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Science Forum Index » Astro - Amateur Forum » Meade's new triplet 80APO
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| Rich |
 Posted: Mon Feb 05, 2007 2:02 pm |
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Guest
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On Feb 5, 4:59 am, Protagonist <szak...@comcast.net> wrote:
Quote: Rich wrote:
On Feb 4, 2:18 pm, Protagonist <szak...@comcast.net> wrote:
Any one using Meade's new 80mm Triplet APO?
Any good?https://www.astromart.com/articles/article.asp?article_id=534
I'm considering to buy it.
Use to own a Pronto few years ago and I miss it.
Pronto's ED doublet was OK, but showed lot of falls color on Mars.
I have a 4" Mak since, but it's not a retractor, no wide field etc...
Also, have a C102F, but it's too bulky for daytime use or travel.
JS
I think you are liable to get a more accurate objective in these
inexpensive ED/apos if you stick with 2 elements instead of three.
Nowadays, the gains in colour control going from FPL-53 doublets to
triplets are minor, but the chances of getting three good elements
instead of just two are not as good. A test I read some time ago
implied that colour control was better in a 3 element Williams Optic
scope but that star images were more accurate in a 2 element ED
units. It's unlikely either will be "bad" but it does question
whether spending the extra for a triplet is really worth it.
Time will tell!
Ginni is out of the bottle again as better color corrected APOs at lower
cost are hitting the market. Triplets were all ways pricey and made by
top brand manufacturers in the past.
For cost of $590 getting a triplet fast 80mm APO is very tempting.
I remember 5-6 years ago I was looking at APM-s 80 mm triplet APO optics
set, cost some $1500 and that's only the lens set in the cell.
JS
I bought a triplet optics set from APM when it was first announced.
The price was $695.00.
I think it doubled within a month. But in reality, the finest small
scope I've used was Zeiss's APQ 100mm.
Next in line, Tak's FC-100. There have been some pretty bad apo
"misfires" such as Vernonscope's last 80mm, not the Master Birder
which was just an achro. TeleVue's Oracle was very good for it's day,
it was replaced by the disappointing Pronto achro. |
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| micky |
| Posted: Mon Feb 05, 2007 2:10 pm |
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"Protagonist" <szaki10@comcast.net> wrote in message
news:euWdndSTFtljYlvYnZ2dnUVZ_veinZ2d@comcast.com...
Quote: Rich wrote:
On Feb 4, 2:18 pm, Protagonist <szak...@comcast.net> wrote:
Any one using Meade's new 80mm Triplet APO?
Any good?https://www.astromart.com/articles/article.asp?article_id=534
I'm considering to buy it.
Use to own a Pronto few years ago and I miss it.
Pronto's ED doublet was OK, but showed lot of falls color on Mars.
I have a 4" Mak since, but it's not a retractor, no wide field etc...
Also, have a C102F, but it's too bulky for daytime use or travel.
JS
I think you are liable to get a more accurate objective in these
inexpensive ED/apos if you stick with 2 elements instead of three.
Nowadays, the gains in colour control going from FPL-53 doublets to
triplets are minor, but the chances of getting three good elements
instead of just two are not as good. A test I read some time ago
implied that colour control was better in a 3 element Williams Optic
scope but that star images were more accurate in a 2 element ED
units. It's unlikely either will be "bad" but it does question
whether spending the extra for a triplet is really worth it.
Time will tell!
Ginni is out of the bottle again as better color corrected APOs at lower
cost are hitting the market. Triplets were all ways pricey and made by top
brand manufacturers in the past.
For cost of $590 getting a triplet fast 80mm APO is very tempting.
I remember 5-6 years ago I was looking at APM-s 80 mm triplet APO optics
set, cost some $1500 and that's only the lens set in the cell.
JS
Glass is not glass. AP hand picks their materials from the melt. |
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| Rich |
| Posted: Mon Feb 05, 2007 6:29 pm |
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Guest
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On Feb 5, 1:10 pm, "micky" <m...@mouse.net> wrote:
Quote: "Protagonist" <szak...@comcast.net> wrote in message
news:euWdndSTFtljYlvYnZ2dnUVZ_veinZ2d@comcast.com...
Rich wrote:
On Feb 4, 2:18 pm, Protagonist <szak...@comcast.net> wrote:
Any one using Meade's new 80mm Triplet APO?
Any good?https://www.astromart.com/articles/article.asp?article_id=534
I'm considering to buy it.
Use to own a Pronto few years ago and I miss it.
Pronto's ED doublet was OK, but showed lot of falls color on Mars.
I have a 4" Mak since, but it's not a retractor, no wide field etc...
Also, have a C102F, but it's too bulky for daytime use or travel.
JS
I think you are liable to get a more accurate objective in these
inexpensive ED/apos if you stick with 2 elements instead of three.
Nowadays, the gains in colour control going from FPL-53 doublets to
triplets are minor, but the chances of getting three good elements
instead of just two are not as good. A test I read some time ago
implied that colour control was better in a 3 element Williams Optic
scope but that star images were more accurate in a 2 element ED
units. It's unlikely either will be "bad" but it does question
whether spending the extra for a triplet is really worth it.
Time will tell!
Ginni is out of the bottle again as better color corrected APOs at lower
cost are hitting the market. Triplets were all ways pricey and made by top
brand manufacturers in the past.
For cost of $590 getting a triplet fast 80mm APO is very tempting.
I remember 5-6 years ago I was looking at APM-s 80 mm triplet APO optics
set, cost some $1500 and that's only the lens set in the cell.
JS
Glass is not glass. AP hand picks their materials from the melt.
Boy, must that be painful.  |
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| Ed T |
| Posted: Mon Feb 05, 2007 8:07 pm |
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Guest
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"Protagonist" <szaki10@comcast.net> wrote in message
news:K-KdnXFTh41INVvYnZ2dnUVZ_vyunZ2d@comcast.com...
Quote: Ed T wrote:
Fluorite optics here, ED doublet there, no matter what, at f/6-F/7 a
doublet will show some color on bright objects.
My C102F is a Fluorite doublet, no color on any objects in focus, but
than
it is a f/9 retractor.
Color correction is a function of aperture as well as focal length. An
80mm
f7 ED doublet might meet or exceed the color correction of an 100 mm f9
ED
doublet.
Ed T.
TV Pronto is an ED doublet, on high powers it does show color on bright
objects when I used it day time taking pictures.
But than, it's also the function of magnification.
A standard chromate, may not show color at low powers and lot of people
happy with with performance.
Observing Mars with a small scope 3-4", needs high power and most fast /f
doublets show color.
JS
The Pronto is an achromat. The glass may be low dispersion but it has
little no color correction beyond that of a standard achromat in that
scope. Try an FPL-53 or fluorite doublet and you'll see a marked
improvement.
Ed T |
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| Ed T |
| Posted: Mon Feb 05, 2007 8:11 pm |
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"micky" <micky@mouse.net> wrote in message
news:uqKxh.32207$Oa.21491@edtnps82...
Quote:
Glass is not glass. AP hand picks their materials from the melt.
It would be more accurate to say AP compensates for the variabilty of the
glass they buy.
Ed T. |
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| Howard Lester |
| Posted: Mon Feb 05, 2007 9:28 pm |
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Guest
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"Ed T" wrote
Quote: "micky" wrote
Glass is not glass. AP hand picks their materials from the melt.
It would be more accurate to say AP compensates for the variabilty of the
glass they buy.
Ed T.
It is *possible* they could hand pick from the melt, as we did for the glass
used to make the MMT 6.5-m mirror blank (as well as all the spun-cast mirror
blanks). Roland got/gets at least some of his glass from the same
manufacturer that provided ours.
Howard Lester
MMT Observatory |
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| R. Kantrowitz |
| Posted: Mon Feb 05, 2007 9:40 pm |
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Right or wrong, this is how I would try to prove Ed's statement.
The formula for figuring out the color-free focal length of an achromat is
usually given as 3 to 5 times the diameter squared in inches (45 inches for
a color-free 3" achromat). If one generalizes this to other lens
formulations one gets the following formula:
F=k * D^2 where F is the focal length, k is the 3-5 times constant and D is
the lens diameter.
If we define R as the focal ratio, then R=F/D and F=D*R
To solve for the relative color correction of two compound lenses D1 & D2
with the same lens formulations try this:
k * D1^2/k* D2^2 = F1/F2
Since R=F/D, F1/F2 becomes D1*R1/D2*R2 or D1/D2 * R1/R2
Dividing k * D1^2/ k * D2^2 by D1/D2 ==> k * D1/k * D2 = R1/R2
or D1/D2 = R1/R2
Substituting the 80mm, 100mm and f/7 ratio ==> 80/100 = 7/R2
Then R2 = 100/80 * 7 ==> 8.75 hence a 100mm lens would need an f-ratio of
about 8.75 to have the equivalent color correction of an 80mm f/7 made with
the same glasses.
whew --
Ralph K.
P.S. My W/O F6.9 80mm FPL-53 lens has no noticeable color problems on
Sirius or the Moon. I'm still in shock, but very happy about the upgrade.
However, I did upgrade my 1986 4" Apo with one of the more recent AP rack
and pinion focusers w/feathertouch.. The quality and sturdiness of that
focuser is far beyond Crayfords - but quite weighty.
"Ed T" <reply@group.thx> wrote in message
news:C7xxh.19205$yx6.12249@newsread2.news.pas.earthlink.net...
Quote: Fluorite optics here, ED doublet there, no matter what, at f/6-F/7 a
doublet will show some color on bright objects.
My C102F is a Fluorite doublet, no color on any objects in focus, but
than
it is a f/9 retractor.
Color correction is a function of aperture as well as focal length. An
80mm
f7 ED doublet might meet or exceed the color correction of an 100 mm f9 ED
doublet.
Ed T. |
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| micky |
| Posted: Tue Feb 06, 2007 12:30 am |
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Guest
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"Howard Lester" <heylester@dakotacom.net> wrote in message
news:12sfmdteijbl8b0@corp.supernews.com...
Quote: "Ed T" wrote
"micky" wrote
Glass is not glass. AP hand picks their materials from the melt.
It would be more accurate to say AP compensates for the variabilty of the
glass they buy.
Ed T.
It is *possible* they could hand pick from the melt, as we did for the
glass used to make the MMT 6.5-m mirror blank (as well as all the
spun-cast mirror blanks). Roland got/gets at least some of his glass from
the same manufacturer that provided ours.
Howard Lester
MMT Observatory
Now how they go about this I haven't a clue. The whole industry of
making ED glass or whatever and who supplies who is a mystery. |
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| Protagonist |
| Posted: Tue Feb 06, 2007 3:50 am |
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Guest
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micky wrote:
Quote: "Howard Lester" <heylester@dakotacom.net> wrote in message
news:12sfmdteijbl8b0@corp.supernews.com...
"Ed T" wrote
"micky" wrote
Glass is not glass. AP hand picks their materials from the melt.
It would be more accurate to say AP compensates for the variabilty of the
glass they buy.
Ed T.
It is *possible* they could hand pick from the melt, as we did for the
glass used to make the MMT 6.5-m mirror blank (as well as all the
spun-cast mirror blanks). Roland got/gets at least some of his glass from
the same manufacturer that provided ours.
Howard Lester
MMT Observatory
Now how they go about this I haven't a clue. The whole industry of
making ED glass or whatever and who supplies who is a mystery.
ED is like the Cabbage-patch doll industry!
Keep the price high by creating shortages and mystery.
One can buy a 4" achromatic telescope for $200-$300 or lens set for lot
less but now replacing one of the lens element to ED glass, price of the
scope or the lens set goes up 10x. Gee!!!
I heard Fluoride lenses are brittle and during polishing 40% gets
damaged, would make sense for the high price.
JS |
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