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The Tasco 8V

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#1 mpsteidle

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Posted 13 April 2021 - 08:54 AM

I picked up one of these locally recently for a good price, and to be honest I did not expect much from it.

HOWEVER, after an hour spent cleaning and collimating, I am seriously impressed!  The contrast and pinpoint stars from my light polluted backyard surprised me greatly.  An 18mm ortho produced jet black sky and mars was a crisp disk, even at its current distance.

Anyone else enjoy these small scopes?


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#2 apfever

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Posted 13 April 2021 - 09:33 AM

How was collimation? Easy or issues?  wow...pm sent


Edited by apfever, 13 April 2021 - 09:37 AM.

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#3 Geo.

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Posted 28 April 2021 - 03:29 PM

This was a Vixen built Bird-Jones reflector. The FR/corrector is mounted in front of the diagonal. For the 8V the secondary was mounted on an optical window, no spider. The mount was a Vixen Polaris.

 

Celestron sold a version of 8V called the Comet Catcher, Jr. It also had an optical window but the secondary was suspended from a spider. 

 

IIRC, these had a f/4.6 primary. 


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#4 mpsteidle

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Posted 28 April 2021 - 07:11 PM

This was a Vixen built Bird-Jones reflector. The FR/corrector is mounted in front of the diagonal. For the 8V the secondary was mounted on an optical window, no spider. The mount was a Vixen Polaris.

 

Celestron sold a version of 8V called the Comet Catcher, Jr. It also had an optical window but the secondary was suspended from a spider. 

 

IIRC, these had a f/4.6 primary. 

I believe the comet catcher is quite a different scope.  I am under the impression that the comet catcher is a proper schmidt-newtonian, with a larger aperture, totally different tube, and sled focuser.  That said I dont own one and will let someone else chime in on whether I'm correct.


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#5 Terra Nova

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Posted 28 April 2021 - 10:21 PM

I believe the comet catcher is quite a different scope.  I am under the impression that the comet catcher is a proper schmidt-newtonian, with a larger aperture, totally different tube, and sled focuser.  That said I dont own one and will let someone else chime in on whether I'm correct.

The Comet Catcher is indeed a very fast (F3.57) S/N design, and in NO way a for-the-Bird(s)-Jones.

 

https://www.cloudyni...t-catcher-r1219



#6 mpsteidle

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Posted 29 April 2021 - 12:23 AM

I just realized he said "Comet Catcher JUNIOR". I had never even heard of this scope, but a quick google has me agreeing with him.

#7 Terra Nova

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Posted 29 April 2021 - 09:32 AM

The Comet Catcher Jr., being a physically short 125mm x 1000mm Newtonianesque telescope, I’m inclined to agree.

 

https://astromart.co...wroom-condition



#8 apfever

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Posted 30 April 2021 - 12:43 AM

The Comet Catcher Jr., being a physically short 125mm x 1000mm Newtonianesque telescope, I’m inclined to agree.

 

https://astromart.co...wroom-condition

HA, Wow!  Bet that is an andy ad, without membership to know directly. 



#9 apfever

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Posted 05 May 2021 - 02:01 PM

Start by taking the saddle tang inserts out of the two tangs. Insert is circled, locations are at arrows.

 

The left arrow shows the hole where the insert was removed. The right arrow shows the insert still installed. The tip of the insert has a straight slot so it can be unscrewed by running it DOWN out the hole. Don't lose the inserts. They are easy to lose. Keep your original hardware, especially unique items like these inserts. 

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Edited by apfever, 05 May 2021 - 03:05 PM.


#10 apfever

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Posted 05 May 2021 - 02:13 PM

Rotate the rings 180 and bolt the accessory flats to the top of the tangs with standard 1/4-20 bolts. The bolts will go directly through the larger tang holes where the inserts were removed from.  You need to make sure your bolts are SHORT enough to grab the rings but NOT go all the way through and into the OTA. The accessory flats are a thick boss that has plenty of grab. 

 

Notice I used a spacer nut because one of my bolts was too long. This was a quick demonstration from my bolts bin. A 1/4-20 clamping knob with the correct length threads is ideal. No ball peen hammer is needed.  

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Edited by apfever, 05 May 2021 - 02:14 PM.


#11 apfever

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Posted 05 May 2021 - 02:26 PM

Now the bump out in the rings that used to go around the tags, is on top.  This is where I discovered that a standard paint stick makes this mod tooo easy.  Get 4 of them. I always need paint sticks when at the box stores. I'm not saying to swipe any but hey,....I always need some considering my typical paint needs/purchases. Just get 4 or more to adore.  Your there to buy something anyways - right? These will stack perfectly in the ring bump outs.  Now you can tension the OTA into the rings using the original clamp knobs. This will hold the OTA up off the saddle contacts and eliminate the tube crush. 

 

But wait there's more.  Awesome more.

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#12 apfever

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Posted 05 May 2021 - 02:42 PM

This is the super hard part that requires some work. You need to drill two holes in one stick and cut a little off another. That's it. But WAIT for the next entries on alignment. 

 

Drill two 1/4" holes in ONE stick to match the clamp knobs, so the knob threads go into the holes. I set this distance to match the holes in the mount tangs. This way the rings will be held in parallel. This also locks the rings together and makes life beautiful in use. The clamp knobs will go through the holes and still press on the three sticks underneath for fun grip of your OTA. Another easy way to mark the hole locations is to clamp the knobs in. The end of the knobs will press a mark onto the top stick.

 

Another stick needs to be cut a little shorter to clear a cell bolt on the OTA. My short stick is 11" long. 

 

Two of the sticks are left unaltered. 

 

 

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#13 apfever

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Posted 05 May 2021 - 02:59 PM

This is the best part.

Align all the sticks flush to the front of the top ring. This lets the finder mount ride smoothly on the ring and over the end of the sticks as shown. You can loosen the knobs, rotate the OTA, and let the finder bracket hold the OTA  without slipping back in the rings. This tube is so short that any imbalance in this position is negligible. It's a 'gimme'. 

 

The top stick can be seen to be a little separated above the bottom three as it rides up on the knob threads. The bottom stick is a little shorter to clear the cell bolts at the back of the OTA (shown).  The bottom stick is also the perfect thickness to let the others ride over the top of the rear cell ring. 

 

Lightly clamp the top knobs when you remove the OTA from the mount. The rings will now stay in place and be ready to mount back up. No more loose flop slop rings slip sliding on your OTA when not mounted. 

 

Get 4 regular paint sticks, drill two holes, and cut one. This mod has NO altercations to the original system. This also works with the C4.5 that is notorious for the crush. No need to have a crush on your scopes. 

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Edited by apfever, 05 May 2021 - 03:03 PM.


#14 apfever

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Posted 05 May 2021 - 03:22 PM

Here are my two C4.5 with solid sticks I cut from 13 ply Baltic Birch.  In the second picture I loosened one stick and moved it forward to show the 1/4" dimples to nest the top knobs into. Getting the depth of the dimples the same and having the same "feel" clamping into the wood grain isn't easy. Using the paint sticks nails this dead on. Nothing has to be cut for the C4.5, just two holes drilled in one stick. 

 

I guess gluing these together might be a good idea. Put a dab or two between each stick, put them in the scope, and clamp them together till dry. Off set so you don't clamp in the two drilled holes. You'd want to clamp all 4 together for glue. 

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#15 apfever

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Posted 05 May 2021 - 04:42 PM

Found last two photos of this set.

 

The Tasco/Vixen 8V mount came standard with the bubble level and Polar scope. 

The Polar Scope in particular is quite nice. The tripod is also adjustable, came with the triangle storage bin, and nice accessories.

The Celestron C4.5 - not so much.

 

I suggest getting two of the white nylon washers with 5/8" center holes. Easy hardware find. Put one between the open end of the weight shaft collar and mount, and the other between a nut and weight. 

Get an M18X2.0 nut to snug the weight. It's a nice feeling.

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#16 starmason

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Posted 06 May 2021 - 07:00 AM

About 8 years ago I purchased a slightly battered 8V mounted on a beautiful Vixen built Polaris mount.  I read reviews about how difficult it was to collimate these “Bird Jones” OTA’s but since I needed a good GEM mount took the bait and bidded enough to get it.  Was a bit dusty and dented where the ring bolts compressed into the OTA body.  Tested the optics and it was out of collimation - by a lot. Disassembled, tried to smooth out the depressions in the tube, cleaned that spherical mirror (no collimation screws?..) , painted and reassembled back to almost new looking condition.  (Was very happy with the results).  Read some collimation advice and attempted to twist, turn, Allen key and curse my way to what “looked” like decent collimation on that aberration of a telescope design and during daytime the image seemed much less clear and sharp than a small fast Newtonian using similar eyepieces - and image looked a little funky.  The mount was excellent.  Waxing crescent moon and Albireo for “first light” and not expecting much, I was not disappointed when the coma was bad and collimation was still off - by a lot!

Next day attempted again to loosen the front “non corrector” glass plate mounted diagonal assembly and realign that focuser assembly again - this time using a laser collimator.  Took me over an hour for this.

Went to Trapezium that night and could not see sharp stars and coma still evident.  This was frustrating.

Asked our Astro Club ‘resident expert” to try collimating it and he politely refused as he tried collimating another and failed.

It sat around for a few years in my garage and got tossed eventually.  Kept the mount for a few years and adapted it for other vintage OTA’s use.

Bird Jones, by Vixen, in my opinion was “for the birds”.  One of only two OTA’s that I could not collimate...the other being the ES Astroscan. 

Clear skies,

Geo



#17 mpsteidle

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Posted 06 May 2021 - 09:44 AM

I had a very different experience with mine.  Eyeballed it with a cheshire then collimated the secondary on a star like an SCT, final image turned out nice and sharp.  Perhaps it's luck of the draw with these things.



#18 starmason

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Posted 07 May 2021 - 01:54 AM

Must be...trying to tighten/align so many things was frustrating and I had no luck at all.  Glad that you worked out the collimation issues and are enjoying the views with that unique reflector acope.




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