StellaLyra RPL eyepiece

[bomberbaz]

Just wanted to know if anyone has these and what their findings are.

Interesting they quote a modified Ortho design but want to know how that stands up in reality. StellaLyra 30mm 2" KITAKARU RPL Eyepiece | First Light Optics

Cheers all

Steve

[Louis D]

For starters, try reading this CN thread on Kitakaru eyepieces from other retailers in the past.  That's about all I know of them.

[Don Pensack]

They are made by Long Perng in Taiwan and are configured internally as 2 doublet lenses of different diameters.

[MalcolmM]

I have the 45mm and I am very pleased with it, with the following caveat; I am relatively inexperienced having only been in this game for a couple of years and have not done any comparisons with equivalents. I have recently got a Masuyama 32mm which has a virtually identical FOV, but have not been able to do a side by side comparison yet.

That being said, the 45mm feels like a good quality eyepiece, is relatively cheap and, to my eyes, provides a good view.

Malcolm 

[bomberbaz]

20 minutes ago, Don Pensack said:

They are made by Long Perng in Taiwan and are configured internally as 2 doublet lenses of different diameters.

I believe they are closer to plossl than ortho according to the thread link above

[Mr Spock]

I would be interested to know how a four element can work at 62° and f5 without some kind of aberration taking over.

[bomberbaz]

1 hour ago, Mr Spock said:

I would be interested to know how a four element can work at 62° and f5 without some kind of aberration taking over.

I don't think it does very well. Anecdotal evidence from the above thread suggest F7 and above. 

[FLO]

Strictly speaking, 'orthoscopic' means to produce an image with correct and normal proportions.

Back in the 1880's Ernst Abbe was asked by Zeiss to design an eyepiece for microscopy that would provide maximum brightness and not distort the view so accurate, reliable measurements could be made of a specimen. He designed the 4-element Abbe orthoscopic eyepiece. Traditional Abbe orthoscopics are some of the brightest, sharpest eyepieces, with excellent colour correction. Especially when made with modern glass and optical coatings. But they have a narrow field of view, around 44°. 

KITAKARU designed their RPL series to have a wider 62º field of view (65º in the 40mm) whilst retaining orthoscopic characteristics (freedom of distortion, very high contrast, flat fields and excellent colour correction). They achieve this when used with telescope f-ratios around f6-7 and longer. Even when used with an f5 Newtonian, performance is maintained almost to the very edge of the field. 

Whether they are modified Abbe orthoscopics or modified Plossls is moot. 

19 hours ago, Don Pensack said:

They are made by Long Perng in Taiwan 

This is not a secret. We name the manufacturer and country on our product pages. 

HTH, 

Steve 

[Don Pensack]

To back up Steve's remarks: orthoscopic means without rectilinear distortion, not without angular magnification distortion.

It means straight lines and shapes do not distort.

At anything over around 40° apparent field, the lines of RD and AMD diverge, so that correcting one necessarily leaves in some of the other.

 

The good news for us is that a small percentage (up to ~7% of RD) is not seen by our eyes, so in most cases, for astronomy, AMD is reduced to a minimum, leaving a bit of RD in the field.

People who observe the Moon and planets object to this, however, as do people who use their eyepieces for daylight terrestrial observing, so tend to prefer eyepieces with low RD,

leaving in a certain % of AMD.

 

What's important to remember is that no eyepiece over about a 40° field can be free of distortion of one kind or another (or mixed), so, technically, an eyepiece with a 62-65°

field will not be free of distortion, just have a very low level of it that won't be objectionable to the eye.

And, compared to ultrawides or hyperwides, the distortion level at 60° is vanishingly small.

[Whistlin Bob]

Interesting thread.

I bought a 45mm one from the classified section of this site a couple of years ago. The reason for purchase was a 2am decision after a brilliant night using a 30mm Aero in my dob and thinking "yeah- let's go wider" rather than any careful consideration of the lens design or attributes.

I've tried it in 4 scopes:

8" f6 dob. Yields wonderful rich field views of the milky way. Not quite as immersive as the 30mm due to smaller afov, and also seems a touch less bright, but better corrected edge to edge. 

14" f4.7 dob. Edge correction seems to really break down at this speed, but is well restored with a coma corrector. I especially remember startlingly good views of the veil using a coma corrector and Oiii filter where I could easily see huge chunks of the object in one field of view.

127mm Bresser f9.5 frac. It's much more comfortable at this speed: bright, colorful rich sharp views. Scanning the milky way in summer with this is a joy.

Sw 72ed. Annoyingly will not reach focus!

Overall, it's a nice eyepiece. I prefer the 30mm aero because of the wider afov, but for low power observing it's still a fine eyepiece to use. 

[bomberbaz]

8 hours ago, Whistlin Bob said:

Interesting thread.

I bought a 45mm one from the classified section of this site a couple of years ago. The reason for purchase was a 2am decision after a brilliant night using a 30mm Aero in my dob and thinking "yeah- let's go wider" rather than any careful consideration of the lens design or attributes.

I've tried it in 4 scopes:

8" f6 dob. Yields wonderful rich field views of the milky way. Not quite as immersive as the 30mm due to smaller afov, and also seems a touch less bright, but better corrected edge to edge. 

14" f4.7 dob. Edge correction seems to really break down at this speed, but is well restored with a coma corrector. I especially remember startlingly good views of the veil using a coma corrector and Oiii filter where I could easily see huge chunks of the object in one field of view.

127mm Bresser f9.5 frac. It's much more comfortable at this speed: bright, colorful rich sharp views. Scanning the milky way in summer with this is a joy.

Sw 72ed. Annoyingly will not reach focus!

Overall, it's a nice eyepiece. I prefer the 30mm aero because of the wider afov, but for low power observing it's still a fine eyepiece to use. 

Interesting review there, although I would have thought the f4.7 dob would have yielded a washed out view as the exit pupil will be over 9mm. Given your remark on the view in the F6 dob, I think similar would also probably apply.

I bet the views in the 127 frac were sublime though, M45 would be a treat in that.

A 45mm in an F15 cassegrain would be a nice marry up, the views should be spectacular.  

[FLO]

On 04/02/2023 at 09:12, Whistlin Bob said:

8" f6 dob. Yields wonderful rich field views of the milky way. Not quite as immersive as the 30mm due to smaller afov, and also seems a touch less bright, but better corrected edge to edge. 

14" f4.7 dob. Edge correction seems to really break down at this speed, but is well restored with a coma corrector. I especially remember startlingly good views of the veil using a coma corrector and Oiii filter where I could easily see huge chunks of the object in one field of view.

 

On 04/02/2023 at 17:46, bomberbaz said:

Interesting review there, although I would have thought the f4.7 dob would have yielded a washed out view as the exit pupil will be over 9mm. Given your remark on the view in the F6 dob, I think similar would also probably apply.

@Whistlin Bob, @bomberbaz is right. 

The 45mm eyepiece (any 45mm eyepiece) is too long for your Newtonian telescopes.

The resulting exit-pupil is too large - this is why it didn't perform well. 

 

A 30mm eyepiece is a much better match. 

 

HTH, 

Steve 

[Whistlin Bob]

Thanks @FLO- perhaps the real issue is making impulse purchases at 2am!!! 🤣

Funny thing is, I would suggest that whilst it may not have been optimal, it did perform pretty well, and yielded some very enjoyable views that I otherwise would not have seen.

I accept, as a retailer on this forum, you need to guide towards best practice, so I understand the reason for your comment. For everyone else, though, there's fun to be had breaking the rules a little and seeing what happens! 

[Mr Spock]

I don't use my 42mm LVW with the Dob as the exit pupil is too great. The 30mm StellaLyra UFF I have is a perfect match.