Don Pensack

I owned all the Ethos for years, and found the most-used one was the 10mm.  In my 12.5" scope, it had better contrast than either the 8mm or 13mm.

But the sharpest one of all, for Moon, planets, double stars, star clusters (especially small globulars) was the 6mm.  I call it my "100° ortho", LOL.

3 hours ago, stormioV said:

I'm looking for an upgrade eyepiece for my LX90 ACF 8inch at 24mm to get maximum fov for 1.25 fitting. I do not wear glasses. Currently i have BST Starguider and Meade 4000 SP 32mm. I don't really get on with the Meade Plossl, I struggle with eye placement with this eyepiece. Optically it is great. 

I am willing to spend up to £200 new for this. I am thinking about either

ES68 24mm

Stella Lyra(APM, Altair, Celestron) UF 24mm ,

Baader Hyperion 24mm

 

I do use a 2 inch diagonal with 1.25 adaptor so it is an easy switch.  My only 2inch is ES 68 34mm which I find stunning. 

Would I be better looking at 20mm 2 inch such as Stella LYRA 80/Founder optics or stick with my original 1.25 upgrade idea.

Thanks.

 

 

 

 

It sounds like you struggle with the Meade 32mm because of its long eye relief.

You probably need an eyepiece you can get closer to without experiencing blackouts.

That makes the two in the price range most likely to satisfy the 24mm UFF (27.6mm field stop) with eyecup flipped up, and the 24mm ES 68° (27.2mm field stop).

Hmm.  Long focal length, high power, narrow field scope paired with a short focal length, low power, widefield scope--a great combination.

Another report:  I wear glasses and can easily see the entire field of the 22mm T4 Nagler, glasses touching the rubber.  Strange that Mark can't.  His glasses must sit farther from his eye.

I can verify that by putting a brighter star at the edge of the field and then looking direct at the center of the field.  The bright star at the edge is still there in my peripheral vision, as well as the field stop.  Mark should try that.

It is an optical illusion that, somehow, the field looks a lot narrower when staring at the center than it does when you roll your head over to look directly at the edge.

I notice this in all eyepieces wider than about 70°--the field looks wider when you look directly at the edge.  I wonder if that is due to rectilinear distortion in the eye.  Possible.

My scope has over 10x the radius of curvature of his 60mm, and I see no field curvature whatsoever, so it will depend on the scope type and its focal length to determine whether you see FC in a 31.1mm wide field stop. 

9 hours ago, Louis D said:

The Long-Perng made 80 degree series have gotten good reviews in the 14mm and 20mm focal lengths in Orion LHD, SL 80º LER / UWA, and other liveries.  To get long eye relief though, you have to completely remove the eye cup as Don says above.  You might be able to find an alternate eye cup to slip-fit in place of it.

The Founder Marvel Ultra Wide version is also available from FLO for £20 cheaper if you can live with its green instead of red color.

If you're not hung up on 80º and could live with 70º, the 22mm Omegon Redline and its rebranded bretheren is very well corrected, eye glasses friendly with the eye cup removed, and not too heavy.  I have the discontinued Astro-Tech AF70 version.  I retired it only after acquiring a 22mm NT4, but am quite content to use it when I only have my B-Team case available.  The Baader Hyperion M43 screw-on eye cup fits it nicely as an eyeglasses friendly eye cup.  The original eye cup is far too thick and stiff to fold down.  This eyepiece used to be only $99 10 years ago, but it appears to have doubled in price since then.  Unfortunately, it's not such a bargain anymore.

I concur on the 22mm Redline.  It is far better than its price indicates.  The cheapest version of it seems to be the 22mm Astromania SWA 70°, which is about USD$130.  Last I checked, it was available under several different labels.

9 hours ago, groberts said:

In an attempt to broaden my interest in astronomy and occasionally share my hobby with the family and grandchildren (who are already interested), I recently acquired a Starfield 102 f/7 refractor.  I intend to use it for some of the larger / brighter DSOs and variable stars etc but especially for the family and therefore expect the planets, moon and solar will be their most favorite targets.

As we all know in the UK, it's not been the best for clear skies recently but I have managed a couple of short sessions using the Starfield and after a gap of 10-years have enjoyed getting back to observing, though,not surpringly I still struggle with some of my eyepieces to get the best of views, almost certainly because I wear spectacles and in most cases  (I suspect) find the FOV and eye relief inadequate. My signature below lists my current eyepieces, of which I really only get on with the 20mm & 32mm plossls and the Ultra-wide + Long eye relief 6mm.

I would appreciate any recomendations for maybe a couple of other eyepieces that would improve my viewing, bearing in mind the above objectives and problems (planets and spectacles).  I believe since I last did any observing there are some very good eyepieces now available that might be better suited to my needs?

Graham 

        

Graham,

Here are some suggestions:

Baader:  Morpheus eyepieces--all focal lengths

APM: Ultra Flat Field 30mm/24mm/18mm (also available as Celestron Ultima Edge, Meade UHD, Stellalyra UF, Tecnosky UF, Svbony UF, Sky Rover UF, Altair Astro UF, etc.)

Pentax: XW 70° all

Tele Vue: Plössl 25mm and longer;   Delite--all;   Panoptic 27mm and longer;   Delos--all;  Nagler--30mm, 22mm

Long Perng UW/Orion LHD/Stellalyra UW 80/Founder Marvel: all ,but only IF the eyecup is removed and a shorter substitute eyecup is used

Vixen: SLV--all, NPL--any of >25mm

Explore Scientific: 92° 17mm/12mm;   82° 30mm (barely);  68° 40mm/34mm/28mm;  62° 40mm/32mm/26mm;  52° 40mm/30mm 

My personal favorites are the Morpheus eyepieces in my 102mm f/7 apo.

Just really easy to use with glasses on.

6 hours ago, Alan White said:

I am Astigmatic and need to wear glasses at the scope, no choice in this sadly.
This calls for long eye relief down to about a 10mm focal length, so larger exit pupils mean a choice limited eyepiece selection.

I love my APM UFF 30mm, but wish for a step down in exit pupil.
The choices I am pondering are:  SL 20mm 2" 80 UWA or Nagler 22 t4 

I know the t4 will work well with glasses, but will the SL20? 
The description on the web says yes, but many posts on the same EP differing branding say not.
Your thoughts please.

Clearly I prefer the price tag of the SL, but...

And its for mainly the 10" OOUK Dob and the 6" OOUK Newt use.
 

 

Alan, The eyecup they use on the Stellalyra 20mm eats about 8mm worth of its 20mm, and the eyepiece, as-is, is not glasses-compatible, in my experience.

However, if the eyecup is removed, and you added a normal flip up/fold down eyecup to the 50mm threads (a 47mm diameter rubber eyecup works), or glue some black felt to the top of the eyepiece,

then it would be glasses compatible.

OTOH, the 22mm Nagler is glasses-compatible right out of the box.

6 hours ago, LondonNeil said:

I've read good comments on the baader diagonal before,  but wouldn't a  mirror be better than a prism diagonal? 

That depends on the f/ratio of the scope and the price of the prism.

Generally, f/8 and longer scopes are OK with prisms or mirrors.

Shorter than f.8, a prism tends to add lateral chromatic aberration, so a mirror is likely better.

Likewise, an inexpensive prism might be better made than an inexpensive mirror type, but once you head up in price, the mirrors become the equal of prisms and may be better.

One think is for sure--there are a lot more mirror diagonals to choose from.

And it might be worth pointing out that AstroPhysics and Tele Vue, both makers of high-end refractors, both sell only mirror diagonals.

Only one magnification.

Streaked images if longer exposures.

High cost.

If multiple exposures and stacking, stacking errors and the inability to screen out bad seeing.

Not a panacea, but interesting.

Russ, it's OK.  That is also a fine eyepiece.

It's not quite as wide as the APM 24mm UFF (27.6mm field stop) or the Baader Hyperion 24mm (28mm field stop), but unless you go 2", it'll do fine.

The 30mm UFF has a 36.3mm field stop, so quite a bit more "real estate", LOL.

Given where its made, it is like a spiffed-up GSO.

It's probably fine.  It's likely the same maker as William Optics, Astrotech, etc (GSO).

I might recommend something higher end if you had an AstroPhysics 6" or something like that.

But your only risk is internal collimation, which you can fix if you take your time.

1 hour ago, Louis D said:

I measured 24.1mm FL in the center and 20.5mm FL at the edge for my 24mm APM UFF.  I measured the FS at 27.5mm, the AFOV at 63°, eAFOV at 65°, and the usable eye relief at 17mm.

Not too far from Ernest Maratovich's measurements.

He got 27.6mm for the field stop, AFoV at 64°.

I also measured 17mm as effective eye relief.

I can't explain why he found a focal length of 24.7mm.  I think he uses an instrument to measure that.

(a calculated focal length makes assumptions about other measurements and can often be wrong).

Since the eyepiece has some AMD due to its low RD, I'm inclined to think your focal length measurement may be close to accurate.

It does make my earlier point, however, that the TF = AF/M formula is simply not an accurate one.  In the absence of field stop dimensions, however, it's probably

best to do a star-timing if you want to know the accurate true field size.

5 hours ago, RobertI said:

I’ve just cleaned some eyepieces which were used during an outreach session last night (people must have really greasy eyelashes!). Whilst checking my other eyepieces in the case I noticed my 38mm Panaview had three or four spots of fungus on the outer edge. After cleaning with Baader Wonder Fluid, the fungus is gone, but there are areas which look like water marks which cannot be removed - I am assuming this is permanent damage to the coating? Interestingly the ‘watermarks’ appear more widespread than the original fungus so I’m wondering if some of the fungus was not visible?

I’m not bothered, I’m pretty sure there will be no impact to the views and it’s a cheap eyepiece anyway, but just wondering what people think. 

PS: I don’t normally remove lenses, but the fungus was creeping under the retaining ring. 

It could be water spots from the fluid, and/or, perhaps, the cleaner isn't strong enough.

To find out, try pure acetone on one of the spots to see if it comes off.

If it doesn't, it is likely to be coating damage.

On 07/04/2024 at 14:24, dobbyisbest said:

Hi Don,

Original responder here. Would you perhaps mind elaborating on the math/logic?

My workings are 1250mm/24mm = 52.083, and then 68deg/52.083deg = 1.30568 FOV.

Am I missing something?

I was trying to give a good, honest answer to OP, but if I didn’t succeed, I’d be grateful to know where I went wrong.

If I didn’t manage to provide the OP with the best recommendation, I’d be happy to buy the eyepiece from them if there is something better. 

 

 

 

 

It's very simple.

The TF = AF/M formula is only accurate if there is no distortion in the eyepiece.  Since all eyepieces have distortion, this formula overstates the True Field by 5-10%.

IF the Field Stop in the eyepiece is known, this determines the true field of the eyepiece since the field stop is laid on the focal plane of the scope in the same manner a sheet of paper with a hole cut in it, laid on a map,

determines how much map is seen.

So the Field stop formula ignores distortion and yields an accurate true field for the eyepiece.

TF = (FS/TFL) x 180/pi

or True Field = (field stop/telescope focal length) x 57.2958

You can use 57.3 for the last number, which converts radians to degrees.

In this case, the 24mm Hyperion's field stop is known--28.0mm, so the true field calculation follows.

You'll notice that this formula also ignores eyepiece focal length, which can be in error by several tenths of a mm.

The 24mm APM Ultra Flat Field is labeled 24mm, but actually measures 24.7mm, so the magnification formula will be way off.

In tests, the 24mm Hyperion focal length seems accurate, but the field stop measured 28.8mm !!

That means the true field will be 28.8/1250  x 57.3 = 1.32°, or 1°19' !

In truth, the Field Stop formula isn't going to be dead accurate either because we rarely know the EXACT focal length of the scope.

When scopes are made, there is always a variation in mirror and lens focal lengths.  Unless it has been measured on a test bench, it is likely not known exactly.

There is only one easy, non-instrument, way to accurately assess true field exactly, and that is to time the passage of a star on the celestial equator across the field of the eyepiece from edge to edge.

You would take 3 timings and use the longest one.  Then convert it to decimal minutes (e.g. 1 minute 13 seconds = 1.217minutes) and divide by 3.99 to convert to degrees.

If you want, you could then find the exact field stop diameter in your eyepiece by using the true field formula and solving for field stop:

FS = (TF x TFL)/57.3

Knowing the field stop means you can figure out the true field seen in any telescope by merely plugging in the focal length of that scope.

Just be aware it won't be any more accurate than the stated focal length of the scope.  That error is tiny compared to the TF = AF/M formula, however.

4 hours ago, John said:

I think the main drawback is that you are opening the eyepiece up to install the FT ring. It goes between the upper body optical set and the lower set. Except for the 24mm which, as Don says, does not have a lower optical set.

I guess it's a fiddly thing to do in the dark and there is always the possibility of dust getting onto the internal lenses of the eyepiece.

 

Though because the eyepieces coma apart easily and the lenses are held in with retaining rings, they are easy to clean if necessary.

I think many use them to create a different focal length for a night, and don't change them often in the dark.

Of course, you will need more eyepieces, because objects in the sky differ in size and brightness.

I recommend, with that size of scope, steps of 40x magnification up to about 200x.

So, since you have 50x covered, eyepieces yielding 90x, 130x, and 170x at least.

That is focal lengths of 14mm, 10mm, and 7mm

The Pentax XW eyepieces fit right in with the 24mm Hyperion.

For less money, the 13mm Baader Hyperion plus 2 fine tuning rings can provide focal lengths of 13mm, 10.8mm, 9.2mm, and 8.1mm in one eyepiece.

The 10mm Hyperion can yield 10mm, 8.4mm, 7.1mm and 6.1mm.

If you don't mind threading the rings on in the dark, that makes the Hyperion eyepieces very versatile, reducing your cost for eyepieces significantly

https://www.baader-planetarium.com/en/baader-hyperion-finetuning-ring-14.html

Click on the graph on the left to see the details about every Hyperion with the Fine Tuning Rings added.

The 24mm Hyperion isn't used with the rings, as it has no lower lenses to move farther from the upper section of the eyepiece.

4 hours ago, Dibp said:

Not that I am at all impulsive but 

Baader Hyperion 24mm has just been ordered. I am more than a little excited to see how it compares

Thank you for the recommendation Dobbyisbest

I will update as soon as the clouds go. 

A little error in the math from an earlier post.

The True field of the 24mm Hyperion will be 28/1250 x 57.2958 = 1.28°, or 1°17', at 52x.

That's a nice wide field, and good for a number of large objects--an excellent low power eyepiece in a 5" scope.

I've always liked the C5--it has great portability and enough light grasp for thousands of deep sky objects (in dark skies).

That is nostalgia speaking.  You'd be disappointed, when comparing to the Morpheus eyepieces.

The 30mm UFF is a FAR better eyepiece, one of the finest eyepieces at any price.

The 30mm to 17.5mm gap is not bad in your scope, either.

With a 1218mm focal length, that would be 41x (30mm) and 71x (17.2mm, the actual focal length of the 17.5mm Morph.)

I can't conceive of needing magnifications closer together than that.  The 24mm UFF would be way too close to the 17.5mm's magnification (only 20x).

The 12.5mm Morph.(actually 12.4mm) is 98x, so the 30mm>>17.2mm>>12.4mm is a pretty even spread.

he next logical focal length after that is the Morpheus 9mm (really an 8.9mm).

In your 8", magnifications from 40-150 will be heavily used.

It is possible to dissolve the glue and re-cement the elements, but unless you want to do it for the experience, you'd have to value your time at zero to make it worthwhile.

You have a stain on the lens that will impact its usability, so you have three choices:

1) buy a new eyepiece

2) separate the lenses and clean them, then re-cement.

3) find a used version of the same eyepiece and snitch an element from it.

FWIW, the fact water got in is an indication it was improperly cemented in the first place.

I'm not clear on your picture.  Why isn't the diagonal simply inserted into the visual back?

The visual back on the 127 looks like this:

https://www.cloudynights.com/topic/624516-sw-127-mak-adapters-accessories/?p=8699550

And the external threads serve no useful purpose if a 1.25" diagonal is inserted.

1 hour ago, Louis D said:

In the case of GSO 2" to 1.25" adapters, it maintains parfocality between 2" and 1.25" eyepieces if both have their focal plane at the same distance relative to their shoulders.  Notice below how the 1.25" adapter's opening is recessed exactly as much as the thickness of its lip so the shoulder of the 1.25" eyepiece will be at the same level as a 2" eyepiece's shoulder in the absence of the adapter:

It actually works quite well to avoid lots of refocusing if your eyepiece collection is parfocal between 2" and 1.25" eyepieces.

IF your 1.25" eyepieces don't rest on the outer lip of the adapter, like Hyperion, Morpheus, LVW, and many other 1.25" eyepieces.

1 hour ago, Scosmico said:

Lung, If you want to embark on this hobby, something that was really valuable to me, in terms of eyepiece, was to learn how to differentiate a standard eyepiece from a good one. And no eyepiece gave me more understanding about contrast, sharpness, than  orthoscopic eyepieces. They are in the low budget spectrum, not because of the quality but because of the limited field of view. They are great for long focal length telescopes delivering a sharp planetary views. That is my advice about what type you could go first. All tips given before are very good.

Good luck.

IF the scope tracks.  And if the use is on planets.

But if the scope is on a manual mount, a long focal length instrument combined with orthoscopic narrowfield eyepieces require the scope to be pushed every few seconds.

And short focal length (10mm and shorter) Abbe Orthos require an extremely close eye position, which is uncomfortable even without glasses.

It works for planets, because you can simply pull your eye back, which narrows the field you see, and you can still see the planet well.

But pulling the eye back doesn't work as well for objects larger than planets (e.g. the Moon), and it means even more pushing of the scope to follow the turning of the Earth.

Well-made Plössls fall into the same category--nice and sharp, with good contrast, but uncomfortable in shorter focal lengths.

These are some of the reasons why wider apparent fields are popular, and why longer eye reliefs are popular (examples: Delites, SLVs, X-Cel LX, HD60, et.al.).

And even at high power in a tracking scope, wider fields with good lateral correction work are more enjoyable to use on the Moon.

52 minutes ago, Louis D said:

I just wonder if the Baader Hyperion Aspheric 36mm is enough better than the TS Paragon ED 35mm to justify the additional cost.  I have the latter, and it's pretty decent, but not great, at f/6.

Don't waste your money, Louis.  I could see serious lateral astigmatism in the Baader 36mm at f/10 !.

6 hours ago, Roy Challen said:

I agree with everything in your post except this. Baader sell an inexpensive compression ring adapter that screws directly on to this thread, making a much nicer way of holding the diagonal. Looks nicer too!

I was not referring to the threads on the back of the scope.  I was referring to the "visual back", the piece that threads onto the scope, into which the diagonal inserts.

On its outer end are 10mm of thread that do nothing other than to force the inserted diagonal to be 10mm farther from the back of the scope.

The thumbscrew that holds the diagonal is closer to the scope, in the solid, un-threaded, portion of the visual back.

Removing the 10mm of threaded section on the visual back, which was intended to be used with some obscure camera adapter,  allows the diagonal to move in toward the scope,

which shortens the focal length of the scope and yields a wider true field with every eyepiece.

The Baader adapter to which you refer, I believe, threads directly to the scope and replaces the visual back that comes with the scope.

Are you referring to the 2" to 1.25" adapter, where the thumbscrew fits in a slot in the 2" body of the Barlow, like in this picture of a similar one: