Jump to content

Banner.jpg.39bf5bb2e6bf87794d3e2a4b88f26f1b.jpg

Eyepiece Designs and Sacrifices


Naemeth
 Share

Eyepiece Design Sacrifices  

54 members have voted

  1. 1. What is the most important characteristic?

    • Astigmatism Control
    • Distortion Control
    • Field Curvature Control
    • Lateral Colour Control
      0
    • Cast of Colour Control ('Warm' vs 'Neutral' Tone)
      0
    • Good Contrast
    • Internal Reflection Control
    • Eye Relief
    • Kidney Beaning Control
    • Ghosting Control
    • Sharpness
  2. 2. What is the least important characteristic? (that you are willing to sacrifice)

    • Astigmatism Control
    • Distortion Control
      0
    • Field Curvature Control
    • Lateral Colour Control
    • Cast of Colour Control ('Warm' vs 'Neutral' Tone)
    • Good Contrast
      0
    • Internal Reflection Control
    • Eye Relief
    • Kidney Beaning Control
    • Ghosting Control
    • Sharpness
      0


Recommended Posts

  • 2 weeks later...

I killed this thread lol

Thats because you have a Pentax XO 5.1mm :p

If another one comes up - I'm going for it ! :smiley:

BTW - how would you rate a Powermated 8mm Ethos against the XO ?

(I've recently acquired a 2x PM you see .....)

  • Like 1
Link to comment
Share on other sites

Colour cast is important to me, but not 'the most important'. I much prefer the neutral cast of the Pentax XW and TV Delos over the warmer tones of some other TV and Meade eyepieces that I have tried. Eyerelief is the most import feature for me, (followed by aFOV but you didn't list that one), I also ticked contrast but I really mean light throughput lifting DSO's out of the background rather than planetary detail.

Least important for me is astigmatism control. Astigmatism / coma / field curvature...they all give stars that are not sharp at the edge if they are sharp in the middle. It doesn't matter much to me, what shape the 'not sharp' stars are.

Link to comment
Share on other sites

Thats because you have a Pentax XO 5.1mm :p

If another one comes up - I'm going for it ! :smiley:

BTW - how would you rate a Powermated 8mm Ethos against the XO ?

(I've recently acquired a 2x PM you see .....)

LOL. The xo is the best planetary eyepiece I've used. Completely neutral with no internal reflections. I never bother with a barlowed ethos as a result. To heavy and I like to keep the 1.25 adaptor in so I can switch between nag zooms, speeds zoom and 8mm plossl (due to coffee tint gives my favorite view of jupiter). I dont use the 8mm Ethos much actually apart from when I want a wider view at high mag (e.g. Orion nebula and moon).

Speaking of the moon the XO reveals details that just cant be seen in other eyepieces. this is where you notice the lack of internal reflection, the high contrast and sharpness. The eyepiece snaps into focus beautifully.

As stated earlier I like little eye relief which seems to go against the norm.

I always want the 2.5mm xo but it wouldn't get used and I have the nag zoom covering this area. Shame they never released other eyepieces.

Link to comment
Share on other sites

Thats because you have a Pentax XO 5.1mm :p

If another one comes up - I'm going for it ! :smiley:

BTW - how would you rate a Powermated 8mm Ethos against the XO ?

(I've recently acquired a 2x PM you see .....)

LOL. The xo is the best planetary eyepiece I've used. Completely neutral with no internal reflections. I never bother with a barlowed ethos as a result. To heavy and I like to keep the 1.25 adaptor in so I can switch between nag zooms, speeds zoom and 8mm plossl (due to coffee tint gives my favorite view of jupiter). I dont use the 8mm Ethos much actually apart from when I want a wider view at high mag (e.g. Orion nebula and moon).

Speaking of the moon the XO reveals details that just cant be seen in other eyepieces. this is where you notice the lack of internal reflection, the high contrast and sharpness. The eyepiece snaps into focus beautifully.

As stated earlier I like little eye relief which seems to go against the norm. I considered the 2.5 xo but it just wouldn't get used and I have the nag zoom which covers this area. Shame they never released other eyepieces in the range.

Link to comment
Share on other sites

Colour cast is important to me, but not 'the most important'. I much prefer the neutral cast of the Pentax XW and TV Delos over the warmer tones of some other TV and Meade eyepieces that I have tried. Eyerelief is the most import feature for me, (followed by aFOV but you didn't list that one), I also ticked contrast but I really mean light throughput lifting DSO's out of the background rather than planetary detail.

Least important for me is astigmatism control. Astigmatism / coma / field curvature...they all give stars that are not sharp at the edge if they are sharp in the middle. It doesn't matter much to me, what shape the 'not sharp' stars are.

It's funny how everyone has there own preferences. What you have said is basically the polar opposite of what I like. I hate eyepieces which have blurry stars at the edges. I like everything to be pin sharp :)

Link to comment
Share on other sites

It's funny how everyone has there own preferences. What you have said is basically the polar opposite of what I like. I hate eyepieces which have blurry stars at the edges. I like everything to be pin sharp :)

You misunderstand; I don't like blurry stars at the edge either, so I bought nice eyepieces to avoid EP astigmatism...now I see the OTA coma instead, so I still have blurry stars at the edges :rolleyes: I don't like it, but it doesn't bug me enough to buy a Parracor. One thing I really don't like is pincushion distortion. Probably a big part of why I prefer XW's to Panoptics. I love the ~70° aFOV though. I find that diameter image circle just right.

Link to comment
Share on other sites

An eyepiece I buy MUST have sharpness, minimal reflections and lack of scatter to maximize contrast if I am going to even consider a purchase of it.

I HATE eyepieces that have ghosting, scatter halos around bright stars, and a soft focus.

  • Like 1
Link to comment
Share on other sites

coma can't be corrected by an eyepiece, it's a feature of the primary. the astigmatism of lesser quality eyepieces can mask coma though, although when you replace the eyepiece with a better one, the coma is then revealed in all it's glory (until you then buy a corrector of course!). and the treadmill of spending trudges on :grin:

Sorry to disagree with you. The "Pretoria" eyepiece was specifically designed to correct for coma in F/4 telescopes.

Nigel

  • Like 1
Link to comment
Share on other sites

Nigel,

I think Shane was talking in general terms, though it's nice to see that someone addressed the issue. Was it a one off or are they available because I have never heard of them?

Alan.

Edited by alan potts
Link to comment
Share on other sites

They were designed in the 1980's by a couple of guy's ( Klee and McDowell ) at the CSIR ( I think ) in Pretoria, South Africa (hence the name ). University Optics made them for a while but they are rare. I don't think that many were made. F/4 telescopes were not very common at the time ( even though I had one, but not the eyepiece! ).

Nigel

Link to comment
Share on other sites

Nigel,

Thank you for that I have learnt something there. I guess it must be a bit of a collectors item by now then. I should imagine that if they were corrected for a F 4 scope they would show distrortions in say an F 8 scope and so on.

Alan.

Link to comment
Share on other sites

I guess one way to find out is to put a Newtonian coma corrector into a refractor and see what happens. I'd think it will introduce some undesirable effects in coma free scopes.

From what I read, long focal lengths XW were designed to correct field curvature in refractors, and they produced significant FC when used in Newtonian which has the opposite field curvature to refractors. I guess the same problem will also occur for coma correcting system

Link to comment
Share on other sites

Sorry to disagree with you. The "Pretoria" eyepiece was specifically designed to correct for coma in F/4 telescopes.

Nigel

no apology needed at all Nigel and thanks as I too learned something here. never heard of that eyepiece although thinking about it, technically, a Paracorr is an eyepiece in a way so my assurance was incorrect (or at least badly worded) on a number of levels :smiley:

Link to comment
Share on other sites

Sort of makes you wonder why it hasn't been taken up by one of the big boys and pushed to a new level.

Alan

May be because TV invented the Paracorr? An eyepiece that only work on fast Newtonian vs a fast Newt corrector that will work with any eyepiece.

I think the choice is obvious.

I don't know what's the inflation like in the last 22 years, but I guess $225 eyepiece in 1989 is probably more expensive than a $600 Ethos today.

Edited by E621Keith
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.