I find my 7mm nagler a little to much power at times (just) and was looking at something a little longer for my 12" f5..this eyepiece does pop up alittle around the net but little info ..anyone useing one in a fast scope ?
how do you find it ?...good/ bad points etc
I have one which slots between my 7mm and 10mm Pentax XW's, for use in an 18"/F4.5 Obsession.
An absolute cracker of an eyepiece and almost the equal of the 7mm and 10mm XW series.
Highly recommended irrespective of cost, but at the value price of about $200+ it represents exceptional value. It is a superior eyepiece to the 8mm TV Radian and the 8mm Hyperion/Stratus IMO.
One other rather specific point about this eyepiece: the combination of light weight, compact size & good eye relief make it perfect for use in binoviewers & binoscopes. I use a pair of XF 8.5s as my high power eyepieces in my bino (which is F/5 btw). Of course it is also great in cyclops mode.
A post on the Astromart forums states that this eyepiece is not good for lunar observation - too much glare from poor baffling and no edge blackening of the field group. Can anyone here comment on this? Also how would the amount of glare compare to that seen in the Burgess Planetary eyepieces?
A post on the Astromart forums states that this eyepiece is not good for lunar observation - too much glare from poor baffling and no edge blackening of the field group. Can anyone here comment on this? Also how would the amount of glare compare to that seen in the Burgess Planetary eyepieces?
The Pentax 8.5 XF is a better eyepiece in every respect than the Burgess Planetaries. So they should be considering the price of each.
I use the 8.5XF in an 18" telescope which will exacerbate the glare problem compared to a smaller telescope due to the infinitely brighter image, and I don't have a problem. You only get the glare when you position your eye at an angle to the exit pupil which isn't how most people try to observe.
Thats not a problem for me tony as my lunar observing consists of wishing it would bugger off so the sky gets dark again...
I went and ordered one today from japan .. couldn't find the xf line here in oz ..after I ordererd I noticed bintel stock them ..I wasn't aware they stocked pentax eyepieces and the price was very similar.
I have been out a couple of times with this eyepiece and find it
great to use . ( 12" f5 dob)
As by pic its very compact and weight wise is very light
While there is a little info out there it does seem a little scarce when you go looking ..A review of the 12 mm did mention some noticable f/c .. while I don't intentionally go looking for problems with eyepeices switching between my 27 panoptic and 28 mm pretoria I did notice a little in the panoptic over time..Though my eyes must accomodate it fairly well as I don't find it annoying. The 8.5 pentax seems pretty good in regard as far as i can tell ..while I like my naglers ..I must admit the views through a couple of
other shorter f/l xws are just that "little" more natural looking ..this one
has me thinking the same.
overall for $190 this is great value imo
tony I can't see any glare in brighter objects with this one so far
my naglers show a little change in fringe colours on really bright objects
I would say in comparisson its quite noticable that the pentax dosn't
seem to show this at all ( so far ) .. maybe in time i'll change my mind
but to be honest for the asking price theres not much wrong with this
bit of glass...other than maybe it should have a higher price tag
Good to hear about the lack of glare Graham - this eyepiece is at the top of my list if I need one at that focal length. I was interested in peoples opinions here since glare was reported by one of the experienced guys on the other forum (Mike Hosea from memory - but don't quote me on that). Of course, regardless of other peoples experience, you never know until you try it yourself. Burgess Planetaries are a good example - their reputation exceeds their performance in my experience - not a bad eyepiece, but not the bees knees either IMHO.
(thought I should edit and add the IMHO - it's damn scary expressing opinions here - you never know where the flak will come from)
You only get the glare when you position your eye at an angle to the exit pupil
John when i finished my 12 " I was picking up a little glare at low power
this had me wondering if its the the truss design or not enough
black paint inside the uta, more stray light etc ,etc..Anyway after attending to these little things it seemed to dissappear..A while later through some more tinkering my 12" was out of action so I grabbed my 10 " ..and there was the glare again at low power ... never had a problem with it ever before .. Both focusers were at a slightly differant oriantation to one another.. and on reading your comments above now believe while I was very used to the eyepieces I was getting my eyeplacement just a little wrong ... cheers graham
John when i finished my 12 " I was picking up a little glare at low power
this had me wondering if its the the truss design or not enough
black paint inside the uta, more stray light etc ,etc..Anyway after attending to these little things it seemed to dissappear..A while later through some more tinkering my 12" was out of action so I grabbed my 10 " ..and there was the glare again at low power ... never had a problem with it ever before .. Both focusers were at a slightly differant oriantation to one another.. and on reading your comments above now believe while I was very used to the eyepieces I was getting my eyeplacement just a little wrong ... cheers graham
i have the 8.5 and the 12 they are used on 16 12 10 and 8 reflectors and 8 and 11 sgt. the are better than hyperions stratus and radians they compare with williams uwans 7 and 4 but i think the williams are better due to their wider field of view.However on planets moon,clusters and most messier objects they are very good value.their low weight means that you can also use them on an etx without worring about the gears being stripped and for most scopes you dont need to worry about balance issues.Bintel were very good on service and i cant see the point of buying them overseas when you want a warranty qld
Have you guys (especially qld) compared the xf 12 with nagler 12 T4 before? I know they are in different league, but I am just curious about the difference in contrast and sharpness they might have. Also, does xf12 have field curvature problem in a 16" f4.5?
Thanks.
Have you guys (especially qld) compared the xf 12 with nagler 12 T4 before? I know they are in different league, but I am just curious about the difference in contrast and sharpness they might have. Also, does xf12 have field curvature problem in a 16" f4.5?
Thanks.
not on my 16 lightbridge . i have not compared this ep with the nagler 12
the views of the jewel box on my astro 8 newtonian (f6) are breathtaking ,the stars are sharp, colour is distinct (carbon star stands out)contrast background to stars almost like a mak velvet black.ON my orion ed80 the views are better still, why bother with the nagler, i dont with my other ep when i want a 12 ep......and they are so light to handle and easy to keep warm in my pocket on a dewey night qld
The 12mm XF will likely show some FC in most scopes to some users, myself included. Others have better adaptability in their eyes and will not notice so easily (because their eyes immediately refocus when looking away from the centre of FOV). It is best to try for yourself and spend some time with the EP if possible (also because perceived FC can be minimised by getting used to the EP and tweaking the focuser just right). I love the 12mm XF. The FC is not such a big deal for me now as it was when I got it.
Thanks for your feedback, qld and janoskiss.
I am interested to know more about this eyepiece. I know from the review in cloudynights that it is very contrasty. How well is the correction it offers in a f4.5 scope? Do you notice any astigmatism at the edge? Do you see any colour at the edge for bright objects like moon or Sirius? Any pincushioning? Will 60 deg fov post a though job for my unguided dob since xf12 will offer 152X, 2.66 mm exit pupil and 23.6 arcmin true field?
Thanks.
Thanks for your feedback, qld and janoskiss.
I am interested to know more about this eyepiece. I know from the review in cloudynights that it is very contrasty. How well is the correction it offers in a f4.5 scope? Do you notice any astigmatism at the edge? Do you see any colour at the edge for bright objects like moon or Sirius? Any pincushioning? Will 60 deg fov post a though job for my unguided dob since xf12 will offer 152X, 2.66 mm exit pupil and 23.6 arcmin true field?
Thanks.
well i think that you should put hand in pocket and buy one, incidently
the 8.5 is also great they both seem to work on any telescope and the wow factor is there qld
Thanks for your feedback, qld and janoskiss.
I am interested to know more about this eyepiece. I know from the review in cloudynights that it is very contrasty. How well is the correction it offers in a f4.5 scope? Do you notice any astigmatism at the edge? Do you see any colour at the edge for bright objects like moon or Sirius? Any pincushioning? Will 60 deg fov post a though job for my unguided dob since xf12 will offer 152X, 2.66 mm exit pupil and 23.6 arcmin true field?
Thanks.
The observed field curvature of the eyepiece is dependent on the curvature of the focal plane of the telesope, either positive or negative field curvature and the ability of the observers own eye to accomodate minor focus adjustments at the edge of field. It will appear worse to some people than others in the same telescope. In terms of newtonian reflectors the field curvature is dependent on the focal length of the scope (radius of curvature of the paraboloid) and not its F-ratio. In other words you will see less field curvature stemming from the eyepiece/telescope interaction in a 16"/F4.5 than you will in say a 12"/F5 or a 10"/F6 scope because the larger scope has a longer focal length and thus a larger radius of curvature.
That having been said most other aberrations including off axis astigmatism and coma, will manifest at faster F-ratios without regard to the telescope focal length.
I haven't used the 12mm XF in my 18"/F4.5 Obsession so can't comment on its field curvature issues. I can tell you that if there are any they will be less noticeable in your 16"/F4.5 than they will be in smaller newtonians with a shorter focal length.
..I wasn't aware they stocked pentax eyepieces and the price was very similar.
... never had a problem with it ever before .. Both focusers were at a slightly differant oriantation to one another.. and on reading your comments above now believe while I was very used to the eyepieces I was getting my eyeplacement just a little wrong ... cheers graham
