I have had a physics class but in my job as a research engineer, I deal with those things I learned in physics on a daily basis.

In this situation, based on some simple moment of inertia calculations for a typical Dob, it looks to me like the forces required to move the scope at tracking speeds is almost entirely used to overcome the friction of the bearings and essentially none of it goes into accelerating the mass of the scope.

I think that is desirable, with the effort going into friction and not momentum, it means that when the observer stops pushing, the scope stops moving. As evidenced by the large bearings on the fancy scopes, friction is actually the observer's friend, it's a question of how much...

Jon


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McUH
member


Reged: 05/29/13

Re: Eyepieces of similar weight ... what's your range? new [Re: Jon Isaacs]
      #5959314 - 07/07/13 05:32 PM

Quote:

In this situation, based on some simple moment of inertia calculations for a typical Dob, it looks to me like the forces required to move the scope at tracking speeds is almost entirely used to overcome the friction of the bearings and essentially none of it goes into accelerating the mass of the scope.




Yes I understand. For example let's say you need force of 1N to overcome friction, then only the part above this will be used for moving scope. My argument is, that if you need to apply 1N+something, your "push precision" will be lower than if you need to apply only lower force (say 0.5N). It will be individual and maybe not issue with these values. But try to move a cabinet and it will be very hard to push just "little bit more than necessary" :-).
Yes, it is necessary to have it smooth, otherwise you can't control it.


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Jon Isaacs
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Re: Eyepieces of similar weight ... what's your range? new [Re: McUH]
      #5960112 - 07/08/13 07:40 AM

Quote:

My argument is, that if you need to apply 1N+something, your "push precision" will be lower than if you need to apply only lower force (say 0.5N).




It is worth recognizing the forces needed to move the scope are in the range of the weight of the eyepiece. If the scope is to stay put with the eyepiece both in and out of the focuser, that means the friction must deal with a differential on that order. So the forces are in the range of a pound or two. It is also worth recognizing that the azimuth force is almost always greater than the altitude force and that balancing the two is part of the key to a smooth scope.

Add in the fact that the big scopes with the big bearings are the ones with the best action, I think friction and somewhat higher forces are the observer's friend and the key is freedom from "sticktion" rather than an absence of friction.

Jon


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