Thank you for your great review. I purchased the same prism diagonal for my C8 sct and it is excellent indeed. I purchased it primarily for planetary viewing and it is considerably better than the stock diagonal. Clear Skies.
I didn't know about T2 compatibility. Just screwed it on my mak 127, and from now on there will be no more slop due to only 2 screws. Thanks for pointing out this nice feature.
Hi Bogdan, I am really enjoying your channel. I have a question: I am purchasing an Evolution 8 SCT, and I plan to upgrade the diagonal and and eyepieces. Assuming I want to upgrade to a 2” diagonal, do I have to order any special parts aside from the diagonal itself? Example….the Baader click lock 2” diagonal, or the Televue Ever Brite…..I cannot find a specific answer (even looking at Baader & Televue sites) as to whether I need to buy any additional connector or whether these diagonals will connect directly to the Optical tube. Would appreciate any additional info, assuming you see this :-) Cheers and I am now subbed!
@bcdrummer1962 Hi! I'm not sure about the Everbrite but the Baader 2" diagonals should fit just nicely. The C8 has a 38mm opening at the back and standard SCT (M48 threading) around this opening. The 2" BBHS prism from Baader should be compatible with this threading so that you can attach it directly to the tube without the 2" nosepiece. On their website www.baader-planetarium.com/en/baader-2inch-bbhs-mirror-diagonal-with-2inch-clicklock-clamp.html Baader lists this under Inner Connection (lens sided): M482"/SCT Thread (50.8mm)M55. Also this on page 13: www.baader-planetarium.com/media/mageworx/downloads/attachment/file/1617/EN_baader-mirrors-prisms_A4_RGB-LR_0321.pdf So it should work.
I purchased the 2" prism version for my VMC260L. I Love it for planetary & random starfields :) previous diagonal was a WO 1.25'' dielectric (which is very good but not as good as the Baader)
Hi Baadan Great review video and very informative.. Thanks for your work. I've a nexstar 8SE SCT, will this prism diagonal work with the 8SE.. original is a 1.25" diagonal
@arjun1910 The 2" mirror diagonal from ES is a good choice as well. The added compatibility with 2" eyepieces is definitely a nice thing. Keep in mind though that it uses up considerably more light path than the prism which might lead to problems with the back focus if you plan on using binoviewers in the future.
I bought a 1.25 inch SvBony SV188P Dielectric mirror Diagonal ($43 on Amazon) to replace my Meade one that came with my 6 inch Meade refractor I bought from a friend. I tested both on my desk. Looking them, the Meade turned my brown desktop into kind of a grey. Looking through the SvBONY, the desk looked virtually identical to the naked eye. I also have a 2 inch diagonal that the same friend picked up at recycle store for $5. It also produced outstanding results. Unfortunately I don't know the brand as it has no markings on it anywhere. It is made out of metal. It may or may not be a prism type as I can't tell.
I enjoyed this video a lot. I recently bought a Vixen AX103s and wanted to use it in day time as well as night, so I bought a 2” Baader Amici Prism. I don’t have anything to compare it to, and whilst it’s certainly very good by day, I don’t know if I’m losing anything at night.
@Alan price I'm glad you enjoyed the video. I haven't tested the 2" Amici prism from Baader yet, but I don't think that your are missing anything when using it for nighttime observations. Daytime observations are usually more demanding than nighttime observations. So if it performs very good during the day, then it should be great at night as well.
@@BogdanDamian I read that this prism is suited for use with maxbright bino dirrected attached, or if with cheaper william optics or tsoptics bino you need a glass path corrector or screw barlow in front….did you used binoviewer? I read is a gamechanger on planets improving the views more than any other accesory or premium eyepiece
Great video! I have a hobby killer deluxe (Tasco 60x900) that I replaced my mirror with an Astromania erecting prism. At that focal length, with the prism diagonal, a Celestron Omni 2x barlow, and Omni 15mm Plössl, the view of the moon with my budget accessories was actually outstanding to my beginner eyes! There was zero CA or distortion, just a crisp bright view of the craters at 120x! I put it on my new hobby killer (Gskyer 90x600 I picked up at an auction for 32 bucks!) and the moon still had no CA halo! Leaves when looking at trees during the day definitely had a “purple haze” Jimi Hendrix vibe though! Lol! For longer focal lengths I don’t know why anyone would choose a mirror!
Thank you for the very good review. I have a Celestron 102mm aperture and 660 FL. Would the baader prism diagonal still be a good choice, without creating too much chromatic aberrations with my scope? Thanks
@christophercullen6523 I'm glad you liked it! Yes, the prism diagonal from Baader will make a good choice for your telescope. It should reduce the amount of aberrations significantly.
Hello Bogdan! Thanks for your videos, they are very helpful! I bought a Nexstar 8SE, it has a diagonal prism with coating 1.25"(Celestron Diagonal-1 94115-A), not a mirror like yours. Baader Zeiss will cost me at least 300-350 euros, is there any point in changing the standard prism? So far I have ordered an Explore Scientific 82 11mm eyepiece, I am planning 24mm, but it already 2". Perhaps it would be better to invest in other 1.25" eyepieces without changing the prism? Thanks!
Would it make sense to get a MAK to SC adapter and go for a 2" diagonal on the MAK to be able to use 2" eyepieces? That way eyepieces with more than 40mm FL could be used on the MAK getting it closer to optimal or max pupil? Or be able to use a SC reducer to make the MAK faster e.g. for photography and deep sky observations. I have a Celestron 127/1500 MAK and want to upgrade it.
@schotoka A 2" adapter would make little sense in a 4" or 5" Mak because the opening at the back of the optical tube is so small that 1.25" is perfectly sufficiente. In other words the diameter of the light beam reaching the back of the telescope can be fully utilized by a 1.25" sized eyepiece. A 2" eyepiece would have the same light information at its disposal to generate the image only spread on a slightly larger exit pupil. I believe the improvements would be minimal.
I recently bought this diagonal for a my 60mm f6 refractor. I understand the CA risk but expect it to be low. I've only been able to view some stars with it so far and was amazed. You've described it exactly right. I have two Apertura 99.9% mirror diagonal and I could immediately see the difference. Even without looking side by side. I will have to start saving my pennies for a 2" prism diagonal for my other scopes! One thing I noticed though is that it requires me to focus out much farther than other diagonals.
@Carpe Noctem The path the light has to travel in case of a prism diagonal is generally longer than in the case of a mirror diagonal. That is why the focuser needs to move outwards more to obtain focus. It's definitely something to take into considerations when shopping for a prism diagonal. Thanks for pointing this out!
Greetings Bogdan. Recently purchased a Meade model 395 refractor (D=90mm, F=1000mm, f11) for planetary viewing. Everything appears to be in very good condition, though the stock mirror diagonal may need updated/upgraded. I would like your opinion on what type of diagonal would be best given the telescope specs. Mirror or Prism? And any specific recommendations would be welcomed. Thank you for all the great content. Ken
@Kenneth Dorn Hi Ken! Congrats on your new telescope. If you are looking to replace the stock diagonal, then I would recommend the 1.25" prism diagonal from Baader. The high quality glass will definitely improve the views compared to the stock diagonal. As a good alternative you could also look at the 1.25" everbrite mirror diagonal from Tele Vue. That is also a very good diagonal. But because of the harder and more durable glass surface I would still get the Baader prism diagonal. Bogdan
Hello Bogdan. Love your videos! They helped me understand a lot regarding this amazing hobby. Currently I have an SCT Celestron Evolution 6. It came with a 1.25 diagonal. My question is, given I'm upgrading, is it worth and even possible to put a 2'' diagonal? Will it work?
@dragomirescucristiangabrie3606 Hi! It is possible to add a 2" diagonal to your telescope without a problem. The Evolution 6 features a 2" SC-thread on the back of the optical tube so it can accept 2" accessories. It is also worth getting 2" accessories for your telescope, as they will allow for longer focal lengt options whick in turn will offer a wider field of view.
To be pedantic a bit, this won't work on all SCT's and probably not all Maks either, for example you would need a machineshop to custom machine some form of adapter to be able to use it on a B&L Criterion series SCT(I have one, just checked). This is likely to affect some refractors too, or rather it for sure does affect some.
I believe you said that the image in this Baader diagonal is upright, but flipped right to left. My preference is for a diagonal that has the same view of the night sky in the eyepiece as I see in the sky with my eyes. That would be the main reason I opt for a new prism diagonal. Partly because then and only then does the image match the sky viewing applications like Sky Safari or Stellarium. Anything else is a bit confusing for visual use. Is there a high quality diagonal that meets those image criteria that you can recommend?
@JPAstroGuy It's difficult to find a quality Right Angle Correct Image diagonal. Unfortunately none of the popular premium brands offers them. I only know of this one and it's just a budget option: agenaastro.com/gso-1-25-90-erect-image-prism-diagonal.html Try searching for RACI diagonals, maybe you have more luck than I had in finding one.
No mention that Prism diagonals will aide with in focus issues (in focus meaning racking into scope)? Please advise if you know how much this will help..Thanks
@V. M. Thanks for your feedback. It is true that a prism diagonal compared to a mirror diagonal will add significantly less to the length of the path the light needs to travel in order to reach your eye. Depending on the glass type used and the size of the prism one could save up 10-30mm of travel. The effective light path length can be determined by dividing the light path thru the glass by the refractive index of the glass. So for a prism diagonal with a length of 70mm and made out of BaK4 glass you get 70/1.566=44,69mm. A mirror diagonal equivalent will just offer 70mm of path length to the system. This can be helpful when using accessories like binoviewers for example which extend the light path by 110 - 140mm. In this case using a prism instead of a mirror diagonal might just make enough of a difference to reach focus. I hope this helps.
Is the chromatic aberration issue with prism diagonals a function solely based on focal length or focal ratio? I have 80mm ED f7 refractor with an inexpensive mirror diagonal that I may replace eventually. I have been told it is a toss-up between chromatic aberrations and light scatter. So far, the inexpensive mirror diagonal works for me.
@@cattaraugustonawanda4426 The focal ratio is directly influenced by the focal length, which can have an effect on the amount of chromatic aberrations shown by a telescope+diagonal combo. However, if the telescope's objective lens corrects the light reasonably well, like in the case of a good APO, then a quality prism won't induce any additional chromatic aberrations or light scatter to the optical system.
@@BogdanDamian Thanks for your reply! Then my two elements of ED glass (SVBONY 503 80ED) should negate most chromatic aberration issues. Your videos are very helpful !
Hi Bogdam I have got a SC Celestron Explorer 6 that came with a erecting prism diagonal. Have I got improvement if I change to a dielectric mirror? (the prims is reflecting 99% of light in theory. Thanks a lot. Clear skies
@Manuel worlddigest Hi! If your telescope came with a prism diagonal, then it should be pretty decent. I wouldn't upgrade to a dielectric mirror diagonal unless you notice any visible aberrations when looking through it.
I have TS-CF 130mm FPL-55 APO, f/7. Is that prism ultimate for it? Baader 2" BBHS ® Prism Star Diagonal Prism Or better to grt Baader T2 Zeiss spec prism? Which of these two would give better picture? Will 2" Baader prism induce more false colours?
@denis0007dl I would get the 2" BBHS prism diagonal. It's broad band coatings ensures a exceptional reflexivity even over longer periods of time. If the quality of the diagonal is high, then a larger 2" version will not introduce any noticeable aberrations compared with the smaller 1.25" version.
Mistake No.1 Prisms diagonal do not refract light to change its path. It uses total reflection (inability of light to escape from glass to air in certain angles). Mistake No 2. slight chromatic aberration of prism is not dependent on focal length but on F-ratio - 60mm telescope f:10 wil have less chromatic aberration in prism diagonal than fast 150mm telescope f:4 despite both havihg focal length of 600mm. Chromatic abberation is dependent on angle of light cone not on focal length.
@George L. Correa Theoretically yes, but the resulting angle would be a bit awkward for a dob and I don't know how it would mess with the focal point. But at the same time it would also be a fun experiment to try out 🙂
Prism diagonals also reflect , like mirrors do , as their main job ! Refraction in prisms occur when are passed by non telecentric rays . Usually , they manifest overcorrection of chromatic and spheric aberration . That's why , prisme improve a bit the image of long achromatic refractors .
@efx245precor3: I prefer prisms, especially if they are constructed with BAK4 glass. They usually last longer than mirrors and they give you a right-way-up view (mirrors give you a "mirror image" where left & right are flipped, which can be confusing).
That's a great overview of the different types of diagonals!
I couldn't believe the mirror quality in the televue diagonal truly a mouth drop great worth aiming for this and thanks for the confidence
Thank you for your great review. I purchased the same prism diagonal for my C8 sct and it is excellent indeed.
I purchased it primarily for planetary viewing and it is considerably better than the stock diagonal. Clear Skies.
@Horacio Dortona Glad to see that you also enjoy this diagonal. Clear skies!
I didn't know about T2 compatibility. Just screwed it on my mak 127, and from now on there will be no more slop due to only 2 screws. Thanks for pointing out this nice feature.
Hi Bogdan, I am really enjoying your channel. I have a question: I am purchasing an Evolution 8 SCT, and I plan to upgrade the diagonal and and eyepieces. Assuming I want to upgrade to a 2” diagonal, do I have to order any special parts aside from the diagonal itself? Example….the Baader click lock 2” diagonal, or the Televue Ever Brite…..I cannot find a specific answer (even looking at Baader & Televue sites) as to whether I need to buy any additional connector or whether these diagonals will connect directly to the Optical tube. Would appreciate any additional info, assuming you see this :-) Cheers and I am now subbed!
@bcdrummer1962 Hi! I'm not sure about the Everbrite but the Baader 2" diagonals should fit just nicely. The C8 has a 38mm opening at the back and standard SCT (M48 threading) around this opening. The 2" BBHS prism from Baader should be compatible with this threading so that you can attach it directly to the tube without the 2" nosepiece.
On their website www.baader-planetarium.com/en/baader-2inch-bbhs-mirror-diagonal-with-2inch-clicklock-clamp.html Baader lists this under Inner Connection (lens sided): M482"/SCT Thread (50.8mm)M55.
Also this on page 13: www.baader-planetarium.com/media/mageworx/downloads/attachment/file/1617/EN_baader-mirrors-prisms_A4_RGB-LR_0321.pdf
So it should work.
I purchased the 2" prism version for my VMC260L. I Love it for planetary & random starfields :) previous diagonal was a WO 1.25'' dielectric (which is very good but not as good as the Baader)
Hi Baadan Great review video and very informative.. Thanks for your work.
I've a nexstar 8SE SCT, will this prism diagonal work with the 8SE.. original is a 1.25" diagonal
@arjun1910 Hi! Glad you enjoyed the video. The prism diagonal will work very well together with the 8SE.
@@BogdanDamian how about explorer Scientific 2" dielectric diagonal it's same price as the prism. Between the 2 what do you recommend. Thanks
@arjun1910 The 2" mirror diagonal from ES is a good choice as well. The added compatibility with 2" eyepieces is definitely a nice thing. Keep in mind though that it uses up considerably more light path than the prism which might lead to problems with the back focus if you plan on using binoviewers in the future.
@@BogdanDamian I went with televue dielectric 2" diagonal. Yes I do plan to add binoviewer someday. What do you recommend at that time?
@arjun1910 That's a great choice. How do you like it so far?
I bought a 1.25 inch SvBony SV188P Dielectric mirror Diagonal ($43 on Amazon) to replace my Meade one that came with my 6 inch Meade refractor I bought from a friend. I tested both on my desk. Looking them, the Meade turned my brown desktop into kind of a grey. Looking through the SvBONY, the desk looked virtually identical to the naked eye. I also have a 2 inch diagonal that the same friend picked up at recycle store for $5. It also produced outstanding results. Unfortunately I don't know the brand as it has no markings on it anywhere. It is made out of metal. It may or may not be a prism type as I can't tell.
I enjoyed this video a lot. I recently bought a Vixen AX103s and wanted to use it in day time as well as night, so I bought a 2” Baader Amici Prism.
I don’t have anything to compare it to, and whilst it’s certainly very good by day, I don’t know if I’m losing anything at night.
@Alan price I'm glad you enjoyed the video. I haven't tested the 2" Amici prism from Baader yet, but I don't think that your are missing anything when using it for nighttime observations. Daytime observations are usually more demanding than nighttime observations. So if it performs very good during the day, then it should be great at night as well.
Awesome review. This will definitely be my diagonal when I buy an SCT.
@tornadopakoštane1965 Nice! Hope you get your SCT soon.
Bogdan how is the Baader prism working with sv503 as that one is F7 right at the border of getting CA due to fast focal ratio below f7
@PauI__ Its working very well together. No problems at all. I find the resulting image to be better than with the mirror diagonal from Svbony.
@@BogdanDamian I read that this prism is suited for use with maxbright bino dirrected attached, or if with cheaper william optics or tsoptics bino you need a glass path corrector or screw barlow in front….did you used binoviewer? I read is a gamechanger on planets improving the views more than any other accesory or premium eyepiece
Great video! I have a hobby killer deluxe (Tasco 60x900) that I replaced my mirror with an Astromania erecting prism. At that focal length, with the prism diagonal, a Celestron Omni 2x barlow, and Omni 15mm Plössl, the view of the moon with my budget accessories was actually outstanding to my beginner eyes! There was zero CA or distortion, just a crisp bright view of the craters at 120x! I put it on my new hobby killer (Gskyer 90x600 I picked up at an auction for 32 bucks!) and the moon still had no CA halo! Leaves when looking at trees during the day definitely had a “purple haze” Jimi Hendrix vibe though! Lol! For longer focal lengths I don’t know why anyone would choose a mirror!
Thank you for the very good review. I have a Celestron 102mm aperture and 660 FL. Would the baader prism diagonal still be a good choice, without creating too much chromatic aberrations with my scope? Thanks
@christophercullen6523 I'm glad you liked it! Yes, the prism diagonal from Baader will make a good choice for your telescope. It should reduce the amount of aberrations significantly.
Hello Bogdan! Thanks for your videos, they are very helpful! I bought a Nexstar 8SE, it has a diagonal prism with coating 1.25"(Celestron Diagonal-1 94115-A), not a mirror like yours. Baader Zeiss will cost me at least 300-350 euros, is there any point in changing the standard prism? So far I have ordered an Explore Scientific 82 11mm eyepiece, I am planning 24mm, but it already 2". Perhaps it would be better to invest in other 1.25" eyepieces without changing the prism? Thanks!
Would it make sense to get a MAK to SC adapter and go for a 2" diagonal on the MAK to be able to use 2" eyepieces? That way eyepieces with more than 40mm FL could be used on the MAK getting it closer to optimal or max pupil? Or be able to use a SC reducer to make the MAK faster e.g. for photography and deep sky observations.
I have a Celestron 127/1500 MAK and want to upgrade it.
@schotoka A 2" adapter would make little sense in a 4" or 5" Mak because the opening at the back of the optical tube is so small that 1.25" is perfectly sufficiente. In other words the diameter of the light beam reaching the back of the telescope can be fully utilized by a 1.25" sized eyepiece. A 2" eyepiece would have the same light information at its disposal to generate the image only spread on a slightly larger exit pupil. I believe the improvements would be minimal.
@@BogdanDamian thx a lot. Really like you videos. Freue mich auf viele neue interessant Inhalte.
I recently bought this diagonal for a my 60mm f6 refractor. I understand the CA risk but expect it to be low. I've only been able to view some stars with it so far and was amazed. You've described it exactly right. I have two Apertura 99.9% mirror diagonal and I could immediately see the difference. Even without looking side by side. I will have to start saving my pennies for a 2" prism diagonal for my other scopes! One thing I noticed though is that it requires me to focus out much farther than other diagonals.
@Carpe Noctem The path the light has to travel in case of a prism diagonal is generally longer than in the case of a mirror diagonal. That is why the focuser needs to move outwards more to obtain focus. It's definitely something to take into considerations when shopping for a prism diagonal. Thanks for pointing this out!
Greetings Bogdan. Recently purchased a Meade model 395 refractor (D=90mm, F=1000mm, f11) for planetary viewing. Everything appears to be in very good condition, though the stock mirror diagonal may need updated/upgraded. I would like your opinion on what type of diagonal would be best given the telescope specs. Mirror or Prism? And any specific recommendations would be welcomed. Thank you for all the great content. Ken
@Kenneth Dorn Hi Ken! Congrats on your new telescope. If you are looking to replace the stock diagonal, then I would recommend the 1.25" prism diagonal from Baader. The high quality glass will definitely improve the views compared to the stock diagonal. As a good alternative you could also look at the 1.25" everbrite mirror diagonal from Tele Vue. That is also a very good diagonal. But because of the harder and more durable glass surface I would still get the Baader prism diagonal. Bogdan
@@BogdanDamian Thank you Bogdan, I greatly appreciate the recommendation.
Hello Bogdan. Love your videos! They helped me understand a lot regarding this amazing hobby. Currently I have an SCT Celestron Evolution 6. It came with a 1.25 diagonal. My question is, given I'm upgrading, is it worth and even possible to put a 2'' diagonal? Will it work?
@dragomirescucristiangabrie3606 Hi! It is possible to add a 2" diagonal to your telescope without a problem. The Evolution 6 features a 2" SC-thread on the back of the optical tube so it can accept 2" accessories. It is also worth getting 2" accessories for your telescope, as they will allow for longer focal lengt options whick in turn will offer a wider field of view.
To be pedantic a bit, this won't work on all SCT's and probably not all Maks either, for example you would need a machineshop to custom machine some form of adapter to be able to use it on a B&L Criterion series SCT(I have one, just checked). This is likely to affect some refractors too, or rather it for sure does affect some.
I believe you said that the image in this Baader diagonal is upright, but flipped right to left. My preference is for a diagonal that has the same view of the night sky in the eyepiece as I see in the sky with my eyes. That would be the main reason I opt for a new prism diagonal. Partly because then and only then does the image match the sky viewing applications like Sky Safari or Stellarium. Anything else is a bit confusing for visual use. Is there a high quality diagonal that meets those image criteria that you can recommend?
@JPAstroGuy It's difficult to find a quality Right Angle Correct Image diagonal. Unfortunately none of the popular premium brands offers them. I only know of this one and it's just a budget option:
agenaastro.com/gso-1-25-90-erect-image-prism-diagonal.html
Try searching for RACI diagonals, maybe you have more luck than I had in finding one.
No mention that Prism diagonals will aide with in focus issues (in focus meaning racking into scope)? Please advise if you know how much this will help..Thanks
@V. M. Thanks for your feedback. It is true that a prism diagonal compared to a mirror diagonal will add significantly less to the length of the path the light needs to travel in order to reach your eye. Depending on the glass type used and the size of the prism one could save up 10-30mm of travel. The effective light path length can be determined by dividing the light path thru the glass by the refractive index of the glass. So for a prism diagonal with a length of 70mm and made out of BaK4 glass you get 70/1.566=44,69mm. A mirror diagonal equivalent will just offer 70mm of path length to the system. This can be helpful when using accessories like binoviewers for example which extend the light path by 110 - 140mm. In this case using a prism instead of a mirror diagonal might just make enough of a difference to reach focus. I hope this helps.
Is the chromatic aberration issue with prism diagonals a function solely based on focal length or focal ratio? I have 80mm ED f7 refractor with an inexpensive mirror diagonal that I may replace eventually. I have been told it is a toss-up between chromatic aberrations and light scatter. So far, the inexpensive mirror diagonal works for me.
@@cattaraugustonawanda4426 The focal ratio is directly influenced by the focal length, which can have an effect on the amount of chromatic aberrations shown by a telescope+diagonal combo. However, if the telescope's objective lens corrects the light reasonably well, like in the case of a good APO, then a quality prism won't induce any additional chromatic aberrations or light scatter to the optical system.
@@BogdanDamian Thanks for your reply! Then my two elements of ED glass (SVBONY 503 80ED) should negate most chromatic aberration issues. Your videos are very helpful !
Hi Bogdam
I have got a SC Celestron Explorer 6 that came with a erecting prism diagonal. Have I got improvement if I change to a dielectric mirror? (the prims is reflecting 99% of light in theory. Thanks a lot. Clear skies
@Manuel worlddigest Hi! If your telescope came with a prism diagonal, then it should be pretty decent. I wouldn't upgrade to a dielectric mirror diagonal unless you notice any visible aberrations when looking through it.
@@BogdanDamian Thank you so much. I really apreciate all of your videos. Thank you for sharing with us
Photos to compare or didn't happen :)
I have TS-CF 130mm FPL-55 APO, f/7.
Is that prism ultimate for it?
Baader 2" BBHS ® Prism Star Diagonal Prism
Or better to grt Baader T2 Zeiss spec prism?
Which of these two would give better picture?
Will 2" Baader prism induce more false colours?
@denis0007dl I would get the 2" BBHS prism diagonal. It's broad band coatings ensures a exceptional reflexivity even over longer periods of time.
If the quality of the diagonal is high, then a larger 2" version will not introduce any noticeable aberrations compared with the smaller 1.25" version.
Mistake No.1 Prisms diagonal do not refract light to change its path. It uses total reflection (inability of light to escape from glass to air in certain angles).
Mistake No 2. slight chromatic aberration of prism is not dependent on focal length but on F-ratio - 60mm telescope f:10 wil have less chromatic aberration in prism diagonal than fast 150mm telescope f:4 despite both havihg focal length of 600mm. Chromatic abberation is dependent on angle of light cone not on focal length.
I can't use this on my 12" Dob right ?
@George L. Correa Theoretically yes, but the resulting angle would be a bit awkward for a dob and I don't know how it would mess with the focal point. But at the same time it would also be a fun experiment to try out 🙂
William optics dielectric mirror is the way to go and affordable.
👍👍👍
Prism diagonals also reflect , like mirrors do , as their main job ! Refraction in prisms occur when are passed by non telecentric rays . Usually , they manifest overcorrection of chromatic and spheric aberration . That's why , prisme improve a bit the image of long achromatic refractors .
A mirror is better than a prism right
@efx245precor3: I prefer prisms, especially if they are constructed with BAK4 glass. They usually last longer than mirrors and they give you a right-way-up view (mirrors give you a "mirror image" where left & right are flipped, which can be confusing).