I know those erect-image ones is not as good as those mirror image ones in terms of light transmission. But is the difference really noticeable?
My finder is straight and my diagonal is mirror image. Initially a bit confusing, but after a while, its ok. But I prefer a true image, so thinking of getting the erect-image diagonal. Any recommendations?
Sorry for hijacking the thread.
Mirror vs Prism Diagonal
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weixing
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Hi,
I think almost all erect-image diagonal use amici prism. IMHO, the main problem for Amici prism diagonal is that it'll create a diffraction spike on bright object and most don't perform well above 100x... unless you get those very high quality (and expensive) amici prism diagonal.
Have a nice day.
I think almost all erect-image diagonal use amici prism. IMHO, the main problem for Amici prism diagonal is that it'll create a diffraction spike on bright object and most don't perform well above 100x... unless you get those very high quality (and expensive) amici prism diagonal.
Have a nice day.
Yang Weixing
"The universe is composed mainly of hydrogen and ignorance."
"The universe is composed mainly of hydrogen and ignorance." -
Canopus Lim
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Hi,andeelym wrote:I know those erect-image ones is not as good as those mirror image ones in terms of light transmission. But is the difference really noticeable?
My finder is straight and my diagonal is mirror image. Initially a bit confusing, but after a while, its ok. But I prefer a true image, so thinking of getting the erect-image diagonal. Any recommendations?
Sorry for hijacking the thread.
Erect prisms are not that good for high magnification work because of the diffraction lines from the prism itself. This lines will cause a slight loss of contrast on the object you are viewing at higher magnification. At low magnification, it is inconsequential.
For high power work, it will be good to use either a mirror or a prism diagonal (not erect version, will get a mirror image).
AstroDuck
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weixing
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Hi,
Basically, mirror diagonal can be use on basically all scopes, but will give a mirror image.
Prism diagonal may cause chromatic aberration when used on short focal ratio scope, but not a problem on long focal ratio scope. Prism diagonal also give a mirror image.
Amici roof prism diagonal give a correct image, but usually transmit less light and may cause optical aberrations because the light need to reflect on many surface. They don't perform well at higher magnification and will create a diffraction spike on bright object. As a result, Amici prism diagonal are usually use for low power viewing and mostly use in spotting scopes for terrestrial viewing.
Have a nice day.
Basically, mirror diagonal can be use on basically all scopes, but will give a mirror image.
Prism diagonal may cause chromatic aberration when used on short focal ratio scope, but not a problem on long focal ratio scope. Prism diagonal also give a mirror image.
Amici roof prism diagonal give a correct image, but usually transmit less light and may cause optical aberrations because the light need to reflect on many surface. They don't perform well at higher magnification and will create a diffraction spike on bright object. As a result, Amici prism diagonal are usually use for low power viewing and mostly use in spotting scopes for terrestrial viewing.
Have a nice day.
Yang Weixing
"The universe is composed mainly of hydrogen and ignorance."
"The universe is composed mainly of hydrogen and ignorance." 
I've used both a cheap Chinese and the Baader amici diagonal. The Baader Amici is probably the best on the market. The contrast is excellent with minimal observerable differences at low to medium powers when compared to an Astro-Physics mirror diagonal. For high powers planetary or double star observation where you want the most optimal optics train, one is better of with a good mirror diagonal. One night I did a comparison between the Baader amici and the AP mirror diagonal on Rigel using my Traveler. There is a faint but distinct companion to Rigel as you know. With the Baader amici, the faint companion was much harder to spot compared to the AP diagonal- so there is some difference. For viewing nebulas and galaxies there is no perceptible difference to me. I think if you star hop using maps, having a correct image diagonal might be helpful.
The Amici does give diffraction artifacts on bright objects but it is not too objectionable in my opinion except when used on superbright objects like planets and the moon.
For bird watching, the cheap Chinese one is surprisingly usable at moderate powers.
Slight topic change: An interesting thing about mirror diagonals that I've never experienced in Singapore is that if you take your scope out during the winter when it is below freezing, the mirror in the diagonal can actually distort and give you astigmatism images of stars until properly equilibrated.
Ivan
The Amici does give diffraction artifacts on bright objects but it is not too objectionable in my opinion except when used on superbright objects like planets and the moon.
For bird watching, the cheap Chinese one is surprisingly usable at moderate powers.
Slight topic change: An interesting thing about mirror diagonals that I've never experienced in Singapore is that if you take your scope out during the winter when it is below freezing, the mirror in the diagonal can actually distort and give you astigmatism images of stars until properly equilibrated.
Ivan