Don Pensack

In my f/7 apo, the 24mm APM UFF has a better edge of field than the ES 24x68.

Both are not quite up to the standard of the TeleVue 24mm Panoptic, though.

But the APM is the only one of those 3 24mm eyepieces compatible with glasses.

As for true field size, the 22mm 70° eyepiece Louis mentions is a great alternative if you have 2" eyepiece capability.

Now sold as:

They might be available used as an Astrotech AF70, an Olivon 70, or a Celestron Ultima LX

My calculations show a 26.9mm field stop in that eyepiece versus a 27.2-27.3mm field stop in the APM, which is close enough the field size is pretty much the same.

Measurements of the others show 27.0-27.2mm, so all of these can be safely considered to have roughly the same true field size.

Looks like 2" 40mm widefield eyepieces are scarce.

Here is what I found:

Of the above, the one that stands out is the 40mm Pentax XW.

Not cheap, but much less than the 41mm Panoptic.

This eyepiece from KunMing United Optics (KUO) has been around since 2006 and has been sold under many labels.

The new Meade PWA 28 is this same eyepiece with a pared-down top.

Here is an older review:

https://www.cloudynights.com/articles/cat/cn-reports/eyepiece-reports/cn-report-the-uwan-eyepieces-r1388

19 minutes ago, Deadlake said:

Does anyone know how the BBHS or prism works in a F6 APO scope, I presume the BBHS is the one to go for? 

The prism also is available with the hypoteneuse surface BBHS coated, So there are both mirror and prism BBHS diagonals.

A prism is not recommended below f/7, but I'd put it at f/8, because I saw a lot of prismatic chromatic smear at f/7 with the prism.

The BBHS mirror prisms were all recalled last fall due to a bad quality on the mirrors.  Baader has yet to replace the stock with good ones,

so finding one might prove impossible right now.  If you find one, you want to be sure it is not from the batch made in the Fall.

The quality of the mirror after coating is the truly critical factor, which is the reason for the high cost of the AstrPhysics MaxBright and TeleVue EverBrite.

19 minutes ago, John said:

Does this spell the end of the dielectric dominance of the diagonal world ?

 

Not at all. 

First, silver coatings are expensive, and even more so when the necessary UV enhancement dielectric coatings are added to silver.

Second, the long term durability of silver coatings is still a question.  The jury is still out, so to speak.

Third, having a high output above 650nm is essentially unimportant for scotopic vision.

Fourth, diagonals get dirty and scatter light easily.  We know about the durability in cleaning of pure dielectric coatings.  We don't know about silver.

Fifth, a lot of high end scope manufacturers like TeleVue and AstroPhysics offer dielectric coated diagonals for sale with their refractors.  Takahashi offers prisms.

Sixth, the reflectivity at long visible wavelengths is close to the same.

Ultimately, should enhanced silver coatings prove durable, they could be another choice for high end stuff.

But they won't replace the dielectric coated ones in the more affordable range.

The original versions of the Meade Series 4000 UWA eyepieces had some issues:

1) apparent fields actually quite a bit smaller than claimed--more like 76-78°

2) serious spherical aberration of the exit pupil.  This bothered the 14mm more than the shorter focal lengths, but it was present nonetheless.

3) some actually uncoated interior lens surfaces.  I took my set apart several years after getting them to clean interior surfaces and blacken lens edges and was shocked to see that.  Explains Louis's comments.

4) some shiny spacers that were very much improved by blackening with flat black paint.

It's highly likely these were made by Kowa, the manufacturer of the 5-element S.4000 "Super Plössls" and the S.4000 SWAs, which would explain the high polish on the lenses.

Deep red is the only color that will not cause damage to one's night vision by "bleaching" the rhodopsin in the rod cells.

At the same intensity, green light is many times more injurious to night vision.

The key is a red LED with very little transmission in the orange or shorter wavelengths.

I installed a #29 red filter in my red LED flashlight to make it redder.

If it's too dim to read your notes, bring it closer to the page.  I use mine about 1" away from the page as I write my notes.  If I can hold it 6" and still read, it's too bright to maintain night vision.

This sums it up nicely:

https://www.cloudynights.com/topic/705418-red-light-or-green-light-to-preserve-night-vision/?p=10851252

Perhaps not, but someone he shares views with might and if he owns the eyepiece several years, he might too.

A person who doesn't wear glasses can use an eyepiece with long eye relief, but a person who does wear glasses cannot use an eyepiece with small eye relief.

A complicating factor here is that the 24mm APM is also compatible with the TeleVue DioptRx.

It sounded like he didn't want to spend the price of a 24mm Panoptic, which is the best of the 3 optically.

I'd get the 24mm APM and not look back.  It's the only one of the three with a glasses-friendly eye relief.

2 hours ago, michael.h.f.wilkinson said:

Regarding the MaxVision 24 mm 68 degree EPs, they work well down to F/5, but I tried one in an F/4.2 scope and that showed a lot of astigmatism. At F/4.7 this might also be an issue.

JOC's eyepieces all have induced astigmatism in the outer field at f/5.  I see it easily in my 12.5" f/5.75 (the coma corrected f/ratio).

The exceptions are the 92° 17 and 12mm

2 minutes ago, AlexK said:

TV Ethos 17mm with my 12".

Somehow its 88x 100 deg wide AFOV window having a hypnotizing effect on me. Sometimes I'm just aimlessly wandering the Milky Way gas clouds with it for hours (even without NBs). It's giving me a lightspeed warping between stars sensation.

With that size of scope, the 17..10..6mm set could be all you'd ever need.

But add a 30mm for the widest field and a 3.7mm for planetaries and Moon, and you have a complete set.  Filling in in between is likely not necessary.

On 23/01/2021 at 11:21, mikeDnight said:

I did read somewhere, probably on CN, that Takahashi used their influence to stem the flow of this five element Masuyama design from Japanese manufacturers to such companies as Celestron, so as to keep it for themselves. Have you any idea if there's any truth in this Don?   Having said that, I think the 25mm Parks Gold and 35mm Ultima are leaps and bounds better than the 25 & 30mm Tak LE's.

I doubt it.  Meade stopped making theirs (it was from the high-end company Kowa) when they moved from Japan to Taiwan and then on to China.

Celestron changed suppliers and changed hands, ending their Japanese connections.

Meade did the same thing in pursuit of a higher profit margin.

Parks lost the monetary ability to import large quantities, which put an end to their relationship.

Orion changed suppliers to mainland China and stopped their Japanese imports.

I don't know what happened to Antares, Tuthill, Omcon, et.al. but I suspect when they were no longer available from the factory, that ended it.

Ohi Optics eventually stopped making the eyepieces.  Baader was one of the last to bring them in.

No one I've read has been able to pin down Takahashi's source for the LEs.

I think the true reasons for the demise of the 5-element eyepieces were:

--everyone moving to China to lower costs

--the increasing popularity for wider fields of view

--the Japanese stopping the manufacturing of the product as the orders disappeared

--the move downward in prices.  People paid more for simple eyepieces back then, but they expect to pay much less today.

On 23/01/2021 at 14:10, Ally8446 said:

Would this be suitable.....? 

http://apm-telescopes-englisch.shopgate.com/item/333631373637

I have one and it is simply magnificent. 

In my opinion, that eyepiece is superb in every way at f/5.

It has become my dark sky low power eyepiece, and was stunning on the Veil Nebula with a good O-III filter.

18 hours ago, niallk said:

My O-III and UHC 2" filters are in my EP case

and I keep my 1.25" filters in a cheap but wonderful filter wheel:

One of these days I'd like a 2" Astrocrumb filter slide for my 15" dob.

Careful--they're not protected from dew in a slide, whereas they are in a filter wheel.

7 hours ago, Marki said:

Does anyone know if the Mark IV zoom is a significant improvement on the Mk III? I have the latter - its pretty heavy, and I think the 8mm highest setting is somewhat "soft" compared to all the other settings. Mine is a good few years old now and coming very loose inside (it rattles) and was wondering about upgrading to the IV. The barlow for this zoom is very good though - I recommend it.

 

They changed the focal plane position to be usable in more spotting scopes.  It's a bit lighter, and the click detents are softer and less noticeable at the request of hunters and bird watchers.

The 8mm end is softer than the lower powers, but for two reasons not related to the eyepiece: the seeing conditions are not as good when using the high magnification, and the optics in the scope have to be well-done to handle an 8mm focal length, often.  That being said, what is true of all zooms from all manufacturers is that the zoom has its best correction at one setting and as you move away from that setting, the eyepiece has gradually increasing aberrations, especially spherical aberration.  And it is not, usually, the highest power setting where the eyepiece is best.

18 hours ago, mikeDnight said:

I tend to use eyepieces having around a 50°  apparent field in my binoviewer. For most deep sky targets i prefer to observe without a binoviewer given my scope has only 100mm aperture.  The binoviewer is spectacular when viewing the Moon and planets, and I usually use a binoviewer with a 2X barlow  which amplifies around 4X due to the extended light path. I've found that my 18mm Ultima's and 16.8mm Orthoscopic's are the ones that I use most. My 25mm Parks Gold (same 5 element design as the Ultima and Tak LE), give awesome wide-ish lunar views. I believe that Parks Optical still sell the Gold series eyepieces.  Baader Eudiascopic are the same, but you can also get the Takahashi LE's which are also great. Televue Plossl's are beautiful for lunar and planerary in a binoviewer, but I'd steer clear of the shorter focal lengths and use longer fl's along with a barlow instead. That would give you more eye relief and greater comfort when observing for long periods.

Parks closed in 2012.  Baader Eudiascopic eyepieces are no longer available.  Celestron Ultimas haven't been made for 25 years.  Takahashi LEs are still available.

On 19/01/2021 at 12:34, Louis D said:

The Chula Vista Trailhead parking lot at Mt. Pinos, perchance?  If I'm ever in CA with a telescope, I'll have to give it a try based on your ceaseless praise of that site.

Yes.  A # of things make and keep the site popular:

--tall pine trees surrounding the parking lot which block all horizon light up to about 20° or so.  It's amazing how much difference that makes for the suppression of peripheral light in your eyes and in the scope.

--high altitude  The air, as a result, is usually very transparent, even when the sky darkness is not great.

--convenience of getting to the site.  You just drive up the road and it dead-ends in a parking lot big enough for a couple hundred scopes (assuming few motor homes).

The site will die as a dark site fairly soon because a large number of houses have been approved to build only a few miles away (over 20,000 homes).  Fortunately, that will take several years, but the site, which has averaged 21.45 at night for the last 15 years will be growing lighter with each passing month.  Several of us are actively looking for other sites (all, unfortunately, farther away).

51 minutes ago, Ships and Stars said:

Great comment Don, there is a ton of really good information, much of it I flat out didn't know or know how to explain other than pure filter wizardry

A little off topic and not doubting you that OIII isn't optimal for M42, but a few weeks ago I happened down to M42 with a 20mm APM and Astronomik OIII on the 20" at a 21.5ish dark site after looking at the Rosette and was treated to quite a different and stunning view of M42 I don't recall seeing in my short time observing.

I've seen it before with a UHC but got into the habit of generally not using a filter and concentrating around 42/43 area and not covering the full extent under dark skies, because I'm usually chasing things I can't see from home.

The overall normal extent of M42 around the Trapezium and normal swathes or 'wings' were present with the OIII. While tightly defined, it blocked a fair bit of the usual detail, but enhanced other areas. So that in itself was a mixed bag, but the thing that really made me sit up was the clearly defined, narrow ring which completely extended well past my FOV and back up to the other side of M42. I don't think I've seen this huge feature before, probably because I don't have a widefield scope (other than bins) and it was striking. The central area was completely empty of nebulosity as I recall, but the outer edge was magnificent and absolutely glowing. I thought it was some kind of stray reflection or eyepiece fogging at first, but glass and mirrors were clear. It was complete except one small area where this band necked down. 

I took the OIII off and could barely see this band in comparison, but it was still there, very faint. Didn't try UHC, don't have one in 2" (yet).

So my question, and this is for anyone really, is M42 a mixed object with different emission lines, incl HII, etc that different filters enhance at the expense of others, or does this large circular feature maybe have its own name/ID? I don't see it in photos, though that entire area is ablaze in long exposures. 

*edit I took the creative commons wiki page photo for M42 (thank you Keesscherer) and desaturated it and boosted blacks. The bottom photo is along the lines of what I was seeing with OIII, but not that striking. It was like an inverted image, the red arrow points to the dark gap I noticed. Very pronounced!

Will try the TV Nebustar II next time. 

 

 

 

 

all large Hydrogen emission nebulae, like M42/43 emit most of their energy at H-α and H-ß

But, all of them also emit light from the excitation of other ions, like O-III, S-II, N-II and various Helium wavelengths.

So looking at M42, say, with an O-III filter will reveal different details than you might see in a narrowband UHC-type filter simply because the contrast on the O-III features will be boosted.

But, that will be at the sacrifice of the H-ß features.  The combination of the H emission and O emission will probably yield the largest view of the nebula.

M42 is so bright, it is a special case.  I've verified several times that it damages your night vision because of its brightness, which is why it is one of a very small handful of nebulae in which color is seen.

I usually see the most color and the largest extent of nebula in that one with a broadband filter (example Baader UHC-S) or a UHC filter with unrestrained red (examples: Astronomik UHC or DGM NPB),

but, so far, nothing has beaten the view of the nebula in my 12.5" at a high altitude site (2550m) under skies of mag.21.95 mpsas (essentially pristine--no light pollution at all) without a filter.  That night, not only were greens and reddish hues visible, but also beige-yellow and dusty rose, and bluish hues. And nebulosity was seen all the way to NGC1977, which appeared distinctly blue.

On 16/01/2021 at 15:39, SiriusB said:

Any chance you could expand on this please for the benefit of all?

I'd been given  to believe the best(bandwidth) nebula filters work best with larger scopes due to light loss? If you've only a small scope......

Thanks.

Since I've used narrow bandwidth filters with 50mm finders and even with the naked eye, I'll try to explain:

The narrower the bandwidth, the greater the suppression of non-nebular light and the greater the contrast between the nebula and sky.

Some people with smaller scopes have remarked that this makes the overall field image too dim for the small scope because it dims the stars and the sky, leaving mostly the nebula,

and the nebula is fairly faint in the first place in their scopes.

I think at least part of that, and the reason some have said the narrower filters are better in larger apertures is that they are not using the filters correctly.

There are some "parameters" of use that have to be followed for them to work well:

1. You must be completely dark adapted--at least 30-45 minutes outside away from all lights--for the sensitivity of the eye to increase to its maximum.

2. You should use low powers: a maximum of 10x/inch of aperture, or an exit pupil of 2.5mm and larger.

3. the filters don't work well in a hazy, cloudy, or otherwise not clear sky, and I KNOW a lot of observers tend to observe in those conditions, despite the poor results.

4. the nebula in question should be higher than 30° from the horizon or extinction due to the atmosphere will reduce its visibility

5. nebula filters work better if the background sky is not so bright that the improvement isn't sufficient to enable you to see the nebula.  Nothing can make a faint nebula visible in bright city lights.

6. Use the right filter on the right nebula.   An O-III filter isn't the right filter to use on a large hydrogen emission gas cloud like M42, M8, M20, M17, M16 because it suppresses the light from hydrogen emission.

The nebula filters work by dimming the background by 2.5 to 3 magnitudes while only dimming the nebula by about 0.05-0.1 magnitude.  A wider filter dims the background less so doesn't improve contrast to as great a degree,

Hence, the visibility of the nebula will also be less.  Yes, there will be some contrast enhancement, but the extra brightness of the background will only reduce the size of the nebula seen and reduce the details seen in the nebula.

When I have used an O-III filter to see the Veil Nebula with a 50mm finder scope, the field did darken, but the nebula became visible.  That's the purpose for the filters, right?  To make the nebulae more visible to the eye when looking through a telescope.  

In a really big scope, where the nebula is easily visible without a filter, paradoxically a wider filter can be used and still see a good view of the nebula.  Less contrast enhancement still works when there is aperture to waste.

Still, even there the narrower filters improve visibility more and create greater contrast.  

And contrast enhancement even works at very dark sites by suppressing sky glow.

So, other than price (the main motivator for the purchase of a lesser-performing filter), might there be a reason to prefer a filter with less contrast enhancement?  Maybe, if the overall field + nebula is what the observer is viewing.  NGC2359 is in a rich Milky Way field and seems to sit suspended in front of a background haze of faint stars.  The best contrast for the nebula suppresses the starlight and reduces that impression of the field of the nebula.  If studying the nebula only, the narrowest O-III filter is best.  But if looking for an overall aesthetic experience, a wider filter might be the choice.  But I can say that because I view with 32cm in a dark sky, dark enough to see the Veil Nebula with an O-III filter held up to the eye, and Barnard's Loop in Orion with an H-ß filter held up to the eye.  With a little more light pollution, the nebula would disappear, and ONLY the narrowest of filters would make it visible at all.

So, back to the small scope: if the small scope has any chance at all to see the nebula, it is by yielding the best contrast enhancement possible, and that is with a narrower filter.  But it is a matter of using the filter correctly, as I outlined.

To be fair, ANY contrast enhancement will still be.....contrast enhancement.

But some economical filters with better bandwidths include DGM, Orion (US), Omegon, SkyWatcher, Zhumell

Yes, that's fungus.

The eye relief on the 9mm is 2mm longer than the eye relief on the 5.5mm.

You might also look at the 9mm APM XWA, which has 0.5mm more eye relief than the ES9.

The half-way point in magnification between your 5.5mm and a 13mm is a 7.7mm, not a 9mm.

8mm would be closest.

APM's 7mm 100° is about a month away.

On 11/01/2021 at 12:27, Louis D said:

Are you implying the Delos's upper barrel is also aluminum and only the lower barrel is brass?  What has been the industry standard for the upper barrel?  I know chromed brass has been the standard for the lower barrel for years, but I really have no idea about the upper barrel metal.

Siebert has been using aluminum upper barrels to make his eyepieces lighter than they would otherwise appear to be.  Russell uses Delrin for his eyepiece barrels that makes them even lighter yet.

The Delos' upper barrel, like all TeleVue eyepieces, is aluminum.

I forgot about the two-part adjustable eyecup on the Delos.  Add the weight of that plus the chromed brass lower barrel, and that pretty much accounts for the weight difference with the Morpheus.

On 11/01/2021 at 13:40, michelbechara said:

Hello!

I have a 130/920 Reflector telescope and want to buy either this 6mm eyepiece  or 7 mm eyepiece. 

I know that the maximum magnification for that telescope is x260.

The 6 mm will give me x153 magnification - with 2x Barlow x306 - with 1.5x Barlow x230
The 7 mm will give me x131 magnification - with 2x Barlow x260 - with 1.5x Barlow x197

The objective is to observe the planets and gets the most useful closeup image, mainly for Saturn and Jupiter. 

By looking at these, do you think I should go with the Planetary 6 mm or Cronus 7 mm to achieve the best viewing of the planets with the 1.5 Barlow lens?

The planetary 6mm seems to achieve also higher contrast and clearer images compared to the 7mm and can have a good magnification with the 1.5 Barlow.

What do you think or am I having a wrong approach to the topic? Any help/guidance is much appreciated!

 

I assume you mean later in the year when Jupiter and Saturn are higher in the sky.  Right now, they're down in the muck and even low power sees a bad image.

The planet "season" is over.

With a 130mm reflector, you'll be lucky to break 200x and get a clear image even when they are high in the sky.

As a general rule, magnifications over 30x/inch (154x in your scope) get questionable and require pretty darned good seeing conditions, rare when the planets are high in the sky, but

impossible below 20°, where they are now.

I would suggest you make sure your lower powers are filled in.

For example, a good collection of eyepieces for you might be 28mm, 20mm, 14mm, 10mm, 7mm

You have a good way of looking at it--achieve ultra-high powers with a Barlow--but the number of nights you'll be able to use any magnification over 200x will be few

and the Barlow will receive very little use.  

I'd get the 7mm--it'll receive a lot more use.

But also look to filling in your lower powers if you don't already have them.

11 hours ago, John said:

It's nice to be able to experiment with different filters on different targets to see the effects. Alternating between no filter, a UHC, an O-III and an H-B on Messier 42 for example shows some really interesting differences in extent, the enhancement and sometimes the diminishment of the various parts of this complex target 

 

A great comment!  It points to the enhancement of different details with different filters.  That's especially true of M42/43.  Even a broadband filter like the UHC-S is wonderful on that object.