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SMC Pentax XF 6.5-19.5mm Zoom Eyepiece

Moonshane

By Moonshane
in Discussions - Eyepieces

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Moonshane

Moonshane

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I have pondered on one of these for a while and when one came up at a decent price on SGL the other day I bought it. I have been using my Seben 8-24mm zoom for a while on both of my solar scopes (white light and Ha) and have been pretty impressed with the results. I suspect that for solar observing this eyepiece will work very well based on what people say online. As I raised enough funds from the sale of other items, I will keep the Seben as an outreach eyepiece and for my (primary) school club.

I am not so sure of the night performance as there are a number of suggestions online that CA is an issue off axis. If I do use this it will be mainly for double stars, lunar and planetary observing in my 80mm f11 refractor (138x-46x) and possibly also my 6" f11 newtonian (246x-82x) as balance is rather critical in both and using a zoom will be very helpful, especially as I also have a 6-3mm Nagler zoom. Whether it will encourage me to sell my BGO/Radian eyepieces is doubtful for the time being.

The initial impression is very positive as it's clearly a well built eyepiece and the coatings are excellent, the zoom precise and smooth and the adjustable rubber eyecup a nice surprise.

I'll report back once I can get it in a scope and hopefully with continued favourable comment.

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John

John

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I'll be very interested to hear what you think of the Pentax XF 6.5 - 19.7 Shane. It's an eyepiece that I've considered a few times but I've never actually taken the plunge. Pentax eyepieces are beautifully put together. Like the XW's I think the XF zoom was designed for terrestrial spotting scopes but I fully expect that it aquits itself well for astro use as well.

Goodness knows what they could produce if Pentax really put their minds to astro products !

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Moonshane

Moonshane

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Indeed John. They seem content with the (presumably larger) birding market. One thing I forgot to mention is that the field stop softens a lot as you increase magnification when peering through the eyepiece in the hand. I don't think this will affect things greatly but perhaps is indicative of reasons why there are reported edge problems and CA for night time observing.

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F15Rules

F15Rules

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Hi Shane,

I'll be interested to hear how you get on with your Pentax zoom. I bought one about 3 years ago in mint used condition. I hated it. :huh:  :huh:  I couldn't believe how much CA was visible in my scopes when using it (TBH I can't be sure which scopes they were but I suspect it would have been a Tal 100RS and the Lome Ylena 6" Mak (and of course the Mak, being effectively an APO, couldn't have been the source of the bright purple CA). I also saw the very soft field edges that you described.

Of course it's possible that I had a bum unit, or that it wasn't compatible with my scopes. But I literally tried it once and sold it on as I really disliked it. I hope that your experience is different!

About 18 months ago I did a lot of online research into the Pentax SMC 8-24mm Zoom, which is the "big brother" (literally, it's a large unit!) of yours. Now that one gets glowing reports but is very pricey at around £400...http://www.firstlightoptics.com/pentax/pentax-xl-8-24mm-zoom.html

In the end I bought a Leica Vario 7-22mm which was superb, but I'm sure the big Pentax would have matched it or close to..

Do post a report on yours Shane, it would be nice to hear that my experience wasn't reflective of the usual performance of this eyepiece :laugh:

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spaceboy

spaceboy

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blumming hell !!! you beat me to it again Shane. Although in truth he did say there were a few others that beat me to the mark :rolleyes:

The reviews all look excellent for solar but not so favourable for night observing. My guess is because they probably use the same coatings as they do for their camera lens than what they would use for their astronomy eyepiece's. I come to this conclusion as the XF 6.5-19.5mm Zoom is as far as I'm aware for their spotting scopes which are often used during the day for stuff like bird watching. Dealing with UV/IR, haze and all the rest of that while giving the best colour and sharpness. I guess they also work in tandem with the spotting scope lens to give the best results? I doubt there is much concern for lifelike colour in astronomy eyepieces so I assume there priority is for coating allowing every bit of light through they can while keeping a flat field and reducing light scatter. Right tool for the job so to speak. Of course I may have it all wrong :grin:

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nightfisher

nightfisher

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I have to confess, when i read about quality zoom ep`s i start to toy with selling the volcano tops and cut back on the ep collection, but i dont see me doing this as i still really like the circle T`s and get on well with them, good luck with the Pentax, they do make some superb gear

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Mark at Beaufort

Mark at Beaufort

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I had the Pentax zoom since May of last year and bought it for solar viewing and for double star work with my 4" frac and 180mm Mak/Cass. I like it so much I bought a second Pentax zoom to use with my binoviewers - it did not work very well - optically okay but nose too big.

So I sold the Pentax zoom this week but kept the other.

I found the Pentax zoom great in the PST and for double stars. I also used it on occasions in the 10" Dob and 6" Newt for DSOs mainly planetary nebs. I never noticed any CA to be honest and just loved the zoom. I never used it much for DSO work because I had the 8mm, 13mm and 21mm Ethos.

I rarely use single EPs to view the Moon or Planets preferring the view using the binoviewers.

So Shane I hope you like it and I am sure you will.

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Moonshane

Moonshane

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Hi mate

Not really of any value at this stage. Based on my first impressions this morning with Jupiter and this afternoon with the sun I think my initial suspicions will prove correct, ie sun great, bright objects at night not so good off axis at least.

In Ha today it was excellent but in truth only as good as the seben zoom and TV plossl. The eye placement is a little easier with the Pentax though so it is the winner on solar currently although based on a single season on a classically difficult object in poor conditions, I won't be selling any of my fixed focal length eyepieces just yet.

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Moonshane

Moonshane

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Just had a further brief session with the Pentax zoom and my Vixen 80mm f11 refractor. This morning I used my 12" f4 dob with paracorr and this afternoon my 100mm pst mod based on a Tal. The Pentax was compared with the radian only in the dob and both the Seben zoom and radian in the frac.

. broadly the results are the same.

Ha - really excellent and provided fine detail and good eye placement. The detail was as good as the Seben zoom and tv plossl but eye placement better in the Pentax. The Pentax seemed to be a better match for my bf 5.

Jupiter and double stars-immediately when off axis there was a large amountof CA compared with the Seben and the Radian. All the detail was visible but the CA very distracting. The Seben held it's own against the radian in the f11 frac. More to follow

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Solar_observer

Solar_observer

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Just bought a 5mm vixen slv to use on those really good days to allow me to get up close and personal with active regions, proms etc.

this will give me 100x, I know I can reach this magnification as I used a 5mm bgo and the results were good even though the seeing and transparency that day was rubbish. I just couldn't get on with the eye relief, so the vixen should be a lot more comfortable.

Sent from my iPhone using Tapatalk

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