114 replies to this topic

[MrsM75]

Premium diagonal vs premium eyepiece, which matter more to get the most performance out of your scope visually?

Let say you trying to improve the seeing of your OTA, do you need a Premium Diagonal more, or a Premium eyepiece more?

 

I actually have nothing premium, I collect cheap eyepieces as well as cheap diagonals over time. My most expensive diagonal is the GSO Dialectric diagonal for $70 so there that.

 

I was wondering if the Diagonal matter more or the eyepiece matter more?

 

Maybe I should invest in a premium diagonal.

 

 

[MrsM75]

I would make sure the diagonal is the best I can afford.  About 1/10 wave should be fine.  You have to get a good image first for the eyepiece to view it.  You may find that you don't need a premium eyepiece.  

That is what I think too Sir, that the diagonal is more important than the eyepiece, due to you have to get as much lights as you can here before it transfer to the eyepiece, like you say a good image.

 

So do you think the $110 William Optics Everbright 99% Dialetric diagonal is good enough for my small aperature Maks?

 

Televue is out of my budget. 

[MrsM75]

The William Optics Durabright it $110 and 99% Dialetric, 

The Celestron click clock it 99% dialetric too but it $145

 

If I can go cheap I go cheap. I do want to upgrade to a good diagonal for all my small Maks. So far I only have the stock plastic diagonal and the $70 GSO diectric one.

[Astro-Master]

I would guess the GSO Diagonal is better than your cheap eyepieces, one way to test the diagonal is to borrow a quality eyepiece and try it out with the GSO Diagonal and without the diagonal using the eyepiece straight through the back, if you can't see a difference the GSO Diagonal is fine.

[MrsM75]

I would guess the GSO Diagonal is better than your cheap eyepieces, one way to test the diagonal is to borrow a quality eyepiece and try it out with the GSO Diagonal and without the diagonal using the eyepiece straight through the back, if you can't see a difference the GSO Diagonal is fine.

 

I'm sorry English is my 3rd language, straight through the back you mean put the eyepiece straight to the "visual back" right Sir? The visual back where the diagonal is put in right? But instead put the 1.25 eyepiece in right? 

 

I totally didn't know you can view it it like that, I thought it not see-able if you just put the eyepiece straight into the visual back.

 

But I will try, thank you Sir.

[triplemon]

Your light is passing through both, the mirror and the eyepiece. So either one can degrade the quality of your view. A mirror can not make up for a poor eyepiece or vice versa.

 

But

 

a good enough mirror for a diagonal is comparatively easy to make. As that mirror has a single optical surface only (eyepieces have 6 to over 20 !!!) and it needs to be only flat across a very few millimeters at a time. Basically as large as the light cone is that gets combined to a single point in the eyepiece. That is VERY different from the requirements for a newtonian telescope secondary mirror, those sit much further from the focal plane and those mirrors need to be flat almost across the entire surface.

 

That said, even a flat enough mirror can still have scratches, poor reflectivity or other gross issues, but that is rare. So unless you buy a super cheap five dollar mirror diagonal, its unlikely that your diagonal is holding you back. Any differences in quality will not be visible unless you have a very good telescope AND a very good eyepiece to pair it with.

Edited by triplemon, 17 May 2025 - 09:48 PM.

[MrsM75]

Well I don't have premium scope or premium eyepiece so there that. I was thinking would the Wiliam Optics Durabright dialectric, or the Celestron click click dialetric, would be enough for my small Maks.

 

I am sure my diagonal is cheaper than $5, it the stock one that come together with my Maks OTA. I do have one I bought for $70 that GSO dialectric one. 

Edited by MrsM75, 17 May 2025 - 09:22 PM.

[rachnoman]

Both.

[Sketcher]

1st priority:  the observer -- their knowledge and experience

2nd:  the quality of one's sky -- darkness, seeing, and transparency

3rd:  the quality/aperture of one's telescope

4th:  the quality of the diagonal

5th:  the quality of the eyepiece -- assuming one is primarily concerned with on-axis performance.

 

I suspect that most would see no difference in performance between a $70 diagonal and a premium diagonal.

 

Eyepiece quality:  I've seen more detail on Jupiter using a very high quality 130mm telescope (costing $3000 in 1995) with an eyepiece consisting of 4 uncoated plastic lenses that came with a $15 telescope than I was able to see with an average quality 152mm telescope (costing $750 in 2015) used with a TeleVue eyepiece -- all utilizing similar magnifications.  Eyepiece quality should be a low priority unless one is obsessed with apparent field of view, eye-relief and/or edge-of-field sharpness.

[MrsM75]

1st priority:  the observer -- their knowledge and experience

2nd:  the quality of one's sky -- darkness, seeing, and transparency

3rd:  the quality/aperture of one's telescope

4th:  the quality of the diagonal

5th:  the quality of the eyepiece -- assuming one is primarily concerned with on-axis performance.

 

I suspect that most would see no difference in performance between a $70 diagonal and a premium diagonal.

 

Eyepiece quality:  I've seen more detail on Jupiter using a very high quality 130mm telescope (costing $3000 in 1995) with an eyepiece consisting of 4 uncoated plastic lenses that came with a $15 telescope than I was able to see with an average quality 152mm telescope (costing $750 in 2015) used with a TeleVue eyepiece -- all utilizing similar magnifications.  Eyepiece quality should be a low priority unless one is obsessed with apparent field of view, eye-relief and/or edge-of-field sharpness.

 

 

I very very much agreed with you Sir. I doubt a Televue eyepiece would show the same quality in a $5 all plastic diagonal with plastic mirror. 

 

I actually find the diagonal to be more important than eyepiece, because on axis, tbh when "on xias" all eyepieces look same in my Maks. 

It the fast focal ratio scope that has to deal with the outer edges correction.

[triplemon]

I am sure my diagonal is cheaper than $5, it the stock one that come together with my Maks OTA. I do have one I bought for $70 that GSO dialectric one. 

So, do you see any difference between the GSO and the stock diagonals ?

[TOMDEY]

"Premium diagonal vs premium eyepiece, which matter more"

 

I'm still working on premium apple vs premium orange. I measures a bunch of commercial Star Diagonals years ago (wavefront, spectral transmission, alignment) and found that only 2/15 were premium performers, 4/15 acceptable performers and the other 9 deficent or unusable. That's a 40% batting average... implying that a good ~premium~ diagonal is a prudent purchase. That, and you get to use it with most all of your eyepieces... so it's most likely in the chain most of the time.

 

Excerpts from my white paper >>>    Tom

 

 

Attached Thumbnails

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[MrsM75]

So, do you see any difference between the GSO and the stock diagonals ?

 

I do Sir, I do see the difference with the $70 GSO dialectric comapred to the stock diagonal that come with my scopes.

 

That is why I asked if I should upgrade the $70 GSO to the William Optics Durabright dialetric one, or to the Celestron click clock Dialetric one. As those are over $100+ range, more expensive than the GSO one.

[triplemon]

Well, your cheap diagonal might well be outright broken. So replacing it with pretty much anything could get you an marked improvement, the GSO dielectric could already be MUCH better than any of the other components.

 

As a super crude rule of thumb I'd say unless you spend at least 10x on the on the telescope than on the diagonal and more on the eyepiece than on the diagonal, you're likely not spending your money very wisely.

 

IIRC your scopes short of the Maxvision one are the kind of price class where I would not neccesarily expect the diagonal has even a first surface mirror.

Edited by triplemon, 17 May 2025 - 10:49 PM.

[Procyon]

If you have this one already https://agenaastro.c...ssion-ring.html

 

I'm not sure how much better this one will be https://agenaastro.c...r-diagonal.html

 

The Celestron one seems to have some issues with threading and clicklock becoming loose they say, 

 

I just got a 2" WO Durabright and it's pretty good. I don't know enough about the GSO one, does it feel nice and heavy in your hand or light and plasticky? 

 

If yes, get the WO one. 

Edited by Procyon, 17 May 2025 - 10:46 PM.

[MrsM75]

Well, your diagonal might well be outright broken. So replacing it with pretty much anything could get you an marked improvement, 

 

Sir, are you saying the plastic stock diagonal that comes with the scope is same quality as the "dialectric" diagonal? I don't think so. Even if my stock diagonal not broken, I do not see how it can be better than the 99% dialectric one. I read that the stock diagonal only has like 94% of lights, while the dialectric one it 99% of lights.

 

Sorry am I misunderstanding your writing because English is my native language. But if the stock daigonal is so good then nobody need to replace their stock diagonal anymore, why bother buy the GSO dialectric one if the stock diagonal is just as good.

Edited by MrsM75, 17 May 2025 - 10:52 PM.

[Procyon]

The stock diagonal is good to hold paper that flies away from the wind. But it might not be heavy enough.

[triplemon]

The plastic housing is not the problem. Giiven the total cost of those scopes which usually come with the tripod and all the other acessories, those diagonals are not even the $5, but more like $1 level. The mirror often metalized plastic, thats why the super low weight. Certainly not any optical grade first surface mirror.

Edited by triplemon, 17 May 2025 - 11:00 PM.

[Procyon]

"Premium diagonal vs premium eyepiece, which matter more"

 

I'm still working on premium apple vs premium orange. I measures a bunch of commercial Star Diagonals years ago (wavefront, spectral transmission, alignment) and found that only 2/15 were premium performers, 4/15 acceptable performers and the other 9 deficent or unusable. That's a 40% batting average... implying that a good ~premium~ diagonal is a prudent purchase. That, and you get to use it with most all of your eyepieces... so it's most likely in the chain most of the time.

 

Excerpts from my white paper >>>    Tom

We need to send Tomdey new William Durabright diagonals, as well as some Baader ones to test and put on that famous list. Some GSO's also.

Edited by Procyon, 17 May 2025 - 10:59 PM.

[siriusandthepup]

You must have a good diagonal. It affects EVERY eyepiece you use.

 

You don't need a super expensive diagonal though. Get a decent one here on CN classifieds.

 

 

**** Note **** All your scopes are long focal ratio - f/13, f/14, f/14 /f/15. Long focal ratio scopes do very well with simpler design eyepieces AKA - cheaper/ non premium eyepieces.

 

Save your money. Get a decent set of Plossls to start. Later you can treat yourself to a "premium" if you just have to have one.

Edited by siriusandthepup, 17 May 2025 - 11:11 PM.

[betacygni]

There is another thing to consider, eyepieces can drastically change the overall experience. A diagonal (unless very bad) will not.

What do I mean? Generally premium eyepieces don’t buy you significantly better on axis performance (though they will give you better off axis if you have a fast scope), what they can get you is comfort (longer eye relief) or immersion (wider apparent field of view). For example an eyepiece with a 82* apparent field of view will feel vastly different observing than with a cheaper 50* plossl. Details you can see won’t differ much, but the feel of the telescope and experience will.

Edited by betacygni, 17 May 2025 - 11:12 PM.

[PKDfan]

Hi MrsM75 !

IME a great eyepiece can get away with a good stock dielectric diagonal.

The ones that ship with the SkyWatcher Evostars is perfectly okay IF you stay directly on-axis but if you should move away from directly overtop the center of the exit pupil then the layers of metal can cause some off-axis scattering.

That eventually caused me enough grief after three years that i searched for what others observers reviewed as exemplary diag. options such a Baaders BBHS mirror or Tele Vue Everbrite diags.

I ended up buying both not wanting to change out when changing to my other scope if i use both simultaneously.

Now any aberrations are not visible no matter how hard i try to detect them.

Yes they are very expensive and if you don't need 2inches configuration then much cheaper to get just 1 1/4" stuff. Your scopes can use that smaller size and really don't need anything larger.

They are transparent in the optical chain now so i can fully concentrate on noticing micro contrast details without scatter messing things up.

Good Hunting for a solution that works economically for you !

Your way ahead of the game because of your slow optics so Plössls will work exceptionally well.

Good luck sorting it all out !


Lance
CSS

[MrsM75]

The ones that ship with the SkyWatcher Evostars is perfectly okay IF you stay directly on-axis but if you should move away from directly overtop the center of the exit pupil then the layers of metal can cause some off-axis scattering.

 

 

Thank you Sir PKDfan, you mean the Skywatchher Evostars as in the Doublet Refractor that cost $1,300 dollars? yah. that diagonal looks metal.

 

My scope is $170 dollars 90mm Skymax Mak, the diagonal is plastic, lol.

 

yah. no competition here between a $1,300 scope vs a $170 scope.

 

Thank you for your input Sir. I guess my $70 GSO dielectric diagonal is okay then, lol.

[PKDfan]

Thank you Sir PKDfan, you mean the Skywatchher Evostars as in the Doublet Refractor that cost $1,300 dollars? yah. that diagonal looks metal.

My scope is $170 dollars 90mm Skymax Mak, the diagonal is plastic, lol.

yah. no competition here between a $1,300 scope vs a $170 scope.

Thank you for your input Sir. I guess my $70 GSO dielectric diagonal is okay then, lol.

Lol I didn't mean to suggest you buy an Evostar just to get the diagonal...that would be silly MrsM75 !

I meant just to relay that the ±100$ dielectric was profoundly okay until I finally saw its limitations and that took a few years.

PM and i'll send you my stock SW dielectric 2" for free if your scope can use it. Glad to bear the shipping costs to you as its just collecting dust in its plastic bag. Can't be more than 50dollars to ship it out overseas.

My Celestron prism is mostly plastic and works very well and with a slow Maksutov an especially cheap way to get a Quality diag. image.

I need to build some good karma and quite frankly its just getting in the way now.

As i said I'm Glad to do it.


CSS
Lance

[MrsM75]

Lol I didn't mean to suggest you buy an Evostar just to get the diagonal...that would be silly MrsM75 !

I meant just to relay that the ±100$ dielectric was profoundly okay until I finally saw its limitations and that took a few years.

PM and i'll send you my stock SW dielectric 2" for free if your scope can use it. Glad to bear the shipping costs to you as its just collecting dust in its plastic bag. Can't be more than 50dollars to ship it out overseas.

My Celestron prism is mostly plastic and works very well and with a slow Maksutov an especially cheap way to get a Quality diag. image.

I need to build some good karma and quite frankly its just getting in the way now.

As i said I'm Glad to do it.


CSS
Lance

 

A question for you Sir, are you saying that "Prism" is better for a Mak than the "dielectric mirror" one? 

 

And your so nice Sir pkdfan, but all my cheap scopes are all 1.25 inch visual back, thank you for your kindness, it the thoughts that count, I will never forget.

Edited by MrsM75, 18 May 2025 - 02:23 AM.