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1.25" Diagonal with 4" Tak Frac

jabeoo1

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jabeoo1

jabeoo1

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As above, 

I am after a 1.25" Diagonal for my FC-100.

I want to go for a dielectric coated 1/10 wave upwards.  

Are the high end Televue ones really worth the £'s? Are there others about with the same views for half the price ? 

I don't want to buy again so its now this once. 

 

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John

John

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I'm the other way around on the WO diagonals - the 1.25" is great quality but has a thick ring inside the drawtube which vignettes the FoV of wide field stop 1.25" eyepieces.

The GSO / Revelation ones are decent for their cost. The Tak 1.25" prism gets lots of praise for performance, a little less for it's plastic body.

The TV Everbright 1.25" is a lovely little thing and all machined from a single block of alloy but admittedly pricey.

 

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John

John

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1 minute ago, jabeoo1 said:

Thanks everyone for your input:

So will the 1.25 WO cause vignetting when using a 24mm Panoptic but not in the Everbright ?

I think it will. I can recall getting a fuzzed out edge of the field of view when I used a 32mm plossl with the 1.25" WO and that had the same field stop diameter as the 24mm Panoptic does.

Here is a pic "down the throat" of the WO 1.25" dielectric mirror diagonal and you can see the thick ring that I'm on about. I think it's used to create a strong fastening between the body and the barrel but it's just a bit too thick IMHO:

 

odia-wo-cfdig125di-4_2.jpg

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jabeoo1

jabeoo1

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Shame about the design of that WO.  I guess the Tak prism is looking better and better for price and performance.  Should have listened to you before John instead of researching in a big circle. 

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iPeace

iPeace

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Do have a snoop around SGL for comment on the Tak prism - especially regarding the twist-lock mechanism for securing the eyepiece. It seems - if I recall correctly - that eyepieces with a "safety groove" in the barrel require a bit more twisting to secure, and a bit more wiggling to remove. I believe @Stu can comment on this. This is not meant to put you off, just so you know about others' experiences.

:happy9:

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Stu

Stu

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3 minutes ago, iPeace said:

Do have a snoop around SGL for comment on the Tak prism - especially regarding the twist-lock mechanism for securing the eyepiece. It seems - if I recall correctly - that eyepieces with a "safety groove" in the barrel require a bit more twisting to secure, and a bit more wiggling to remove. I believe @Stu can comment on this. This is not meant to put you off, just so you know about others' experiences.

:happy9:

That's right. The Tak is optically very nice, and sturdy enough but lightweight which is generally a positive although an all metal body might be better.

The twist lock works beautifully with my BGOs as they are smooth sided, but can be a right pain with my 24mm Panoptic, as the locking ring gets stuck in the undercut on the barrel. It never gets totally jammed, but it does mean you end up having to undo it almost all the way to release the eyepiece.

Budget dependent, the Baader Zeiss T2 Prism is about as good as it gets, and with a nice 1.25" Baader Click lock fitted does not suffer from the same problems.

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jabeoo1

jabeoo1

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3 minutes ago, iPeace said:

Don't worry, I'll send it back to you if you need it. :happy10:

Haha nice gesture but I already made my mind up to not spend £200 + on a prism & nose piece.  I think I can make do with a slightly sticky undercut and save the difference.  Anyhow why don't people use the baader turret in the Tak prism and just spin 4 Ep's around ?

Would that be a way out of messing about all the time ?

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Dave In Vermont

Dave In Vermont

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56 minutes ago, John said:

I think it will. I can recall getting a fuzzed out edge of the field of view when I used a 32mm plossl with the 1.25" WO and that had the same field stop diameter as the 24mm Panoptic does.

Here is a pic "down the throat" of the WO 1.25" dielectric mirror diagonal and you can see the thick ring that I'm on about. I think it's used to create a strong fastening between the body and the barrel but it's just a bit too thick IMHO:

 

odia-wo-cfdig125di-4_2.jpg

Actually, John, that 'thick ring' is there on purpose - by WO's design - to prevent anything getting past that point and coming into contact & damaging the dielectric mirror's surface. I know abit about these as I currently have 4 of them!

Fan of the William Optics dielectrics -

Dave

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Highburymark

Highburymark

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1 hour ago, John said:

I'm the other way around on the WO diagonals - the 1.25" is great quality but has a thick ring inside the drawtube which vignettes the FoV of wide field stop 1.25" eyepieces.

The GSO / Revelation ones are decent for their cost. The Tak 1.25" prism gets lots of praise for performance, a little less for it's plastic body.

The TV Everbright 1.25" is a lovely little thing and all machined from a single block of alloy but admittedly pricey.

 

Hmm - interesting point on vignetting. Haven't tried that combination in the Tak.

I tested the 1.25" WO diag against the 2" WO and Skywatcher diagonals the other day and it had noticeably better colour control in an Equinox.

The other option is the non-Zeiss Baader prism - apparently pretty close to Zeiss quality and under £100.

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Highburymark

Highburymark

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27 minutes ago, Dave In Vermont said:

Actually, John, that 'thick ring' is there on purpose - by WO's design - to prevent anything getting past that point and coming into contact & damaging the dielectric mirror's surface. I know abit about these as I currently have 4 of them!

Fan of the William Optics dielectrics -

Dave

Wish the Baader prisms had protective rings....

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iPeace

iPeace

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4 minutes ago, Highburymark said:

Wish the Baader prisms had protective rings....

You can use a T-2 spacer ("extension tube") between the prism and the eyepiece clamp to keep your longest 1.25" eyepieces off the glass. They come in 7.5mm and 15mm.

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John

John

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35 minutes ago, Dave In Vermont said:

Actually, John, that 'thick ring' is there on purpose - by WO's design - to prevent anything getting past that point and coming into contact & damaging the dielectric mirror's surface. I know abit about these as I currently have 4 of them!

Fan of the William Optics dielectrics -

Dave

Other designs have that stop as well Dave (though not the Baader Zeiss T2 but thats a modular unit). The TV Everbright has it machined into the barrel but it is nowhere near as thick as WO (and the clones) use, so no vignetting.

I like WO diagonals but I was annoyed that I could not benefit from the full FoV of my longer focal length 1.25" eyepieces, thats all :smiley:

 

 

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John

John

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9 minutes ago, iPeace said:

You can use a T-2 spacer ("extension tube") between the prism and the eyepiece clamp to keep your longest 1.25" eyepieces off the glass. They come in 7.5mm and 15mm.

Yep, I use the 15mm one :smiley:

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