Send it back, get a refund, buy something better.

Premium diagonal vs premium eyepiece, which matter more to get the most performance out of your scope?
#101
Posted 20 May 2025 - 05:54 AM
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#102
Posted 20 May 2025 - 02:00 PM
For the record, Star Diagonal Alignment >>> Technically, a Star diagonal is "properly aligned" when the incoming and outgoing mechanical tube axes are imaged upon each other by the folding flat (or prism) inside. This is a 4 degree of freedom alignment. But moving and tip-tilting the mirror or prism around can only address (any) 3 of those four, leaving the remaining one at the mercy of how accurately the mechanical chassis was machined. This tacitly assumes that the glass itself is not clipping the aperture. The "dangling" degree of freedom is typically the lateral displacement of the axes from each other in the direction normal to the triangular sides of the chassis.
[I get the feeling that precious few folks are immersed in these nuances. Most Commercial Star Diagonals are off the mark by ~15 arc-min angular and ~1mm lateral, many more than that, a few better than that. This also explains why a camera relocated downstream from a SD may spontaneously manifest differential field tilt and decenter. We here didn't become hypersensitized to such things until the advent of large field solid state cameras and ~experienced~ imagers sort of took over the hobby. Thankfully, In the "eyepieces" arena... admittedly... it doesn't matter nearly as much!]
Key Words:
> optomechanical
> datums
> degrees of freedom (DOF)
> subassembly
> tolerancing (budget)
> tilt
> decenter
> systems engineering/analysis
Nearly all of the popular literature talks around alignment topics... with a lot of folklore tossed in. Tom
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#103
Posted 20 May 2025 - 02:31 PM
Tighten the 1.5mm hex screws on the side in the center, they require a 1.5mm Allen wrench or one of those small interchangeable screw driver bits
The small screws my finger is pointing to.
Hi Sir, I tried what you said, but it seem like the prism inside it still loose, it only help a bit, it was not able to tightening it fully.
So, I have a report of my viewing. How do I say this, let me try to describe it. The Prism diagonal the outer 20% of the edges has this greyish glare brightness. It like Edge of Field Brightness that how people describe it in eyepiece, but this time it the diagonal.
I do not see this in my GSO dielectric mirror diagonal, also does not see it in the William Optics durabright dielectric.
So I do know why 20% of the edge of the Prism diagonal it showing me this greyish glare, it just like edge of field brightness.
I think I have to return it, it only $40 plus tax, I am sure billionair amount company Amazon would not mind a $40 return. Their iphones it already thousands of dollars and people even return those.
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#104
Posted 20 May 2025 - 02:36 PM
Hi Sir, I tried what you said, but it seem like the prism inside it still loose, it only help a bit, it was not able to tightening it fully.
So, I have a report of my viewing. How do I say this, let me try to describe it. The Prism diagonal the outer 20% of the edges has this greyish glare brightness. It like Edge of Field Brightness that how people describe it in eyepiece, but this time it the diagonal.
I do not see this in my GSO dielectric mirror diagonal, also does not see it in the William Optics durabright dielectric.
So I do know why 20% of the edge of the Prism diagonal it showing me this greyish glare, it just like edge of field brightness.
I think I have to return it, it only $40 plus tax, I am sure billionair amount company Amazon would not mind a $40 return. Their iphones it already thousands of dollars and people even return those.
You found any difference between GSO and WO?
Yeah, return the Prism. Not sure if you want to try another.
Edited by Procyon, 20 May 2025 - 02:37 PM.
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#105
Posted 20 May 2025 - 03:00 PM
Sorry, I don't know why you are seeing a gray edge on the diagonal, your should return it.... also unless you've taken off the thumbscrew, that will rattle and it may seem like the diagonal is loose but actually its the thumbscrew you are hearing rattling.
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#106
Posted 20 May 2025 - 07:48 PM
You found any difference between GSO and WO?
Yeah, return the Prism. Not sure if you want to try another.
The William Optics is like a tat brighter than the GSO. Perhaps William Optics has better coating on the mirror.
Will return the $40 prism, Amazon is too rich, they will be okay over $40 item return.
How about you Sir, which Diagonal you use?
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#107
Posted 20 May 2025 - 07:51 PM
The William Optics is like a tat brighter than the GSO. Perhaps William Optics has better coating on the mirror.
Will return the $40 prism, Amazon is too rich, they will be okay over $40 item return.
How about you Sir, which Diagonal you use?
I used the Baader Prism Zeiss T2 for a long time than switched to 2" Baader Clicklock Dieletric Mirror. I prefer Mirror for DSO.
I also have 2" Williams Optics DuraBright now, for shorter light path for binoviewers, it's good too.
I like Clicklock mechanism better than screws.
Edited by Procyon, 20 May 2025 - 07:56 PM.
#108
Posted 20 May 2025 - 08:04 PM
I'm the opposite, when I had my Vixen Prism diagonal that I bought from Amazon Japan it show me more on DSO as in galaxies due to it dimmer, as compared to the DuraBright of WilliamsOptic.
BUT when it come to planets, the Vixen Prism has this bluish subtle glare on the outer edge of bright planets.
So I prefer mirror for planets and prism for DSO, or in my case it like that.
And if your read this link right from Baader website: Prism vs Mirror comparison from Baader site in. PDF
https://www.baader-p...n-w-paolini.pdf
Read the items where it say Vixen Prism and Celestorn Prism (this chart is written from Baader website), it show exactly like that, but I saw that subtle bluish tint on Jupiter and Mars. I never view the Moon so I wouldn't know.
I am very sorry Prism fans, I have a hard time seeing how a Prism can be better for a mirror scope than a Dieletric. And Maks are mirror scope, the one with ED lens are Refractor, Maks are Mirrors.
Edited by MrsM75, 20 May 2025 - 08:06 PM.
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#109
Posted 20 May 2025 - 08:17 PM
Lol, : ) That's BillP's Prism vs Diagonal big compara. He liked Prisms.
I like my mirrors : )
Edited by Procyon, 20 May 2025 - 08:22 PM.
#110
Posted 20 May 2025 - 08:25 PM
And if your read this link right from Baader website: Prism vs Mirror comparison from Baader site in. PDF
https://www.baader-p...n-w-paolini.pdf
Read the items where it say Vixen Prism and Celestorn Prism (this chart is written from Baader website), it show exactly like that, but I saw that subtle bluish tint on Jupiter and Mars. I never view the Moon so I wouldn't know.
I am very sorry Prism fans, I have a hard time seeing how a Prism can be better for a mirror scope than a Dieletric. And Maks are mirror scope, the one with ED lens are Refractor, Maks are Mirrors.
I'm sorry, MrsM75, you've missed an important conclusion made by Bill based on his comparisons
Quality prisms are prime candidates for the diagonal component in telescopes with focal ratios of f/7 or greater. Prism diagonals tested did not introduce any visually apparent chromatic aberration or spherical aberration in f/7 or f/8 telescopes and showed views just as brightly while notably higher in planetary contrast and notably lower in scatter on all celestial targets than similar high quality aluminum or dielectric mirrors.
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#111
Posted 20 May 2025 - 08:31 PM
And even though mirrored scopes have less CA they are not totally free of it, the corrector plate will introduce a very minor amount of blue the edge of some objects, though I'm not certain I've ever noticed it with my C11, it may only be visible with AP cameras.
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#112
Posted 20 May 2025 - 08:33 PM
I'm sorry, MrsM75, you've missed an important conclusion made by Bill based on his comparisons
Quality prisms are prime candidates for the diagonal component in telescopes with focal ratios of f/7 or greater. Prism diagonals tested did not introduce any visually apparent chromatic aberration or spherical aberration in f/7 or f/8 telescopes and showed views just as brightly while notably higher in planetary contrast and notably lower in scatter on all celestial targets than similar high quality aluminum or dielectric mirrors.
I agreed with premium quality prism, but a $40 prism (Celestron prism) and $45 (Vixen prism) is not a premium prism. I thought the preium one cost like $300 to $400
I report what I see in my own scope and I use a f/14 and f/15 scope. I had a Vixen prism before that I bought from Amazon Japan (it made in China btw). I see a subtle bluish tint on the outer edge on Jupiter and Mars. This is why I keep the GSO and William Optics Dielectric instead.
I guess to each of it own eyes, and I do not ever think a $40 Prism can outbeat a William Optics Durabright, sorry.
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#113
Posted 20 May 2025 - 10:48 PM
I guess to each of it own eyes, and I do not ever think a $40 Prism can outbeat a William Optics Durabright, sorry.
I agree with the former, but not with the latter. Several years ago I compared my "budget" 1.25" Tak Prism (rejected by BillP as "inadequate" in his comparison) with my 1.25" TV Everbrite (Premium type, isn't it ) on my SV102ED Access frac and the "budget" prism easily edged the Premium on double stars and planets. Exactly what BillP said -- in contrast and light scatter department. The difference was not day and night
but noticeable. Especially important for splitting of close double stars of unequal brightness. My WO Durabright is an excellent performer on all other less bright objects and at lower magnifications.
BTW, if you dig up this forum you'll find tons of positive reviews of that 1.25" Celestron prism.
Edited by CeleNoptic, 20 May 2025 - 10:50 PM.
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#114
Posted 21 May 2025 - 11:06 AM
It is not exactly collimated, which I plan to fix, but even so it gives very nice views even though I have an f/6 refractor... and I like it a bit better on planets as it seems more contrasty (or maybe just dimmer or both) than my 2" mirror... but either way for $40 it's staying.
with these budget Astro things one has to be ready to diy a bit.. or just spend the $$ for higher quality instead of time invested in diy.
** mine did not rattle...
Edited by rgk901, 21 May 2025 - 11:11 AM.
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#115
Posted 22 May 2025 - 11:54 AM
Both are important. Get the best you can afford.