23 replies to this topic

[DRodrigues]

The linear binoviewer have the advantage of equivalent to Zero light path i.e. doesn't change focus position of the eyepieces. However have some different characteristics that can minimize their usability as the case of erecting the images and the clear aperture of 17.3mm.

The image erecting characteristic is interesting for those that want to do straight observation with telescopes, that is my daylight case. So I remembered to use also a Siebert PMW with 3x increasing factor (old model with 4 lens cells), with a pair of Baader Morpheus 14mm, to avoid vignetting. With this setup the minimum magnification should be 36x, that might be a limiting factor for some people but not really for me.

 

 

 

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[DRodrigues]

The minimum magnification image quality and AFOV are great. However, when "zooming" vignetting start to visible at the 3rd mag position and increases with the following mags - the attached image show the minimum and maximum magnification AFOVs.

[DRodrigues]

So I remembered to test if the 2" TS 0.5x reducer would work well - I remembered using the 2" to try to avoid vignetting.

The reducer was positioned just before the 2" to 1.25" adapter, after the PMW.

 

The FOV increased 68% and no longer shows vignetting increasing magnifications - photo show AFOVs of the minimum and maximum magnification - 2.79x increase factor! The resulting magnifications should range from 24.6 to 68.6x! 

 

Now a pair of Morpheus 12.5mm or a pair of APM HI-FW 12.5 / Doctor 12.5mm, start to tempt me - 28.7-80x...

Don't know if a pair of Morpheus 9mm wouldn't be too much - 41.1 to 114.7x...

 

Will test this solution with a C5, when will have time available...

[DRodrigues]

Just remembered to mention that the APM SuperZoom shows vignetting with both solutions, although reduced with the second. Vignetting disappears at the 14mm position.

Will test the Baader zoom also. 

[DRodrigues]

...

 

Now a pair of Morpheus 12.5mm or a pair of APM HI-FW 12.5 / Doctor 12.5mm, start to tempt me - 28.7-80x...

...

Just to let you know that the APM and Docter 12.5mm are out since probably will vignette, because have FS >19mm...

 

If any of you use successfully any of these 2 eps with the LBV, please let us know.
 

Edited by DRodrigues, 22 August 2023 - 08:09 PM.

[DRodrigues]

...

Will test the Baader zoom also. 

There is no vignetting with the Baader zoom, at least with the second solution!

On the second solution I added a 5mm 2" spacer between the reducer and the 2" to 1.25" adapter, to avoid that the 1.25" nose-piece of the LBV touches the reducer lens. 
 

Edited by DRodrigues, 25 October 2023 - 06:02 PM.

[DRodrigues]

The LTX115!!!

See more at https://www.birdforu...64/post-4556001

 

Attached Thumbnails

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[DRodrigues]

So I remembered to test if the 2" TS 0.5x reducer would work well - I remembered using the 2" to try to avoid vignetting.

...

The FOV increased 68% and no longer shows vignetting increasing magnifications - photo show AFOVs of the minimum and maximum magnification - 2.79x increase factor! The resulting magnifications should range from 24.6 to 68.6x! 

...

For those that didn't the maths, it would be like using a pair of Morpheus 23.5mm (that don't exists...), on a Baader MKV, that probably would show vignetting...
 

[titanio]

Hi, 

 

You can use a kasai 1,25"  0.66X reducer threaded to the binoviewer.

 

 

Greetings

 

Toni

[DRodrigues]

...

 

You can use a kasai 1,25"  0.66X reducer threaded to the binoviewer.

 

...

I know, but I didn't found a seller within EU. Did you?
 

[titanio]

Only in Japan,  you must send an e-mail to kasay trading and ask for it, he will give you all the information and the paypal address, once you made the payment he will ship the kasai reducer.

 

This is the dealer:

 

Kasay trading

 

korder@kasai-trading.jp

 

Around 50 euro total cost 

 

Greetings

 

Toni

Edited by titanio, 22 April 2024 - 04:07 AM.

[DRodrigues]

Only in Japan,  you must send an e-mail to kasay trading and ask for it, he will give you all the information and the paypal address, once you made the payment he will ship the kasai reducer.

 

This is the dealer:

 

Kasay trading

 

korder@kasai-trading.jp

 

Around 50 euro total cost 

 

Greetings

 

Toni

I know (I contacted them looking for a EU seller...), but I fear the EU customs taxes that can result on more than 2x the original cost...

[titanio]

You will pay 21 % VAT plus around  6% customs duty 

 

Greetings

 

Toni

[Olle Eriksson]

Just to let you know that the APM and Docter 12.5mm are out since probably will vignette, because have FS >19mm...

 

If any of you use successfully any of these 2 eps with the LBV, please let us know.
 

I wrote about this exact topic in https://www.cloudyni.../#entry13799188.

 

I was a bit surprised to find that the difference in unobstructed AFOV looking through the APM Hi-FW and the Morpheus 12.5 just holding them up next to each others (without a bino or a telescope) appears to be very small actually. Others have said the same. Maybe a couple of degrees tops. I've heard the Morpheus 12.5 might actually be 78 degrees. And the APM is pretty much right between my ES82 24mm and the Morpheus 78deg in terms of AFOV. So that would make the APM Hi-FW about 80 degrees, not 84, if the ES82 is on the mark. All this feels correct to me. And the APM Hi-FW is still my favourite eyepiece by the way because of its transmission and clarity.

 

Also more importantly, in the linear binoviewer, the APM Hi-FW actually is vignetted to where its AFOV is slightly smaller than the Morpheus 12.5. This was verified using a method described at the link above. If the Morpheus 14mm is also 78 degrees, which I saw Don Pensack mention, and if that eyepiece is really not vignetted then it sounds like the 14mm Morpheus would perhaps be the best fit for the linear.

 

Surprisingly, my SvBony UFF 18 which I thought wasn't vignetted actually showed significant vignetting, from the specified 65 degrees down to maybe 59 degrees or so, which I had not expected, just slightly less than the UFF 10 which should be have an AFOV of 60 degrees. Note that I haven't tested this outdoors on the night sky yet but I feel pretty confident in these numbers.

[DRodrigues]

...

 

Also more importantly, in the linear binoviewer, the APM Hi-FW actually is vignetted to where its AFOV is slightly smaller than the Morpheus 12.5. This was verified using a method described at the link above. If the Morpheus 14mm is also 78 degrees, which I saw Don Pensack mention, and if that eyepiece is really not vignetted then it sounds like the 14mm Morpheus would perhaps be the best fit for the linear.

 

...

The photos above show there is no vignetting with the Morpheus 14 with the LBV. However, as also showed at #2, some total optical combinations can induce other type of "vignetting" - the LBV is a complex optical system...

Regarding the APM Hi-FW Tammy measured it's pseudo-AFOV as 88º, so it might has true AFOV of 80º but its aberrations result on a much larger TFOV. It would be interesting if you could compare the TFOV with the Morpheus 12.5 measuring it as done at the photos of #2 and #3, with and without the LBV...
 

[titanio]

Hi,

 

Best eyepice with linear binoviewer from my experience are orthos around 18 mm, 18 better than 25 mm TAO 18 is much better tham TAO 25  even the 18 TAO with kasai reducer. The ED Flatfield 18 Nirvana, TS or other models with 60° FOW vignetting. The TS 19 Flat Field eyepieces with 65° FOW also vignetting, both models can  be used  at night   but the FOW is reduced of courses, so better use orthos no longer than 25mm and with FOW around 50-53.

Edited by titanio, 17 November 2024 - 01:56 PM.

[nof]

I am using and am quite pleased with 20mm ES 52 degree eyepieces for maximum FOV, sharpness and color. When combined with the Kasai reducer they are the equivalent of 30mm eyepieces and the view is pleasing.

[careysub]

Are all of the linear binoviewers (all in the same price range) really the same unit from the same factory, just rebranded?

 

I was looking at the Long Perng on Agena Astro (out of stock) but saw this by Founder Optics in stock:

 

https://agenaastro.c...binoviewer.html

[jprideaux]

Hi,

Best eyepice with linear binoviewer from my experience are orthos around 18 mm, 18 better than 25 mm TAO 18 is much better tham TAO 25 even the 18 TAO with kasai reducer. The ED Flatfield 18 Nirvana, TS or other models with 60° FOW vignetting. The TS 19 Flat Field eyepieces with 65° FOW also vignetting, both models can be used at night but the FOW is reduced of courses, so better use orthos no longer than 25mm and with FOW around 50-53.

I agree. A good rule for the linear type binoviewer is to look for eyepieces that have the product of their AVOV and focal-length at or under 1000 to guarantee no vignetting. My go to eyepieces for my linear BV are the Baader 18mm orthoscopics that have an AVOV of 52 degrees. Inexpensive as well.

[Lentini]

Are all of the linear binoviewers (all in the same price range) really the same unit from the same factory, just rebranded?

 

I was looking at the Long Perng on Agena Astro (out of stock) but saw this by Founder Optics in stock:

 

https://agenaastro.c...binoviewer.html

They’re mechanically identical looking, except the color, so I assume so.

[Olle Eriksson]

[...] Regarding the APM Hi-FW Tammy measured it's pseudo-AFOV as 88º, so it might has true AFOV of 80º but its aberrations result on a much larger TFOV. It would be interesting if you could compare the TFOV with the Morpheus 12.5 measuring it as done at the photos of #2 and #3, with and without the LBV...

 

Alright, I had myself a bit of fun over the holidays.

 

I tried to reproduce the type of test you had done. So I setup my Sky-Watcher ST-120 mm refractor with 600mm focal length indoors, pointing towards the wall 10m/33ft away. On the wall I taped a graph paper with a grid with squares (9 or 10mm wide) and a ruler. I made sure the paper and ruler was completely flat against the wall, so any distortion you see is definitely the effect of the eyepiece. I then inserted the eyepieces one by one and took a photo through them. I should say that I hand-held the camera, but I was pretty steady and had to very precisely center the camera over the exit pupil to not get optical defects. You could really easily see the different types of distortions the different eyepieces produce.

 

Here is the APM Hi-FW 12.5mm 84° compared to the Morpheus 12.5mm. 

 

 

What the photos above show is how close in terms of AFOV the two eyepieces are. I know, it's not a perfect test, but I think it says something. I haven't moved anything between the tests, and the camera has to be at a very precise focal point to not be vignetted, so I consider the images "to scale". Counting pixels the APM is just a little over 1% wider, which would be about 1 degree AFOV wider. My completely subjective visual assessment if you remember was about 2 degrees wider.

 

It was also pretty clear that the Morpheus has a lot more pincushion distortion, while the APM has a really what I would call flat (distortion-free) field. I've never really understood the "flatness" of flat eyepieces, I thought it had more to do with having less field curvature (not same focus in the center and at the edge) and maybe it does. It was clear during this test that some eyepieces could not focus both in the center and at the edge, and the APM was actually one of those, but at the same time I don't know if the test setup is suitable for drawing conclusions on this since the grid paper was really close (10m/33ft) and the ST-120 also has a really short focal length. But out of all my 10-12 eyepieces I tested like this, it was primarily the three eyepieces that are marketed as "flat" that also had the "flattest" non-distorted field in this test, the APM Hi-FW, the UFF18 and the UFF10, so I found that pretty interesting.

 

In any case, the pincushion distortion of the Morpheus really reduces the TFOV by magnifying the edges more than the center. I count 217mm on the ruler for the APM Hi-FW and 186mm for the Morpheus 12.5. That's a 16.7% increase for the APM, approximately 89 degrees if the Morpheus is considered 76 degrees. So that to me explains why they can both be considered 12.5mm eyepieces, have almost the same AFOV, yet be marketed with such different FOVs.

Edited by Olle Eriksson, 30 December 2024 - 05:35 AM.

[Olle Eriksson]

 

Also, I bought myself a pair of Morpheus 14mm now and I can confirm that they are not vignetted in the Linear binoviewer. Well, just about, but for all intents and purposes there is nothing. When I did my indoor test with holding the BV up with the eyepiece inserted, and a bit of backlight, I could just about make out a super thin ring. It took a few moments before I actually saw it even when looking for it, and I think maybe it's half a degree or something, so practically nothing. 

 

Here are the three eyepieces, Morpheus 14, APM Hi-FW 12.5, and Morpheus 12.5 in the test I described in the previous post, without the linear binoviewer and with it. As can be sean by the width of the images, the 12.5 shows no vignetted. And neither does the 14mm. I couldn't see the thin 1/2 degree vignetting visually when I actually tested it in the telescope, though if I counted mm on the ruler I think half a millimeter or so was missing, but it was the same on the Morpheus 12.5 so I think that is something the BV does with all eyepieces.

 

Looking at the photos afterwards it's clear that the BV does appear to introduce a bit of pincushion distortion, of which the Morpheus 14 already has plenty.

 

You can also see how the APM Hi-FW is vignetted quite a bit. Note how you only see it on the right side. That's because the eyepiece was in the right eyepiece holder of the BV. It appears to vignette primarily on one side.

 

Pay no attention to the focus since I hand-held the camera.

 

So, now I'm just waiting for the weather to clear before trying out the Morpheus 14 in the BV on the night sky. I am a little worried though that the pincushion distortion will be too much for me. I have just learned that all the eyepieces I normally get a little queezy in panning are the ones that the test revealed had a lot of pincushion distortion. The APM Hi-FW doesn't, and neither do the UFF18.

[DRodrigues]

... I count 217mm on the ruler for the APM Hi-FW and 186mm for the Morpheus 12.5. That's a 16.7% increase for the APM, approximately 89 degrees if the Morpheus is considered 76 degrees. So that to me explains why they can both be considered 12.5mm eyepieces, have almost the same AFOV, yet be marketed with such different FOVs.

Thank you for your tests - saved me the idea of getting the Hi-FW... 

Just add that the AFOVs, on degrees, don't vary directly as the FOVs i.e. you must use a trigonometry formula (don't have time to search for it now...), so the AFOV increase is smaller than 16.7%.
 

[Olle Eriksson]

Thank you for your tests - saved me the idea of getting the Hi-FW...

Just add that the AFOVs, on degrees, don't vary directly as the FOVs i.e. you must use a trigonometry formula (don't have time to search for it now...), so the AFOV increase is smaller than 16.7%.
 

Yeah I agree. I figured it would be more or less negligible but you're right.