Don Pensack

9 hours ago, vagk said:

What I have read about 12mm 92° is that you observe whole 92° AFOV at a glance instead of ethos or es 100° which you must move your head and eye to capture whole field of view. This must be spectacular.

Isn't worth the sacrifice of ergonomics and weight for 32 degrees extra AFOV with the same eye relief ?

Be careful.

Human vision can see well beyond 100° with peripheral vision.

You can see the whole field at a glance in a 120° eyepiece with peripheral vision, but NOT direct vision.

Foveal vision--the center of the retina we use to look directly at something--cannot be redirected to the side of a field larger than about 68-70° without rolling the head over and looking through the eyepiece at an angle

(as you would do with a porthole to see farther at the edge).  Much of the time, whether you are even aware of doing so is simply related to your experience with the field size.

I have used 100° eyepieces since 2007, so I found the 92s easy to use and about the same as the Ethos eyepieces I was familiar with.

But if you want to look directly at the edge (and in practice you really don't), you have to roll your head over.  If you try to simply avert your eye to look at the edge, you would move your pupil away from the exit pupil of the eyepiece.

To look with direct vision at the edge means you are looking through the eyepiece at a 46° angle.  Try doing that without rolling your head over and you'll see your pupil moves several millimeters to the side to do so.

And that doesn't work with eyepieces.

So the people who maintain you can take in the whole field at a glance with direct vision are blowing smoke.  It's anatomically impossible.

Peripheral vision is easy.

I compared ROR to Windex and a lens cleaner that was a mix of isopropyl alcohol and water.

ROR was vastly superior to the other two.

I also compared it to a Nikon lens cleaning fluid you don't mention.  The Nikon fluid was very close, but ROR was still better at removing oils and mascara stains.

6 hours ago, Louis D said:

Basically, since California requires this label, it's cheaper and easier to stick it on every box regardless of where it's being sold.  If CA was a small market, it would probably be ignored and/or boycotted by manufacturers.

California's latest effort to bend the world to its will is P12 which effectively bans the sale of out of state pork in their state.

Is that a bad thing if other states raise pigs in a cruel and inhumane manner?

As for Prop.65, more information for the consumer is not a bad thing.  A label that identifies the potential problems with one product allows me to decide whether or not it is important to me.

Lead in eyepieces glass is not important to me, while lead in glassware I drink from is.

Since there are not thousands of knowledgeable inspectors checking each and every product, nor is the state willing to pay for that, the only alternative is to put the label on every product containing lead-containing glass.

Lots of studies of areas with concentrations of particular cancers point to environmental factors being a root cause, and rarely is it a single thing.

We are all lab rats for industry, who basically only responds to a problem AFTER it has caused a problem.

Far better to require they prove safety for humans BEFORE the product comes to market.

Well, at least you have corrected the coma.

However, where eyepieces are concerned:  Inexpensive, well-corrected to the edge, widefield--choose any two.

A fast scope unfortunately requires eyepieces designed for the fast f/ratios, and that does not describe most lower priced eyepieces.

The APM Ultra Flat Fields are a notable exception, though they were designed to yield excellent star images at f/5.  They may not fare as well at f/4, though I know the 30mm does fine.

It would just seem a shame to correct the coma to get better star images and then use eyepieces that have substantial astigmatism in the outer field at that f/ratio.

The APM Ultra Flat Field series is also available under the Meade UHD label, Celestron Ultima Edge, TecnoSky Ultra Flat, Altair Astro Ultra Flat, and Orion Ultra Flat names, and few focal lengths from China under the Svbony label.

That might not be a bad place to start.

Add a good 2X Barlow to cover all the necessary magnifications.

5 hours ago, ONIKKINEN said:

I keep reading about this notion that fast telescopes require some sort of different types of eyepiece to work well, for instance the explore scientific 68 degree ones say they work well at f5 and above, which my scope is not. Actually my scope is more like f4.2 with the TS maxfield 0.95 coma corrector so worse for this case. Are some eyepieces really so picky about this? I would assume if i pay more than plössl-type money for an eyepiece it would work with mine, but i could be wrong.

I have 3 eyepieces at the moment, all Omegon branded. Omegon Cronus 7 and 9mm (i think 60 degree) and an Omegon flatfield 19mm 65 degree. I think the flatfield is like any other "apm clone" out there as it looks identical to many others from other brands. I also have a good quality 2.5x barlow to extend the range.

What i know i am missing is the extremes and something in the middle. Maybe a 5mm for planets and close ups of the Moon and a 25-30mm wider field eyepiece for rich fields and making it easier to find stuff? Also what i could get is the hyperion zoom eyepiece which sounds very convenient, but lacks the wide fields because of the narrower field of view in the lower power range. Also i keep reading of this "fixed focal length eyepieces are better" type of thing compared to zoom eyepieces.

I am woefully under educated on visual stuff because for some reason visual always had a backseat for my telescopes. Last night i had a great time at the eyepiece with no cameras involved so i am looking to complement that with kit that seems missing from my setup. The budget would be somewhere around the price of the hyperion zoom plus or minus a bit since its not an exact number. I realize i could get just 1 great eyepiece, 1 zoom eyepiece or a few decent ones but i have no idea which ones are the best bang for my buck.

 

The assumption that paying more money means the eyepieces will work at a faster f/ratio is a false one.

Eyepieces have to be designed to not yield astigmatism in the outer field at f/4, and very few eyepieces are.

This is one of TeleVue's claims to fame.  I would also add Pentax, Nikon, Leica, and Zeiss to that list.

So far, very few Chinese eyepieces make that list.  The APM XWAs do well at f/4 (and the other brand names for the same eyepieces).

The APM 30mm Ultra Flat field is also a good performer at f/4.

Every eyepiece design has a "critical f/ratio" below which edge of field astigmatism increases.  Explore Scientific has not really aimed their designs at the f/3-f/5 market

except the 92° series, which does work quite well in faster f/ratios.  The Orion LHDs also work fine at faster f/ratios.

I've explored many lower-priced eyepieces in scopes of f/3.45-f/5.18 (all coma corrected).  Baader does not make anything appropriate, though they work OK at f/5.1 (f/4.4with Paracorr).

All the older designs: Ramsden, Huygens, Kellner, Plössl, König, Erfle, Abbe Orthoscopic, Monocentric, should be avoided if you are looking for correction to the edge.

As we get older and glasses earing becomes more important, we look for longer eye reliefs in eyepieces.

Were it not for that fact, I would still be using Ethos eyepieces at each focal length instead of just below 9mm.

We do have more choices, today, in LER eyepieces, just very few of 80° and larger.

3 hours ago, Voyager 3 said:

Hi Louis , 

I too haven't seen a direct comparison but @Don Pensack has tried it and maybe he will chime in . 

I have used the new 8.5mm, 6.5mm, and 4.5mm.

They are not good, with the most internal light scatter I've ever seen in eyepieces.

Additionally, the 4.5mm has serious chromatic aberration.

The older 8.8mm, 6.7mm, and 4.7mm were better eyepieces.

ES does not make "planetary" focal lengths with long eye reliefs.

The post by vlaiv points out a few that might work.

18 hours ago, Louis D said:

Except that @Paz specifically wants a pair for binoviewing, so I'm assuming limited to 1.25" eyepieces.  I would think a pair of 17.5mm Morpheus might be a good fit in that case.  Anyone know the difference in field stop diameters between these two eyepieces?  Regardless, a pair of either would add quite a bit of weight to a BV setup.

17.5mm Morpheus--21.75mm field stop

22mm LVW--24.9mm field stop

22mm Barsta 2"--26.8mm field stop.

24mm Panoptic--27.0mm field stop

Not really a fair comparison, since one is not usable in a binoviewer.

I would caution that many people cannot use the Morpheus eyepieces in binoviewers either because they are 54mm in diameter.

3 minutes ago, F15Rules said:

You and loads of others, Chris!! Join the orderly queue now...😂🤣

Seriously,. wonderful eyepieces, the LVW22mms..

Dave

If you have 2" capability, the 70° Super Wide Angle eyepieces from Barsta are just as good and have more modern coatings, so a little bit brighter.

Available as:

Arcturus Ebony

Omegon Redline

Astromania SWA

Skywatcher SWA

Tecnosky SWA

Telescope Service Expanse ED

OK, I'll bite.

I range from 61x (5.2mm exit pupil) to 493x (0.6mm exit pupil):

My 3 most-used:

14mm (130x), 11mm (166x) and 9mm (203x), all medium powers.

Honorable mentions (used very often):

17.5mm (104x) a low power, and 7mm (261x) a high power in the 12.5".

Less frequently used but do get some focuser time:

22mm (83x), 8mm (228x) and 6mm (304x).  The 6mm is my most used planet eyepiece, but I don't look at planets much (those little balls of light pollution).

Least used except under special circumstances:

30mm (61x), 12.5mm (146x), 4.7mm (388x), 3.7mm (493x)

Some of the eyepieces I consider redundant, but how do you part with an eyepiece you really like, even if it isn't used that much?

CO2 snow would not be used to clean eyepieces, though.

1 hour ago, 12green said:

I'm looking to upgrade my BST Starguiders for Lunar/Planetary observing. Will Vixen SLV 9/6mm give me that in F10 SCT

I may be a contrarian here, but I don't regard that as an "upgrade".

A true upgrade to the Starguiders would be the TeleVue Delites.  They are optically better in nearly every way.  But don't expect miracles.  We're talking maybe 5% better.

22 hours ago, John said:

Yes, I was a little disappointed overall with the Vixen SSW's as I indicated in my report on them.

It was great of FLO to loan me a set - it would have been expensive to have to buy them to do that review and then to sell them on, no doubt at a loss, afterwards.

I heard they were also discontinued by Vixen.

15 hours ago, Voyager 3 said:

Don , please do report us how your eyepieces work in your new fast 16" (Congrats!) . 

I'll be a year older before it sees first light, LOL.

20 hours ago, John said:

Once you have tried an optic that seems a noticeably better performer than other alternatives you have, it's quite difficult to give the others much use I've found 

 

True words.

Though I have found some eyepieces that are bargains in that department.  At f/5.75, my current coma-corrected dob scope is not exceptionally hard on eyepieces.

I have seen eyepieces that function better in that scope than in my f/7 apo refractor.

So if an eyepiece performs well in the dob, that doesn't mean it will perform well in all scopes, especially refractors, with their much more strongly curved focal planes.

I discovered, for instance, that the Baader Morpheus line works exceptionally well in the dob, and in a friend's f/5.18 (f/4.5, coma corrected) dob, and in another friend's f/4.8 (f/4.2 coma corrected) dob.

They performed quite poorly in a friend's f/3.45 dob (f/3 coma corrected).  

The point is that the scope will make a lot of difference in the performance of a lot of different eyepieces.

The good news is that if an eyepiece works well at f/4, it will work well in longer f/ratios.

The bad news is that if an eyepiece works well at f/6, it might not work well at faster f/ratios.

And if you are bothered by field curvature, it's best to keep the radius of curvature longer than 1000mm.  That's easy in a reflector, but hard in a refractor, where, unless the scope has a built-in field flattener,

the radius of curvature is only about 1/3 the focal length on average.  There aren't too many refractors out there with 3000mm focal lengths or longer.

The FC issue is one of the reason I keep the apparent fields to 60-63° in my short FL apo.  And one of the reasons I really regret selling my TeleVue NP101.

Q-Tips and any decent cleaning fluid will do it.

Here is what TeleVue says:

https://www.televue.com/engine/TV3b_page.asp?id=103

In my experience, the exit pupil is better controlled, with less spherical aberration (SAEP) in the SLV line than it was in the LV line.

I think the LV line was also sold by Orion under another name.

With SLVs, you want to either buy new or have the right to return it if used.

Early versions of the SLV had a bright shiny spacer under the eye lens that resulted in massive internal reflection in the eyepiece.

Later versions fixed this problem, apparently.  If you buy used, you may not know which version it is.

Of course, that doesn't matter if taking an eyepiece apart and blackening interior pieces is not intimidating.

53 minutes ago, Louis D said:

I guess I'm in the minority, but I use a Barlow to reach focus, slow down the light cone, and enable using long eye relief, long focal length eyepieces at the higher powers needed for planetary viewing, which is the majority of my binoviewer usage.

But you are probably not using another GPC/OCA with the binoviewers, in which case the Barlow is serving that function.

It will work, sure, but the Barlow probably isn't anywhere near its rated power when doing so.

lens nearest the eye: eye lens

lens nearest the scope: field lens

tube the lenses are in: Upper barrel and lower barrel.  Lower barrel also called the insertion barrel

The field lens in that eyepiece is desperately in need of edge blackening.

Coatings look good.

1 hour ago, Andrew_B said:

If you're using a binoviewer is there any advantage to using a tele extender over a standard Barlow lens or does it not matter?

If you use the Barlow under the Binoviewer, the magnification will not be the stated magnification because of the large distance between the Barlow and the eyepiece.

If you use a telecentric Barlow, like the TeleVue PowerMate, the magnification will barely change at all with distance from the lenses.

If you use the Barlow under the eyepiece (you'd need 2!), then a Barlow would be fine.

But most Glass Path Correctors (OCAs) used with binoviewers already impart a magnification.  Typically, it's 1.6-2.5x.

So a 24mm eyepiece will give you the magnification of a 15-9.6mm focal length.

That's one of the reasons people don't typically use Barlows with binoviewers.

There is a lens tool you can buy on-line (it's cheap)--it's a small suction cup with a bulb attached.

You can attach it to a lens to pick up the lens and place it in the eyepiece barrel without touching it with anything that will leave lint or a mark.

Here is an example:

https://www.amazon.com/SE-EL-VP6-7-Piece-Vacuum-Interchangeable/dp/B00XSDHPEK/ref=asc_df_B00XSDHPEK/?tag=hyprod-20&linkCode=df0&hvadid=309811990469&hvpos=&hvnetw=g&hvrand=15807450112636400556&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9030974&hvtargid=pla-570530083398&psc=1

1 hour ago, PeterC65 said:

I've gone for the Explore Scientific 68 degree 24mm. I picked up the last one they had at the Widescreen Centre (the last one anyone seemed to have). Since the recent Baader price hike, the Hyperion is now £133 which is almost as much as the better rated ES.

If you were comparing to the Hyperion 24mm, you got the better of the 2.

In the US, the Baader is now $169, while the ES is $269.99, so there is a much bigger difference in price.

On 14/11/2021 at 16:55, Louis D said:

Going to a 2" visual back and 40mm SWA eyepiece easily overcomes the increase in focal length to get to a wider field of view with a Synta 127 Mak with about 40% vignetting near the edge.

Louis,

I notice the right side of each image is in better focus than the left edge.  Is your scope's objective tilted relative to the target?

7 hours ago, PeterC65 said:

For maximum sky coverage (TFoV) I went for the 40mm Celestron Omni because of the larger exit pupil size compared with shorter FL EPs. It gives me a 3.4mm exit pupil on my Skymax 127, so still not that large. Observing M42 recently (and for the first time) with an Astronomik UHC filter, the view though the 40mm Celestron Omni showed noticeably better contrast than that through my Baader Zoom at 24mm so going for the larger exit pupil size seems to be justified.

With the Skymax 127 being F11.8, the best TFoV I can get (with 1.25" EPs) is just under 1.1°. Initially I did consider upgrading to a 2" diagonal and EPs but I've since decided to accept the limitations of the scope when it comes to TFoV and stick with 1.25".

I only have two EPs at the moment, the 40mm Celestron Omni and the Baader Zoom, so don't have much to compare. This post started with a discussion about shorter FL EPs compared to the Zoom, and I now have two Baader Classic Orthos (6mm and 10mm) on order to provide a comparison at the high magnification end.

I've also been wondering about the low magnification end ...

My understanding is that a 68° EP FoV is optimal for the human eye. Any wider and you can only see part of the presented image and so have to look around within the wider image presented by the EP. Any narrower and the presented image is smaller than what your eye can take in so you see a circular image surrounded by black. I can't say I've really experienced either of these things but then I'm new to all this.

If a 68° EP FoV is optimal, and given I'm sticking with 1.25", then the TFoV will max out at a FL of 24mm. So I'm wondering whether a 24mm 68° EP might be a useful addition?

While the Baader Zoom does 24mm, the EP FoV is then 42° so the TFoV is not maximal. I'm thinking that a 24mm 68° EP will give me the maximum magnification possible whilst showing me the maximum amount of sky and using the maximum amount of retina. So the same amount of sky as the 40mm Celestron Omni but more magnified and therefore bigger by virtue of using more retina.

The downside seems to be the smaller exit pupil size with a 24mm 68° EP. It would be 2.03mm I believe rather than the 3.4mm I get with the 40mm Celestron Omni and so the image may be darker, particularly when it's been filtered.

As ever, I will only know when I can compare the two side by side!

 

Some notes:

1) the Sky & Telescope test of the 127mm showed the actual clear aperture is about 121mm because lateral rays from the corrector diverge enough to miss the primary (this kind of Gregory-Maksutov should have had a primary mirror about a half inch larger to field all the lateral rays from the corrector), and the measured focal length at the back with the provided 1.25" diagonal and provided visual back was 1540mm.  That makes the as-delivered scope about f/12.73

2) the focal length grows on this scope with increased back focus distance.  It grows by approximately 3.75mm for every mm of additional back length.  So adding a 2" diagonal and visual back is probably going to add at least 80mm to the back focus distance (maybe more), so  that means a focal length of about 1840mm, for f/15.2

3) Hence, a 40mm eyepiece would yield about a 2.6-2.7mm exit pupil.

The way to increase the exit pupil and field size at low power is to use as short a visual back as possible and use a 1.25" prism diagonal  AND use a 40mm 1.25" eyepiece.  You can get the focal length as short as 1500mm that way (f/12.4), and get both a lower low power and a larger exit pupil.