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Hi all, sorry another newbie question,
When referring to the 60lb maximum capacity weight of the G11, are the balance weights including in that total, or is the 60lb total just the telescope and add-ons..
Promise i will find something more technical to ask when the UK weather decides to let us do some star gazing!
Thanks
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That's the total weight of equipment only, not including counterweights. It is supposed to be rated for 60 lbs ?imaging payload, though I am not sure how that's determined.
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I'd like some definition on that specification, too, Arun.
Generally the accepted standard for the Asian mounts has been 1/2 of the rating.
So I kept my weight from the clamp up less than 15 pounds for my AVX.
But now with my 811 I'm way below 1/2 of the mounts rating. And 3.2 times below the 50 pound rating.
My telescope is like a fly on an elephants back now.
--
SonnyE
(I suggest viewed in full screen)
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I'd actually like a definition similar to how AP defines it for their Mach 2 - they have two graphs, one for RA the other for DEC:
The capacity is not a single number but the lower of the two numbers in the RA and DEC graph.?
I currently own two mounts - the 811 and the AP Mach 1. My current set up is well under half the weight of either. I also have experience from other members of my club who use Asian mounts. Both the Losmandy and the AP mount are clearly better than similarly specified Asian mounts.?
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>>>
It is supposed to be rated for 60 lbs ?imaging payload, though I am not sure how that's determined.
That's pretty much it. Losmandy specs for max payload is for the Telescope side of the mount, so it does not include the counterweight side or the counterweights.
Yes the tube length can play a role, but we don't really customers putting 20" tubes on the G11
I will see if we have more details
Brian
That's the total weight of equipment only, not including counterweights. It is supposed to be rated for 60 lbs ?imaging payload, though I am not sure how that's determined.
-- Brian?
Brian Valente portfolio
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Brian,
While you're looking into more details, can you also include piggybacked devices as they effect a greater moment than devices on the saddle.? For example, a hefty guide scope piggybacked on a fat SCT.
I use a side-by-side plate to avoid this.? Also allows me to balance the load better as.
John
On Sunday, 30 August 2020, 11:06:52 am AEST, Brian Valente <bvalente@...> wrote:
>>>
It is supposed to be rated for 60 lbs ?imaging payload, though I am not sure how that's determined.
That's pretty much it. Losmandy specs for max payload is for the Telescope side of the mount, so it does not include the counterweight side or the counterweights.
Yes the tube length can play a role, but we don't really customers putting 20" tubes on the G11
I will see if we have more details
Brian
That's the total weight of equipment only, not including counterweights. It is supposed to be rated for 60 lbs ?imaging payload, though I am not sure how that's determined.
-- Brian?
Brian Valente portfolio
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Hi John
The AP graph (Arun referenced earlier) is a good illustration and fairly accurate for Losmandy as well, just substitute the weight capacity of the G11 for the Mach2.
here it is, hopefully Roland won't mind i borrowed it for posting here ;)
Brian,
While you're looking into more details, can you also include piggybacked devices as they effect a greater moment than devices on the saddle.? For example, a hefty guide scope piggybacked on a fat SCT.
I use a side-by-side plate to avoid this.? Also allows me to balance the load better as.
John
On Sunday, 30 August 2020, 11:06:52 am AEST, Brian Valente < bvalente@...> wrote:
>>>
It is supposed to be rated for 60 lbs ?imaging payload, though I am not sure how that's determined.
That's pretty much it. Losmandy specs for max payload is for the Telescope side of the mount, so it does not include the counterweight side or the counterweights.
Yes the tube length can play a role, but we don't really customers putting 20" tubes on the G11
I will see if we have more details
Brian
That's the total weight of equipment only, not including counterweights. It is supposed to be rated for 60 lbs ?imaging payload, though I am not sure how that's determined.
-- Brian?
Brian Valente portfolio
-- Brian?
Brian Valente portfolio
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PS
>>>can you also include piggybacked devices as they effect a greater moment than devices on the saddle.?
I included that graph because it also shows how to measure the effect of piggyback scopes as well
On Sat, Aug 29, 2020 at 9:39 PM Brian Valente via <bvalente= [email protected]> wrote: Hi John
The AP graph (Arun referenced earlier) is a good illustration and fairly accurate for Losmandy as well, just substitute the weight capacity of the G11 for the Mach2.
here it is, hopefully Roland won't mind i borrowed it for posting here ;)
Brian,
While you're looking into more details, can you also include piggybacked devices as they effect a greater moment than devices on the saddle.? For example, a hefty guide scope piggybacked on a fat SCT.
I use a side-by-side plate to avoid this.? Also allows me to balance the load better as.
John
On Sunday, 30 August 2020, 11:06:52 am AEST, Brian Valente < bvalente@...> wrote:
>>>
It is supposed to be rated for 60 lbs ?imaging payload, though I am not sure how that's determined.
That's pretty much it. Losmandy specs for max payload is for the Telescope side of the mount, so it does not include the counterweight side or the counterweights.
Yes the tube length can play a role, but we don't really customers putting 20" tubes on the G11
I will see if we have more details
Brian
That's the total weight of equipment only, not including counterweights. It is supposed to be rated for 60 lbs ?imaging payload, though I am not sure how that's determined.
-- Brian?
Brian Valente portfolio
--
Brian?
Brian Valente portfolio
-- Brian?
Brian Valente portfolio
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Thanks all, looks like I won't have to worry with my kit.
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Thanks for the graph. To balance the scope would you use heavier weights closer to the RA axis to minimise moment of inertia or lighter weights further from the RA axis to reduce overall weight on the RA?
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Heavier weights closer in every time ¨C it¡¯s the moment of inertia that gets you. ? David ?
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From: [email protected] [mailto:[email protected]] On Behalf Of marc@...
Sent: 02 September 2020 13:00
To: [email protected]
Subject: Re: [Losmandy_users_io] Maximum weight ? Thanks for the graph. To balance the scope would you use heavier weights closer to the RA axis to minimise moment of inertia or lighter weights further from the RA axis to reduce overall weight on the RA?
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>>> Heavier weights closer in every time ¨C it¡¯s the moment of inertia that gets you.
agreed
Heavier weights closer in every time ¨C it¡¯s the moment of inertia that gets you. ? David ? From: [email protected] [mailto:[email protected]] On Behalf Of marc@...
Sent: 02 September 2020 13:00
To: [email protected]
Subject: Re: [Losmandy_users_io] Maximum weight ? Thanks for the graph. To balance the scope would you use heavier weights closer to the RA axis to minimise moment of inertia or lighter weights further from the RA axis to reduce overall weight on the RA?
-- Brian?
Brian Valente portfolio
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Correct - angular momentum is I*Omega where I is the moment of inertia.
For the simple case of a counterweight on the shaft, angular momentum is M*L^2*Omega where M is the Mass, L is how far it is placed, and Omega is the angular velocity.
For a given angular velocity, it is much harder to make a guiding correction when the mass is placed father from the point of rotation (either the RA or DEC axis).
This is the reason why that AP graph shows allowed weight going down with length of scope and diameter. Even for the same mass, it becomes harder and harder for guiding corrections to be effective if diameter or length increase.
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Sorry, but it is my opinion oft times these details get overly worried about.
I recently Piggybacked my Guide Scope up on my ED80T CF which I put WO rings on a while back. The WO rings gave me the ability with M6 threaded holes.
So a DUP7 D-bar, and two DVR66 mountings. Total weigh change registers as 17.9 pounds (8.119 kilo) on the weight watchers digital scale. (sorry, it's what I've got. Please Don't mention my trespass to the wife.)
So my GM811G still has a 2.7932 ratio advantage over my total Photographic Load.
Or as I like to think about it, maybe a fat fly on an elephants back now. ;^)
I have every confidence in Scott's engineering, and my mounts abilities to handle anything I might ask of it. (Which won't ever be excessive. I don't have that much gold or silver.)
Something I noticed right away about my mount was how the Gemini II ramps up in speed. I liken it to the soft-start of industrial systems I use to work with.
The Gemini II is Light-years ahead of the slam-bang of my past Asian mount.
To me, the function of soft-starting not only aids the power supply in not having a huge current load imposed on it, but in particular easing the mechanics of the mount into motion.
In other words, the moment of Inertia, as you folks like to call it, is eased into motion without the 5-8 times surge of current we in the electrical industry saw.
A small piece of trivia for you: A 100 watt incandescent light bulb had a 17 amp inrush at the moment it was energized until it's element became white hot, the current tapering down rapidly.
So that "Moment of Inertia", to me is the ramp up of current and magnetic reluctance helping the horse dig in it's hooves. Maybe that clarifies why we have a saddle clamp on our mounts?
Keep your butt planted. 8^0 LOL!
Clear Skies!
--
SonnyE
(I suggest viewed in full screen)
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You are certainly right not to worry about it for your system. But it is definitely an issue when you go with larger loads or smaller image scales.
A simple thought experiment - is it easier to control a mass at the end of a long rod or a short rod if you are rotating it with your hand? The same logic applies to counterweights.
The issue in autoguiding isn't soft starting from rest to sidereal rate. It is (at least in RA) precisely slowing or speeding up the axis in response to the movement of the guide star. That is an angular acceleration, which is achieved through the servo motor applying a torque. The greater the moment of inertia, the greater the torque and the more demand is placed on the servo motor. Overshoots and undershoots also become harder to correct since there is more inertia involved to correct. Hence the advice to place counterweights closer in. If you place twice the mass half way up the shaft to balance your scope, you will balance it just as well, but will have half the moment of inertia and hence less torque required to correct.??
On the DEC axis side, counter weights don't matter since the scope balances itself. But for the same weight, a longer scope will give you more problems with guiding.
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Dave_Kentsbeer
David C. Partridge