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Eyepieces of similar weight ... what's your range?

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#1 karstenkoch

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Posted 03 July 2013 - 09:48 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?

#2 Mark9473

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Posted 03 July 2013 - 10:15 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).

#3 Sarkikos

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Posted 03 July 2013 - 11:45 AM

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

#4 spencerj

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Posted 03 July 2013 - 12:59 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.

#5 Sarkikos

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Posted 03 July 2013 - 01:15 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

#6 Starman1

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Posted 03 July 2013 - 01:19 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.

#7 cjc

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Posted 03 July 2013 - 02:22 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".

#8 Sorny

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Posted 03 July 2013 - 02:29 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...

#9 karstenkoch

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Posted 03 July 2013 - 02:34 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!

#10 Jon Isaacs

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Posted 03 July 2013 - 04:24 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

#11 Sarkikos

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Posted 03 July 2013 - 07:05 PM

Karsten,

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

#12 Arizona-Ken

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Posted 03 July 2013 - 08:01 PM

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

Arizona Ken

#13 karstenkoch

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Posted 03 July 2013 - 08:03 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... :idea:

#14 Sarkikos

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Posted 04 July 2013 - 10:21 AM

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

#15 Wade J

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Posted 04 July 2013 - 10:52 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.

#16 Arizona-Ken

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Posted 04 July 2013 - 11:30 AM

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

#17 McUH

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Posted 04 July 2013 - 12:51 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 :shameonyou:.

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

#18 Jon Isaacs

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Posted 04 July 2013 - 06:41 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

#19 Starman1

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Posted 04 July 2013 - 06:56 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

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.

#20 Jon Isaacs

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Posted 04 July 2013 - 07:46 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

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

#21 Ebbisham

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Posted 05 July 2013 - 06:37 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.

#22 iluxo

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Posted 05 July 2013 - 08:29 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.vixenopti..._eyepieces.html

#23 JustaBoy

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Posted 05 July 2013 - 08:41 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.co...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

#24 McUH

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Posted 06 July 2013 - 02:53 PM

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 :smirk:.

#25 Jon Isaacs

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Posted 06 July 2013 - 04:32 PM

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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