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Vixen Polaris load capacity

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#26 orlyandico

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Posted 24 November 2012 - 04:18 PM

I saw a photo somewhere when I still had my Polaris.

I think the ETX125 will be not a problem at all. It is short physically and presents a small moment arm.

I have not tried a C8 on the Polaris. The C9.25 was way too much, a 100ED is ok-ish, still not optimal, but can be lived with. The 100ED has a 1-meter long tube, so the ETX125 should not pose a challenge at all.

#27 Ducky62

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Posted 24 November 2012 - 11:03 PM

Used mine last night - extremely lightweight and reasonable stable. I added a simple Celestron motor drive for tracking.


A four year old thread and finaly a picture! :grin: Carved out of a solid block of aluminum this one may have a higher payload but I still would not stick a C-8 on it. ;)


Hey! You have the early "New Polaris". What 'scope came on that? I have 3 Polaris mounts but only one of them is like the one pictured.No lat scale but it is so much nicer than the later two. So it is milled and not cast? I need one of those original drives. Have you ever measured the PE? I have suspicions the early ones are whole different animals.

#28 roscoe

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Posted 25 November 2012 - 08:09 AM

I have some weight info that I got from somewhere on the net, that lists a Polaris at 10 lbs, a GP at 16, a SP at 18, and a GPDX at 22.
I had a Celestron C-80 on mine, it was fine for that scope.
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#29 Geo.

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Posted 25 November 2012 - 01:44 PM

To get the ETX125 to balance correctly the tube's center of gravity should be a little forward of the center of the mount's Dec axis. IIRC the 125 has a rather queer ring size. Probably easiest to add a Vixen format dovetail saddle and a 6" bar to the ETX.

An 11-13 pound C8 is a bit too much I'm afraid. A C4 or 6 would be fine.

I think you'll find that the Polaris is machined from aluminum alloy castings not from billet. As mentioned the RA worm wheel is 130 teeth, think Dec is 70.

The Polaris was sold under Celestron and Tasco scopes. Think the C6 was sold on it. Tasco sold a Synta made drive for it. It was very similar to the EQ-3, CG-4 drive.

I don't understand the comments about early models. There has only been one Polaris configuration. Although, I've seen them in three colors.

#30 orlyandico

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Posted 25 November 2012 - 02:02 PM

i had a polaris and it was definitely 144 teeth...

#31 zjc26138

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Posted 25 November 2012 - 02:14 PM

Beside mounting my WO 110 on the Vixen, I also mount a Meade 8in SCT. I forget what model it is. I had the mount setup in Alt-Az. It handled the scope ok. It was better than not mounting the scope at all.

#32 ohioalfa64

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Posted 27 November 2012 - 05:04 PM

Thanks for the advice on the ETX-125 mounting. What if instead I attempted at 150mm iOptron Mak on the Polaris? It is 20 inches and somewhere around 14 lbs without the standard Finderscope or Aluminum Dew shield (another 7 inches longer). Instead of answering in yes or no terms, tell me what impact I would face by doing this. Will it break; do I need another weight on the couterbalance, etc. A laser pointer and Astrozap wrap dew shield reduce weight and decrease the forward moment arm. Or am I just creating a monster?

#33 Geo.

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Posted 27 November 2012 - 11:01 PM

I wouldn't worry about breaking it with a static load. It might just be a bit shaky, like a C9.25 on a CG-5. The Dec axle is about the same size as the Triumph spindles Chapman used on his early F1 cars. Of course, those spindles did occasionally fail ... no high speed turns please.

#34 Starhawk

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Posted 28 November 2012 - 10:51 PM

I just posted the pix of my own vixen Polaris mods in the Super Polaris drive thread.

-Rich

#35 StarStuff1

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Posted 28 November 2012 - 11:33 PM

Years ago I acquired a used Polaris mount. I called Celestron Customer Service (remember those days?)to ask about the mount capacity. IIRC the lady said 24-25lbs. I was surprised to hear this. The OTA I mounted on it was a 114mm f/12.5 achromat that weighed about 17 lbs fully loaded. Everything worked fine unless there was wind. BUT, I did build a hd wood tripod for the mount as the original mount was for a 6-in f/5 reflector.

#36 orlyandico

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Posted 29 November 2012 - 02:01 AM

24-25lb seems excessive. as i said above, i tried putting my C9.25 (22lb) on the polaris and it was scary spindly... (to the point of unusability)

i guess celestron's penchant for overstating mount capacity (35lb on the CG-5 anyone?) didn't start recently.

#37 ohioalfa64

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Posted 11 December 2012 - 04:36 PM

I need more counterweight to balance the 150mm iOptron Mak. I have a 6.5 lber all the way out on the 1/2 threaded shaft (fine threads). I need to find another or make some sort of makeshift weight using nuts/washers to hold it in place. Plobably need another similar 6.5 lber. Luckily its been completely cloudy since I got the Mak.

#38 gmussman

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Posted 11 December 2012 - 11:20 PM

I recently added a dovetail shoe adapter from scopestuff to my polaris. It messed everything up, sort of -- My 80's Japanese Tasco 114 f/8 reflector (metal tube) now needs the entire length of the shaft for adequate counter-weighting because it pushes the scope too far out. However, it is still rock-stable, and I haven't abandoned the mod yet. I think without the dovetail shoe bracket, a light 6 inch reflector would do fine.

On a different note, a few people have thrown drive comments in their posts -- I modded an eq-3 drive with an uprated crystal to compensate for the 144 teeth on the polaris versus 130 on the EQ-3. It was a $1 fix, and it tracks great.

I'm pretty sure that makes it the only cheap thing I've ever done with a telescope ...

#39 Geo.

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Posted 14 December 2012 - 04:46 PM

There were two different length counter weight shafts sold with the Polaris, one about 8" and the other about 12. Any GP clone 19mm CW shaft will work with the Polaris. The Meade LXD55/75 shafts are nice as they are a little longer than most.

I modded an eq-3 drive with an uprated crystal to compensate for the 144 teeth on the polaris versus 130 on the EQ-3. It was a $1 fix, and it tracks great.


Can I ask what the frequency of the crystals were and are? Thanks.

#40 gmussman

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Posted 14 December 2012 - 05:24 PM

This is a nice page with pictures of the procedure on the single-axis drive for an EQ-1, which only has 100 teeth so the calculation has a different result but is done the same way.
I did the same procedure with with the EQ-3 dual-axis (and made a declination bracket as well). I think the original crystals are the same 3.56 MHZ. By my calculation, I needed a 3.96 MHz chip, but to custom make one was like $50, and a 4.0 MHz was $1. The tracking difference is a few arc-minutes per hour, more than adequate for visual or (probably) guided AP, though it'd have to be an awfully light guide rig to go on the mount.

#41 gmussman

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Posted 14 December 2012 - 05:24 PM

Forgot the link: http://orlygoingthir...nt-hacking.html

#42 ohioalfa64

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Posted 15 December 2012 - 08:02 PM

All I need now is someone smart enough to follow that microprocessor replacement detailed above.

#43 gmussman

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Posted 16 December 2012 - 08:23 AM

Ha! It's not that bad -- just take it apart and swap the crystal (the skinny silver thing). I'm not great at soldering, so I got a TV repair guy to do it for 5 bucks. Took him maybe 5 minutes.

#44 gmussman

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Posted 16 December 2012 - 08:30 AM

You can PM me if you want to talk it through.

-Grant

#45 orlyandico

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Posted 16 December 2012 - 09:07 AM

took me longer to take the pictures and make the web page :tonofbricks:

although finding the exact right crystal was pretty hard..

#46 gmussman

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Posted 16 December 2012 - 12:00 PM

Hi, Orlyandico!

Thanks for putting up that web page -- great results with my Polaris! Great pictures, too. A great guide, for sure.

Edited to add: the 4mhz was much easier to find! A shop down the street had one in stock.

#47 SteveG

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Posted 17 December 2012 - 02:21 PM

A $30 Celestron drive (93511) will bolt on and run the Polaris just fine. Due to the length of the RA slow-motion shaft, I had to mount the motor on the other side of the mount (why it looks upside-down). I simply drilled and tapped a thread right into the side of the housing. The down-side is there's no clutch, so I just loosen the RA axis and move it manually to adjust. This drive has a speed control, and as the 9V battery gets weak, you can adjust it to track properly.

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#48 SteveG

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Posted 17 December 2012 - 02:23 PM

Here - showing the mounting:

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#49 SteveG

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Posted 17 December 2012 - 02:23 PM

Another view:

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#50 ohioalfa64

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Posted 17 December 2012 - 03:21 PM

Very nice, and very simple--even better.






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