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Old Sunday 8th May 2016, 16:55   #1
PSBT
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XW 3.5/5mm eyepieces with PF80ED-A?

Hey!

Does anyone has experience with these eyepieces in this scope? I can't find information about them in the official webpage (http://www.ricoh-imaging.co.jp/engli.../xw/index.html), which might be an indication that these eyepieces are not intended to be used in spotting scopes?

What's confusing is that in various sellers pages I see: XW 3.5mm, 5mm, 7mm, 10mm, 14mm, 20mm eyepieces may be used with Pentax PF series Spotting Scopes (except PF 63 Zoom).

According to the 50x/inch rule, the PF80ED-A highest useful magnification should be 157.5x, so the 3.5/5mm eyepieces should work fine (148x and 103.6x considering a scope's focal length of 518mm).

I ask all these with the idea of using those short focal length eyepieces for astronomy (watching the moon and planets).

Any suggestions?

Thanks a lot!
Pedro
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Old Monday 9th May 2016, 17:18   #2
billb9430
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Pedro, I have the Pentax XW 5 and 3.5 mm eyepieces and can confirm that they will work nicely in the PF80EDa IF viewing conditions permit and your PF80EDa has good optics. Daytime viewing conditions rarely allow this, however. I use those eyepieces in my astronomy scope, but do not even bother taking them along for birding or wildlife watching. I do take an old Pentax 5.2 mm XL occasionally when doing "outreach" as some inexperienced folks ask for "high power".

More commonly, I carry a little 2x Barlow lens adapted to fit the Pentax spotters. See another old thread in this forum about how to do this. The little screw in the bottom of the Pentax eyepiece "well" that catches in the zoom notches is the problem that must be circumvented to use a Barlow. If you carry 10 mm and 7 mm XW's for regular use, using them with the Barlow lens will give the equivalent of 5mm and 3.5 mm eyepieces with less weight and cost for the few times you might use them.

I have not used my Pentax PF80EDa astronomically and for terrestrial use just keep a 26 mm adapted 2 inch barrel diameter SWA eyepiece in the focuser. (See another thread in this forum for info about this.) That eyepiece gives 20x, a great 3.5˚ field, and is low cost. I only occasionally change to shorter FL eyepieces to view greater detail at higher magnification. HTH - Bill

Last edited by billb9430 : Monday 9th May 2016 at 17:22. Reason: Omitted word
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Old Tuesday 10th May 2016, 00:00   #3
PSBT
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So, with the XW 3.5 and 5mm the viewing conditions considerations also apply during the night? I mean, are these eyepieces usable for planetary viewing with the PF80ED-A at 104x and 148x for objects high in the sky (not near the horizon), or night conditions also have to be perfect to take advantage of these eyepieces?

Thanks for the barlow info Bill. I'll keep that in mind! Those barlow tweaks also apply for the TV Powermate or can that one be used without any modifications (probably better to ask this in the other old thread)?
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Old Tuesday 10th May 2016, 14:53   #4
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Pedro, in daytime, refraction from non-uniformly heated air near the ground (sometimes called "heat waves or mirage") distorts light traveling to the scope, making sharp higher power viewing impossible. This is usually not a problem at night unless you are viewing over a surface still warm from the day or near a fire. I suspect the XW 5 and 3.5 would show fine astronomical images if your scope optics are good. I have not personally used my PF80EDa in this way, however. I have used the XW5 and XW3.5 astronomically in a Newtonian reflector and astronomical refractor with right angle prism. They give excellent images in those scopes.

Regarding Barlow use in the Pentax PF spotting scopes, the problem with the GSO 2x Barlow is that it won't seat far enough into the scope "well" to allow eyepieces to come to infinity focus because the end of the Barlow hits the little screw head protruding into the bottom of the "well". By filing or milling a notch in the Barlow body, the Barlow can slip past the screw head and reach the bottom of the eyepiece "well". In that position, all eyepieces I've tried will come to infinity focus in this Barlow. Be sure to read all the posts in the Barlow thread, since I had not learned the "notch filing or milling" method when the first post was made.

The only other Barlow I've tried is the discontinued University Optics 2.8x Klee Barlow. It works without any modification in the Pentax PF scopes, but at 2.8x works best with the longer FL 20, 14, and 10 mm XW's. Those combinations give equivalent eyepiece FL's of 7.1, 5.0, and 3.6 mm. Using that 2.8x Barlow seems to reduce the Afov somewhat, however. I have not tried other brands/types of Barlow nor TV Powermates and so cannot comment on whether they will come to infinity focus or work well with the Pentax PF spotters. -Bill
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Old Tuesday 10th May 2016, 17:00   #5
jring
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Hi,

don't have a Pentax scope but some el cheapo 80mm ED doublet. Works nicely at 120x with a 5mm Nagler on bright astro stuff or terrestially. 140x with a barlowed Baader zoom seems to be the limit of what is usable on planets, 170x also with the Baader zoom and barlow is not really better.

Joachim
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Old Tuesday 10th May 2016, 18:52   #6
PSBT
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Thanks Bill! Really clear answer!

Thanks Joachim! What's the focal length of your scope, so that I can more or less compare the magnifications you provided taking into account the PF80ED-A's focal length (518mm).
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Old Tuesday 10th May 2016, 19:14   #7
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Hi,

my Evostar ED80 has 600mm.

Joachim
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Old Tuesday 10th May 2016, 19:32   #8
PSBT
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Oh I could have figured that out easily by multiplying 120 x 5. Anyway, thanks!
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Old Tuesday 10th May 2016, 22:57   #9
DRodrigues
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Pedro,
I find the 5mm eyepieces usable for daylight but not the 3,5mm, at least on 100mm spotting scopes. Have a look at cr-telescopes on www.pt-ducks.com
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Old Wednesday 11th May 2016, 12:42   #10
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Great! Thanks David for sharing your experience...
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