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Tasco Vixen 8v

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#1 Steve_M_M

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Posted 02 May 2009 - 05:31 PM

This scope was on Ebay last week and no one bid on it. So, after the auction ended I sent the seller an email and made an offer that was accepted. I knew at the very least would end up with a very nice Vixen Polaris mount with a rare polar axis finder.

The package arrived yesterday...OMG. It was new and unused. I was pretty excited. Everything from the scope, to the mount, to the tripod was all in mint condition with no signs of even being used or even exposed to the elements-even inside :)

The package came with 125mm Vixen Cat Newt (not really) FL1000m (really 500mm with a 2x barlow in front of the secondary), Vixen Polaris mount with polar axis finder, Vixen 6x30mm finder, a very nice Vixen 18mm .965" Ortho ep, and the not so nice Vixen 5mm Ortho eyepiece.

But, the real point of this post is to provide information on collimation. I found the collimation set up to be intricate, but accurate, and the machining tolerances to be Takahashi Like.

So, here is a picture of the telescope...

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  • 3081566-Tasco 8V.jpg


#2 Steve_M_M

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Posted 02 May 2009 - 05:33 PM

The front correct and secondary assembly. Like Tony White, I see no corrective properties of the front glass.

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  • 3081568-Tasco 8va.jpg


#3 Steve_M_M

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Posted 02 May 2009 - 05:35 PM

Secondary unscrewed from front of corrector. I have the housing turned in this picture so it looks closed.

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  • 3081571-Tasco8Vb.jpg


#4 Steve_M_M

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Posted 02 May 2009 - 05:38 PM

Corrector Plate with lock nuts still attached, secondary housing clearly showing barlow, and secondary stalk and mirror.

1) Aligning the secondary under the focuser-you can see the secondary stalk has a large collar at the front with a lock nut around that collar. The corrector plate has a corresponding lock nut on the other side of the glass. You adjust the position of the secondary mirror by threading or unthreading the lock nut and then locking it down with the one on the other side of the glass. This is easy to accomplish with everything on the scope set up properly.

2) Primary Mirror-Fixed in what appears to be a very nice, unadjustable cell.

3) Secondary adjustment-You can see the 3 set screws. These press on the stalk holding the secondary and adjust the secondary just like any other secondary. Seemed easy to use.

I hope at least pictures may help future buyers of this very nice telescope.

Steve

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  • 3081579-Tasco 8vc.jpg


#5 Steve_M_M

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Posted 02 May 2009 - 05:52 PM

I really love these Polaris mounts...

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  • 3081601-Polaris Mount.jpg


#6 tim53

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Posted 02 May 2009 - 06:12 PM

Wow, I've never seen one of those apart before. Such nice craftsmanship!

-Tim.

#7 DAVIDG

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Posted 02 May 2009 - 08:04 PM

The optical design of your 'scope is a Bird-Jones. It uses a spherical primary and negative corrector lens to correct for the spherical abberation of the primary and also increase the focal length.
Collimation is important in these 'scope so you want to use laser collimator to get things dead on the money.
In small apertures this design works well.

- Dave

#8 Steve_M_M

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Posted 02 May 2009 - 10:15 PM

Interesting. I have never heard of that design.

I do have a laser collimator and hope to get it out under the stars tonight.

Steve

#9 Brian Risley

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Posted 03 May 2009 - 06:23 PM

Someone has an 8V OTA out on AM now!
Brian

#10 Starpoke

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Posted 03 May 2009 - 11:00 PM

Thank you Steve. I have been fussing with my 8V for at least 6 months trying to figure out how to adjust it. I suppose I really need to get a colimator now that I know how to get at the secondary. Glenn

#11 Steve_M_M

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Posted 03 May 2009 - 11:30 PM

Just got in from night 2 with the 8V. It is throwing up some very good images up to 150x. Over that, I am going to need to spend some serioud time on collimation. I have it near perfect, but I can see not quite perfect. One key seems to be to make sure you have the lock ring snug on the inside of the tube when you put it back together. Use the
outside lock ring to allow positioning under the focuser and rotational alignment. Then, make sure this lock ring is very tight. I failed to do this when I went outside last night for a star test. When I was adjusting the lateral set screws (hard to get at) to adjust the secondary, I ended up rotating the entire assembly.
It is really easy to pull off the front glass and remove the secondary. So, if you can confirm the one on Astromart has the barlow/corrector in front of the secondary, it will also be easy to repair the dents. A nice 5" Vixen, rings, with the very nice 18mm ortho and 6x30 finder seems like a decent deal for $75 or less.

I am not gong to fuss with collimation anymore until I see the master (Clint) later this month :)

Steve

#12 DAVIDG

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Posted 04 May 2009 - 09:30 AM

What you might try to do to get perfect alignment is to first remove the primary mirror. With a laser collimator in the focuser, adjust the secondary so the beam exits the exact center of the barlow/corrector. Install the primary mirror and adjust the whole front assembly so the laser beam hits the center of the primary. Now adjust the primary so the returning beam falls back on the exact center of the barlow/corrector. I know that both the primary and the front assembly have no easy way to adjust them but there might be enough play in the mounting screw holes to get things lined up or a way to shim the optics.
What is critical is that the optical axis of the barlow/corrector is the same as the primary. If the lens is tilted or has the it optical axis offset from the primary, the image will suffer greatly.
One other thing to check, be sure that the diagonal mounting assembly is mounted so it is centered in the optical window and the window is centered in the cell.

- Dave

#13 Jae

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Posted 04 May 2009 - 08:10 PM

I really love these Polaris mounts...

Steve,

How much lighter are these compared to the SP/GP mounts ?

I always liked the 8v, just out of curiosity......glad it has good optics. 150x is what my Red Tasco 10VR can handle pretty easily.

Jae

#14 Roel

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Posted 05 May 2009 - 04:31 AM

Nice telescope! I also like the Polaris mount, the only one I'll never sell! Mine has a threaded shaft to hold the counterweight, yours seems to be smooth (?)

I don't have a polar finder though... But looking at your picture: doesn't the polar finder need to be shoved more into the mount?

Otherwise when switching to AZ-mode (within a matter of second with this mount) the scope will hit the base plate.

#15 Brian Risley

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Posted 06 May 2009 - 07:00 PM

There is another one out on Tampa Craigslist.
http://tampa.craigsl...1157155935.html

#16 Steve_M_M

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Posted 06 May 2009 - 08:37 PM

Wow, they are showing up everywhere! I would love to have the Vixen drive.

Jae, you are right, the polar axis finder does go nicely up into the mount, basically hidden from view. As to size, I would say the polaris is about 60% of the SP. My CW shaft is threaded. Not sure I have seen a smooth one before.

Steve

#17 Starpoke

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Posted 10 May 2009 - 02:35 AM

As long as the Polaris mount has already hijacked this thread I will play along. In previous discussions in this forum it was claimed that BOTH the Polaris and SP are rated for about 15 lbs. The upgrade to SP was primarily to provide for dual axis drive. The upgrade actually made the mount less versatile by eliminating the Alt/Az option but the change was a response to the growing interest in astrophotography among small scope owners.
My Polaris at present has a smooth counterweight bar which I swapped out of my CG-5. (Isn't it nice that all the polaris series mounts and their Celestron clones share the same threads on those bars) I am currently using two 7 lb. weights to balance my Brandon with all the heavy attachments hanging off it and that is probably as much weight as it will take gracefully. (My mount also came with a Tasco 8V so I am not totally off topic.)
Although Celestron never made a dec drive for this mount JMI did and I was fortunate enough to acquire one from a fellow CNer. The dec drive control attaches to the MD-6 hand paddle so everything is together.
Clear skies and strong backs to all
Glenn

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  • 3095600-CNDecDrivePolaris.jpg


#18 Brian Risley

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Posted 10 May 2009 - 05:22 PM

I am using that same controller setup on my SP mount. I hijacked a clutch/gear from my original sky sensor, so I have a clutched direct gear arrangement. I also made a bracket to keep the motor from moving using the original dec bracket. I found it moved a lot using just the worm gear nut.
Brian

#19 starmason

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Posted 12 May 2009 - 02:48 PM

I just purchased the 8V on Amart. It needs collimation.
Optics look okay. Not in very good condition but I'll attempt to collimate it anyway. Looks a lot tougher to collimate than my C6/C8's and Newts.
George
NY

#20 TimD

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Posted 11 July 2009 - 04:13 AM

I have always loved the 8V's. They certainly got that model "right"

#21 albert1

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Posted 13 July 2009 - 07:34 PM

The one I had gave some nice views too. That Vixen mount was solid and quite beautifully done. Looks like just a smaller version of the SP. The only problem with the scope was how easily the OTA dented when mounted.

Nice, an unused one. Congradulations.


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