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Equipment Discussions >> Mounts

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schluterdude
super member


Reged: 08/05/13

Loc: Centerville, OH
Re: Arrrgh new [Re: shakafell]
      #6157001 - 10/25/13 09:02 AM

I would.... If you tighten them too much, kinda defeats the purpose...

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MartinTreadgold
super member


Reged: 04/17/13

Loc: Netherlands
Re: Arrrgh [Re: shakafell]
      #6161873 - 10/28/13 05:01 AM

should be firm, but don't force it.

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Live_Steam_Mad
sage


Reged: 07/24/07

Loc: Moss Bank, St.Helens, England
Re: Arrrgh new [Re: MartinTreadgold]
      #6180269 - 11/07/13 12:51 AM

Hi, can someone confirm please that the Celestron Advanced VX (AVX) mount has NO "back drift" / "rubber banding" at say 250x ?

My local friend Jon H. has an LX90 that we are having rubber banding problems with ;-

http://tech.dir.groups.yahoo.com/neo/groups/lx90/conversations/topics/84960

i.e. I make the star go to the left edge of the FOV in the 8mm eyepiece and then come back to the centre and it stays there, same with the star being made to go to the right hand edge of the FOV and then coming back to centre it stays there also, BUT with the vertical direction, it does NOT cooperate properly. When I ask it to make the star go to the top of the FOV and then bring it back to the centre, it then drifts downwards about 1/4 of the FOV towards the bottom edge, and MUCH worse when make the star go down to the bottom edge of the FOV and then back up to the centre, it drifts back down by 5/8 or nearly 2/3 of the FOV until it's near the bottom edge of the FOV. I trained drives carefully at 250x and did callibrate motors and GOTO's are pretty accurate and tracking at 250x is good but it does this rubber banding thing and it annoys me.

Do the AVX / CG5 / EQ-5 / HEQ5 / EQ6 / GM11 / GM8 / LXD75 mounts do this?

I want to buy a GEM that does NOT have this rubber banding issue at all, I was going to maybe buy an LX90 but the problems are putting me off and I might well get a GEM instead.

Regards,

Alistair G.

Edited by Live_Steam_Mad (11/07/13 12:55 AM)


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Skunky
sage


Reged: 09/16/13

Re: Arrrgh new [Re: Live_Steam_Mad]
      #6180288 - 11/07/13 01:26 AM

It's called backlash.. and all those mounts listed will have backlash..

You can spend $15,000 on a AP1100 with encoders if you don't want backlash... or any belt driven mount.. 10 micron too.. Your not going to get a backlash free mount under 8k, At least not an Equatorial Mount.


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orlyandico
Postmaster
*****

Reged: 08/10/09

Loc: Singapore
Re: Arrrgh new [Re: Skunky]
      #6180307 - 11/07/13 01:48 AM

Yup, backlash in RA is normal, and expected. My Mach1 has backlash in RA (not much, but there). In theory I can tune it out with the backlash setting, but why bother.. it would screw up the autoguiding.

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rmollise
Postmaster
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Reged: 07/06/07

Re: Arrrgh new [Re: Live_Steam_Mad]
      #6180486 - 11/07/13 08:15 AM

Quote:

BUT with the vertical direction, it does NOT cooperate properly. When I ask it to make the star go to the top of the FOV and then bring it back to the centre, it then drifts downwards about 1/4 of the FOV towards the




"Vertical" is meaningless in this context, so I can't tell you which axis is affected, but I would guess declination. A little backlash (what is "rubberbanding"?), especially in dec, is to be expected in this and similar mounts at this price level.


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Live_Steam_Mad
sage


Reged: 07/24/07

Loc: Moss Bank, St.Helens, England
Re: Arrrgh new [Re: rmollise]
      #6193539 - 11/13/13 09:28 PM

Quote:

"Vertical" is meaningless in this context, so I can't tell you which axis is affected, but I would guess declination. A little backlash (what is "rubberbanding"?), especially in dec, is to be expected in this and similar mounts at this price level.




In the above link I explained what I mean by rubber banding. You move the star in the Alt axis on the LX90 (it's Alt-Az mounted, no wedge) from the bottom of the eyepiece to the centre, and then when you let go of the handset, the star drifts back down to 2/3 of the way towards the bottom edge of the eyepiece of my 8mm Radian (250x).

I found out what is happening in Jon's LX90, it's due to the spring loaded worm block on the Alt axis deflecting more than 1/16th inch up and down every time you reverse the Alt drive, which results in this IMHO enormous backlash. The spring loading is NOT adjustable BTW, only the worm end play and pivot screws can be adjusted.

Since the AVX mount does not have this spring loaded worm block that the LX90 does, so I have been told, and this seems to be true looking at the pictures of the Dec axis on the AVX stripped down to the worm housing / block, then I was hoping that the backlash would be much less.

If you have an AVX mount, can you tell me please how much backlash you are finding in each of the 4 axes please, at 250x or so, i.e. for example, 1/4 of the way from centre to edge of the Field Of View (FOV) etc, or by how many Jupiter diameters
if the backlash is really small, when moving a star to the near the edge of the FOV and then back to the centre then letting go of the handset and seeing if the star drifts back /forth again (backdrift, backlash, rubber banding). I suppose a reticle eyepiece (crosshairs) would make this easier to see but it's not crtitical at all to be able to see what backlash is there.

If anyone else also would care to tell me what their AVX is like in this regards I would also really appreciate it so I can get representitive sample of what the AVX mounts out there are like with this aspect of things.

I really like the mount with it's 2" sturdy legs, black color, more powerful motors than CG-5, All Star Polar Alignment (ASPA) where I don't need to be able to see Polaris (which I need when I observe from the bottom of the garden to clear the house to see things lower down in the East), Guided Tour, good Goto's and tracking, just about affordable price, low weight, etc.

Regards,

Alistair G.

Edited by Live_Steam_Mad (11/13/13 09:34 PM)


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Carl N
sage
*****

Reged: 03/18/12

Loc: San Diego, CA
Re: Arrrgh new [Re: Live_Steam_Mad]
      #6193779 - 11/13/13 11:54 PM

Alistair,
If you check your owners manual, or download one, you will find there are settings in the menu for minimizing and managing the backlash. The instructions on how are a little light, but by trial and error I was able to adjust the backlash down. Also, if you be sure that you make your final adjustment in the correct directions, usually down and right as described in the manual, you won't see what you call rubber banding.

Carl


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Carl N
sage
*****

Reged: 03/18/12

Loc: San Diego, CA
Re: Arrrgh new [Re: Live_Steam_Mad]
      #6193790 - 11/14/13 12:03 AM

That down and right thing, again usually and I will leave the complexities to the manual, is really important.

Understand that by doing this there should be NO backlash. The reason is backlash or your rubber banding is really just the worm having to take up the "slack" on the gear when it switches direction. If you make your final adjustment in the direction the worm will turn when tracking, then there is no slack to take up. The worm just keeps turning at tracking rate in the same direction it was going in slewing rate when you made the final adjustment.

My guess is that it isn't that simple on an alt-az mount. Don't know.

Edited by Carl N (11/14/13 12:06 AM)


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dragonslayer1
Pooh-Bah


Reged: 02/25/12

Loc: SLC, UT
Re: Arrrgh new [Re: Carl N]
      #6194019 - 11/14/13 06:53 AM

I thought it was up and right??
Kasey


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mclewis1
Thread Killer
*****

Reged: 02/25/06

Loc: New Brunswick, Canada
Re: Arrrgh new [Re: dragonslayer1]
      #6194042 - 11/14/13 07:08 AM

It actually doesn't matter what direction (up/right, down/left, etc.) is used as long as ...

1) you're consistent in using that direction to finish all movements during your initial alignment
2) it matches the Goto Approach direction set (under Scope Setup)


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rmollise
Postmaster
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Reged: 07/06/07

Re: Arrrgh new [Re: Live_Steam_Mad]
      #6194159 - 11/14/13 09:05 AM

Quote:



In the above link I explained what I mean by rubber banding.




What you are seeing is backlash, and it is completely unrelated to the "rubber-banding" in your friend's Meade mount. For visual, you can enter backlash compensation into the hand control. For imaging, it's best to leave that alone. The mount guides well as is. I haven't tried to quantify the backlash in my VX, but it is less than in my CG5, and is only really apparent on the declination axis. Whether declination corresponds to your "vertical," only you can determine.

Edited by rmollise (11/14/13 09:09 AM)


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bunyon
Post Laureate
*****

Reged: 10/23/10

Loc: Winston-Salem, NC
Re: Arrrgh new [Re: rmollise]
      #6194192 - 11/14/13 09:25 AM

Yeah, I just want to echo that turning off backlash compensation when guiding is important. I had it set, then did some guiding and the thing went crazy. Terrible autoguiding. Turned the backlash compensation off and it guides fine again.

For visual, I'm not sure why you'd worry about it. Just get used to how the mount behaves and compensate for it. But you can mostly eliminate it by playing around with backlash compensation under menu (I think it's under scope setup, but the manual will get you there).


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carlcat
sage
*****

Reged: 11/26/07

Loc: Northern California
Re: Arrrgh new [Re: bunyon]
      #6206212 - 11/20/13 06:21 PM

I'm planning of buying a VX mount but I'm not familar with goto mounts. My past mounts were just dual axis drives powered by an AC/DC adapter(6volt) and I used 4 D batteries on the rare times I left my back yard to check out deep sky. Now that I plan on getting this mount I'm not sure how to power it. Can I use a AC/DC converter like this particular one that I happen to own? http://www.amazon.com/Replacement-Monitor-Adapter-Power-Supply/dp/B0023Y9EQC/...
If not, what AC/DC converter adapter can I use? Also, I will now need some kind of DC power supply for the rare times I go to a dark site(mostly into moon and planets). Are there any other power supplies that I can use other than the Celestron power tanks? The thought of powering a tank all year for the one or two times I go to a dark site seems wasteful. Another concern is ruining the tank by under of over charging. Are there tanks that have an over charge protection where I can just leave it plugged in all the time? Do I have to worry frying my hand control by too many amps or as long as it's 12volts and over 3 amps I need not worry about too many amps? Thanks, Carl


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SkipW
sage


Reged: 02/03/11

Loc: Oklahoma, USA
Re: Arrrgh new [Re: carlcat]
      #6206846 - 11/21/13 01:44 AM

Quote:

... Now that I plan on getting this mount I'm not sure how to power it. Can I use a AC/DC converter like this particular one that I happen to own? http://www.amazon.com/Replacement-Monitor-Adapter-Power-Supply/dp/B0023Y9EQC/...
If not, what AC/DC converter adapter can I use? Also, I will now need some kind of DC power supply for the rare times I go to a dark site(mostly into moon and planets). Are there any other power supplies that I can use other than the Celestron power tanks? The thought of powering a tank all year for the one or two times I go to a dark site seems wasteful. Another concern is ruining the tank by under of over charging. Are there tanks that have an over charge protection where I can just leave it plugged in all the time? Do I have to worry frying my hand control by too many amps or as long as it's 12volts and over 3 amps I need not worry about too many amps? Thanks, Carl



No such thing as "too many amps" capacity other than mundane matters of weight and cost. If your supply is "12V" (so-called 12V is probably between about 12V and 14V), the load (your mount) will draw the current it needs; if the supply has more current capacity, that's just cushion - it won't be used.

If the DC plug on your AC/DC adapter is the right size and polarity it should work fine. If not, you can adapt it, but do be careful of the polarity!

If you're starting from scratch, a small, cheap 7 Ah jump-start battery pack with built-in charging circuit and cigarette lighter receptacle from WalMart or auto supply store may be just the ticket. With this, if you're at home, you won't need an extension cord to hassle with and possibly trip over to power the mount, and it will power your mount all night long in a remote site to boot! As for leaving it plugged in all the time, I recharge mine overnight after using it, and every now and then if not used for many weeks at a time, but not constantly. It was cheap, about $40, but still going strong after three years. It may stand being constantly on charge, but I don't want to test this, and is easy enough to not do.


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carlcat
sage
*****

Reged: 11/26/07

Loc: Northern California
Re: Arrrgh [Re: SkipW]
      #6207576 - 11/21/13 01:22 PM

Quote:

Quote:

... Now that I plan on getting this mount I'm not sure how to power it. Can I use a AC/DC converter like this particular one that I happen to own? http://www.amazon.com/Replacement-Monitor-Adapter-Power-Supply/dp/B0023Y9EQC/...
If not, what AC/DC converter adapter can I use? Also, I will now need some kind of DC power supply for the rare times I go to a dark site(mostly into moon and planets). Are there any other power supplies that I can use other than the Celestron power tanks? The thought of powering a tank all year for the one or two times I go to a dark site seems wasteful. Another concern is ruining the tank by under of over charging. Are there tanks that have an over charge protection where I can just leave it plugged in all the time? Do I have to worry frying my hand control by too many amps or as long as it's 12volts and over 3 amps I need not worry about too many amps? Thanks, Carl



No such thing as "too many amps" capacity other than mundane matters of weight and cost. If your supply is "12V" (so-called 12V is probably between about 12V and 14V), the load (your mount) will draw the current it needs; if the supply has more current capacity, that's just cushion - it won't be used.

If the DC plug on your AC/DC adapter is the right size and polarity it should work fine. If not, you can adapt it, but do be careful of the polarity!

If you're starting from scratch, a small, cheap 7 Ah jump-start battery pack with built-in charging circuit and cigarette lighter receptacle from WalMart or auto supply store may be just the ticket. With this, if you're at home, you won't need an extension cord to hassle with and possibly trip over to power the mount, and it will power your mount all night long in a remote site to boot! As for leaving it plugged in all the time, I recharge mine overnight after using it, and every now and then if not used for many weeks at a time, but not constantly. It was cheap, about $40, but still going strong after three years. It may stand being constantly on charge, but I don't want to test this, and is easy enough to not do.



Thanks for info. On my AC/DC adapter, there is no polarity marker on the tip. Is there any way to find out the polarity? I'm assuming it needs to show + matching Tip. I do have another variable AC/DC adapter that goes up to 12volts, the polarity is switchable at the prong which is presently set at + and Tip on the same side. I'm assuming it means positive. The only problem is this one is only 3amps, I'm guessing borderline amps? The largest scope I'll be using on this mount is a 7" meade Mak, the weight is 17lbs. No camera or heavy second scopes, just one giant 24oz eyepiece.
If I buy the jump start battery pack, does it come with the proper wire/tip/polarity to attach to my hand control or do I need to buy something else? I'm assuming I attach the power source to my hand control first like my previous mounts or do I attach the power source dirctly into the mount and it will power the hand control as well. Thanks again.


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Pak
super member
*****

Reged: 09/15/12

Loc: The Great Arc
Re: Arrrgh [Re: mclewis1]
      #6207917 - 11/21/13 04:43 PM

Quote:

It actually doesn't matter what direction (up/right, down/left, etc.) is used as long as ...

1) you're consistent in using that direction to finish all movements during your initial alignment
2) it matches the Goto Approach direction set (under Scope Setup)




I am not so sure I agree with this. The reason for up and right is it takes up the backlash in the proper direction. If you went the other way and centered a star and then watched for a bit you would see it drift while it takes up the backlash so the star wouldn't be centered any longer. Up and right you center the star and it stays there. The mount compensates for the backlash then and puts the objects much closer to center.

At least that has been my experience and follows with what the manufacturer recommends.


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dragonslayer1
Pooh-Bah


Reged: 02/25/12

Loc: SLC, UT
Re: Arrrgh [Re: Pak]
      #6207992 - 11/21/13 05:17 PM

if your set-up for go-to is positive, positive,,,,, which way is positive??? , Kasey

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SunBlack
scholastic sledgehammer


Reged: 05/05/11

Loc: Rome (IT)
Re: Arrrgh [Re: dragonslayer1]
      #6209668 - 11/22/13 03:03 PM

Will PEC playback does/replicates Dec corrections i did on training, on AVX?

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rmollise
Postmaster
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Reged: 07/06/07

Re: Arrrgh [Re: SunBlack]
      #6209807 - 11/22/13 04:22 PM

Quote:

Will PEC playback does/replicates Dec corrections i did on training, on AVX?




Uhhhh... Hard to say, muchacho. If you're asking whether declination corrections are recorded and played back, the answer is "yes."


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