Don Pensack

I don't recommend Hyperions below f/6, and I don't recommend the 31mm and 36mm Hyperions below f/8

Sure, they can be used in faster scopes, but they will have a lot of outer field astigmatism.

It's like the Morpheus, which I don't recommend below f/4.  In my f/5.75, the 14mm Morpheus is near-perfect.

In my friend's f/3.45, it was not good at all.

23 hours ago, Louis D said:

I always keep my 10mm Delos cup all the way down and have never experienced this.  Perhaps because I bought it around 2011 when it first came out, they were using a different lower cap back then?  I'll have to check how tight mine is the next chance I get.

The Delites have a different lower cap in black that fits the barrel very tightly.  Too tight, in my opinion.

There is an answer I could have used, in retrospect--simply using some light sandpaper on the interior surface of the caps--it would have taken me only seconds per eyepiece--but I didn't thin of it at the time.

On 18/06/2021 at 02:02, NGC 1502 said:

I’ve sorted the undercut problem with hard plastic tape. Dymo tape for label making is ideal. On the eyepieces I’ve used that on the undercut was just a fraction deeper than the tape. This worked fine, no snagging job done. Regular electricians tape is too soft.

Ed.

I used copper tape, which also works great--it's thin enough you need a couple wraps but it serves the same function and makes removal and installation a lot easier.

On 17/06/2021 at 14:14, Ricochet said:

Mine are the same. Optically they are excellent eyepieces, but the mechanically they are awful. The sliding section doesn't lock, the rubber eyecup is uncomfortable, the undercuts catch on everything and are so deep that the collets on my cheap binoviewer can't even grip the eyepieces, and the choice of a painted metal as the exterior surface allows radiative cooling making the eye lens prone to dewing. 

Painted metal?

The outer surfaces are:

--chrome plated lower barrel

--black anodized upper barrel

If you are referring to the iris in the sliding eyeguard, the upper surface is black-anodized aluminum.

If the eyeguard is used raised at all, even one notch, it acts like a dew shield for the upper lens, not to mention a light trap to reduce peripheral light scatter.

I own all 9 focal lengths and the eyeguards lock tightly in place, so "doesn't lock in place" just isn't true.  You just not be tightening them sufficiently.

I do note you cannot lock them using only one hand.  One hand has to hold the lower section while the other hand tightens the top.

The bottom caps, though, are just way too tight and even with a pinhole in them, they still are very difficult to remove.  I recommend replacing them with something else--anything else.

We are in agreement about undercuts, though they are of the recent beveled edges, so catch a lot less.

I agree totally, but the problem isn't the aluminum collet, it's the lower eyepiece cap.

They're made far too tight and are difficult to remove and install.

I replaced all of mine with looser-fitting translucent plastic caps and the eyeguard doesn't move when installing or removing the cap.

On 17/05/2021 at 04:41, Astro Noodles said:

Hi Kimboman

Is this the one titled 'Uranometria Deep Sky Atlas' ?

No.  That is the Tirion Sky Atlas 2000.0 Field Edition, which prints the sky on 26 charts.

Uranometria 2000.0 prints the sky on 220 charts (2x that in edition 1), a hugely larger scale.

On 16/05/2021 at 16:07, Stu said:

White stars on black looks great, and works for my brain, which does struggle with the inverse which is much more common.

But, far less readable at night than black writing/stars on a white page.

10 hours ago, 12green said:

Hello, I've  also been waiting for ES68 24mm to get back in stock in UK.

Would Altair Astro UFF 24mm be a suitable alternative and be a noticeable upgrade from my BST Starguider 25mm.

I do like ES eyepieces. I only have ES82 14mm &68 34mm

I have F10 SCT and don't require glasses.

Thanks

The Altair would be a noticeable upgrade, but a caveat: It has a very long eye relief.

Even with the eyecup raised, which you would do if not wearing glasses, it is possible to get too close to the eyepiece and get blackouts therefrom.

You do need to "hover" over the eyepiece.

19 minutes ago, Kon said:

I just did a quick google search on ES 24mm and I came across this site:

https://www.boxallx.com/explore-scientific-68deg-ar-eyepiece-with-emd-multilayer-coating-and-argon-filling-various-sizes-p-888127.htm

It cannot be a genuine one for the price can it?

 

(another search shoed as fraudulent site), so avoid!

Yes, a fraud site.  Unless it's used, no one sells a product below manufacturing cost.

This is only one of many such sites.

Like the Nigerian Prince scam we all avoid, in the modern world there are scammers in every field.

Sale or no sale, I just wish they were available, period.

There is so much pent-up demand.

10 hours ago, Zermelo said:

Interesting discussion. I think vlaiv is talking about the same rectilinear/angular distinction here.

So some of the discrepancies between claimed fields of view and the upper limit of the barrel format are not necessarily typos (or outright lies), they could be nuances of distortion. I suppose it's a subjective point as to whether you'd prefer a more "honest" 65° field or a more "immersive" 72°, even if you're not getting any more TFOV with the wider field.
I also recall (but can't find) a recent thread discussing astronomical eyepieces vs spotting scope eyepieces, which said that the design compromises were weighted towards different types of distortion in each case (and therefore an EP designed for spotting scopes might not perform so well in a telescope).

In spotting scopes, it's important to keep straight lines straight across the field.  So a design for a spotting scope eyepiece would reduce rectilinear distortion to a minimum, leaving in angular magnification distortion at the edge.

For astronomy, it's more important to maintain the same size and separation of points across the field, so angular magnification distortion is reduced to a minimum, leaving in a fair amount of rectilinear distortion.

Tracking scopes seem to tolerate both forms of distortion, while scanning scopes usually prefer a very low RD.

But, distortion is distortion, as they say, and if you don't want distortion in the field, confine the eyepiece purchases to narrow fields of view.

2 hours ago, vlaiv said:

How does that work?

What about simple drift timing method?

Simple drift timing will yield the true field and the field stop, but not the apparent field.

There is an easy way to measure the apparent field:

https://www.cloudynights.com/topic/574401-an-easy-way-to-measure-apparent-field-of-view/?p=7959408

and the posts that follow.

Measure carefully, and you can easily get within 0.5° of apparent field.

I can't tell you what will or won't be visible in white skies, but in a B2-B4 environment, every object can be seen in a 100mm refractor.

In a nutshell: the smaller the exit pupil, the more problem you'll have with floaters on the Moon and planets.

Floaters are not usually a problem on stars.

Your pictures show normal amounts of rectilinear distortion in the form of pincushion.

Distortion of this type means the timing of a star across the field will likely yield a field stop that, in turn, yields a smaller apparent field than the one seen.

The outer edge of the field is stretched radially, as is the case with pincushion distortion.

It is quite normal.

A 48mm field stop is a bit large for a 42mm eyepiece, indication they accepted a small amount of vignetting as a compromise.

A 65° field calculates to a 47.65mm field stop.  48mm translates to just a little over 65°.

So how do you get 72° out of the eyepiece?  By stretching the edge.

It's the same in the 24mm TeleVue Panoptic, which has the same form of distortion and where the focal length and field stop don't match.

It should have an apparent field of 64.5° for its 27mm field stop diameter but one sees a 68° field in the eyepiece.

It's also likely both the 65° and 72° figures are not accurate.

Those are the new 100° glasses. 😆

Much to my embarrassment, I once commented about a 30mm eyepiece that it suffered from astigmatism, only to learn that my eye had deteriorated and now had noticeable astigmatism.

When I looked through that eyepiece wearing glasses, it had remarkably improved--stars were now points to the field stop.

I think almost all humans have astigmatism with dilated pupils at night--we draw the stars as 5 or 6 pointed objects, a sign of astigmatism.  No one I have ever met sees the stars as points at night.

Most of the people I meet don't even see the stars as points with glasses on, showing their prescriptions are out of date.

It was a revelation to not only see all the stars as points with the naked eye when I first got a really good prescription, but to also see about a half magnitude fainter stars.

Those really faint pinpricks had been blurred to extinction by my uncorrected vision.

And that is with only 1 diopter of astigmatism.  If you have more, then glasses should be pretty much essential at the telescope for all eyepieces, favoring long eye reliefs of 18mm and longer.

As for a dedicated single vision pair of glasses for astronomy, I'm with Louis.  There's just one problem: I cannot then read my notes or the screen of my DSC.

I have presbyopia too, so I cannot see anything near without strong correction.  So I got a pair of large lensed glasses and had them made as bifocals with only a very small bifocal section at the bottom.

I can successfully keep the "reading" section out of the field of view when looking through the eyepiece, and use the lower section when looking at notes away from the eyepiece.

Only Costco gave me the option of choosing how tall to make the reading section.  So finding a lab to do the same for you may require a bit of research on your part if making glasses

good for astronomy.  I normally use progressives in daily life, but they sure don't work for astronomy.

2 hours ago, johnturley said:

Would be interesting to see how it would compare to the now discontinued Tele Vue 26mm Nagler eyepiece, I don't suppose that there would be any comparison in an f5 Newtonian.

I can't understand why Tele Vue decided to discontinue their 26mm Nagler, leaving a large gap between the 22mm and the 31mm.

John  

I can see it from TeleVue's position: you have an eyepiece that barely sells (as a dealer I can tell you that only the 2.5mm Nagler sold less), and you need to reorder and there is a minimum of 300 pieces to get a price that allows the wholesale and retail price to stay the same.

It's going to be many tens of thousands of dollars that would better be spent in another product, like the 22mm, for instance, that is a good seller.

So you slowly discontinue the ones that really don't sell--the 26mm, 20mm, 12mm, 11mm, 2.5mm and let them run out.

That still leaves you with a fairly complete 82° lineup--31, 22, 17, 16, 13, 9, 7, 5, and 3.5mm.  That's still 2 more focal lengths in an ultrawide line than any other seller.

The 31mm to 22mm jump is not large at all--only 39x to 55x in a 1200mm focal length, a difference of 16x, or a 41% increase, which is commensurate with TeleVue's position about having a 40% difference between magnifications.

In case you wonder where that comes from, it turns out the true field, if all eyepieces have the same apparent field, is exactly 1/2 the size by area when magnifications increase by a factor of 1.414 between eyepieces.

Starting with the 31mm as a low power, the next focal length in a set would be 22mm, which is probably why the 26mm never sold well.

Plus the fact that the magnification difference between the 31mm and 22mm is small in most scopes.  My scope is longer (1826mm), yet I never use a 31mm or 22mm on the same night--they're both low powers.

3 hours ago, Virtus said:

I have and would recommend the APM 24 UFF. It's available under several other brands - the Orion version can be used as both 1.25" and 2".

Yes, APM Ultra Flat Field, Altair Ultra Flat, Orion Ultra Flat, Meade UHD, and Celestron Ultima Edge, 

Especially recommended if you need to wear glasses at that focal length.

Replace the thumbscrew with a nylon screw and tighten it down without any scratches.

I've never understood the reluctance to tighten down a thumbscrew.  A slight mark will not damage the eyepiece in any way that affects it.

Do you really only ever buy eyepieces expecting to re-sell them in "new" condition?

All the eyepieces I've resold (hundreds of them) had marks on the barrels and they sold instantly anyway.

As for the weight in the focuser and scope balance, as others have said, a simple counterweight on the tube will suffice to balance it with a heavier eyepiece.

But, you already have quite a set, so go ahead and use the LVWs with a Barlow and they'll work quite well.  Adding a counterweight is just part of using a dob under 20".

7 hours ago, FLO said:

This is not a secret 🙂 

We always share who manufactures our StellaLyra eyepieces when we introduce them: 

 

 

The same is true for the StellaLyra Kitakaru eyepieces mentioned in the same introduction. 

Our StellaLyra SuperView series are also made in Taiwan but by a different manufacturer - Guan Sheng Optical (GSO). Again we shared this info here at SGL: 

HTH, 

Steve 

Very few companies import the whole range.  Kudos.

"Paracor 35mm"???

For this particular eyepiece, it is Long Perng, and it has been sold under many labels, from Stellarvue to Orion to StellaLyra, etc.

Long Perng offers them in 3, 5, 6, 9, 12.5, 14.5, and 18mm focal lengths.

When the air is clear and dry, the light scatter goes way down and I have seen 5th magnitude stars with averted vision.  That isn't common this time of year, but is in the Fall.

This time of year as Orion sets over the water you can see 9-10 stars in Orion if it's clear (about 1 night in 10).

In contrast, averted vision reaches magnitude 7 on a regular basis where I drive in the mountains to observe.

8 hours ago, Soligor Rob said:

The seed was planted that my collimation might not be good so I bought a Laser tool and found it was actually out a tad, have to say what a fantastic tool the laser is, it made the job so much easier for me than using the Cheshire.

 

Hopefully, your laser was collimated.  You can check it by rotating it in the focuser and clamping it at 90° intervals.  If the dot stays in one spot on the primary, you can use it as a collimation tool.

If not, it isn't collimating your scope to use it.  You can look up the links on line to collimate a laser collimator in that case.

As for collimating the primary, you need to use a barlow to be accurate enough when using a laser.  The beam itself is not accurate enough--it can only get you in the ballpark.

I'll attach an article on the Barlowed Laser collimation technique.

BarlowedLaserInstructions.pdf