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The Shortest F/L Eyepiece Ever?

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37 replies to this topic

#1 HellsKitchen

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Posted 16 May 2021 - 09:39 AM

Is the Vixen 1.6mm the shortest focal length eyepiece ever made for the amateur market? What would one use such an eyepiece for? I have one, and my answer is for the moon and planetary nebulae, shall the weather ever improve. This year has been hideous.  Hopefully June brings the high pressure systems in gear with their freezing rock hard conditions. There was one night last year in July, where my 3mm Delite was not short enough.

 

 

NCJqmHN.jpg


Edited by HellsKitchen, 16 May 2021 - 09:42 AM.

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#2 csrlice12

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Posted 16 May 2021 - 02:12 PM

There's a .007, but I hear it's an eye killer.wink.gif


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#3 CHASLX200

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Posted 16 May 2021 - 02:47 PM

I would love a 2mm Delite.


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#4 HellsKitchen

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Posted 16 May 2021 - 10:37 PM

I would love a 2mm Delite.

 

It's fun to dream smile.gif  If TV came out with a 2mm Delite, I would be falling over myself running to the order button. 


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#5 Voyager 3

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Posted 16 May 2021 - 11:20 PM

Have you ever got the chance to try the HR Sab ? 



#6 HellsKitchen

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Posted 17 May 2021 - 12:22 AM

Have you ever got the chance to try the HR Sab ? 

 

Nah, the weather over the last several months has been pure trash. Just endured the worst summer in history, nothing but cold fronts, jetstreams and absurd winds. This May is fast proving to be Southern Victorian, abnormal levels of clouds and that infernal wind. No stagnant high pressure to speak of. Hopefully June delivers.


Edited by HellsKitchen, 17 May 2021 - 03:18 AM.

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#7 Jon Isaacs

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Posted 17 May 2021 - 04:06 AM

I use the 5 mm and 3.5 mm Naglers with a 2x Barlow n a regular basis, that's 2.5mm and 1.75 mm.

 

My scopes all track manually so a 1.6 mm with a 42° AFoV is not practical. I calculate the TFoV in my 10 inch F/5 to be 3.2" at 780x. The 3.5 mm + 2x Barlow + Paracorr provides 5.7" at 820x..

 

Jon



#8 izar187

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Posted 17 May 2021 - 04:26 AM

What would one use such an eyepiece for? I have one, and my answer is for the moon and planetary nebulae, shall the weather ever improve.

 

-------------------------------------------------

For the 130mm perhaps?

And the 80mm(s) and 72mm I presume.



#9 Sarkikos

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Posted 17 May 2021 - 07:21 AM

AFAIK, the 1.6 HR is the shortest focal length eyepiece that is commercially available.  

 

I've used mine mostly in my fast to mid-range f-number refractors.   It is a good eyepiece for double stars.  I can also see using it for planetary nebulae.   

 

I would not dare using the 1.6 HR for the Moon.  It would make my eye floaters unpleasantly obvious.  It's borderline for bright planets.

 

None of my mounts track.

 

What I'd really like to see is a 2.7mm Ethos-SX 110 degree!

 

Mike


Edited by Sarkikos, 17 May 2021 - 07:24 AM.


#10 25585

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Posted 17 May 2021 - 08:01 AM

I would love a 2mm Delite.

Barlow a 4mm.



#11 TayM57

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Posted 17 May 2021 - 08:27 AM

Barlow a 4mm.

My thoughts exacty. Powermate 2x + 4mm Delite = 2mm Delite. A 2mm Delite is one I wouldn't buy, given the limited use.


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#12 Voyager 3

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Posted 17 May 2021 - 09:30 AM

Barlow a 4mm.

Or 1.25" PM a 5mm wink.gif .



#13 25585

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Posted 17 May 2021 - 10:13 AM

My shortest FL prime ep is a Vixen LV 2.5mm, but it hardly gets used. Mostly I Barlow zooms, having a TAL 4x Barlow, an 8-24 becomes a 2-6mm, so just right.


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#14 rkelley8493

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Posted 17 May 2021 - 10:45 AM

I use a different route.. a convertible/variable barlow that yields about 3.5x at focus. With a 5mm eyepiece, the effective focal length is 1.43mm. However, the exit pupil is very small & dim, and floaters are a nuisance. 7.5mm [2.14mm effective FL] is usually as low as I go with the convertible barlow in the optical train. 



#15 Sarkikos

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Posted 17 May 2021 - 10:51 AM

I have Barlows, but I hardly ever use them anymore.  In practice, I find it easier and faster to switch eyepieces rather than put in a Barlow plus an eyepiece, or worse, screw a Barlow assembly onto the barrel of an eyepiece.  And a shorter focal length eyepiece w/o Barlow tends to be lighter and more compact than a longer focal length eyepiece w/ Barlow.

 

But I can see several advantages to a Barlow:  (1) reduces the number of eyepieces you need to carry out with you, (2) reduces the number of eyepieces you need to buy, (3) can provide longer eye relief at higher power*, (4) can provide wider apparent and true fields of view at higher power*, (5) can improve the perceived optical performance of some eyepieces*.

 

* depending on the eyepiece you Barlow vs the eyepiece you would use w/o Barlow for the equivalent magnification

 

Mike


Edited by Sarkikos, 17 May 2021 - 11:41 AM.

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#16 Astrojensen

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Posted 18 May 2021 - 06:20 AM

 

In practice, I find it easier and faster to switch eyepieces rather than put in a Barlow plus an eyepiece, or worse, screw a Barlow assembly onto the barrel of an eyepiece.  And a shorter focal length eyepiece w/o Barlow tends to be lighter and more compact than a longer focal length eyepiece w/ Barlow.

Sure, but sometimes it's the only solution available. A 2mm 82° eyepiece doesn't exist, for example. 

 

 

Clear skies!

Thomas, Denmark


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#17 Sarkikos

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Posted 18 May 2021 - 06:25 AM

Sure, but sometimes it's the only solution available. A 2mm 82° eyepiece doesn't exist, for example. 

 

 

Clear skies!

Thomas, Denmark

Yes, see #4 above.

 

But I'm still waiting for the 2.7mm Ethos-SX 110 degree!

 

:grin:

Mike


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#18 Astrojensen

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Posted 18 May 2021 - 06:48 AM

What would be sweet would be a 3.5mm, 3mm, 2.5mm and 2mm ES82's. I'm pretty sure they could make them by simply using different Smyth lenses on the existing 4.7mm. 

 

 

Clear skies!

Thomas, Denmark



#19 Sarkikos

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Posted 18 May 2021 - 07:07 AM

There is a 2.5 Nagler.  But it has been discontinued.  I bought one used years ago, sold it, then later bought another.  I'm keeping this one.

 

Mike


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#20 turtle86

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Posted 18 May 2021 - 07:45 AM

Yes, see #4 above.

 

But I'm still waiting for the 2.7mm Ethos-SX 110 degree!

 

 

Probably won't ever happen, since the 2.5mm Nagler was discontinued and a 2.7mm Ethos would be more expensive.  But if Televue ever changed its mind, I'd buy one in a heartbeat.  


Edited by turtle86, 18 May 2021 - 07:46 AM.

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#21 junomike

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Posted 18 May 2021 - 02:30 PM

I'd like a 1mm eyepiece and then instead of changing EP's to obtain magnification, I'd just change OTA's. Makes for easier math grin.gif


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#22 CHASLX200

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Posted 18 May 2021 - 06:44 PM

I use the 5 mm and 3.5 mm Naglers with a 2x Barlow n a regular basis, that's 2.5mm and 1.75 mm.

 

My scopes all track manually so a 1.6 mm with a 42° AFoV is not practical. I calculate the TFoV in my 10 inch F/5 to be 3.2" at 780x. The 3.5 mm + 2x Barlow + Paracorr provides 5.7" at 820x..

 

Jon

Once i go over 1000x hand tracking a Dob is a job bob. Be nice if it was EQ mounted then ya just gotta deal with one motion.  600x and under i am fine with hand tracking.



#23 Gregrox

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Posted 18 May 2021 - 07:24 PM

I'd like a 1mm eyepiece and then instead of changing EP's to obtain magnification, I'd just change OTA's. Makes for easier math grin.gif

That reminds me of something Mel Bartels wrote in his Richest Field Telescopes page https://www.bbastrod...ns.com/rft.html

 

A final provocative thought...

Notice how the field of view is darker at higher magnifications? You can see more detail not only because the image is magnified but also because the background is darker. Do you ever stop the aperture down in order to darken the field at the given magnification? No?

Let's say you are observing Orion's Great Nebula, M42. And let's say that the magnification is set at say 100x. Would you choose a 6 inch scope with a darker background at this 100x or a 12 inch scope with a brighter background at 100x? Choose the 12 inch?

Then doesn't it follow that you should settle on a single eyepiece and a progression of apertures, say 6 inch, 12 inch and 24 inch?

 

Shoot, I mean, in a world where you can get acceptable OTAs for the same price or less as premium eyepieces...



#24 hoof

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Posted 18 May 2021 - 07:44 PM

I’ve used my 2.4mm once on the moon on my 15” F/4.1, it’s the highest power I’ve gone on the moon ever and had the view be sharp. My 1.6 has been used to look at the double-double with my 80ED, the four stars looked like little discs. The 2.0 hasn’t really been used yet except for trying it out, I mostly got it to complete the set :) The 3.4mm gets used quite a bit, however.

Edited by hoof, 18 May 2021 - 07:45 PM.


#25 wrvond

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Posted 18 May 2021 - 09:37 PM

I use my 2.5mm Nagler with a 3x Barlow all the time.

 

Just kidding, I don’t have any Barlows…. rofl2.gif


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