What is the longest focal length 1.25" eyepiece

[spaceboy]

Hi All

As above basically. Would be interested in knowing all suggestions but would obviously prefer those of at least moderate quality.

Thanks in advance

[RikM]

I have a 40mm TV Plossl. The quality is first rate but the apparent field is quite narrow at only 40ish degrees. A 32mm would be better as it would show the same field but at a higher magnification. A 24mm Panoptic would show a similar true field but a higher magnification again. All are 1.25"

[alan potts]

I think the longest you get is the 40mm but it only has a 43 degree FOV, the 32mm is next down and that shows the same AFOV but at a high power, then you tend to jump to the 24mm 68 degree FOV which is showing the same AFOV as both but at higher power.

Myself I would go for a decent 32mm like a Televue Plossl.

Alan

[estwing]

yep got a 40mm myself..

[John]

You can get them as long as 55mm but the apparent field gets very claustrophobic at less than 30 degrees within the contstraints of the 1.25" barrel.

The 35mm Celestron Ultima / Orion Ultrascopic gave a 49 degree apparent field and were excellent quality. They are out of production now but the design lives on under the Baader Eudiascopic name:

http://www.firstlightoptics.com/baader-planetarium/baader-eudiascopic-ed-eyepieces.html

Expensive now though !

[spaceboy]

Thanks for the quick replies guys. Should have said I'm not all that fussed for FOV it's more about getting the lowest magnification as possible in a 1.25" format

[ollypenrice]

Thanks for the quick replies guys. Should have said I'm not all that fussed for FOV it's more about getting the lowest magnification as possible in a 1.25" format

Pure curiosity on my part but why would you want low magnification without wider field of view?

Olly

[spaceboy]

I guess I should have pointed this out but was curios anyway. For use in a quark Olly. With the x4.2 barlow built in there is no other cheaper method of lowering the magnification.....a f/4 refractor being the alternative I assume ??

With the 21mm field stop of the Quark being the deciding factor regards FOV there would be no need for 52° or larger eyepieces.

[ollypenrice]

I guess I should have pointed this out but was curios anyway. For use in a quark Olly. With the x4.2 barlow built in there is no other cheaper method of lowering the magnification.....a f/4 refractor being the alternative I assume ??

With the 21mm field stop of the Quark being the deciding factor regards FOV there would be no need for 52° or larger eyepieces.

All is revealed! 

Cheers,

Olly

[RikM]

Sounds like a 32mm Plossl is just the job.

[Ruud]

A while ago I made this chart which shows which eyepieces will fit in which barrel. Everything below the red curve should fit in a 1.25" barrel, everything below the blue curve in a 2" barrel, etcetera.

The chart shows, for instance, that a 60mm eyepiece is limited to a 30° AFOV (apparent field of view) in a 1.25" barrel. That would be really narrow! A 32mm 52° eyepiece would also just fit in a 1.25" barrel, as would an 18mm 82°.

The chart is not 100% precise because you never know how much pincushion a design will have, but it comes close.

Bye

[Stu]

Nick, I tried a 40mm TV Plossl in the Quark and personally didn't find it added much. The already narrow fov is made even smaller by the 21mm etalon and it just felt too claustrophobic for me. Others may find differently though.

I tend to think that shorter focal length scopes or focal reducers are a better answer.

I'm going to play around with my Genesis and a D-ERF and x0.8 focal reducer which will give a 400mm f/l with 101mm aperture. In theory I should get full disk views with near optimum aperture for our skies.

Stu

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[ronin]

Someone in the US produces or produced a 1.25" plossl of 52 - 56mm focal length.

Was actually not expensive, slight problem is I cannot recall who as the (possible) link was lost when a PC threw a wobbly and I lost everything.

[Charic]

as #3 suggests, TV 32mm?  Check out the  Daystar  Quark tutorial  at  www.youtube.com/watch?v=nEYCC8mDL9s 

[John]

I've got an ex-military brass 55mm plossl machined to fit a 1.25" focuser by Orion Optics. It has massive eye relief and a tiny AFoV despite using the inside of the barrel as the field stop. I bought it before I understood a bit about how eyepieces work

[spaceboy]

Nick, I tried a 40mm TV Plossl in the Quark and personally didn't find it added much. The already narrow fov is made even smaller by the 21mm etalon and it just felt too claustrophobic for me. Others may find differently though.

I tend to think that shorter focal length scopes or focal reducers are a better answer.

I'm going to play around with my Genesis and a D-ERF and x0.8 focal reducer which will give a 400mm f/l with 101mm aperture. In theory I should get full disk views with near optimum aperture for our skies.

Stu

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Now I'm confused. Does the field stop of the quark not mean that what ever eyepiece you use produces a fov of that what you would get in a 25mm 52° eyepiece. I'm aware that the shorter the focal length of the scope your using it allows for more FOV . 

Although the image isn't going to offer any wider a fov the longer the focal length eyepiece you use but would the reduction in magnification allow for better contrast not to mention less susceptible to seeing conditions ?

[Dave In Vermont]

Back around 2003, I bought a new Orion HighLight Plossl 40mm EP. Had/has a 43-degree F.O.V. This thing is excellent optically - sharp & bright edge-to-edge across it's easy-to-swallow 43-degree FOV. It was quite inexpensive back then at around $50 - which was a bargain back then. Only later did the reviews begin rolling in from all over in the astro-press, extolling the amazing clarity and sharpness of this particular addition to the Orion Plossl's. Their better-known Sirius-line of Plossl EP's were an average Plossl - not bad, and not amazing. But this particular EP clearly stood out from the rest.

And thus a minor celebrity was born. I enclose an image below.

Clear Skies,

Dave

[spaceboy]

So you could say the 40mm was the highlight of the range......... I'll get me coat.

Seriously though, thanks for the heads up

[Luke]

With the Quark I prefer the 32mm Plossl to the 40mm, I would pick the 32 out of the two, no question. I tend to use the 32mm the most, followed by the 25mm, when there's a feature I fancy seeing a little closer up.

[Owmuchonomy]

Back around 2003, I bought a new Orion HighLight Plossl 40mm EP. Had/has a 43-degree F.O.V. This thing is excellent optically - sharp & bright edge-to-edge across it's easy-to-swallow 43-degree FOV. It was quite inexpensive back then at around $50 - which was a bargain back then. Only later did the reviews begin rolling in from all over in the astro-press, extolling the amazing clarity and sharpness of this particular addition to the Orion Plossl's. Their better-known Sirius-line of Plossl EP's were an average Plossl - not bad, and not amazing. But this particular EP clearly stood out from the rest.

And thus a minor celebrity was born. I enclose an image below.

Clear Skies,

Dave

 Looks identical in all respects to my Celestron Omni 40mm 43' Plossl which has always been a favourite EP of mine for use with the .9.25.

Orion HighLight Plossl 40mm EP with 43degree FOV.jpg

[Stu]

Now I'm confused. Does the field stop of the quark not mean that what ever eyepiece you use produces a fov of that what you would get in a 25mm 52° eyepiece. I'm aware that the shorter the focal length of the scope your using it allows for more FOV .

Although the image isn't going to offer any wider a fov the longer the focal length eyepiece you use but would the reduction in magnification allow for better contrast not to mention less susceptible to seeing conditions ?

Sorry to confuse Nick. What you are saying is correct, and was what I was trying to say :-).

The 40mm already has a narrower AFOV than the 32mm and shows the same amount of sky. What I found was that, although it shows the same actual field of view on the sun, the perception is of being closed down more because the etalon fieldstop intrudes more into the fov.

As I said, some may find this an acceptable compromise but when I asked the question on the forum before, the 32mm was the clear favourite eyepiece for the quark.

Using a focal reducer may be another option to consider too. Without a D-ERF this would have to go after the Quark so the FOV would still be limited. With a D-ERF you could put it ahead of the diagonal and get the wider fov from and effectively shorter f/l scope.

Stu

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[spaceboy]

When solar observing I'm not one for swapping out eyepieces and prefer to just stick with the one that offers me the most pleasing views but even so it sounds like there really is only a choice of 2 ep's for the quark ??

[Luke]

I still like to use the 40 sometimes with the Quark, I can't really explain why other than it gives a different view. I think I might have used the 20mm a few times (I got one with my Tele Vue 85), but not certain on that, there seemed to be no mention of it in the Quark manual. But with my grab and go, it's just the two, 25 and 32, that I take. I would feel fine having just those two. And I would be okay about having just the 32. Some sessions, especially during lunch, I just use the 32. There's something I particularly like about being lazy

Oh and to add, I like using the Plossls for the night time stuff too. Handy to take on hols as they are so compact and light. I had changed to Ethos and Delos eyepieces and was missing my 19mm Panoptic a bit due to its light weight and size. Glad to have the Plossls to fill that gap now

[Peter Drew]

A main FOV limiting factor of the Quark and other Ha systems is the size of the blocking filter. The Quark has a 12mm aperture, if you place a 12mm stop in front of your eyepiece, a wide field eyepiece has no benefit over a narrow one. 

[Stu]

A main FOV limiting factor of the Quark and other Ha systems is the size of the blocking filter. The Quark has a 12mm aperture, if you place a 12mm stop in front of your eyepiece, a wide field eyepiece has no benefit over a narrow one.

Peter, do you know what the effective fieldstop of the Quark is?

I have used 21mm in my calculations which seems to give around the right results ie easy full disk views in the FS-60 whereas 12mm does not.

Stu

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