Don Pensack

I have both the 30mm APM (61x) and the 22mm Nagler (83x).  The 22 gets 90% of the eyepiece time.

Field sizes are 36.4mm and 31.1mm respectively.  In my scope, 1.14° and 0.98° respectively.

That makes the 30mm 17% wider in true field.  I use it when the wider field and lower magnification are needed, which isn't often.

Normally, I prefer the darker background of the 22mm, and that is in a site with a 21.4+ sky (~mag.6.9NELM).

4 hours ago, Kon said:

I thought this might be the best forum to ask my silly question but how often is it safe to clean the EPs with cleaning fluids? I have purchased the Baader Optical Wonder and a  Hurricane Blower; I also have the Celestron Lens pen but I prefer the Baader. I noticed that not all small particles are removed after blowing them with the blower so I probably need to use the Baader fluid more often. Would that have an effect on the coatings or is it safe to use it often? Would cleaning every 2-3 viewing sessions be an overkill and just leave some of these dust particles (most likely oily particles from eye lashes thus the sticking)on the EP?

I look at my eyepieces between each session and clean if necessary.  The ones I use with glasses rarely need cleaning.  The ones I use without glasses sometimes get cleaned each time, sometimes every other time.

I have had eyepieces 20+ years old, cleaned >100x, which still looked new.

I lent the 12.5mm APM to a friend and he commented, unsolicited,  "the edge is brighter".

He noticed it right away.

I have seen a lot of eyepieces with EOFB, and on a scale of 10. 10 being the worst, this one is a 4--noticeable, but not so bad the eyepiece is unusable.

It is comfortable to use and quite sharp, with well-controlled field curvature and chromatic aberration.

I suggest soliciting comments from users to develop a consensus on the eyepiece.

Acetone won't harm glass or metal, but it will dissolve plastics and rubber, so be sure to remove any rubber around the cleaning area (like an eyecup).

It won't harm coatings at all.  In fact, it is the cleaning material of choice at TeleVue.

22 hours ago, Deadlake said:

I'm short sighted, no eyeglasses required. Presume the Panoptic would be the pick? 

No,  The 19mm and 24mm Panoptics, and the 10mm and 15mm APM Ultra Flat Field are not compatible with glasses.

The 18mm and longer in the Ultra Flat Field are compatible, as are 27mm and longer Panoptics.

Other Glasses-compatible eyepieces from TeleVue:  Delites, Delos, 32mm and 40mm Plössl, 22 and 31mm Nagler

Other glasses-compatible eyepieces from APM: 12.5mm Hi-FW 84°

Some others: Baader Hyperions, Baader Morpheus, Pentax XW to name a few.

But, no eyeglasses required, then great binoview eyepieces include the 24mm and 19mm Panoptics, the 16mm Nagler,

The APM Ultra Flat Field 18mm, The Type 6 Naglers, to name a few.

On 07/09/2021 at 07:07, Barry-W-Fenner said:

Afternoon all,

Some stunning clear Blue skies here at the moment, Looing forward to setting up the 300p later for some moonless views.

I am going to experiment tonight by taking of the extension rings on my 9 & 17.5 morphs and attempting some viewing with my glasses on. I have very weak/low power "concentration" glasses as I have been diagnosed  long sighted. Looking up at the night sky with my glasses on last night stars were a very nice sharp point of light, I never realised how fussy they were to my eye until I put the glasses on. I am looking forward to seeing if this sharpness is replicated through the ep!

Cheers

It will be.  And, thusly, you start down the road to finding eyepieces compatible with glasses.

As the focal lengths get shorter, you will need glasses less and less until, with some particular focal length and shorter, you will no longer need to use glasses.

For me, that is 9mm (1.57mm exit pupil), but you will likely be at a longer focal length if you see only a minor improvement in the stars with the naked eye.

For me, naked eye stars look like stick men with long hair, without glasses, and tiny points, with glasses.

Your astigmatism is minor if you only see a small bit of improvement with distance vision glasses.

Very good!

You didn't quite get it all, but since the eyepiece will need cleaning again, you can wait till next time.

If it is fungus, you must remove it immediately or it will spread.

Try acetone on a Q-Tip first, something stronger if acetone doesn't work.

It's difficult to know if the 18mm is a negative/positive design without dismantling one.

That information is not published anywhere.

Clean the outside  of the lens first.  Better get used to it, as all eyepieces need frequent cleaning.  It's not hard--just use cotton Q-Tips and isopropyl alcohol

or a lens cleaner fluid from Nikon, Zeiss, Baader, or ROR.

That looks to me as if it is all on the outside surface and would clean off immediately.

THEN look at it again to see if anything is inside.  Till the outside is cleaned, you won't be able to tell.

If the spots are inside (and it is unlikely), they can also be cleaned, but the eyepiece will need dismantling to do so, which requires a bit of skill and a couple tools.

I would, since you're a newbie, then send it directly to TeleVue.  They'll clean it inside and out for a fee.  Their phone number is on their website.

The 18mm has one fewer lens than the 15mm.  The 15mm is 6 elements, the 18mm is 5.

Either the negative lens is gone, and the correction is applied in the upper positive design, or a very weak negative lens is place close to the upper section.

This eyepiece is excellent, and recommended.

It's available under the names APM Ultra Flat Field, Meade UHD, Celestron Ultima Edge, Altair Ultra Flat Field, Tecnosky Ultra Flat, and Orion (US) Ultra Flat.

Some differences:

APM--all aluminum, 1.25", smooth barrel, no undercuts

Meade--all aluminum, 1.25", undercut on barrel

Celestron--all aluminum, 1.25", undercut on barrel

Altair--Stainless steel bottom barrel, 1.25", safety "kerfs" on lower barrel (accts like a smooth barrel when inserting)

Tecnosky--all aluminum, 1.25", smooth barrel, no undercuts

Orion(US)--all aluminum, 1.25" with removable 2" skirt, undercuts on barrel.

The 21mm and 17mm are the best in the set, and work at a slightly faster f/ratio than the others.

The 24mm is not the equal of the others, optically.  The 13mm has significant edge of field brightening.

You can do better at each focal length.

Careful if buying used, as I recall the 17mm was revised at some point, and the new one is better optically.

But I do not know how to tell them apart.

I recall it being measured at 74° +/- with the flashlight test.

With the other focal lengths at 78°, and just the 6.5mm at 79°

1 hour ago, jetstream said:

100% agree.

Get a good OIII first IMHO.

I wouldn't recommend O-III filters as a "first" nebula filter purchase, because they don't work as well on the large hydrogen gas clouds like M42/43, M8, M17, M20, M16, etc. as a narrowband filter.

They do, however, work a bit better on planetary nebulae, some supernova remnants (though I think a narrowband works better on M1), and Wolf-Rayet excitation nebulae.

Ultimately, I think astronomers should have a set of at least 2 nebula filters--one good narrowband, and one good O-III.

But, since the narrowband does pass the O-III lines and is usable on more different nebulae, I'd start with that one first.

On 31/08/2021 at 23:09, Dantooine said:

Can someone explain why there is a 12.5mm being so close to the 14mm?

sorry if the question seems a little dim 😊

A 40% jump between magnifications, starting with the 17.5mm runs:

17.5...12.5...9...6.5...4.5  Now you know where the focal lengths came from.

So why a 14mm?  Because it was the longest focal length possible in the original formulation of the design.  It really wasn't in sequence with the other focal lengths.

They tried 3 different designs for the 17.5mm until they landed on a good design, but the 17.5mm is different internally than the others, and has different eye relief (longer), a different apparent field (slightly smaller),

and one note: the Baader data is incorrect--the field stop in the 17.5mm is 21.7mm, not the 23.5mm Baader quotes.  I think this was changed somewhere in between the 3 prototypes they tried.

Frankly, I don't know where Ernest's figures come from.

Take his "essentially perfect" 10'.

In a 100° eyepiece, that would be 1/600 the width of the field if talking linear field size in an angular sense.

Would 1/600 the width of the field appear perfect?  No way.  A 10' star would be a blob.

So I view his figures as "relative", meaning an eyepiece yielding a 20' spot size would be a spot 2x as wide as one yielding a 10' spot size.

One eyepiece I know has a design 1µ spot size on axis and 1.5µ spot size just inside the field stop, and shows on his list as <5' on axis and 11' at field edge.

1.5µ is a lot smaller than the Airy disc in an f/5 scope, so, correcting for coma (many times as large), the eyepiece should yield stars at the edge

indistinguishable from perfect.  And his f/10 numbers are perfect, so f/4 just falls below perfect only at the very edge.

That is consistent with the design specs.

So, however the numbers are derived, they do have some basis in comparative reality.  

I do think choosing f/4 and f/10 is somewhat arbitrary, though.  Few scopes are as long as f/10 these days, and those that are have other significant aberrations affecting the star images.

And it is largely the very big scopes (say, 20" and larger) that are commonly as short as f/3-4.  And really big scopes have a "spot of bother" yielding tiny star images for a variety of reasons.

I would have picked f/4.5 and f/9 to more closely correspond to more of today's scopes.

One thing the numbers do tell, and that is if f/4 is too fast for the eyepieces to yield excellent star images across the field.

It's unfortunate his list doesn't contain more of the contemporary eyepieces.

1 hour ago, Louis D said:

I've got that same situation with a $50 dielectric diagonal from Amazon.  It's a very nice diagonal except for the fact it pushes all 2" undercut eyepieces up and out of the holder because the compression ring is too close to the top.  I'll have to try removing the ring and replacing the screw with nylon one to see if that improves matters.

Ironically, this happens with TeleVue 1.25" eyepieces in TeleVue 1.25" star diagonals.

You have to press inward on the eyepiece as you tighten or the thumbscrew side lifts slightly.

16 hours ago, jetstream said:

Its amazing the lengths we go to with regard to collimation only to have tolerances sneak up on us- I tighten the focuser screws in the same order on the eyepieces as I do on the laser lol! My Moonlights are pretty good for consistency though.

If you have a Moonlite focuser, use only 2 screws to tighten something into the focuser--remove the 3rd screw and keep it in you spare parts kit.

Screw 1 presses against the other side of the drawtube but allows wiggle.

Screw 2 presses against the other side, making a 3-point contact--no wiggle possible.

Screw 3 presses the inserted accessory away from the drawtube wall, which is a negative for accurate registration.

This is because the 3 screws are at 120° apart.

Ernest Maratovich (apologize if name spelled wrong) has measured the Morpheus at:

http://astro-talks.ru/forum/viewtopic.php?f=32&t=1483#p41976

4.5mm--78°

6.5mm--79°

9mm--78°

12.5mm--78°

14mm--78°

Within the margin of error, that matches Louis' figures.

The weakest one at the edge at f/10 is the 12.5mm and 14mm, but, based on his figures, essentially perfect.

At f/4, the14mm is worst.

in my coma-corrected 12.5" f/5.75 (the CC-corrected f/ratio), even the 14mm is pinpoint at the edge and a star stays point-like past the field stop.

I've used these in scopes from f/3.45 (CC-corrected) to f/8 (refractor) and would say their "critical f/ratio" is about f/4.5 and that they are not well corrected below that f/ratio.

So the f/4 figures don't indicate flaws in the eyepieces, merely their use at too short an f/ratio for the design.

In other words, not the best design for the ultra-fast scope.

As for effective eye relief, the eyepieces in question are all usable by me with glasses on.

If wearing glasses, what do I have to do to see the field edge? 

These are all just compared on my 4" apo on a distant land target:

17.5mm Morph--glasses 2mm away from rubber,   MFR eye relief 23mm, maybe 20mm effective

14mm Morph--glasses touching rubber, pressure light , MFR eye relief 18.5mm, maybe 17.5mm effective (pressure compresses the eyecup)

12.5mm Morph--glasses just touching rubber, no pressure, MFR eye relief 20mm, maybe 18mm effective

30mm APM--glasses just touching rubber, no pressure,  MFR eye relief 22mm, maybe 18mm effective (top lens recessed a couple mm)

22mm Nagler T4--glasses touching rubber, pressure moderate,  MFR eye relief 19mm, maybe 17mm effective

20mm Pentax XW--glasses touching rubber, pressure moderate,  MFR eye relief 20mm, maybe 17mm effective

It took me a while to realize exactly how much eye relief I actually needed to see the entire field of view in an eyepiece with glasses on.

And, I suspect like many glasses wearers, I don't really need 20mm of "effective" eye relief--17 to 18mm will do.

The only figure where I disagree with Louis is the eye relief of the 30mm APM.  I couldn't see the entire field at 16mm effective eye relief, yet it's easy to do so.

Hope those impressions help someone looking for a long eye relief eyepiece.  I should note I have fairly deep-set eyes and the distance my glasses are from my eye exceeds

the width of my little finger, so those whose glasses sit closer to the eye might find all of those eyepieces to have even more eye relief than I found.

52 minutes ago, globular said:

May be then @Don Pensack your previous closing remark should have been:

"I feel like Job.  My life has been filled with wars, economic chaos, a pandemic, cancers, and injury.  I just want to live out the few years I have left without the plague of Paracorr eyepiece holders.😆"

Touché.

However, I have more than one scope and it is the same in the other scopes which do not use a Paracorr.

They do, though, use brass split ring binding systems.

I need to investigate other types of binding and compatibility with my focusers, though.

Maybe a Twist-Lock diagonal.

2 hours ago, globular said:

I feel your frustration @Don Pensack.  I'm not making light of the very real issues you and others face.

It sounds like the design of the Paracorr holder has a) thumbscrews that compress a compression ring when tightened  and b) relies on the springiness of the compression ring to retract itself back into the housing as the thumb screws are loosened. 

Is that right?

If so, from your description above, it sounds like the compression ring in your Paracorr has lost some of it's spring and is not retracting itself fully when the thumb screws are loosened.

This only partially retracted ring does not snag on straight barrels because there is nothing to snag on.  But an undercut barrel needs the ring to retract at least as far as the extra diameter of the barrel verses the undercut or it might snag.  The latest tapered undercuts may snag less, as they help to retract the ring as the EP is removed, although I suspect they will have issues to from time to time too with faulty rings.

I can see how you would blame the undercuts for this... as it only happens on barrels with undercuts... but the real problem lies with the holder. i.e. straight barrels do not highlight the fault in your holder, but undercut ones do.

I suspect a nice new springy compression ring will fix the problem. 

I see you have your thinking cap on.  ES gave that some thought, too, and used stainless steel for the ring instead of brass.  Much springier.

My immediate cure was to remove the brass split ring and use delrin screws to press directly on the eyepiece barrel.

And to use a focuser drawtube with a smooth bore that has no brass split ring in it.

There is a cure with leaving the brass split ring in place, and it is a sanding of the split ring so its cross section is not || , but ().

I did that for a customer a couple years ago and it solved his problem.

But some eyepieces hang up on the top lip of the Paracorr, above the groove where the split ring resides.  Only a smooth internal bore on the top would solve that problem.

It just shouldn't be this much work to remove an eyepiece.

3 hours ago, Highburymark said:

Wouldn’t a Baader clicklock solve your problems Don?

No, because all 4 of the eyepieces with problems are 2", so no adapter is used, and a Paracorr resides in the focuser 100% of the time.

The Baader Click Lock adapter isn't a cure, since it has an undercut on the outside, so it's no better than the TeleVue adapter.

Several other adapters have smooth sides and work great with the Paracorr, but the 6mm and 8mm Ethos need a "Hi-Hat" style adapter to safely use them as 1.25" eyepieces,

which means the TeleVue Paracorr adapter.

I could use a Twist-lock, smooth-sided, adapter for the 9mm, 12.5mm, 14mm Morpheus eyepieces, but the 17.5mm needs an in travel adapter, and I draw the line at 2 different adapters, not 3.

Plus, they work fine in the Paracorr adapter since they don't have undercuts.

I am leaning toward attaching 2" adapters to all the 1.25" eyepieces and just using them all as 2".  I would need a number of adapters, but it could be a permanent fix.

Unfortunately, where you have positioned your rings means that in some focusers and adapters and star diagonals, the thumbscrews will press on the edge of the undercut and probably tip the eyepieces.

There is a cure for that, however: add barrel extenders to all the eyepieces and place the parfocalizing rings in the middle of the undercut.  You could keep all the eyepieces parfocal that way,

albeit at a somewhat inward movement of the focuser.