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  #1  
Old 18-09-2018, 10:16 AM
Outcast (Carlton)
Still a Noob....

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Join Date: Oct 2008
Location: Cairns, Qld
Posts: 101
Quality eyepieces

Okay, I am considering upgrading my eyepieces but, my budget is maybe up to $200 per eyepiece, a little more for the wideview. If I can spend less, I will & I am certainly open to purchasing secondhand. My scopes are 8"SCT & 80mm ED APO (F6)

My current range of eyepieces are listed in my signature; nothing very exotic & to be honest, I know I can get away with less. The 4000 series Plossls came with the SCT. The TMB II is a genuine TMB planetary purchased from VTI Optics a number of years ago. What if any of my current eyepieces are worth keeping?

Looking for a small selection (perhaps around 4 of each) of wideview eyepieces for DSS, etc & eyepieces for planetary & lunar use.

Considering the following:

Planetary (28, 18, 12 & 8mm or thereabouts): Edmund Optic RKE, Fujiyama Orthoscopics, Vixen SLV, Pentax XF & Televue Plossls

Wideview2 (32, 20, 12 & 8mm): ES 82*, Meade UWA for DSS/wideview

Thoughts? Opinions?

Do I need this many?? Not trying to go minimalist.. just looking for quality (on a budget) not necessarily quantity.

I cannot afford Panoptics, Ethos, Delos or Delites.. never gonna happen.

Last edited by Outcast; 18-09-2018 at 12:11 PM.
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  #2  
Old 18-09-2018, 12:58 PM
N1 (Mirko)
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Location: Dunners Nu Zulland
Posts: 925
Hi Carlton,


No, you don't need that many. But you may find you want that many, which is different, and less rational I've been there, done that.

I'd consider one (or a combination) of these two approaches:


1. Exit Pupil

I've found that 2-3 eyepieces per scope pretty much covers what I need (as opposed to want) By exit pupil (EP focal length divided by scope f ratio), that would be:

one for the 0.5-1mm bracket
one for the 2-3mm bracket
one for the 4-5mm bracket.

Assuming you are happy to use your Powermate whenever needed (so aren't put of by the extra weight etc), the resulting number of EPs will not be all that many.



2. Experience with existing gear

The good news is that of your existing EPs, none are truly junk. Even the "least" favourable (the GSOs) are far from crappy, and all should be pretty darn good on-axis (centre of field). The bad news is that the main areas of performance gain by upgrading will therefore relate to off-axis-stuff like AFOV, coma correction, off-axis sharpness, distortion. On-axis, you are unlikely to gain over what you have already (if you insist, the best on-axis performers of all the EPs you list, are the TV Plössls IMHO). So find the EPs from your current lineup that give you the best views on-axis.

Once you have identifed the focal lengths that work best based on 1 or 2 above, you can decide what you'd like to improve off-axis (more AFOV, better edge performance, etc), and for ergonomics (mainly eye relief and eye placement), then go from there.

As a minimum, I'd be keeping the PM and the 6.7 Meade.
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  #3  
Old 19-09-2018, 12:55 PM
Outcast (Carlton)
Still a Noob....

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Join Date: Oct 2008
Location: Cairns, Qld
Posts: 101
Hi Mirko,

Thanks for the advice; I have managed to pickup some Fujiyama Orthoscopics just now for a great price via the ISS classifieds.

Had done a fair bit of research regarding these vs the TV Plossls & concluded that performance wise they should be on par. Given the narrow FOV that orthoscopics provide, I concluded that off axis performance should not really be an issue however, again, my research indicates that off axis performance of these should be on par with the TVs.

Will have a couple of gaps to fill once these arrive but, that will have to wait til I am a little more cashed up.

Currently looking at the Explore Scientific 82* eyepieces to fulfill my wideview needs but, again, they will have to await the accumulation of funds. I do like the Meade UWA so, may see if I can pickup the FL I need in those, perhaps secondhand if they come up on here.

I'll now look to move on some of my surplus eyepieces to fund new purchases. Will keep a selection of the Meade Plossls for community ASTRO nights that I have just become involved with; will save wear & tear on the good eyepieces.

Cheers

Carlton

Quote:
Originally Posted by N1 View Post
Hi Carlton,


No, you don't need that many. But you may find you want that many, which is different, and less rational I've been there, done that.

I'd consider one (or a combination) of these two approaches:


1. Exit Pupil

I've found that 2-3 eyepieces per scope pretty much covers what I need (as opposed to want) By exit pupil (EP focal length divided by scope f ratio), that would be:

one for the 0.5-1mm bracket
one for the 2-3mm bracket
one for the 4-5mm bracket.

Assuming you are happy to use your Powermate whenever needed (so aren't put of by the extra weight etc), the resulting number of EPs will not be all that many.



2. Experience with existing gear

The good news is that of your existing EPs, none are truly junk. Even the "least" favourable (the GSOs) are far from crappy, and all should be pretty darn good on-axis (centre of field). The bad news is that the main areas of performance gain by upgrading will therefore relate to off-axis-stuff like AFOV, coma correction, off-axis sharpness, distortion. On-axis, you are unlikely to gain over what you have already (if you insist, the best on-axis performers of all the EPs you list, are the TV Plössls IMHO). So find the EPs from your current lineup that give you the best views on-axis.

Once you have identifed the focal lengths that work best based on 1 or 2 above, you can decide what you'd like to improve off-axis (more AFOV, better edge performance, etc), and for ergonomics (mainly eye relief and eye placement), then go from there.

As a minimum, I'd be keeping the PM and the 6.7 Meade.
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  #4  
Old 26-09-2018, 11:10 PM
Wavytone (Nick)
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Join Date: Jul 2008
Location: Killara, Sydney
Posts: 3,207
Hi Carlton,

With an SCT you need:

1 low-power eyepiece that gives the widest true field available for the size of the barrel - this means an eyepiece with no field stop inside the barrel. Focal length isn't important - could be anywhere from 25mm to 38mm. The type of eyepiece isn't important either as low-power ones are easy to design. A SWA for example would do nicely and these are under $100, an Erfle or a Plossl will do fine.

A couple of medium power eyepieces around 18 and 12mm, 12mm being a real sweet-spot for SCT's.

A couple of high-power eyepieces - for an f/10 SCT you will find 10, 9 and 7 useful.

Last edited by Wavytone; 26-09-2018 at 11:30 PM.
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