47 replies to this topic

[oshokry]

Hi all,

Thanks for accepting me here. This is my first post with one simple question:

- Is the "Meade Series 4000 Super Plössl 40mm (1.25")" truly a 52 degrees FOV?

I see that comparable 40mm Plossls are all 43 degrees FOV but surprisingly Mead's web site states that their 40mm Plossl does have 52 degrees FOV:

http://store.meade.c...-40mm-1-25.html

Is this a mistake? Did anybody try this particular eyepiece?

Thanks in advance - oshokry

[youngamateur42]

It sounds like a mistake, the field stop will restrict what would be a 52 degree to around 40. I believe so anyway. Someone can correct me if necessary. On a side note, a 32mm Plossl will have the full 52* AFOV and will provide max true field in 1.25" scopes.

[jrbarnett]

"Is the "Meade Series 4000 Super Plössl 40mm (1.25")" truly a 52 degrees FOV?"

Nope.

http://www.adorama.com/MD40SP.html

"Meade 40mm Series 4000 1.25" Super Plossl Eyepiece with 44 Degree Field of View."

44 degree AFOV.

- Jim

[oshokry]

Thanks for your response. This cleared my doubt. My purpose here is to get the widest TFOV in my 90mm Maksutov which accepts only 1.25 inch eyepieces.

- I got the Mead 32mm Plossl already but I'm not happy with it after the first try tonight. What is the best 32mm 1.25 inch Plossl?

- In general, any suggestion for a 1.25 inch eyepiece that offers the widest true FOV in my telescope?

[CosmoSat]

What is it that u didnt like about the 32mm plossl u hve?

[Sarkikos]

Orion Ultrascopic 35mm or one of its clones, if you can find one. Sharp field stop. Five elements in three groups, FMC, edge blackened, neutral tone, 49 degree AFOV, 25mm eye relief, 6.9 oz. Parfocal with Sterling Plossls. Provides a little more TFOV than its 28.9mm field stop alone should allow, at the cost of slight vignetting at edge of field.

Mike

[JustaBoy]

Hi Mike,

Speaking of clones brings up the question: Which came first, the Orion Ultrascopic or the Celestron Ultima?

My bet is on Celestron.

[Sarkikos]

I'm sure the answer is somewhere here on CN. Probably in Bill Paolini's book, as well. It just isn't something I bother to keep in my memory.

I was using the term "clone" loosely. I didn't mean to imply that the Orion Ultrascopic came first.

Mike

[Sarkikos]

This thread has some interesting info on the Ultrascopic 35mm and its clones ... siblings, cousins, fraternal twins, fellow travelers, you pick the term.

Masuyama 35mm ? Worth it?

Mike

[oshokry]

Hi CosmoSat,

When a planet or a bright start is just outside the FOV of my Mead 32mm Plossl, a "ring of noisy light" appears extending from the edge of field inwards. Excuse my loosely term here, I'm sure there is a more proper name for that.

[jrbarnett]

Well, both of those eyepieces (40mm 46-deg and 32mm 52-deg) will have a similar TFOV. Simple eyepieces, like Plossls also have scaling eye relief. The longer the focal length of the eyepiece, the more eye relief the eyepiece provides. Eye relief up to about 25mm is a positive. Over that, it starts to move towards a negative as eye placement becomes tricky and blackouts occur when placement is not correct.

You could go the other way, too, and achieve a similar TFOV, albeit at higher magnification, by looking at 24-25mm wide fields (65-72 degree AFOVs). The "king" of such eyepieces is the 24mm Panoptic. Not cheap, but awful purty. A used 22mm Vixen LVW would be awesome too in this role; around $140 used typically).

Moving to the ultra-wide class (80-84 degree AFOV), a 16mm Nagler Type 5 would come close to but a bit smaller than the same TFOV. Also an expensive option.

- Jim

[SteveG]

I had and really liked the Ultrascopic 30mm (also Celestron, Parks, etc). It has the 52 deg afov, but a little more power, nice flat field at f8 and above, and can be purchased cheap ($70-80).

If the scope had a shorter focal length I still prefer the 24mm 68 deg widefields, such as Panoptic or ES.

[oshokry]

Is the Mead Plossl 32mm a good eyepiece? I don't have much experience to judge myself but I will keep it if you guys tell me it's OK. I know it is a simple Plossl so I do not expect perfection here. Good enough is good enough for me.

I requested a return and it is approved. Shall I keep it instead?

[jrbarnett]

Some Meade 32mm Plossls are good, and some are defective. I've read reports, for example, of recent vintage Meade Plossls missing elements.

You might have a bad'un. One meeting the design spec, though, should be about as good as any other similarly priced 32mm Plossl.

- Jim

[Starman1]

Hi Mike,

Speaking of clones brings up the question: Which came first, the Orion Ultrascopic or the Celestron Ultima?

My bet is on Celestron.

Whether Celestron, Orion, Antares, Omcon, Parks, Baader, Tuthill, etc., they all came from the same manufacturer.

[Starman1]

Hi all,

Thanks for accepting me here. This is my first post with one simple question:

- Is the "Meade Series 4000 Super Plössl 40mm (1.25")" truly a 52 degrees FOV?

I see that comparable 40mm Plossls are all 43 degrees FOV but surprisingly Mead's web site states that their 40mm Plossl does have 52 degrees FOV:

http://store.meade.c...-40mm-1-25.html

Is this a mistake? Did anybody try this particular eyepiece?

Thanks in advance - oshokry

Without abnormally high distortion not found in the Plossl/Symmetrical design,
40mm maxes out at 43 degrees.
32mm maxes out at 50 degrees
Both the above assume a 27mm field stop diameter.
A slightly larger true field can be obtained with a field stop larger than 27mm, but this requires putting the field stop above the barrel.
Examples:
35mm Orion Ultrascopic/Celestron Ultima with a 29mm field stop
24mm Baader Hyperion with a 28.5mm field stop.

You should look at apparent field figures as advertising fluff. The truth is in the field stop diameters.

[Starman1]

To figure the true field with field stop figures, the formula is:
True field in degrees = (field stop of eyepiece/focal length of scope) * 57.3

[CosmoSat]

Hi CosmoSat,

When a planet or a bright start is just outside the FOV of my Mead 32mm Plossl, a "ring of noisy light" appears extending from the edge of field inwards. Excuse my loosely term here, I'm sure there is a more proper name for that.

Oh ok.. I too had seen a similar effect using an 8.8mm meade series 5000 uwa. Not sure what its called or what causes that either.

[JustaBoy]

The product of the focal length and the apparent field of a 32mm 50° eyepiece is 32x50 = 1600.

40x43° = 1720.

Notice anything strange here since both eyepieces have the same 27mm field stop?

Somehow this Myth about a 43° apparent got started, and we see it to this day.

The 40mm TV Plossl is listed as being 43° apparent. - Is there a lot more distortion relative to the 32mm TV that could account for the stretch of the AFOV? - Both use the Same field stop.

Here's what I say, and I'm sure is only an approximation:

32mm = 50°

40mm = 40°

The 52° apparent is just some Marketing BS started by Meade for their "Super Plossls", along with their 67° and 84° fields when they first challenged TV with their 50° - 65° - 82° Plossls, Widefields, and Naglers. - Meade had 2 more degrees on TV every step of the way - Yeah Right!

This being before the Internet, they could get away with it. - Now we know that what Meade stated was just not true.

[Starman1]

Chuck,
You're correct, as I see it.
With the exact same percentage of distortion that allows a 32mm Plossl to get to 50 degrees, a 40mm Plossl should get to 40.8 degrees, not 43.
It is possible that the 40mm does have more distortion, but it is more likely that the 43 degree figure is "kinda loose".
It is also equally possible that 32mm Plossls don't quite get to 50 degrees, either.
Star timing could determine the truth.
But if we use the math to derive the apparent field, then a 27mm field stop in a 40 degree eyepiece would yield a true field of 2.865 degrees in my NP101 and, back-calculating, yields 38.7 degrees apparent field (3.8% distortion) in the 40mm, and 48.3 degrees in the 32mm (5.6% distortion).

I think I agree with you that 40 degrees seems more likely than 43 degrees.

P.S. My Meade Series 4000 24.5mm SWA Japanese-made 67 degree field eyepiece of yesteryear, by star timing, had a 61.8 degree apparent field.
Advertising hype, indeed.

[Jon Isaacs]

Somehow this Myth about a 43° apparent got started, and we see it to this day.

The 40mm TV Plossl is listed as being 43° apparent. - Is there a lot more distortion relative to the 32mm TV that could account for the stretch of the AFOV? - Both use the Same field stop.

Here's what I say, and I'm sure is only an approximation:

32mm = 50°

40mm = 40°

Chuck:

The way I look at it: The "myth" is that there is a direct relationship between the AFoV and the TFoV.

Both are measurable and depending on the amount and type of distortion, there is some approximate relationship. My gut feeling is that the major sources of error are field distortion and advertising distortion.

Jon

[JustaBoy]

Please forgive, Guys...


As much as I like some of Meade's products (14mm Series 4000 UWA being one, and curiously I don't even like field angles that great) sometimes I just gotta love Meade, but Hate what they do!

I stand for Truth, Justice and The American Way!

[jrbarnett]

"(a) Truth, (b) Justice and © The American Way!"

One of these things is not like the others. One of these things doesn't belong. Can you guess which one before I finish my song?

Not beating up on Lady Liberty, mind you, but we, like every nation before us, and every nation now in existence or that one day will be, have, have had and will continue to have our share of inequities, injustices and deceptions. We're only human, after all. © is akin to "marketing hype" to any student of history.

- Jim

[EuropaWill]

My GSO 40 and 32 Plossls are probably 43-44 and 49-50 degrees respectively. This is counter to their claimed 45 and 52 degree AFOV's.

Marketing departments take way too much liberty. There should be a truth in advertising penalty each time a company does this.

[JustaBoy]

Jim,

You make too much of it...

It's just that in my senility I think I'm Superman!