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Smoothside Meade 4k 8.8/14 Parfocal?

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#1 Brian Risley

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Posted 21 November 2012 - 11:37 PM

I am not sure if the 8.8/14mm I got used had the bottom 1.25 barrels (with lens) swapped. If someone has both and uses them in 2" focuser, are they somewhat close to parfocal or do you need to do a lot of turns to get them to focus?
In swapping them around, I find that the actual field of view is either very similar when looking at the moon, or very different. Without another one to compare to, I can't tell. (I do have a TV 13mm Type 1 I can compare to, should the 14 be similar to its view.)
Brian

#2 The Planetman

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Posted 21 November 2012 - 11:41 PM

Hi Brian.
I had both and the 8.8 requires about 3/8" out travel on the focuser in comparison to the 14mm if I remember correctly.
RW

#3 Brian Risley

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Posted 22 November 2012 - 12:08 AM

Thanks Ross. I just compared the 14 to the TV 13 and with the units swapped from the way I got them, when looking at Jupiter, its moons and some background stars, the fields are just about the same. With them the way I got them, the field on the 14 was quite a bit tighter. In that config, the 14 and the 8.8 had about the same field of view. With them swapped, the 8.8 is quite a bit tighter (can just get Jupiter and its moons in my 2120 LX-6) while the 14 has the moons and several outlying stars, so I suspect they were swapped when I got them.
Brian

#4 ji4m

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Posted 22 November 2012 - 03:28 AM

The series 4000 8.8 UWA does require racking the focuser outward about a half-inch compared to the 14 UWA. Strangely, I don't have the number recorded as I have measured the focus position of my eyepieces. The field stop location of the 14 is about 7mm below the 2" shoulder. I remember the 8.8 being close to parfocal with the Nagler 11mm Type 1, which has a field stop located about 20mm below its shoulder. These measurements are for the smoothside version without rubber eyecups.

I've never taken mine apart so I can't help with the "swapped field lens" configuration. It sounds like you have it fixed.

#5 astrodon

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Posted 22 November 2012 - 11:20 AM

I wonder if when they are swapped, the eyepieces are different fls?

#6 ji4m

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Posted 22 November 2012 - 08:24 PM

Went back and checked. The 8.8 UWA field stop is about 21mm below the shoulder, so that is 14mm different from the 14 UWA, or just over a half inch.






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