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I thought I read somewhere that the Paracorr is supposed to be placed in the Powermate/barlow,so the Powermate/barlow won't scratch the Paracorr lens???
Al

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Some Poster in another thread yesterday said:

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I especially wouldn't want to use a Big Barlow/Paracorr/Ethos combo!

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So, in the spirit of scientific experimentation for the benefit of the astro community....well, ok maybe it's more the astro equivalent of an Evil Knevil stunt to titillate your voyeuristic curiosity and my sense of reckless adventure...HERE ARE SOME PICS of some of the most gnarly, scary eyepiece/barlow/parcorr combos that can possibly be conjured up. (Actually, those are TV Powermates, not barlows in the pictures, but...for present purposes, that's not important). The point is whether these absurd combos are fun to look *at*, not whether they're ideal to look *through*.

OK, LET'S GET STARTED: First, here's a picture of:
31 Nagler => 2x 2" TV Powermate => TV Parcorr (=> Moonlite Focuser) hanging off an Orion XT12i reflector. Notice that there's a difficult dilemna here to setting up these pics: I don't want to get the scope too far off vertical because of balance issues, but leaving the scope too close to vertical leaves the eyepiece optical train hanging rather precariously horizontal off the scope. Therefore, the combos didn't stay mounted any longer than necessary to take the pics.

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I've used this combination in the field. You have the Paracorr and Powermate reversed, though. The PowerMate goes first, then the Paracorr and eyepiece. It's important to maintain a correct distance from the Paracorr's lens to the focal plane of the eyepiece.

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Don Pensack
12.5" Truss Dob, 5" Maksutov
Sustaining Lifetime IDA member, TeleVue junkie

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WOW! Whats the magnification on that stack?

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it's about 12100x

If I replaced those barlows with five 5x Powermates, it'd be over 1,200,000x

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S 38º 00' E 145º20'

Custom 12" F/4.6 dob
10" GSO dob
4.5" Meade Newtonian
Set of Vixen LVWs + TV barlows + powermates
Astronomik 0III, UHC, H-beta filters

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You are correct, sir, but I think it's to keep the same spacing between the EP and Paracorr and is only with the 2" 2X powermate or 2" barlow. Obviously, a 1.25" powermate/barlow would have to come after the Paracorr.

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The only caveat would be *not* to use a Barlow with the tunable top Paracorr. According to TeleVue, the Barlow might contact the Paracorr lens:

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If it inserts as deeply as their own 2x barlow. Many do not, and Televue specifically says this advice does not hold for their own 1.25" Powermate either.

I used a 1.8x TMB barlow, and you couldn't insert it deeply enough for it to stop requiring lots of focuser in-travel. I'm using a Baader/Zeiss now, and there's no way to make the barlow contact the Paracorr lens - not even if you set the tunable top to the lowest setting.

There are other slightly dangerous combinations that don't involve barlows at all -- a 13mm Ethos with a stack of filters (e.g. a variable polarising filter plus a Baader Moon&Skyglow) definitely *is* dangerous if you forget to set the tunable top high.

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400mm f/4.46 David Lukehurst truss Dobsonian on Tom Osypowski equatorial platform
Orion Starblast (114mm f/4 reflector, Alt/Az)

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I've used this combination in the field. You have the Paracorr and Powermate reversed, though. The PowerMate goes first, then the Paracorr and eyepiece. It's important to maintain a correct distance from the Paracorr's lens to the focal plane of the eyepiece.

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There are other slightly dangerous combinations that don't involve barlows at all

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As I found after trying a 2" OIII filter on my 31 nagler and discovered it wouldn't seat fully into the paracorr.

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Geoff
15" SDM truss dob | Vixen r130sf | GSO 10" dob

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