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Testing my eyepieces head to head......how?

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#1 spongebob@55

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Posted 02 April 2013 - 10:15 PM

I was out with my 102mm f/9.8 refractor 2 nights ago.
But I was trying to have a shoot out between my Pentax XW and Ex Sci and Baader Ortho 'similars' and outside of the eye relief of the Pentax, and the different FOVs, I couldn't really tell the difference in VISUAL object comparison. I was using Jupiter, M3, M42, and the double cluster. I want to sell one or the other, but can't decide. Seems the the Pentax focuses slightly easier, but has that overly huge eye relief, difficult eye placement and no eye cup, (at least for me personally) I have a lot of neighbors lights and so that's a problem. Right now I just have this refractor and a C14.
Seems like the ES shows a touch more false color, but I can't be sure of that, especially with my bad eyes. Any thoughts? They are:
ES 4.7 vs Pentax XW 5mm
ES 6.7 vs Pentax XW 7mm
ES 9mm 100 degree vs Pentax 10mm vs Baader 10mm

I won't get rid of the ES 9mm 100 degree.

How do you 'test' eyepieces?

Thanks
bob

#2 star drop

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Posted 02 April 2013 - 10:56 PM

You are comparing decent eyepieces. So if you don't see a difference in objects being compared that means that for your eyes combined with your equipment and observing conditions the other factors you already noted carry more weight. Don't worry about others when they say that a certain eyepiece enables them to see a tenth of a magnitude fainter object compared to the eyepiece which works better for you.
I test eyepieces by using them for many observing sessions. My case is simpler than yours because I only have one telescope. So use your eyepieces with one telescope for a few sessions. Then try the other telescope and you may pick different favorites. After a while you tend to not use certain ones. It may be that they provide too much magnification for the seeing in your area. Those I would keep to compare on the best nights in the future. The others that don't get used on any of your telescopes are the ones that I would sell.

#3 chrisg

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Posted 02 April 2013 - 11:06 PM

FWIW, I test my eyepieces during the day where there's simply more light and easier objects to observe, greater range of lighting conditions and contrasts to compare eyepieces. Poor seeing while viewing planets can obscure differences between eyepieces. In the end, it's best to confirm what you see during the day with astro objects and see if you like the way the eyepieces frame certain objects..

#4 Scanning4Comets

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Posted 02 April 2013 - 11:37 PM

I was out with my 102mm f/9.8 refractor 2 nights ago.
But I was trying to have a shoot out between my Pentax XW and Ex Sci and Baader Ortho 'similars' and outside of the eye relief of the Pentax, and the different FOVs, I couldn't really tell the difference in VISUAL object comparison. I was using Jupiter, M3, M42, and the double cluster. I want to sell one or the other, but can't decide. Seems the the Pentax focuses slightly easier, but has that overly huge eye relief, difficult eye placement and no eye cup, (at least for me personally) I have a lot of neighbors lights and so that's a problem. Right now I just have this refractor and a C14.
Seems like the ES shows a touch more false color, but I can't be sure of that, especially with my bad eyes. Any thoughts? They are:
ES 4.7 vs Pentax XW 5mm
ES 6.7 vs Pentax XW 7mm
ES 9mm 100 degree vs Pentax 10mm vs Baader 10mm

I won't get rid of the ES 9mm 100 degree.

How do you 'test' eyepieces?

Thanks
bob


Tell you what,

if you don't like the 5mm XW I have two eyepieces I can trade for it. *Wink wink* :lol:

cheers,

#5 Hermie

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Posted 03 April 2013 - 12:23 AM

Bob,

It is difficult to see the differences between eyepieces when you have to take one out, switch, refocus and look again. The differences that some people call huge here in the forums are often not that large. Also, a small aperture makes the difference less clear and seeing is often a larger issue when trying to compare similar eyepieces. Sometimes, other factors like size and weight might be critical for you.

In the end, you have to decide what works for you.

Regarding your XWs, you said that it doesn't have an eyecup. Are you aware that it has a twist-up cup? Just "unscrew" that black rubbery casing.

Hermie

#6 Starman81

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Posted 03 April 2013 - 12:37 AM

Just thinking out loud here... This is what I would do if I were doing a bona fide shootout and what others have done. Reference Bill P's epic 24-26mm EP shootout.

- Make a list of attributes that you feel you can judge: light throughput, 'perceived contrast', comfort/ergonomics, scatter control, color rendition, etc.

- Make a list of common aberrations that you are familiar with and test each eyepiece to see how much (if any) it has of these undesirable characteristics. For example pincushion distortion, barrel distortion, angular magnification distortion, ghosting, fuzzy field stop, edge-of-field brightening, field curvature, astigmatism, spherical aberration of the exit pupil (kidney-beaning), lateral color, etc.

- Pick appropriate targets to observe with the given test eyepieces to test for the above attributes/aberrations.

- Test eyepieces that are the same focal length or very close to the same or else the increased magnification/decreased exit pupil may be a difference-maker depending on how big the gap is between the two eyepieces.

- Do A/B observations as much as possible, switching from Test eyepiece A to Test eyepiece B on the same night at nearly the same time if possible to attempt to negate changing observing conditions.

- Make sure both eyepieces are clean!

But that's probably the long and hard way of doing it. You could just a few looks through both and go with your gut feel. :cool:

#7 Eddgie

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Posted 03 April 2013 - 08:14 AM

FWIW, I test my eyepieces during the day where there's simply more light and easier objects to observe, greater range of lighting conditions and contrasts to compare eyepieces. Poor seeing while viewing planets can obscure

differences between eyepieces. In the end, it's best to confirm what you see during the day with astro objects and see if you like the way the eyepieces frame certain objects..


This is what I used to do, though I no longer test eyepeieces because after going to this method I relized taht differences in performacne are almost impossible to see.

I used a variety of test charts and an indoor test range.

I use professional MTF charts (you can download these free) but you can also use a $20 bill or something similar.

These bills have an enormous amount of fine and low contrast detail to make them hard to counterfit.

I tape my charts in a spare bedroom at the end of a long hallway.

I studied the charts in advance with a high power magnfiying glass to locate the most difficult or lowest contrast detail on the target I could find.

I lower the lighting level in the bedroom, and then using my test telescope (which used to be a Televue 101) I would then view these most difficult target areas with different eyepeices to see which eyepiece showed the detail most easliy.

What I found personally that is was very rare to be able to see some detail on one eyepeice that was not visible in all of the other eyepeices when studying as many as 5 different areas of the bill looking at low contrasts, colors, and high contrast (super-fine printing which is all over modern money).

My favorite test chart was a Malasian $5. It was paled green and covered with large areas of quilted green lineds squares of varius shades of green so I was comparing contrast of green on green so that if the scope and eyepeices were tuned for best performacne on green, the target would be close to that color.

Again, what I personally came to believe after comparing about a dozen high quality 1.25" eyepeices (T6 Naglers, Orthos, Plossls and some combinations with barlows) was that differences in eyepiece performance as so subtle as to be hard to see.

So, that is what I recommend.

Here is my prediction.

If you do it, you still will not be able to see a difference, and this will allow you to just keep the eyepeice you prefer for other reasons and not feel like you are loosing out on anything.

#8 Jeff Morgan

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Posted 03 April 2013 - 08:47 AM

It's pretty simple really. While planetary viewing is the real acid test for any scope or eyepiece, seeing fluctuations make it very hard. So I prefer DSO's as being somewhat less sensitive to seeing.

1) Open cluster drift test. Pick something large (you mentioned the Double Cluster, which is an excellent subject), and allow it to drift across the field. Do several runs per eyepiece, choosing brighter members and see how sharp the focus is center to edge. Repeat with some of the faintest members you can find. If you lose the faint members as they leave the center of the field, this is not very good. Note that field curvature is different than aberrations and can be focused out - but do you want to? For all practical purposes, you don't want to deal with FC on a regular basis and it is as disqualifying as any other fault.

2) The complicated field. What you are looking for is the range of tones. I like areas like M11, M8, Delta Cygni, and M7 for this test. How extensively can you trace the dark and/or bright nebula (no filters allowed)? How fine a point do the faint stars focus to? How pronounced are tint differences in the brighter stars? Along a similar vein, Alvin Huey uses galaxy clusters but that takes a bit of aperture.

3) Most importantly, run a large number of trials over many nights. Conditions fluctuate, as do observer fatigue levels. The only thing you can do to "level the field" is take your time and use a large number of samples. Over the years I have found that the eyepiece decisions I regret are the ones that were made quickly. It's all too easy to be excited about an eyepiece after the initial evening of use.

#9 Tamiji Homma

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Posted 03 April 2013 - 09:08 AM

How do you 'test' eyepieces?



I use eyepiece turret to minimize eyepiece switching time. Before I start comparing eyepieces, I make sure I don't have to touch focuser when I switch eyepiece, I carefully par-focalize all eyepieces in the turret.

I don't trust my visual memory beyond a blink of an eye. So the eyepiece turret is important to me to compare eyepieces.

You can use artificial daytime target as well as real one at night but due to short time visual memory, I choose certain characteristic of eyepiece one at a time.

Comparison may last several months to over a year under various conditions and different scopes. It is sometimes boring unless something new in the comparison.

Interesting to note, I've never had WOW moment while I am comparing eyepieces.

Here is an example of 5mm eyepiece comparison.
Posted Image

PS: I use eyepiece turret with refractor only.

Tammy

#10 spongebob@55

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Posted 03 April 2013 - 11:12 AM

Regarding your XWs, you said that it doesn't have an eyecup. Are you aware that it has a twist-up cup? Just "unscrew" that black rubbery casing.

Hermie [/quote]

Hi Hermie, Thanks for reading my post so very closely. I am embarrassed to say that I didn't realize that; :foreheadslap: I feel so ignorant! But this is how I learn and I'm not too proud to say so to you'all. Thanks!

#11 spongebob@55

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Posted 03 April 2013 - 11:25 AM

Wow, what great information from everyone! I guess what I'll do is first take my time and not make any rash decisions. Then use my C14. Then do some of those star drifts and color tests.
Its interesting what you'all say that its hard to see differences/ no 'aha' moments, b/c I even look through my 'lowly' plossls and say to myself, dag, these things look fine'. Now, of course I'm looking at them right in the center of the view, so....
Thanks so much from this advanced beginner who has more equipment than sense at this moment in time! :bow:
Bob

#12 GeneT

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Posted 03 April 2013 - 01:16 PM

Seems the the Pentax focuses slightly easier, but has that overly huge eye relief, difficult eye placement and no eye cup,


I find the Pentax easy to use regarding eye placement, and the other aspects you mentioned are plus ups for me.

#13 jrbarnett

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Posted 03 April 2013 - 03:36 PM

Matched focal lengths, parfocalizing rings and a turret, and if you can pull it off, some method for "blinding" the observer to what brand/model of eyepiece he or she is using.

:grin:

- Jim

#14 BillP

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Posted 03 April 2013 - 04:37 PM

I...I was trying to have a shoot out between my Pentax XW and Ex Sci and Baader Ortho 'similars' and outside of the eye relief of the Pentax, and the different FOVs, I couldn't really tell the difference in VISUAL object comparison. I was using Jupiter, M3, M42, and the double cluster. I want to sell one or the other, but can't decide. ... How do you 'test' eyepieces?


When testing to decide what to keep or not, the criteria should be heavily subjective and personal. Afterall, you want to keep the eyepiece that you enjoy the most and "fits" best for you.

Of course there is the obvious like your preferences on AFOV and Eye Relief and Size/Weight considerations. Past that though is the visual portrayal of the target. You chose 4 favorites, a Planet a Glob and an Open Cluster and a Nebula. All 4 of these may indeed perform very differently in the eyepieces, so there may not be a clear cut winner. However, for me and my preferences here's what I look for in those targets:

Double Cluster -- I look for how orange the several carbon stars are in those clusters, especially the one that sits about mid way between the two. The other thing I look for is how well the very delicate faintest stars appear (i.e., which show more with adverted vision and which show more with direct vision). Finally, I take a "step back" and look at the cluster as a whole without focusing on any one part. When I do this it is easy to see how dimensional the cluster looks and how much "pop" the brighter stars have in the FOV. In effect, it makes it easier to see how 3-D the cluster is portrayed by the differing eyepieces.

Globs - For these I simply look to see which eyepiece shows me the most stars across the core with direct, then adverted vision. So which eyepiece pulls in more of the faintest, edge of vision stars.

Nebula - Particuarly for M42, I want to see which eyepiece shows the most detail in the "mottled" structure of the nebula. So I want the eyepiece that shows the nebula not just as a non-descript milky-white thing, but I want it to bring out the mottled latticework of bright and dark whisps that are laced throughout the brighter parts of the nebula. I also look for which eyepiece shows the greatest extent of the wings of the nebula and shows the mouth as being most pronounced and most black. Finally, there is Trap E & F and also some faint stars within one of the wings so important to me as to which eyepiece shows these most aesthetically.

Jupiter - For this planet, as with most, about the details visible. But beyond the obvious like the festoons and the swirls around the GRS, I also want the eyepiece that best shows the subtle colors and change of colors and hues in the polar regions. The poles have some very delicate blue hues and the change quite beautifully as they progress towards the pole itself. So usually warmer toned eyepeices do not show this well at all, so cooler toned ones typically do this best for my eye. Also, since the moons of Jupiter can be quite far away, want to make sure that the off-axis, where these moons may be, is relatively free of aberrations so they stay nice points or small orbs.

#15 Alan A.

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Posted 03 April 2013 - 04:39 PM

Eddgie,

Interesting report, how many feet did you test your targets at?

Alan

#16 Starman1

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Posted 03 April 2013 - 05:22 PM

One of my criteria in an undriven dob is to see what happens to the image as a globular drifts across the field. In a smaller scope, a rich open cluster would work.

It's one of the reasons the 13 Ethos has become my favorite eyepiece.
I use a Paracorr coma corrector and my scope's focal length is long enough to be very flat with that focal length of eyepiece. Hence, defocus at the edge of the field is usually due to field curvature, astigmatism, chromatic aberration, or some combination of factors if the stars don't stay focused to the edge of the field.

The first night I used the 13 Ethos, I focused M5, the globular, revealing tiny little pinpoint star images all the way to the center of the cluster, even showing me some tiny little triangles of stars in the center of the globular.
I watched the cluster drift across the field of the eyepiece and leave the edge of the field, still in tight focus, with the tiny little triangles still fully resolved. You simply can't improve upon that, no matter what the apparent field of the eyepiece, but for a 100 degree eyepiece to have that was astounding.

Now both your SCT and your refractor have somewhat more field curvature than my reflector, but the refractor's focal length is long enough that having most, if not all, of the field be free from aberration and in tight focus would seem to be a minimum requirement. Since the eyepieces you own have widely different apparent fields, if you are comparing a 70 degree field with a 100 degree field at roughly the same power, and the 70 degree eyepiece is sharp to the edge, then compare the inner 70 degrees of the 100 degree. Even if it breaks down at 90 degrees, it still has a larger sharp field than the 70 degree eyepiece. So try to compare apples with apples.

One relatively severe test is to put a planet or bright star just outside the field of view of the eyepiece and see what effects you see in the field that are caused by the star immediately outside the field of view. Internal scattered light is a big differentiator of eyepieces, and it can make a difference in seeing those deep-sky objects that are near bright stars, as well as close doubles, planetary details, etc.
Note that hardly any eyepieces pass this test with flying colors, but there are some radical differences among eyepieces that I've tested and owned.

#17 GeneT

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Posted 04 April 2013 - 11:07 AM

When testing to decide what to keep or not, the criteria should be heavily subjective and personal. Afterall, you want to keep the eyepiece that you enjoy the most and "fits" best for you.


I agree. I recommend that one trains their eye to see, then trust what they see. Also, what objects does one view the most? Some eyepieces work better on the planets, globulars and other brighter objects; others reveal a little more galactic structure. Dark skies and transparency are important for galaxies and nebula. I rarely have the opportunity to drive to the dark skies of West Texas, or New Mexico. Plus, galaxies and nebula bring up up the rear of objects I prefer to view. That affects my eyepiece selection. Large eye relief is probably the second or third most important criteria for me when choosing an eyepiece. Long eye relief eyepieces match up will with my favorite objects which are planets, the moon, globulars, and double and multiple stars. I have began to purchase some niche eyepieces such as the 5mm Pentax XO and a 8mm Brandon when I want to bump up a tad more detail on the planets, or when trying to split a close doubel.

Among the better eyepieces, the improvements in views are for the most part slight, but noticeable.

In the final analysis, all that matters is how the eye piece works for the individual.

#18 Sarkikos

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Posted 04 April 2013 - 12:00 PM

I think it's important to compare eyepieces while observing astronomical objects under field conditions. Bench testing or daylight testing eyepieces can yield useful imformation, but I'm not sure how well it extrapolates to what will be seen in the field at night. I have my doubts, judging from my own field experience compared to bench test / daylight results.

Mike

#19 Jaimo!

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Posted 04 April 2013 - 12:26 PM

I agree Mike.

Also use focal length appropriate targets in the sky, there are times I will use multiple targets depending on the eyepiece. After choosing a target, I make sure I am comfortable and have a notebook, and then start evaluating. First start by just basically looking through them and get a feel for each eyepiece, eye relief, field of view, blackness of background, how much focus changing is required between eyepieces... Then, on your chosen target, study the field and look for barely noticeable details: a close double, faint banding details on a planet, ice caps, the spot, etc... anything that is going to push the limits of your instrument. Swap eyepieces looking for the difficult details and record in your notebook. Be meticulous, as finding differences is sometimes VERY subtle. This may take a while as atmospheric conditions ebb and flow. The next step is to watch your target progress from one side of the field of view and look for any kind of aberrations as the target approaches the edge of the field and if you need to constantly re-adjust the focus as the target crosses the field. Also, if I want to be serious about the comparison, it will take most of an evening and I don't plan on doing any other observing so I can focus on the task at hand, I will many times repeat the session on another evening to increase my n.

I'm sure there is many other things to consider and more experienced observers who do other step. However, there are many evenings when I get a new eyepiece and just do a swap to get an idea of performance. But if I'm serious... It'll take an evening or two.

Jamie






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