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jtaylor996
scholastic sledgehammer

Reged: 09/02/08

Loc: North Texas
Re: Advantages of side by side setup? [Re: jrcrilly]
#2951247 - 02/26/09 03:40 PM

Quote:

Balance is balance. There's no difference between balancing two identical loads and balancing two widely dissimilar ones. The dual plate is positioned wherever it needs to be to place the center of gravity over the DEC axis.

I disagree. You need more of a lever for dissimilar loads, which requires a longer arm, and thus a greater polar moment of inertia. Mass distribution counts when it comes to applying motor torque...

In this case (2 very different weights at a larger distance between them), it's probably not as large a difference as the difference between having 2 similar weights close versus 2 similar weights far apart. However, it's still there.

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jrcrilly
Refractor wienie no more

Reged: 04/30/03

Loc: NE Ohio
Re: Advantages of side by side setup? [Re: jtaylor996]
#2951286 - 02/26/09 03:58 PM

Quote:

Quote:

Balance is balance. There's no difference between balancing two identical loads and balancing two widely dissimilar ones. The dual plate is positioned wherever it needs to be to place the center of gravity over the DEC axis.

I disagree. You need more of a lever for dissimilar loads, which requires a longer arm, and thus a greater polar moment of inertia.

I can't see that - and none of my side by side setups ever worked that way. The spacing is what it is, determined by the side by side plate. The most commonly used SBS plate is the Losmandy, at 10" spacing. It doesn't matter how much weight I place on either side - the length is 10".

None of that is relevant to balancing, anyway. If the SBS plate were 20" long the DEC inertia when in operation would be greater, but the process of balancing would be identical - place the COG over the DEC axis. Inertia and lever arm, by the way, are reasons to avoid over-and-under rigs. The increased distance between the top of the taller payload and the bottom of the increased counterweight load is more substantial, and affects the more critical RA axis.

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jtaylor996
scholastic sledgehammer

Reged: 09/02/08

Loc: North Texas
Re: Advantages of side by side setup? [Re: jrcrilly]
#2951371 - 02/26/09 04:46 PM

I agree that most are going to be limited by the standard spacing of the available SBS setups (btw, ADM is also 10"); but that's nothing a drill can't solve

I also agree it's not relevant to the actual process of balancing the SBS setup once the offset is fixed.

The point I'm trying to make is that balance isn't just balance. One balanced setup can be better than another balanced setup, based on polar inertia.

I didn't mean to offend. I probably could have been more specific in the original post about what part I was disagreeing with. I'll have to admit that some of my eagerness to point this could possibly have something to do with the fact that I track a car that has the engine mounted completely behind the rear wheels... I spend a lot of time fighting the polar moment trying to maintain the same balance.

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Timber
professor emeritus

Reged: 11/08/08

Loc: SW foothills of Mt. St. Helens
#2956904 - 03/01/09 01:42 PM

Hi Gary,

I gather that the GT-One is no longer being produced, what is the rated weight limit on your two mounts?

Thanks, Richard

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David Pavlich
Transmographied

Reged: 05/18/05

Loc: Mandeville, LA USA
Re: Advantages of side by side setup? [Re: Timber]
#2959959 - 03/02/09 10:46 PM

Here's my take. First, on the last CGE I had, you could use a SBS setup and can tell the mount that there's an offset. HOWEVER, when you do a typical alignment routine, 2 west and cone error east, the mount thinks the offset is cone error and the east side slews exactly 90° from where it should. I tried everything, but it won't do a 2 star/cone error stars alignment. It does the first 2 just fine, but not the other side. So, to solve the problem, ADM makes an adapter that allows a SBS setup with the CGE pointed in its normal position. It works well, but it adds weight.

And as far as balance goes, especially with two very diverse scopes, it's just about impossible. What I finally had to do was decide which side of the meridian I was going to view on and balance it there. And with a CGE, the Dec motor will tell you in no uncertain terms if you're stuff isn't balanced.

Paul Burke solved it by using a triple setup. He placed the heavy scope (SC) right over the mount and the two outers scopes (refractors) outboard. And if you want to argue the case, call Larry at Mountain Instruments. He's dead set against SBS because there's no way you can get the balance correct.

So....I have a TMB 80/480 piggybacked on a 12" LX200 and it balances easily.

David

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Blixx
professor emeritus

Reged: 12/02/07

Loc: CO. Aurora, USA
Re: Advantages of side by side setup? [Re: David Pavlich]
#2959996 - 03/02/09 11:12 PM

Hi all,
I hope that this is not off topic. I am getting a Skywatcher EQ6pro and am thinkg of going the SBS way with my SVP100 and my C80ed. I have read through this thread and have not seen what I would need to get for this mount. Can anyone help me with this. Thanks,
Dan

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mclewis1

Reged: 02/25/06

Re: Advantages of side by side setup? [Re: Blixx]
#2960151 - 03/03/09 01:27 AM

Dan,

If you are going to stay with the smaller vixen compatible rails try one of the following ...
Losmandy VSBS http://www.losmandy.com/v-series.html
Scopestuff DMD6 http://www.scopestuff.com/ss_dmd6.htm

and then one of the following ...
Losmandy DSBS http://www.losmandy.com/secondary.html

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Chris Rowland
professor emeritus

Reged: 02/28/05

Re: Advantages of side by side setup? [Re: mclewis1]
#2960426 - 03/03/09 08:26 AM

The new handcontrol software for the Celestron GEMs has a Mount orientation option that helps with a side by side setup where the OTAs are at right angles to the normal orientation.

Escape to the menus, find the mount Orientation option and set it to East or West.

Then do the alignment normally.

Chris

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Blixx
professor emeritus

Reged: 12/02/07

Loc: CO. Aurora, USA
Re: Advantages of side by side setup? [Re: Chris Rowland]
#2960633 - 03/03/09 10:30 AM

Thanks Mark. So does anyone know if the Skywacher EQ6-pro has an option to orientate to scopes to the east west direction. if i'm correct, the scopes would be in this position. If it doesn't how do you correct for this?
Dan

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jrcrilly
Refractor wienie no more

Reged: 04/30/03

Loc: NE Ohio
Re: Advantages of side by side setup? [Re: Blixx]
#2960742 - 03/03/09 11:29 AM

Quote:

So does anyone know if the Skywacher EQ6-pro has an option to orientate to scopes to the east west direction.

Like most mounts, it has no way of knowing that you have rotated it before alignment so there's no need to do anything. There's no index switch. The CGE is a rare exception to this.

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CounterWeight
Postmaster

Reged: 10/05/08

Loc: Cloudyopolis, OR.
Re: Advantages of side by side setup? [Re: jrcrilly]
#2960795 - 03/03/09 11:46 AM

Does the CGE Pro also have limit switches like the CGE? Just curious.

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Blixx
professor emeritus

Reged: 12/02/07

Loc: CO. Aurora, USA
Re: Advantages of side by side setup? [Re: CounterWeight]
#2960864 - 03/03/09 12:09 PM

John,
Am I correct in thinking that the scopes would be 90* off when you use the SBS saddle? If this is true, wouldn't your gotos be off by 90*? And how would you correct this.? It just looks to me that the scopes would not be pointing in the right direction, not north south like when you use a standard dovetail.
Dan

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jrcrilly
Refractor wienie no more

Reged: 04/30/03

Loc: NE Ohio
Re: Advantages of side by side setup? [Re: Blixx]
#2960886 - 03/03/09 12:15 PM

Quote:

John,
Am I correct in thinking that the scopes would be 90* off when you use the SBS saddle? If this is true, wouldn't your gotos be off by 90*? And how would you correct this.? It just looks to me that the scopes would not be pointing in the right direction, not north south like when you use a standard dovetail.
Dan

The mount has no way of telling what the initial position is. It presumes that you are beginning with the OTA pointing North, and does the first alignment star slew based on that presumption. If, for some reason, you begin with the OTA pointed some other direction then the first alignment star slew will be way off and will require substantial correction to center the alignment star. After you center the alignment stars, all will be well again. Goto operation is based on the alignment stars, not on any initial, pre-alignment position.

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Blixx
professor emeritus

Reged: 12/02/07

Loc: CO. Aurora, USA
Re: Advantages of side by side setup? [Re: jrcrilly]
#2960896 - 03/03/09 12:18 PM

So once you go through the alignment stars the mount will know where you are and not care that the scopes were 90 out at he begining, is this correct?
Dan

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jrcrilly
Refractor wienie no more

Reged: 04/30/03

Loc: NE Ohio
Re: Advantages of side by side setup? [Re: Blixx]
#2960905 - 03/03/09 12:21 PM

Quote:

So once you go through the alignment stars the mount will know where you are and not care that the scopes were 90 out at he begining, is this correct?
Dan

Yes. There's no reason to begin with the OTA pointed sideways, though. Alignment will be quicker and easier if you begin with the OTA pointed North.

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Blixx
professor emeritus

Reged: 12/02/07

Loc: CO. Aurora, USA
Re: Advantages of side by side setup? [Re: jrcrilly]
#2960918 - 03/03/09 12:25 PM

I have not gotten the eq6-pro yet, so this may be a dumb question. Does the eq6-pro have index marks like the cg5asgt mount that I have now. So I gues my question is, even if it does have index marks, you line them up(even though the scopes will be 90 out) then go through the alignment as normal?
Dan

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jrcrilly
Refractor wienie no more

Reged: 04/30/03

Loc: NE Ohio
Re: Advantages of side by side setup? [Re: Blixx]
#2960929 - 03/03/09 12:30 PM

Quote:

I have not gotten the eq6-pro yet, so this may be a dumb question. Does the eq6-pro have index marks like the cg5asgt mount that I have now. So I gues my question is, even if it does have index marks, you line them up(even though the scopes will be 90 out) then go through the alignment as normal?
Dan

Better to ignore the index marks and point the OTA North. Alignment will be quicker and easier. The mount, having no index switches, will never know that you are not using the index marks.

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donsinger1
sage

Reged: 10/28/07

Re: Advantages of side by side setup? [Re: jrcrilly]
#3018036 - 04/01/09 01:41 PM

So, if I understand you correctly, in using the side by side configuration, with my EM11 and Temma II Jr, I would have to tell a program like TheSky6 or Astromist that the DEC is offset by 90 degrees?

Thanks,
Don

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jrcrilly
Refractor wienie no more

Reged: 04/30/03

Loc: NE Ohio
Re: Advantages of side by side setup? [Re: donsinger1]
#3018164 - 04/01/09 02:35 PM

Quote:

So, if I understand you correctly, in using the side by side configuration, with my EM11 and Temma II Jr, I would have to tell a program like TheSky6 or Astromist that the DEC is offset by 90 degrees?

Nope. Neither the mount nor TheSky knows or cares that the DEC is offset; they just know where the telescope is pointed. Just align or synch as usual. Works fine with my Temma NJP and TheySky6 in sidebyside mode.

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donsinger1
sage

Reged: 10/28/07

Re: Advantages of side by side setup? [Re: jrcrilly]
#3018270 - 04/01/09 03:15 PM

Great!

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