Stellalyra Kitakaru 40mm & 45mm Eyepieces

[John]

Has anyone used one of these 2 inch format long focal length eyepieces in a refractor with a focal ratio of F/7 ish ?

I'm wondering how they do, edge correction and other distortions at that focal ratio, actual AFoV delivered etc, etc.

Can anyone shed any light (so to speak 🙂) on these ?

StellaLyra 40mm 2" KITAKARU RPL Eyepiece | First Light Optics

StellaLyra 45mm 2" KITAKARU RPL Eyepiece | First Light Optics

Many thanks in advance 🙂

[bosun21]

I am actually curious about this range of eyepieces as well especially the 2”.

[Alan White]

2 hours ago, John said:

Has anyone used one of these 2 inch format long focal length eyepieces in a refractor with a focal ratio of F/7 ish ?

I'm wondering how they do, edge correction and other distortions at that focal ratio, actual AFoV delivered etc, etc.

Can anyone shed any light (so to speak 🙂) on these ?

StellaLyra 40mm 2" KITAKARU RPL Eyepiece | First Light Optics

StellaLyra 45mm 2" KITAKARU RPL Eyepiece | First Light Optics

Many thanks in advance 🙂

I have not used these, looked at them often with similar thoughts.
They have been available I think with other branding as well.
Surely someone has tried them?

[MalcolmM]

I've used the 45 in Taks 60CB, 100DC and Mew 180. I'm afraid I can't give you any details other than I like it! I didn't notice any distortions but I don't think I'm a particularly critical observer (or not a particularly skilled observer 🙂). On the FOV, the FLO FOV calculator implied I should be able to see all the Pleiades with it in the Mewlon. This is not quite the case. It's close though.

Malcolm 

[johnturley]

3 hours ago, John said:

Has anyone used one of these 2 inch format long focal length eyepieces in a refractor with a focal ratio of F/7 ish ?

I'm wondering how they do, edge correction and other distortions at that focal ratio, actual AFoV delivered etc, etc.

Can anyone shed any light (so to speak 🙂) on these ?

StellaLyra 40mm 2" KITAKARU RPL Eyepiece | First Light Optics

StellaLyra 45mm 2" KITAKARU RPL Eyepiece | First Light Optics

Many thanks in advance 🙂

With these eyepieces only being 4 element, I can't see them being very sharp at the edge of the 65 degree field.

John 

[Guest]

I do believe these are the eyepieces in question and here is a review from 2018.

 

https://www.skyatnightmagazine.com/reviews/eyepieces/altair-kitakaru-eyepieces

Edited August 16, 2023 by Mike Q

[cajen2]

24 minutes ago, Mike Q said:

I do believe these are the eyepieces in question and here is a review from 2018.

 

https://www.skyatnightmagazine.com/reviews/eyepieces/altair-kitakaru-eyepieces

Interesting, though it has to be said that SaN magazine is not the most critical of reviewers..

I've heard that EOF aberrations are rather pronounced at focal ratios shorter than about F/7, though I've never used one myself.

[Guest]

3 hours ago, cajen2 said:

Interesting, though it has to be said that SaN magazine is not the most critical of reviewers..

I've heard that EOF aberrations are rather pronounced at focal ratios shorter than about F/7, though I've never used one myself.

I do believe they mention something about that in the article 

[Gabby76]

With these being 4 element in 2 groups I am not surprised that there would be colour and artifacts along the EOF. 

Symmetrical work better at 50-55° AFOV.

You would need to be using a long focal length telescope since you get a exit pupil of 7.7 when used in a f/6 telescope.

The 45 mm  would work in my f/15 as that gives a 2.95 mm exit pupil. 

[John]

On 17/08/2023 at 06:08, Gabby76 said:

With these being 4 element in 2 groups I am not surprised that there would be colour and artifacts along the EOF. 

Symmetrical work better at 50-55° AFOV.

You would need to be using a long focal length telescope since you get a exit pupil of 7.7 when used in a f/6 telescope.

The 45 mm  would work in my f/15 as that gives a 2.95 mm exit pupil. 

My F/6 scope would probably be the one that the eyepiece would see little use with. 

I do have the Nagler 31mm and Ethos 21mm already which give very wide fields with more modest exit pupils. I was just curious about the Kitakaru design 🙂

Edited August 18, 2023 by John

[MalcolmM]

Here's my attempt to show the edge distortion in an FS60CB (f 5.9)

The rhs of the FOV is at 0, the lhs at 20 so the total FOV is roughly 65 cm on the ruler. The last 3cm of the rulers on either side are quite difficult to see without squinting and moving your head.

I've no idea how this would relate to star shapes at infinity but to my eyes, the ruler is pretty sharp up to roughly 75% out. But there is definitely a gradual decrease in the sharpness as you move to tbe edge.

Malcolm 

[MalcolmM]

Just for comparison,  here's a Nagler 16mm in the same setup. This time the FOV goes from 0 to 33cm.

Apologies to @Louis D for using his technique; I don't think I have achieved the quality of his images.

Malcolm 

[cajen2]

The Nagler image is nothing to write home about for the price of the EP.....

[John]

2 minutes ago, cajen2 said:

The Nagler image is nothing to write home about for the price of the EP.....

They work very well with scopes under a night sky though, I hardly ever look at rulers with my Nagler 31 these days 😉

 

[MalcolmM]

28 minutes ago, cajen2 said:

The Nagler image is nothing to write home about for the price of the EP.....

My phone camera and technique are probably not helping!

I actually find the Kitakaru much easier to look through than the Nagler, but they are very different eyepieces with very different focal lengths, so probably not a fair comparison. 

Malcolm 

[John]

3 minutes ago, MalcolmM said:

My phone camera and technique are probably not helping!

I actually find the Kitakaru much easier to look through than the Nagler, but they are very different eyepieces with very different focal lengths, so probably not a fair comparison. 

Malcolm 

Well thanks for trying Malcolm.

I agree that the Nagler 31 does take a little getting used to. Likewise a number of other ultra and hyper wide eyepieces that I can think off.

I am rather astonished at the retail prices that the top end Tele Vue eyepieces have reached these days. I paid £200 for my N31, pre-owned but that was many years ago now. 

 

 

[JeremyS]

3 hours ago, John said:

They work very well with scopes under a night sky though, I hardly ever look at rulers with my Nagler 31 these days 😉

 

That’s got to be the quote of the day, John 🤣🤣🤣

[IB20]

Nice planetary nebruler there @MalcolmM.

[Don Pensack]

4 hours ago, MalcolmM said:

Here's my attempt to show the edge distortion in an FS60CB (f 5.9)

The rhs of the FOV is at 0, the lhs at 20 so the total FOV is roughly 65 cm on the ruler. The last 3cm of the rulers on either side are quite difficult to see without squinting and moving your head.

I've no idea how this would relate to star shapes at infinity but to my eyes, the ruler is pretty sharp up to roughly 75% out. But there is definitely a gradual decrease in the sharpness as you move to tbe edge.

Malcolm 

And noticeable edge vignetting, too.

[Don Pensack]

4 hours ago, MalcolmM said:

Just for comparison,  here's a Nagler 16mm in the same setup. This time the FOV goes from 0 to 33cm.

Apologies to @Louis D for using his technique; I don't think I have achieved the quality of his images.

Malcolm 

This one has edge vignetting and chromatic aberration of the exit pupil (aka "Ring of Fire")

[badhex]

Has our friend Ernest on astro-talks.ru covered these before? I looked for details but I can't find anything, unless they go by another brand name and I've missed them.

[badhex]

On 16/08/2023 at 21:56, cajen2 said:

Interesting, though it has to be said that SaN magazine is not the most critical of reviewers

Haha, they of the universal 4/5 score 😂

[Louis D]

4 hours ago, MalcolmM said:

Just for comparison,  here's a Nagler 16mm in the same setup. This time the FOV goes from 0 to 33cm.

Apologies to @Louis D for using his technique; I don't think I have achieved the quality of his images.

Malcolm 

It looks like you don't quite have the camera's entrance pupil lined up with the eyepiece's exit pupil.  I generally keep an index finger and thumb between the top of the eyepiece (with eyecup rolled down or removed) and the back of the phone to maintain a steady alignment and distance.  I vary these two by carefully rolling/repositioning my finger/thumb slightly.  It helps if you can wedge your butt up against a wall to steady your whole body while doing this, or use a sitting position.  Regardless, it takes practice and taking lots of shots to be examined on a big monitor later to choose the best of the bunch.  Sometimes I'll reset and start over if the images are coming out terrible on the camera screen.  Sometimes, if SAEP is at work, there's just not much you can do to get a good image because there is no one best distance for the eyepiece's exit pupil.  If the alignment isn't perfectly centered and the camera isn't perfectly level to the eyepiece, you'll get kidney beaning instead of a perfectly circular black ring midway from center to edge.  If you pull the camera back slightly, you can get another set of images demonstrating what is visible without kidney beaning.

The key to getting a sharp field stop is to start too far away and slowly move the camera in closer until the image edge suddenly snaps into having a sharp edge.  Go too far inward, and you start getting blackouts.  Too far away, and you get vignetted edges.  Off center, you get non-circular images with asymmetric vignetting.  Tipped, you get blackouts on one side.  However, this is useful for getting straight on images of the edge using the center of the camera's imaging field to eliminate the camera's contribution to distortion or aberrations.

Practice, practice, practice. 😁

[MalcolmM]

10 minutes ago, Louis D said:

It looks like you don't quite have the camera's entrance pupil lined up with the eyepiece's exit pupil.  I generally keep an index finger and thumb between the top of the eyepiece (with eyecup rolled down or removed) and the back of the phone to maintain a steady alignment and distance.  I vary these two by carefully rolling/repositioning my finger/thumb slightly.  It helps if you can wedge your butt up against a wall to steady your whole body while doing this, or use a sitting position.  Regardless, it takes practice and taking lots of shots to be examined on a big monitor later to choose the best of the bunch.  Sometimes I'll reset and start over if the images are coming out terrible on the camera screen.  Sometimes, if SAEP is at work, there's just not much you can do to get a good image because there is no one best distance for the eyepiece's exit pupil.  If the alignment isn't perfectly centered and the camera isn't perfectly level to the eyepiece, you'll get kidney beaning instead of a perfectly circular black ring midway from center to edge.  If you pull the camera back slightly, you can get another set of images demonstrating what is visible without kidney beaning.

The key to getting a sharp field stop is to start too far away and slowly move the camera in closer until the image edge suddenly snaps into having a sharp edge.  Go too far inward, and you start getting blackouts.  Too far away, and you get vignetted edges.  Off center, you get non-circular images with asymmetric vignetting.  Tipped, you get blackouts on one side.  However, this is useful for getting straight on images of the edge using the center of the camera's imaging field to eliminate the camera's contribution to distortion or aberrations.

Practice, practice, practice. 😁

Thanks @Louis D, thats lots of great advice. I tried some of the Kitakaru with it's eyeguard rolled down and noticed severe kidney beaning (or maybe blackouts, too far inwards as you mention).

It's certainly a great way to play with kit during the day and when there's full cloud cover!

Malcolm 

[badhex]

13 hours ago, badhex said:

Haha, they of the universal 4/5 score 😂

Honestly, no joke - I wrote this yesterday without reading the review. Have now seen the review itself - 4/5 score 😂