107 replies to this topic

[saemark30]

The problem with Brandons are they are not MC but simply single coated and no fine tuning in the two glass interfaces.

So the math analysis does not account for the glass interface reflections.

 

I prefer the TV plossls for deep sky viewing because of this and the cold tone of the Brandons is not as pleasing to me as the higher transmission TV plossls.

I prefer Clave plossls over the Brandons for similar reasons and they excel on planetary detail.

Edited by saemark30, 24 March 2025 - 11:46 AM.

[Sarkikos]

A little math:

full multi coating on an air-to-glass surface transmits ~99.5% of the light and reflects about 0.5%.

So, the transmission of FMC coatings in eyepieces of:

1 group (monocentric?)--99.0%

2 groups (Plössls, orthos, Kellners, Ramsden, Huygens, Brandon)--98.0%

3 groups (Masuyama, Erfle, etc.)--97.0%

4 groups (many widefields)--96.1%

5 groups (many widefields)--95.1%

6 groups (some hyperwides, some complex designs)--94.2%

7 groups (a few exotic designs)--93.2%

 

There is also a loss of about 1% per inch of glass, so some of the large complex designs may lose another 2-3%.

But, with some exceptions, and there are a few, almost every modern FMC eyepiece falls in the 90-98% transmission range.

There are some transmission figures that indicate sophisticated coatings with >99.5% transmission, but for purposes of this post, I'll ignore those.

 

So, what is the visible difference in terms of light transmission?  about 8% max.

Note that 0.1 magnitude is a 9.6% difference, so the difference in transmission is smaller than 0.1 magnitude among all FMC eyepieces.

 

How does that stack up?

Well,

1. nightly variations in sky darkness and transparency range, but almost always exceed 0.2 magnitudes or more.
2. if we are talking about the visibility of DSOs, the difference of 0.1 magnitude is right at the limit of human vision, where we are likely talking about the difference between visible 20% of the time with averted vision and maybe 10% of the time with averted vision.  We are definitely not talking about the difference between visible with direct vision and invisible to direct vision, a difference that would be significantly larger than 0.1 magnitude.
3. A difference of 0.1 magnitude can barely be seen in a controlled lab experiment, and use of a telescope in the field is hardly a controlled lab environment.

Yet, we all have seen that some eyepieces go deeper than some others and reveal fainter features in DSOs.

Can we attribute that to light transmission in the eyepiece?

 

Perhaps partially.  But other factors enter into the picture as well:

--sharpness of focus.  A smaller spot size in the design might increase the per square arc-second light intensity.

--control of scattered light in the eyepiece.  We see contrast, so reducing scattered light can improve contrast and make fainter things more visible.

--control of scattered light outside the eyepiece--in the scope, the environment.  We all see more in the eyepiece when all peripheral light is blocked.  The tops of some eyepieces do a better job at that than others.

--lens polish.  Reducing scattered light at the lens surface, making coatings more effective.

--control of scattered light in the scope.  One of the advantages to refractors, though reflectors can be optimized for this as well, but don't seem to be very often.

 

So when all the factors are added up, the difference from one eyepiece to another in terms of how faint it sees can be noticeable.

Light transmission, though, is only a minor part of that.  Contrast is the major factor, and there is likely a % of that related to the psychology of use of a particular eyepiece.

"A little math:

full multi coating on an air-to-glass surface transmits ~99.5% of the light and reflects about 0.5%.

So, the transmission of FMC coatings in eyepieces of:

1 group (monocentric?)--99.0%

2 groups (Plössls, orthos, Kellners, Ramsden, Huygens, Brandon)--98.0%

3 groups (Masuyama, Erfle, etc.)--97.0%

4 groups (many widefields)--96.1%

5 groups (many widefields)--95.1%

6 groups (some hyperwides, some complex designs)--94.2%

7 groups (a few exotic designs)--93.2%"

 

But you are assuming that all these eyepieces are FMC.  Brandons do not have FMC coatings.  They have FC, simple single coatings.  I think the level of coatings have more do with light throughput - and perhaps contrast - than the number of elements.

 

I know of only one other eyepiece line that is still produced with FC coatings:  Edmund RKE.  Coincidentally, these are both US companies. 

 

Orion Sirius Plossls were also produced with FC coatings.  

 

Mike

Edited by Sarkikos, 24 March 2025 - 12:49 PM.

[Sarkikos]

The problem with Brandons are they are not MC but simply single coated and no fine tuning in the two glass interfaces.

So the math analysis does not account for the glass interface reflections.

 

I prefer the TV plossls for deep sky viewing because of this and the cold tone of the Brandons is not as pleasing to me as the higher transmission TV plossls.

I prefer Clave plossls over the Brandons for similar reasons and they excel on planetary detail.

Some observers would say that the simple single coating is not a problem with the Brandons, but a feature. 

 

The older version TV Plossls had a definite warm tone.  I've read that the Clave Plossls are even warmer in tone.  I think this is a major reason why they excel for planet viewing.  But another option, which is my preference, is to use neutral eyepieces and then add a contrast filter as needed.

 

Mike

Edited by Sarkikos, 24 March 2025 - 12:54 PM.

[saemark30]

Some observers would say that the simple single coating is not a problem with the Brandons, but a feature. 

 

The older version TV Plossls had a definite warm tone.  I've read that the Clave Plossls are even warmer in tone.  I think this is a major reason why they excel for planet viewing.  But another option, which is my preference, is to use neutral eyepieces and then add a contrast filter as needed.

 

Mike

I have older FC orthos with that "feature".

No one seems to complain about FMC on Zeiss ZAO or Pentax SMC O.

I have to wonder if this is just some marketing invention.

The Brandons aren't neutral but cold in tone though.

Orthoscopics are more neutral in tone.

 

P.S. for planetary I prefer the Brandon's higher contrast over the older and newer TV plossls though.

Perhaps the Brandons have a finer polish than the TVs.

Edited by saemark30, 25 March 2025 - 09:14 AM.

[Starman1]

"A little math:

full multi coating on an air-to-glass surface transmits ~99.5% of the light and reflects about 0.5%.

So, the transmission of FMC coatings in eyepieces of:

1 group (monocentric?)--99.0%

2 groups (Plössls, orthos, Kellners, Ramsden, Huygens, Brandon)--98.0%

3 groups (Masuyama, Erfle, etc.)--97.0%

4 groups (many widefields)--96.1%

5 groups (many widefields)--95.1%

6 groups (some hyperwides, some complex designs)--94.2%

7 groups (a few exotic designs)--93.2%"

 

But you are assuming that all these eyepieces are FMC.  Brandons do not have FMC coatings.  They have FC, simple single coatings.  I think the level of coatings have more do with light throughput - and perhaps contrast - than the number of elements.

 

I know of only one other eyepiece line that is still produced with FC coatings:  Edmund RKE.  Coincidentally, these are both US companies. 

 

Orion Sirius Plossls were also produced with FC coatings.  

 

Mike

I was talking about FMC eyepieces.  But, a 2-group FC eyepiece will have a transmission in the 94% range, so not really a large enough difference to make a noticeable difference without other factors being different.

Where you get larger differences is when some of the internal surfaces are uncoated, as in the Meade Series 4000 UWA and SWA eyepieces in the '80s and early '90s.

Then you start getting transmissions in the mid 80% range (or less).

Edited by Starman1, 24 March 2025 - 01:31 PM.

[Jeff Morgan]

Perhaps the Brandons have a finer polish than the TVs.

 

I suspect that more than coatings, and more than lens count, it is the polish that makes the difference (in the realm of planetary eyepieces). And that only comes from an investment of time on the polishing machines.

 

Good business people that want to stay in business know that Time = Money. Probably the largest reason a Zeiss Abbe Ortho is many multiples the cost of a UO Abbe Ortho.

 

If you spend time in the Refractor forum, you have probably seen the green laser photos people publish to identify lens elements. All the glass types scatter light (excepting fluorite). You can see the beam path thru the glass, because glass itself scatters light along its entire thickness.

 

Ever notice the brightest part of the beams are not the internals, but the surface transitions?

[Sarkikos]

I have older FC orthos with that "feature".

No one seems to complain about FMC on Zeiss ZAO or Pentax SMC O.

I have to wonder if this is just some marketing invention.

The Brandons aren't neutral but cold in tone though.

Orthoscopics are more neutral in tone.

 

P.S. for planetary I prefer the Brandon's higher contrast over the older and newerTV plossls though.

Perhaps the Brandons have a finer polish than the TVs.

"I have to wonder if this is just some marketing invention."

 

Do you mean that FMC is a marketing invention or that FC is?     I don't think either are.  FC came before FMC.  FMC is the innovation, not FC.  I think both have advantages.  

 

The Vernonscope website doesn't say much about the coatings on their Brandon eyepieces, much less play up any advantage to single coatings.  Here's what they say:

 

Vernonscope Brandon eyepieces have excellent contrast and very dark backgrounds when viewing.  This makes them perfect for planetary viewing as well as for resolving double stars.  

https://www.vernonsc...1-25-eyepieces/

 

When describing their new 20mm Brandon, they say:

 

Same coating design as other Brandon's to offer less scatter and reflections.

https://www.vernonsc...w-20mm-brandon/

 

On the website, though, are two newspaper clippings of Vernonscope ads which briefly mention the coatings.  https://www.vernonscope.com/history/  I can't find anything about a high level of polish, though.  Vernonscope doesn't hype specifically FC coatings or a high level of polish.

 

Though, IIRC, somewhere out there is some valid indication that the Brandons have a high level of polish.  Also, FC is supposed to reduce low-angle light scatter, which is an advantage when viewing bright planets and double stars.   

 

Here is a CN thread about FC eyepieces that I started a few years ago: Single Coat (FC) Eyepieces: What Good are They? Any Available New?   https://www.cloudyni...-available-new/

 

Here is a CN thread about narrow angle light scatter:  https://www.cloudyni...-light-scatter/

 

"The Brandons aren't neutral but cold in tone though."

 

I didn't say whether Brandons are neutral or cold.  But I know they aren't warm. 

 

To my eye, often it's more obvious if an eyepiece has a warm tone when compared with an eyepiece that is neutral or cold.  In fact, I didn't realize that the Leica Zoom is slightly warm in tone until I compared it to an XW.  On the other hand, the warm tone of the old version TV Plossls was obviously warm to my eye when viewing Jupiter or the Moon.

 

The point is moot, because whether an eyepiece is neutral or cold, the contrast can be increased by a contrast filter.  I'd rather do that, than begin with an eyepiece that is warm.   With a neutral/cold eyepiece you have the choice of the native neutral/cold tone or using a filter for greater contrast when viewing planets.  With a warm eyepiece, you can't unwarm the tone.  It's as if the warm eyepiece already has a contrast filter built into it that can't be removed.

 

Mike

Edited by Sarkikos, 25 March 2025 - 09:57 AM.

[azure1961p]

I was talking about FMC eyepieces.  But, a 2-group FC eyepiece will have a transmission in the 94% range, so not really a large enough difference to make a noticeable difference without other factors being different.

Where you get larger differences is when some of the internal surfaces are uncoated, as in the Meade Series 4000 UWA and SWA eyepieces in the '80s and early '90s.

Then you start getting transmissions in the mid 80% range (or less).

 

I didn't trust Meade and opted for TV s only. After learning this, I'm so glad now.  At first I loved MEADE, but story after story and review after review... and I was bent on getting a Meade SCT. 

 

Thanks again Don. Hope all been well.

 

Pete

[Sarkikos]

I was talking about FMC eyepieces.  But, a 2-group FC eyepiece will have a transmission in the 94% range, so not really a large enough difference to make a noticeable difference without other factors being different.

Where you get larger differences is when some of the internal surfaces are uncoated, as in the Meade Series 4000 UWA and SWA eyepieces in the '80s and early '90s.

Then you start getting transmissions in the mid 80% range (or less).

I saw an obvious difference in transmission comparing an old CZJ Ortho to modern FMC eyepieces.  Some dim stars were just not visible at all in the CZJ.  I've also seen a transmission reduction in Brandons, but not as obvious.

 

Mike

Edited by Sarkikos, 25 March 2025 - 09:47 AM.

[j.gardavsky]

"I have to wonder if this is just some marketing invention."

 

...

 

To my eye, often it's more obvious if an eyepiece has a warm tone when compared with an eyepiece that is neutral or cold.  In fact, I didn't realize that the Leica Zoom is slightly warm in tone until I compared it to an XW.  On the other hand, the warm tone of the old version TV Plossls was obviously warm to my eye when viewing Jupiter or the Moon.

 

The point is moot, because whether an eyepiece is neutral or cold, the contrast can be increased by a contrast filter.  I'd rather do that, than begin with an eyepiece that is warm.   With a neutral/cold eyepiece you have the choice of the native neutral/cold tone or using a filter for greater contrast when viewing planets.  With a warm eyepiece, you can't unwarm the tone.  It's as if the warm eyepiece already has a contrast filter built into it that can't be removed.

 

Mike

Hello Mike,

 

all Leicas have the UV - blue/violet cut, and so are the Swarovski eyepieces.

This plays a "negative" role when observing the outer spiral arms of the galaxies, where they are dominated by the OB stars associations emitting most of the light in the UV.

 

Higher transmissivity in the UV - blue/violet have the Carl Zeiss West (Pl, E-Pl, W-Pl, ...) eyepieces, but they have not been designed for the short focus length.

 

Back to the polish grade of the lenses.

The highest polish grade used to be specified for the tactical optics eyepieces, like the Hensoldt D16 (wide field), the Carl Zeiss West Ultrawide, when talking just about what I have.

 

Otherwise, a high polish grade is required on the small aperture eyepieces, like on the short focus Abbe and other orthos, Pentax SMC O-, Pentax SMC XO. The polish grade specifications are expected to be similar to those as used for the research grade microscopy optics, where the ratio of the scratches (and digs) sizes (and numbers) across the small lenses surfaces matters.

 

What aslo matters are the microinclusions, and other unwanted "dirt".

 

Best,

JG
 

[saemark30]

"I have to wonder if this is just some marketing invention."

 

Do you mean that FMC is a marketing invention or that FC is?     I don't think either are.  FC came before FMC.  FMC is the innovation, not FC.  I think both have advantages.  

 

 

 

Mike

I am thinking this narrow angle light scatter business with the multicoatings VS single coatings is a red herring as described by Starman1 here:

https://www.cloudyni...tter/?p=3115861

 

The Brandons are made to military specs for the military and hence my preferred for Brandons (for planetary use) has to due with better scratch and dig specs and less micro inclusions

compared to say the TV plossls.

Edited by saemark30, 25 March 2025 - 11:11 AM.

[Sarkikos]

Hello Mike,

 

all Leicas have the UV - blue/violet cut, and so are the Swarovski eyepieces.

This plays a "negative" role when observing the outer spiral arms of the galaxies, where they are dominated by the OB stars associations emitting most of the light in the UV.

 

Higher transmissivity in the UV - blue/violet have the Carl Zeiss West (Pl, E-Pl, W-Pl, ...) eyepieces, but they have not been designed for the short focus length.

 

Back to the polish grade of the lenses.

The highest polish grade used to be specified for the tactical optics eyepieces, like the Hensoldt D16 (wide field), the Carl Zeiss West Ultrawide, when talking just about what I have.

 

Otherwise, a high polish grade is required on the small aperture eyepieces, like on the short focus Abbe and other orthos, Pentax SMC O-, Pentax SMC XO. The polish grade specifications are expected to be similar to those as used for the research grade microscopy optics, where the ratio of the scratches (and digs) sizes (and numbers) across the small lenses surfaces matters.

 

What aslo matters are the microinclusions, and other unwanted "dirt".

 

Best,

JG
 

"all Leicas have the UV - blue/violet cut, and so are the Swarovski eyepieces.

This plays a "negative" role when observing the outer spiral arms of the galaxies, where they are dominated by the OB stars associations emitting most of the light in the UV.

Higher transmissivity in the UV - blue/violet have the Carl Zeiss West (Pl, E-Pl, W-Pl, ...) eyepieces, but they have not been designed for the short focus length."

 

So then, eyepieces with a cool tone should perform better for viewing galaxies, at least for observing the outer spiral arms, while warm tone eyepieces should be worse.  Years ago, I tried a light blue filter when observing M33 and M31 with my 10" Dob at a dark site.  The arms were a bit more obvious, with better contrast, when the light blue filter was in place.

 

Mike

[j.gardavsky]

I am thinking this narrow angle light scatter business with the multicoatings VS single coatings is a red herring as described by Starman1 here:

https://www.cloudyni...tter/?p=3115861

 

The Brandons are made to military specs for the military and hence my preferred for Brandons (for planetary use) has to due with better scratch and dig specs and less micro inclusions

compared to say the TV plossls.

We used to have in depth talks on the optical surface scatter (Lambertian, specular) on the CN in the past, and its effects on the modulation transfer function. 

For myself, I have been in the research and calculations of the scattering of light, and of applications, some results published in the Journal of the Optical Society of America (JOSA).

 

Just to refresh the norms on the optics materials and surfaces:

https://www.degruyte...-2015-0047/html

https://blog.rossopt...-specifications

 

Regarding the transmission of the eyepieces, this has been already discussed in

https://www.cloudyni...n-test-results/

Regarding the transmissivity measurement system used by Konrad Horn, it's been according to the PTB standard (Physikalisch-Technische Bundesanstalt in Braunschweig). Unlike the APM blue list, I have the tables with the measurement data from the Konrad Horn optics laboratory, from the times when they have been on the web.

 

Hoping, this helps,

JG
 

[j.gardavsky]

"all Leicas have the UV - blue/violet cut, and so are the Swarovski eyepieces.

This plays a "negative" role when observing the outer spiral arms of the galaxies, where they are dominated by the OB stars associations emitting most of the light in the UV.

Higher transmissivity in the UV - blue/violet have the Carl Zeiss West (Pl, E-Pl, W-Pl, ...) eyepieces, but they have not been designed for the short focus length."

 

So then, eyepieces with a cool tone should perform better for viewing galaxies, at least for observing the outer spiral arms, while warm tone eyepieces should be worse.  Years ago, I tried a light blue filter when observing M33 and M31 with my 10" Dob at a dark site.  The arms were a bit more obvious, with better contrast, when the light blue filter was in place.

 

Mike

Hello Mike,

 

this is exactly what I have been doing on some galaxies in the past, I took the Baader blue(RGB)CCD filter.

Otherwise, I prefer on the galaxies the Abbe orthos, and when more field is required, than the Pentax 5mm XW.

 

The old Baader blue(RGB)CCD filter is also helpul on the IFNs and on some molecular clouds, which scatter the short wavelengths light. The new Baader blue(RGB)CMOS-optimized filter cuts some blue/violet.

 

Clear skies,

JG

[Wildetelescope]

I only list Mars because the severity of the test sits well there.  I've enjoyed UO HD Orthos, some Volcano Tops (but not much) and TV Plossls, TV barlowed or not with my long newt.  Then there's Brandon's already.  I was once going to seek some then the observer experiences seemed so steeped in critical exceptions to do with seeing, observer champagne ego and so much malarkey.  Is the Brandon that good? I mean come on already?  If it were wouldn't several manufacturers be fabricating these designs?  It's always addressed as some caviar class of oculars, and I love caviar, but isn't that really just a lot of garbage?  It's probably no better than any well made plossl or orthoscopic but perhaps material ownership, hype suggestion or something else is just inflating it into myth when it's really nothing better on Mars than a good plossl or Ortho?  And if Brandon's TRULY had some advantage, would China be knocking them out by now?

 

Not saying they are bad but, come on, tacks and nails, what's the deal.  

I own Brandons and UO orthos.  UO Orthos are truly wonderful Eyepieces and WERE amazing value when they were available.  Brandon's to my eye are a little bit sharper and contrasty.   It is subtle, but noticeable to me.  Have not looked at Mars, but I have done side by sides on Jupiter and Saturn.  Basically I could see all the same features, but features like the cloud bands appeared just a touch sharper.  A friend describes it as removing a very thin film from the image, which I think is accurate.  I do not think I have buyer's bias, since I got my collection of Brandons used for about the same cost as a set of the UO orthos new:-).  My 2 cents.  

 

JMD

[Sarkikos]

I own Brandons and UO orthos.  UO Orthos are truly wonderful Eyepieces and WERE amazing value when they were available.  Brandon's to my eye are a little bit sharper and contrasty.   It is subtle, but noticeable to me.  Have not looked at Mars, but I have done side by sides on Jupiter and Saturn.  Basically I could see all the same features, but features like the cloud bands appeared just a touch sharper.  A friend describes it as removing a very thin film from the image, which I think is accurate.  I do not think I have buyer's bias, since I got my collection of Brandons used for about the same cost as a set of the UO orthos new:-).  My 2 cents.  

 

JMD

This agrees with my experience with Brandons and UO Orthos.  You really have to go to something like ZAO's to achieve much better performance when viewing planets.  

 

Mike

Edited by Sarkikos, 25 March 2025 - 04:03 PM.

[Wildetelescope]

This agrees with my experience with Brandons and UO Orthos.  You really have to go to something like ZAO's to achieve much better performance when viewing planets.  

 

Mike

Once compared my Brandon 24mm against a 24 mm Clave in a Zeiss Telementor.  The Brandon does have a very faint Amber tint compared to the Clave.  Otherwise they were both sharp as my old eyes could tell:-).   

 

Cheers!

 

JMD

[vahe]

This agrees with my experience with Brandons and UO Orthos.  You really have to go to something like ZAO's to achieve much better performance when viewing planets.  

 

Mike

 

I compered 24 mm Brandons and ZAO-I 25mm in bino mode viewing Jupiter (200x), Brandon were just as sharp and just as scatter free as the ZAO.

.

Vahe

[Wildetelescope]

This is timely.   I just returned from a 8 day observing trip that concluded last weekend with the 2024 Black Forest Star Party.  I did a lot of observing as the weather was uncharacteristically great for 6 of the 8 days.  I only took one scope - a Portaball-8 and one complete set of eyepieces - TeleVue Delites.  This was the first extensive use of the Delites over many many hours and many consecutive days of observing.   Sure, I've used them for quick looks with small (92mm) apertures mostly for planets and the Moon.  But never for long sessions over a number of days on many types of objects.

 

I absolutely loved them.  The more I used them, the better I liked'em.  I normally use a set of Nagler T6's as daily driver type of eyepiece.  On this trip I used Delites, exclusively.   My scope was tracking on its Tom O platform so I never had to manually track objects.  This allowed me to concentrate on the eyepiece and the view.    

Posted earlier on my thoughts comparing Brandons to UO orthos.   I like my Brandons a lot.  BUT, I use my set of Delos more;-).  They are the sharpest, most color neutral eyepieces I have looked through.  To be sure there are many fine eyepieces I HAVE NOT lookedthrough, so take that into account.  But for the eyepieces I have owned, they rank the best.   I have a set of 13 mm Delites I got for my binoviewer.  They are every bit the performer that the Delos are, with a smaller FOV.   The Brandons are as sharp, but do not have the eye relief and as I mentioned before, throw up a slightly warmer image.  In the end, I pretty much agree with what Starman1 says.   I feel pretty blessed to be out under the night sky with any of these wonderful eyepieces, including the UO orthos, which are an amazing eyepiece for what they cost.  I was really sad to see UO close up shop.  The owner was a real gentleman.  

 

Cheers!

 

JMD

[Jay_Reynolds_Freeman]

I haven't used University Optics orthoscopics very much (though I do have a few), but on a night of good seeing, observing Mars at close opposition with a 10-inch Astro-Physics Maksutov-Cassegrain, I tried several eyepieces and ended up using an 8 mm Brandon, which had less glare than several others. Low glare was essential in chasing down Deimos. (I also saw Phobos, but it was easier.) A 6 mm Pentax SMC ED orthoscopic was my second choice for this observing session.

 

I know of several sources of glare in eyepieces: Possibly the most common is internal reflections off diffuse surfaces, like unblackened lens edges, and far out-of-focus grazing incidence reflections from metal surfaces of the eyepiece barrel or lens-separating spacers. Eyepieces with field stops close to the field lens and with closely-spaced lens components are less susceptible to the latter. I don't know much about blackened lens edges -- I rarely take expensive eyepieces apart. Another source of glare is poor polish of the lens surfaces themselves, and a third is surface irregularities in coatings. I suspect that the more layers a coating has, the greater the surface irregularities, and the more scattered light to cause glare. No doubt variations in the coating technique used affect this problem. Thus eyepieces with few air/glass interfaces (Brandons Plossls and orthoscopics have four, many wide-field types have ten) and with simple coatings (such as Brandons) may have an advantage here, but it would take careful measurements or other tests to make any definitive statement.

 

 

Clear sky ...

[steve t]

I haven't used University Optics orthoscopics very much (though I do have a few), but on a night of good seeing, observing Mars at close opposition with a 10-inch Astro-Physics Maksutov-Cassegrain, I tried several eyepieces and ended up using an 8 mm Brandon, which had less glare than several others. Low glare was essential in chasing down Deimos. (I also saw Phobos, but it was easier.) A 6 mm Pentax SMC ED orthoscopic was my second choice for this observing session.

 

I know of several sources of glare in eyepieces: Possibly the most common is internal reflections off diffuse surfaces, like unblackened lens edges, and far out-of-focus grazing incidence reflections from metal surfaces of the eyepiece barrel or lens-separating spacers. Eyepieces with field stops close to the field lens and with closely-spaced lens components are less susceptible to the latter. I don't know much about blackened lens edges -- I rarely take expensive eyepieces apart. Another source of glare is poor polish of the lens surfaces themselves, and a third is surface irregularities in coatings. I suspect that the more layers a coating has, the greater the surface irregularities, and the more scattered light to cause glare. No doubt variations in the coating technique used affect this problem. Thus eyepieces with few air/glass interfaces (Brandons Plossls and orthoscopics have four, many wide-field types have ten) and with simple coatings (such as Brandons) may have an advantage here, but it would take careful measurements or other tests to make any definitive statement.

 

 

Clear sky ...

 

Years ago, I asked Don Yeier why he blackened the lens edges of the Dakin Barlow, but not the lenses in Brandons eyepieces. I recall his answer was something like the design of the Brandon made it unnecessary. 

Someone more knowable than me please correct me if I'm wrong.

 

Steve T

[Starman1]

Years ago, I asked Don Yeier why he blackened the lens edges of the Dakin Barlow, but not the lenses in Brandons eyepieces. I recall his answer was something like the design of the Brandon made it unnecessary. 

Someone more knowable than me please correct me if I'm wrong.

 

Steve T

Easy way to tell: put a bright star right outside the field stop.  If you can tell where the bright star is outside the field and you see some glow in the field from that star, 

the eyepiece could benefit from improved baffling and reflection suppression.

Note: almost no eyepieces pass this test, an indication of less than perfect mechanical design, no matter how good the optical design. 

[Olimad]

Easy way to tell: put a bright star right outside the field stop.  If you can tell where the bright star is outside the field and you see some glow in the field from that star, 

the eyepiece could benefit from improved baffling and reflection suppression.

Note: almost no eyepieces pass this test, an indication of less than perfect mechanical design, no matter how good the optical design. 

Interesting Don. Which eyepieces have passed this test? 

[saemark30]

Some observers would say that the simple single coating is not a problem with the Brandons, but a feature. 

 

The older version TV Plossls had a definite warm tone.  I've read that the Clave Plossls are even warmer in tone.  I think this is a major reason why they excel for planet viewing.  But another option, which is my preference, is to use neutral eyepieces and then add a contrast filter as needed.

 

Mike

I am speaking from first hand experience.

In the same period I compared the Claves  to Brandons, Zeiss ZAO and TV plossls in the same Newtonian.

Both the Brandons and Claves are sharp and contrasty, but the Brandons have distinctly less color saturation.

The ZAOs were just excellent, with greater light transmission and great color rendition.

 

Using a premium quality 10" F/6 Newtonian I found to my dismay my old and new TV plossls produced distinctly yellower lunar images than the multicoated Clave plossls from the 80s.

So I would not say they are warmer in tone at all.

In fact, the Claves produced blacker shadows than the TV plossls I found.

 

I believe the major reasons Clave plossls excel is the superior polish and quality of glass.

They also deliver excellent images of Saturn, Mars and deep sky objects such as M13 and nebulae.

 

There are different versions of Claves and Brandons from difference eras and manufacturers.

Can you post a link to what you "read"?

Edited by saemark30, 27 March 2025 - 11:12 AM.

[Starman1]

Interesting Don. Which eyepieces have passed this test? 

I don't remember, off the top of my head.

I vaguely recall one of the Vixen HR eyepieces did.

 

I did this test with binoculars when I worked in a store that sold a lot of them, using a streetlight.

One binocular passed: the Leica DuoVid.  No other binocular did.

 

One difficulty with this evaluation is that bright stars have spikes, and the spikes can extend for quite a distance from the star.

The star may be well outside the field of view and as long as the star in in the field of view of the telescope itself, the spike will be visible in the field.

That is NOT an example of light scatter.  If you move the scope enough, the star leaves the field of view of the scope and the spike disappears abruptly.

If the eyepiece is a high power eyepiece with a small field stop, the spike will not disappear for several fields of view.  It's an interesting phenomenon.

The spike, though is not a generalized glow in the field.  You can have excellent contrast in the field. Ironically, the better the contrast of the eyepiece, the more visible the spike.

 

I have seen a glow (scatter) in the field from a bright star outside the field that:

looked like a small glow at the edge (decent),

loops and spikes in the field (poor),

a general glow that covered the entire field (!) (extremely poor),

a general series of rays emanating from the star (not great, but not devastating),

and a bright glow that was like a half moon inside the field that covered the visibility of anything on that side of the field (poor).

 

Seeing conditions and haze in the air strongly influence the effects in the field of view.  That can make evaluation of this form of light scatter difficult.

No eyepiece passes when the sky is hazy, but it doesn't mean the eyepiece is at fault.

It's like seeing a haze around a planet: Is it the eyepiece or the sky?  Usually, it's the sky.