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Equipment Discussions >> Classic Telescopes

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Larry Geary
Carpal Tunnel
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Reged: 09/24/06

Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: SpaceNetworks]
      #6082903 - 09/15/13 10:05 PM

Quote:

I'm now seeing two possibilities:

1) .965 focuser - Tasco .965 diagonal - .965 to 1.25 adapter - 1.25 ep
2) .965 focuser - .965 to 1.25 adapter - 1.25 prism diagonal - 1.25 ep




3) .965 focuser - .965 to 1.25 adapter - 1.25 ep


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pogobbler
sage


Reged: 09/30/08

Loc: Central Indiana, USA
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: Larry Geary]
      #6083201 - 09/16/13 02:35 AM

I've got a 60mm scope with a .965" focuser. When I got it, I went out and got a .965" to 1.25" adapter and, luckily, my 1.25" eyepieces came to focus with it, but, you know what? I ended up getting some .965" Plossl eyepieces from Hands on Optics and prefer them with the scope. The quality is fine and the size just fits the scope better and doesn't upset the balance of the scope. The eyepieces are around $30 and perform just great. That'd be my recommendation instead of cutting the tube.

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Joe Cepleur
Carpal Tunnel


Reged: 03/18/10

Loc: Dark North Woods
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: photiost]
      #6083519 - 09/16/13 09:34 AM

Quote:

...bring your scope to a local telescope shop and try different diagonals (new + used)




It may be easier to find a nearby club, with members who will be eager to help you test their accessories in your scope. Some mail order houses may also have return policies favoring ordering lots of parts, and keeping only those that work.

My rig (albeit with a different brand and model of telescope) is:

Blue Fireball 0.965"-to-1.25" adapter
Celestron 1.25" prism diagonal

Edited by Joe Cepleur (09/16/13 09:35 AM)


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tag1260
scholastic sledgehammer
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Reged: 10/07/12

Loc: Ohio, USA
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: Joe Cepleur]
      #6083604 - 09/16/13 10:26 AM

Also, have you tried other eyepieces? I know I have eyepieces that will work in one but not another when I use adapters.

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SpaceNetworks
super member
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Reged: 04/21/13

Loc: California
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: tag1260]
      #6090877 - 09/19/13 11:44 PM Attachment (15 downloads)

I received a .965 to 1.25 adapter, and tried it with my Tasco 60mm:

.965 focuser - Tasco Circle T .965 diagonal - .965 to 1.25 adapter - 1.25 ep
Outcome - unable to reach focus

So I tried Larry's suggestion: .965 focuser - .965 to 1.25 adapter - 1.25 ep
Outcome - reached focus with 3/4" of travel left for the focuser drawtube (see attached blurry photo, taken at twilight)
But I doubt I would be willing to do an impression of Galileo (i.e. straight-through viewing) very often.
Does anyone think a 1.25 prism diagonal could be added to this optical path, and reach focus? I dunno.

Getting additional .965 eyepieces to go with my Tasco Circle T 20mm is starting to look like the best option.


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SpaceNetworks
super member
*****

Reged: 04/21/13

Loc: California
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: SpaceNetworks]
      #6114412 - 10/03/13 12:29 AM Attachment (6 downloads)

Postscript to my search for eyepieces to use with this Tasco 12TE, in addition to the original AH 20mm .965, which reaches focus with around 1.5" of focuser drawtube travel to spare:

I tried an Antares 12.5mm .965 Plossl -- unable to reach focus.
I tried a Celestron 12mm KD .965 Ortho -- unable to reach focus!! (close but no cigar)

Go figure. I am nonplussed.

AH 12.5mm anyone?


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semiosteve
sage


Reged: 07/03/04

Loc: NEOhio
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: SpaceNetworks]
      #6114722 - 10/03/13 08:55 AM

I have a Tasco 10TE and can use my Brandons successfully with the Hybrid diagonal. The 10TE has a very long drawtube however, and your mileage may vary...

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BarabinoSr
Pooh-Bah
*****

Reged: 11/17/05

Loc: Slidell La
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: semiosteve]
      #6115011 - 10/03/13 11:55 AM

Hi Eric ! I've read your thread with great interest, and as someone mentioned before, it depends on the eyepiece. Have you considered getting a mirror hybrid diagonal I recently tested a TASCO 9S 700mm f/l 60mm,made by Tanzutsu with a hybrid mirror diagonal .The eyepiece used was an 8mm Televue plossl , and I was able to achieve focus with focal room to spare. I noticed that the 8mm fit almost inside the diagonal itself and I got focus.In many ways your instrument is like my 9TE-5 same f/l. I have maybe 3 1/2 inches of focus travel in this scope, so if you can get some 1.25 eyepieces that will allow the optics of those units to be very close to the mirror of the diagonal it should work for you. Any EP that has the optics any different may not work. Gary

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GlennLeDrew
Postmaster
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: BarabinoSr]
      #6115512 - 10/03/13 03:59 PM

Eric,
How much focuser travel do you have? It seems to me that the best option is to cut about 1-1.5" off the main tube. The loss of that aluminum would be offset by the added weight of the larger stuff inserted. The 'bracing' bar could be dispensed with if you cut into its mounting stud.

Before doing any cutting, remove objective and focuser, strap them to a stick, and experiment to find the 'ideal' separation, hopefully allowing to use all accessories. Then cut the tube to suit. Note that for the purpose of finding focus, critical alignment is not required. Tilt will only introduce astigmatism, not so bad that a reliable focus position cannot be obtained.


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SpaceNetworks
super member
*****

Reged: 04/21/13

Loc: California
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: GlennLeDrew]
      #6116086 - 10/03/13 09:14 PM Attachment (8 downloads)

Quote:

How much focuser travel do you have?




First, let me express how much I appreciate everyone's feedback. I've learned so much by consulting and posting on CN.

Here's the diagnosis: With the focuser tube fully extended, there is 3 7/8" of travel:


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SpaceNetworks
super member
*****

Reged: 04/21/13

Loc: California
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: GlennLeDrew]
      #6116089 - 10/03/13 09:15 PM Attachment (6 downloads)

The Circle T AH 20mm ep reaches focus with 1 7/8" of travel to spare:

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SpaceNetworks
super member
*****

Reged: 04/21/13

Loc: California
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: GlennLeDrew]
      #6116091 - 10/03/13 09:17 PM Attachment (6 downloads)

The Celestron KD 12mm Ortho ep does not reach focus. This was unexpected. It's close, but the focuser tube simply runs out of travel:

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SpaceNetworks
super member
*****

Reged: 04/21/13

Loc: California
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: GlennLeDrew]
      #6116097 - 10/03/13 09:19 PM

The same was true for an Antares 12.5mm .965 Plossl, and for using a hybrid mirror diagonal and 1.25" Plossls.

Prescription???

Perhaps my next gambit should be to look for an AH 12.5mm or H 12.5mm eyepiece.


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BarabinoSr
Pooh-Bah
*****

Reged: 11/17/05

Loc: Slidell La
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: SpaceNetworks]
      #6121903 - 10/07/13 08:55 AM Attachment (11 downloads)

Here's a view of the focuser of the 9S. Looks to be very much like the one on your scope, with the 8mm TV plossl in the hybrid diagonal. That worked. Though I have a few nice .965 eyepieces as well as many 1.25" ones, I'll experiment with it over the next few days and see what I come up with .

Edited by BarabinoSr (10/07/13 09:00 AM)


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fjs
scholastic sledgehammer
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Reged: 03/25/13

Loc: Olympic Peninsula, USA
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: SpaceNetworks]
      #6122179 - 10/07/13 11:14 AM

I'm pretty much a newbie here. This is just not making sense to me. I can't see there being so much of a difference in where the 12mm and 20mm eyepieces reach focus. Do they both have all their elements? I wonder if you had an adapter, what would result by trying them in one of your other scopes.

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SpaceNetworks
super member
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Reged: 04/21/13

Loc: California
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: BarabinoSr]
      #6122376 - 10/07/13 12:41 PM

Quote:

I'll experiment with it over the next few days and see what I come up with.




Thanks. I have a H 12.5mm and a Ramsden 9mm on the way and will post results.


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SpaceNetworks
super member
*****

Reged: 04/21/13

Loc: California
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: fjs]
      #6122779 - 10/07/13 03:36 PM

Quote:

I can't see there being so much of a difference in where the 12mm and 20mm eyepieces reach focus. Do they both have all their elements? I wonder if you had an adapter, what would result by trying them in one of your other scopes.




The Celestron .965 orthos and 1.25 plossls, and the Antares .965 plossl-- all reach focus straight through, that is, when I remove the diagonal from the optical path. So the eps are OK. And yes, I may get a 1.25 to .965 adapter to see how the .965 orthos perform in my Orion ED80.


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SpaceNetworks
super member
*****

Reged: 04/21/13

Loc: California
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: SpaceNetworks]
      #6123811 - 10/07/13 11:24 PM

I tried a H 12.5mm and R 9mm, but with the same result-- just a bit short of reaching focus.

The original Circle T Achromatic Huygenian 20mm, which reaches focus with 1 7/8" of travel remaining, has a field lens that sits noticeably closer to the diagonal glass than the other eps I have tried. I would try an AH 12.5mm or lower, but that's about it as far as other eps are concerned.

I could also try again to fix the original focuser, since it would allow the eps to be slightly closer to the objective than the replacement focuser. Optically this has potential as a solution, but mechanical success with the focuser is uncertain.


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dawsonian2000
Carpal Tunnel
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Reged: 07/26/06

Loc: Riverview, FL, USA
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: SpaceNetworks]
      #6126346 - 10/09/13 04:23 AM

Hi Eric,

Terra did an awesome job of conveying you major issues, along with viable solutions. But, to add to what she and everyone else has suggested, I would try changing the visual back (the screw-on holder at the end of the draw-tube) to a short one. The one that you currently have is about 3/4 of an inch longer than the typical old-school design. If I find one among the collection of spare telescope components I have, I will be more than happy to give it to you in hopes that it will solve your dilemma. Sounds as if you only need a pinch more of in-focus.

Mel


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SpaceNetworks
super member
*****

Reged: 04/21/13

Loc: California
Re: Tasco 12TE: Using 1.25 eyepieces w/ a .965 focuser new [Re: dawsonian2000]
      #6127728 - 10/09/13 07:39 PM

Quote:

Hi Eric,

Terra did an awesome job of conveying you major issues, along with viable solutions. But, to add to what she and everyone else has suggested, I would try changing the visual back (the screw-on holder at the end of the draw-tube) to a short one. The one that you currently have is about 3/4 of an inch longer than the typical old-school design. If I find one among the collection of spare telescope components I have, I will be more than happy to give it to you in hopes that it will solve your dilemma. Sounds as if you only need a pinch more of in-focus.

Mel




Hello Mel,

It's true that I only need a little more in-focus. A shorter visual back could be part of a solution. I believe I would also need to cut the barrel of the diagonal shorter.

I haven't removed a visual back from a focuser drawtube before. Do you suppose it is threaded onto the tube, or is it somehow adhered? Obviously I would need to remove the current visual back without risking damage to the drawtube of other parts of the focuser.

Thanks for your help!


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