ES 68 24mm or ES 82 24mm for BKP 200 DS

[N3ptune]

I use my 25mm Xcel LX often and maybe it would be nice to replace it with a better eyepiece... (why not?)  since It's an important focal length and I like my ES 4.7mm so much. What do you think would be the very best choice for my telescope? Both have a similar eye relief, 68mm is a bit better.

https://explorescientificusa.com/collections/68-series-eyepiece/products/68-24mm

https://explorescientificusa.com/collections/82-series-eyepiece/products/82-24mm

Thanks

[John]

One is 1.25" and the other 2" - does that matter to you ?

I've voted for the 24 / 82 because I like ultra wide fields but do you ?

Quality-wise there is probably nothing in it.

[N3ptune]

Hemmm I read the spec sheet too fast and didn't noticed the 82mm has a 2" barrel. I would prefer a 1.25 barrel so I can use it with my 1.25 barlow..

 

[John]

44 minutes ago, N3ptune said:

Hemmm I read the spec sheet too fast and didn't noticed the 82mm has a 2" barrel. I would prefer a 1.25 barrel so I can use it with my 1.25 barlow..

 

Well you can vote for that and make it 50:50

 

 

[Ricochet]

1 hour ago, N3ptune said:

Hemmm I read the spec sheet too fast and didn't noticed the 82mm has a 2" barrel. I would prefer a 1.25 barrel so I can use it with my 1.25 barlow..

 

I found that the difference between the eye relief and eye up height of the 24mm 68° made it unuseable with a standard barlow extending the eye relief even further. 

[Red Dwarfer]

I voted 24mm 68* , because it`s about half the price as the 2" 82* 

My ES 8.8mm 82* is one of my favourite lenses , but I`d go for the 24mm 68* for the reason above , plus optically , as John said , they`re probably the same .

[Ben the Ignorant]

I am assuming it will be your lowest power eyepiece, so I voted 82° because the lowest power eyepiece needs to have the widest possible field, or your scope produces an image that's not fully displayed. Why have an image as wide as the 2" focuser if you cut off its rim with a narrower eyepiece?

[N3ptune]

4 hours ago, Ricochet said:

I found that the difference between the eye relief and eye up height of the 24mm 68° made it unuseable with a standard barlow extending the eye relief even further. 

Ok that's not a good news... 

4 minutes ago, Ben the Ignorant said:

I am assuming it will be your lowest power eyepiece, so I voted 82° because the lowest power eyepiece needs to have the widest possible field, or your scope produces an image that's not fully displayed. Why have an image as wide as the 2" focuser if you cut off its rim with a narrower eyepiece?

Actually no I have a 32mm 2" eyepiece already. I thought the ES 82d had a 1.25" barrel, the same thing has the 68d, my mistake. My goal was to be able to use the 2x barlow with it.. but has stated previously.. it's not going to be good option or improvement over my actual 25mm with 2x barlow.. (very long eye relief)

 

[alan potts]

I can only speak for the Meade versions of these eyepieces and I had both at the same time, the 82 is much biiger than the 68 and heavier. If this does not matter I would go for the 82, in my view it is a better eyepiece, Wish I had kept it in truth.

Alan

[John]

Barlow lenses have an additional effect of extending the eye relief of the eyepiece they are used with so using them with eyepieces that already have longish eye relief results in the correct eye positioning moving away from the top of the eyepiece and the light shading eyecup. Not a particularly effective way of observing I've found.

If you can get a Powermate, Telextender or Focal Extender or similar, these provide the image amplification without moving the eye relief so they do work better with eyepieces that already have longer eye relief.

The resulting "stack" can be quite tall though ! (ES 20mm / 100 plus 2x Powermate pictured below with the 31mm nagler and 8mm plossl for scale):

 

[Piero]

I answered 24mm 82 deg. Said this, I feel that any answer to your question is completely subjective.

It really depends on your budget, future eyepiece plan, tastes, and who knows what else. 

The 24mm 82 deg can cause balancing issues which can be dealt using counterweights relatively easily. The 24mm 82 will show you more sky and this can be highly desirable for a low power eyepiece, whether used as a finder or for low power observation of nebulae. 

The size of the 24mm 68 deg is more in line with smaller 1.25" eyepieces, so swapping eyepieces will be more straight forward. 

I have a panoptic 24mm which has 68 deg AFOV. Considering the main specs only (24mm f.l., 68deg afov, 15mm eye relief, 230g), it is a powerful eyepiece in a small package. On my dob 8" F6, it gives 1.29 deg fov (it gives 1.55deg with your 8" F5). Although this is completely fine as a low power eyepiece, I prefer a larger fov with this telescope at low power. The 82 deg version will give you nearly 2deg fov, which is nice for the plejades, Orion nebula, North America nebula, and few other large and stunning targets. 

 

Slightly off topic. Whatever you decide to get, I strongly suggest to get 2" nebula filters if you get interested in this area. You can screw these onto a 2"-to-1.25" adapter and use them with 1.25" eyepieces. They cost nearly twice the 1.25" variants, but they are more practical to use and if one day you decide to move to 2" eyepieces, you don't have to replace them. 

[N3ptune]

Hello thanks for your answers again for the choice between the 2 eyepieces.

My objective was to replace the Xcel LX with something better with these factors in this specific order of importance:

1: Gain comfort with the 24mm FL, to have an eyepiece with easy and permissive eye position / to get an even better aberration correction up to the edges.

2 To be able to have  40x and 80x, 2 powers I use often.

3 A gain of AFOV as a bonus.. but I live well with the current 60d.

I notice when using the ES 4.7mm, the eye relief is short but somewhat, the eyepiece is permissive and the position of my eye it's comfortable at whatever angle. With the Xcel LX, it has a very long eye relief and the exit pupil is at a very specific and limited place in space, if I move my head at the wrong angle I lose the image and get black edges all around. That's annoying a bit while sketching and that's the specific thing I wish to improve. Especially with the equatorial mount when the eyepiece is placed at an odd position? it's hard to keep a good balance while observing.

The eye cup of the XcelLX will help but it has it's limitations.

At the beginning I thought the 82d had a 1.25 barrel, that's why I was interested in knowing the difference between them.. but now that I know it has a 2", that's not what I want to do. Mainly to prevent switching eyepiece adaptors during observation.

- I don't search for the lowest possible power or the largest AFOV in this case.

- I don't wish to buy too much things either and have a big bill, plus making thing I already have useless, that's a double waste.

==============

These are my ideas this morning:

ORIGINAL GOAL:

To replace the 25mm Xcel LX by a ES 24mm to get 40x and 80x with permissive eye position, better correction, better FOV, better eyepiece. But likely unusable with the barlow, deal breaker.

SOLUTION A: Budget wise

A. Getting the 24mm 68d eyepiece to use at 40x without a barlow. That's about 230$ with taxes and shipping, which is a decent price for a good EP.

B. The next month, I order 12.7 Orthoscopic Fujiyama with a small AFOV to get the important 80x but with maximum sharpness. That's 140$ all included for new one, very good price.

TOTAL 370$ all included for 2 good eyepieces for the same price has the 24mm 82d (Which should also be useless with my 120$ Barlow)

Downside, I get 42d afov at 80x which is not the end of the world but still annoying a tiny bit.

Bonus: Maybe the 24mm 68d will be better with the current barlow then my current 25mm Xcel LX? That's an untested statement but entirely possible. It could be a temporary solution.

SOLUTION B: Over budget

A. Getting the 24mm 68d eyepiece to use at 40x without a barlow 230$

B. Getting the best Televue Barlow of all time second hand. 280$

That would give me an incredible package of wide field and quality.

TOTAL: 510$

 

 

[Ricochet]

8 hours ago, N3ptune said:

To replace the 25mm Xcel LX by a ES 24mm to get 40x and 80x with permissive eye position, better correction, better FOV, better eyepiece. But likely unusable with the barlow, deal breaker.

Bear in mind that we all have different fact shapes so you may find you do not have the same issues I had. Also, if you look on the second hand market you might be able to find a 24mm Maxvision or Meade SWA, which is the same eyepiece but with a twist up eyecup which you could increase when using it with the barlow (but not waterproof like the new version).

[N3ptune]

1 hour ago, Ricochet said:

Bear in mind that we all have different fact shapes so you may find you do not have the same issues I had. Also, if you look on the second hand market you might be able to find a 24mm Maxvision or Meade SWA, which is the same eyepiece but with a twist up eyecup which you could increase when using it with the barlow (but not waterproof like the new version).

Hello, I am glad you tell me about the flaws the eyepiece has... this thread is very helpful for me. I can know the truth here which would be impossible to know otherwise, or I need to try various eyepieces myself at an event. A seller isn't really an ally either. 

This forum is making mankind go forward with what's good for the consumer or the hobbyist, that's the most important thing. it's pointing bad corporate issue and traps like we saw previously, people can't be fooled anymore.

I am being non reasonable with this eyepiece story, it's not like if my Xcel LX are bad, they are far from bad. At 40x and 80x with the barlow, I could live with them for the rest of my life and be happy, you guys always say the right things to help me take the right decision and protect my money from being wasted.

I'll open the eye, if I see a maxvision or a Meade SWA but right now, I feel happy with the Xcel LX again.  It was a winning bet from the beginning.

But It's not over, I feel it (((: 

[John]

One thing I've learned from trying lots and lots of eyepieces is that what works well for one person might not work well for another. Most of the eyepieces produced today are capable of good performance and all have their quirks.

It's so easy to read some negative feedback on an eyepiece that you have actually rather enjoyed using and start to wonder if the "grass is greener" elsewhere. It's taken me a long time to learn to trust my own feelings (as Obi Wan would say) 

 

[N3ptune]

1 hour ago, John said:

One thing I've learned from trying lots and lots of eyepieces is that what works well for one person might not work well for another. Most of the eyepieces produced today are capable of good performance and all have their quirks.

It's so easy to read some negative feedback on an eyepiece that you have actually rather enjoyed using and start to wonder if the "grass is greener" elsewhere. It's taken me a long time to learn to trust my own feelings (as Obi Wan would say) 

 

I know you are right with your eyepieces suggestions and backing most of the time because of the price..

I know I settle for less with some EPs too, but every time I enjoy the sky very much (has lately) it gives me some motivation to upgrade my eyepieces.. some kind of reward to match my new experiences. In fact, I feel ready for a high quality low power EP for some time now.

On 8/29/2017 at 05:01, Piero said:

I answered 24mm 82 deg. Said this, I feel that any answer to your question is completely subjective.

It really depends on your budget, future eyepiece plan, tastes, and who knows what else. 

The 24mm 82 deg can cause balancing issues which can be dealt using counterweights relatively easily. The 24mm 82 will show you more sky and this can be highly desirable for a low power eyepiece, whether used as a finder or for low power observation of nebulae. 

The size of the 24mm 68 deg is more in line with smaller 1.25" eyepieces, so swapping eyepieces will be more straight forward. 

I have a panoptic 24mm which has 68 deg AFOV. Considering the main specs only (24mm f.l., 68deg afov, 15mm eye relief, 230g), it is a powerful eyepiece in a small package. On my dob 8" F6, it gives 1.29 deg fov (it gives 1.55deg with your 8" F5). Although this is completely fine as a low power eyepiece, I prefer a larger fov with this telescope at low power. The 82 deg version will give you nearly 2deg fov, which is nice for the plejades, Orion nebula, North America nebula, and few other large and stunning targets. 

 

Slightly off topic. Whatever you decide to get, I strongly suggest to get 2" nebula filters if you get interested in this area. You can screw these onto a 2"-to-1.25" adapter and use them with 1.25" eyepieces. They cost nearly twice the 1.25" variants, but they are more practical to use and if one day you decide to move to 2" eyepieces, you don't have to replace them. 

Did you ever tried your 24mm Panoptic with a 2x barlow to double it's power? if so, what were your impressions regarding the comfort, eye position and eye relief?

thanks

[Piero]

12 hours ago, N3ptune said:

Did you ever tried your 24mm Panoptic with a 2x barlow to double it's power? if so, what were your impressions regarding the comfort, eye position and eye relief?

thanks

I never tried it with a barlow but I did with a powermate 2.5x and with a breeder SA 2x barlow (which is a tele-extender, not a barlow, despite the name!). Therefore there was no change in eye relief or eye position. The 24Pan has an eye relief of 15mm, slightly tight if one observed with spectacles, but comfortable without. It works very well with a tele-extender in my opinion. The 24 Pan as well as the 35 Pan show a lot of rectilinear distortion in order to minimise several aberration near the edge. While this is not a necessarily an issue when observing a star cluster, it is when observing large objects like our Moon. This appears like an oval near the edge. Nothing to be worried about but just to be aware of. 

 

I would also like to say that I feel John is quite right when he said "One thing I've learned from trying lots and lots of eyepieces is that what works well for one person might not work well for another."

I'm still learning this and do realise that in a few occasions I also spoke very favourably about some equipment that I like but other people might not. A wise suggestion requires a reasonable amount of experience and knowledge..

[N3ptune]

17 hours ago, Piero said:

I never tried it with a barlow but I did with a powermate 2.5x and with a breeder SA 2x barlow (which is a tele-extender, not a barlow, despite the name!). Therefore there was no change in eye relief or eye position. The 24Pan has an eye relief of 15mm, slightly tight if one observed with spectacles, but comfortable without. It works very well with a tele-extender in my opinion. The 24 Pan as well as the 35 Pan show a lot of rectilinear distortion in order to minimise several aberration near the edge. While this is not a necessarily an issue when observing a star cluster, it is when observing large objects like our Moon. This appears like an oval near the edge. Nothing to be worried about but just to be aware of. 

 

I would also like to say that I feel John is quite right when he said "One thing I've learned from trying lots and lots of eyepieces is that what works well for one person might not work well for another."

I'm still learning this and do realise that in a few occasions I also spoke very favourably about some equipment that I like but other people might not. A wise suggestion requires a reasonable amount of experience and knowledge..

The Panoptic 24mm looks like an interesting choice, thanks for these great informations Piero.

I found this example of the rectilinear distortion, is that it?

I noticed with my ES 4.7mm, it has the negative version of this distortion, I saw it once while moving the telescope over a star field, but it's invisible if the instrument is stable..  I can't see any effects on the moon either, 24mm is not really a FL I use for the moon anyway. On CN, people say the Pan is better overall then the ES but the ES has some supporter saying it's eye relief it's a bit longer.

On 8/28/2017 at 15:20, Ricochet said:

I found that the difference between the eye relief and eye up height of the 24mm 68° made it unuseable with a standard barlow extending the eye relief even further. 

Hello Ricochet, I am rereading what you said previously and I don't understand the difference with eye relief and eye up height.. it's not the same thing?

[Ricochet]

1 hour ago, N3ptune said:

Hello Ricochet, I am rereading what you said previously and I don't understand the difference with eye relief and eye up height.. it's not the same thing?

Hi, sorry there was a spelling/autocorrect error in my previous post. It should have been "eye cup" height rather than "eye up". 

Anyway, eye cup height is the distance between the top of the eye lens and the top of the rubber eye cup. 

Eye relief is the distance between the eye lens and the point floating in mid air where the image forms and you have to put your eye. 

For my face shape, the eye relief was a bit longer than the eye cup height so I had to "hover" over the eyepiece. With the addition of a barlow the eye relief was even further above the eye cup, making viewing even more difficult. 

[Piero]

1 hour ago, N3ptune said:

The Panoptic 24mm looks like an interesting choice, thanks for these great informations Piero.

I found this example of the rectilinear distortion, is that it?

 

 

I'm still learning how optics work, so please don't take my comment regarding this subject as conclusive.  

As far as I've understood, we have rectilinear distortion (RD) and angular magnification distortion (AMD). There are other distortions / aberrations (e.g. astigmatism, chromatic aberration, spherical aberration, field curvature, etc), but we restrict this comment to RD and AMD. Both these distortions are present at the edge of a (wide field) eyepiece. 

RD causes straight lines to bow in toward the center (pincushion distortion) or bow out away from the center (barrel distortion). It's a bit like placing the field on a sphere. In one case we look this field from the inside of this sphere, whereas in the other case we look at it from the outside. In any case, these straight lines bend near the edge. AMD causes a change in magnification between the centre and the edge. This can be detected on double stars (they can become tighter near the edge) or by changes in speed of a star through the fov. 

 

RD and AMD cannot be minimised at the same time. The smaller AMD, the larger RD, and vice versa. As you can see in the plot below, orthoscopic eyepieces are not really affected by this AMD / RD dichotomy. 

This might help: http://www.televue.com/engine/TV3b_page.asp?return=Advice&id=113  

- No RD:     y = f · tan ß

- No AMD:   y = f · ß

(where y is the off-axis distance in the focal plane, ß the image angle from the optical axis, and f the focal length of the eyepiece)

 

Said this, if I were you I would buy s/h if possible so that the eyepiece you get can be tried and possibly re-sold without wasting much money (possibly nothing). There are really many factors in eyepieces. These are not crucial for a nice night out and enjoy this hobby. For many people these details are completely not important. What matters is to have fun with whatever we have. Personal tastes are generally developed gradually and through experience.  

[John]

I find this webpage on optical aberrations quite useful - it's illustrated

http://umich.edu/~lowbrows/reflections/2007/dscobel.27.html

[N3ptune]

1 hour ago, Ricochet said:

Hi, sorry there was a spelling/autocorrect error in my previous post. It should have been "eye cup" height rather than "eye up". 

Anyway, eye cup height is the distance between the top of the eye lens and the top of the rubber eye cup. 

Eye relief is the distance between the eye lens and the point floating in mid air where the image forms and you have to put your eye. 

For my face shape, the eye relief was a bit longer than the eye cup height so I had to "hover" over the eyepiece. With the addition of a barlow the eye relief was even further above the eye cup, making viewing even more difficult. 

Ahhh! ok ok ok, the exit pupil "point floating", that a term I'll remember along with "pupil alignment" and "kidney bean effect" (I am trying to explain things here but always searching for the right terms)

How permissive is the ES 68d regarding the kidney bean effect? My Xcel LX are quite severe, I can't move my head and eye angle much, I have to keep a precise pupil alignment (in height and laterally) with the point floating (yeah!)

@Piero That was a very good explanation with televue's website too. I understand now the purpose of having more or less RD or AMD and the importance of AMD in astronomy with the double star example. It's impossible to have perfect optics.

@John thanks for the webpage, I will look at it has soon has possible, it looks very interesting too.

[Ricochet]

32 minutes ago, N3ptune said:

How permissive is the ES 68d regarding the kidney bean effect?

Based on a quick indoor test with a 24mm Meade SWA (same as the ES68) in my f6 spotting scope there is no kidney beaning at all. Assuming that kidney beaning is the correct term, see the picture below. 

Longitudinal misalignment is the most likely issue because that is the one requiring holding your eye at the correct height above the lens. Lateral misalignment is also possible but lateral eye placement is so easy (at f6) that you would have to do it deliberately. Perhaps in a mak/sct where the exit pupil is much smaller it is more of an issue. 

I'm really being quite picky about the eye height thing. I didn't really notice it that much until I tried using it in the spotting scope. Optically it is a great eyepiece and I should have put my SWA up for sale when I bought a 28mm Nirvana because owning both is not necessary, and yet I still have it. 

[John]

Some eyepiece designs are more prone to "kidney beaning" and other optical effects / issues than others. I think it's also fair to say that some people are more sensitive to some optical effects / issues than others so what one observer finds perfectly acceptable another might not be entirely happy with. Factors such as the ergonomics of the eye cup / eyepiece shape / field lens positioning come into play as indeed do the observers facial shape, visual and general preferences.

No wonder there are so many differing opinions on eyepieces

 

 

[N3ptune]

7 hours ago, Ricochet said:

Based on a quick indoor test with a 24mm Meade SWA (same as the ES68) in my f6 spotting scope there is no kidney beaning at all. Assuming that kidney beaning is the correct term, see the picture below. 

Longitudinal misalignment is the most likely issue because that is the one requiring holding your eye at the correct height above the lens. Lateral misalignment is also possible but lateral eye placement is so easy (at f6) that you would have to do it deliberately. Perhaps in a mak/sct where the exit pupil is much smaller it is more of an issue. 

I'm really being quite picky about the eye height thing. I didn't really notice it that much until I tried using it in the spotting scope. Optically it is a great eyepiece and I should have put my SWA up for sale when I bought a 28mm Nirvana because owning both is not necessary, and yet I still have it. 

Great explicative image there, I am keeping it. My problem with the Xcel LX is definitly the lateral misalignment "defocused edge of exit pupil" that's what I see more then the kidney bean problem.

Thanks for the test with your Meade SWA, that's interesting result, how about lateral misalignment is it fairly permissive?

5 hours ago, John said:

Some eyepiece designs are more prone to "kidney beaning" and other optical effects / issues than others. I think it's also fair to say that some people are more sensitive to some optical effects / issues than others so what one observer finds perfectly acceptable another might not be entirely happy with. Factors such as the ergonomics of the eye cup / eyepiece shape / field lens positioning come into play as indeed do the observers facial shape, visual and general preferences.

No wonder there are so many differing opinions on eyepieces

 

 

Yes, I think I am getting picky too, slowly..

At the beginning, with no experience, the Xcels XL seemed flawless.. I still think they are very good for the price, but not perfect has I though last year.

I might place an order for 24mm 68d ES, there is enough positive proof from users to buy it and It should be an easy eyepiece to sell too, good quality/price.