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2 inch GSO Barlow

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#1 Brian Schmidt

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Posted 14 January 2013 - 08:59 PM

Don't know if this has been discussed before, but I have recently acquired a GSO 2x barlow in the 2 inch format to use with my wide field set for deep sky viewing. Eyepieces in question are the 12 T2 Nagler and 8 Ethos, which both have the 1.25 / 2 inch hybrid barrel. Do you think these eyepieces should be used in 1.25 mode with the adapter to achieve 2x magnification? The paracorr setting calls for them both to be used in 1.25 mode, so I was thinking that using the eyepieces in 2 inch mode would probably result in slightly less than 2x magnification because the eye lens would be closer to the barlow lens. btw-I was not planning on using the barlow and paracorr at the same time.

#2 george golitzin

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Posted 14 January 2013 - 09:14 PM

The paracorr setting has to do with optimal coma correction and is, I think, irrelevant to the barlow question.

It seems to me, just off the top of my head, that to use that barlow with those hybrid eyepieces in 1.25 mode would require something like a "high hat" adapter; the GSO-supplied low-profile adapter would not securely hold the Ethos, I think, because the 2-inch barrel would get in the way. Using the high-hat adapter, a.) you would need significantly more in-travel than otherwise and b.) you'll wind up with noticeably greater than 2X magnification, since you've moved the focal plane of the eyepiece out from the barlow element. OTOH, if you use the eyepiece as-is in 2-inch mode, you might indeed get less than 2x mag--perhaps someone with direct experience can speak to this. But an alternative might be to get the 2-inch barrel extension and use the eyepiece in 2-inch mode in the barlow--but I'm not sure how that compares in height to the high-hat adapter.

-geo

#3 Brian Schmidt

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Posted 15 January 2013 - 07:47 PM

Thanks for the feedback. I figured the distance would impact the magnification. Probably the 2 inch extensions would be the easiest way for me to go. They would also be handy with the paracorr. I see they are on sale right now for 25. May not be a bad idea to pick up a couple.

#4 george golitzin

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Posted 16 January 2013 - 10:20 PM

Good luck with that. I'm a little surprised nobody has chimed in who has direct experience of this combination...hopefully someone will be able to give you a better answer shortly.

-geo.

#5 Brian Schmidt

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Posted 17 January 2013 - 07:45 PM

Thanks. If not, it's no big deal. It was more a curiosity from being board. Been unable to view due to all this rain over the south east.






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