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Old Wednesday 27th October 2010, 21:33   #1
jimbcac
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Pentax PF80 looooong distance recomendations

I have a Pentax PF80eda with the standard
24-80zoom. Problem is I want MORE. More distance for
land viewing. I live in the mountains. Some REALLY pretty ones
are about 2-8 miles (as the crow files) from me. I bought a
Konus 30-90x70 before I knew any better. Thing is that while
the optics are really awful I LOVE that 90xzoom. So now I have
the PF80..at the top with the 8-24 I guess I am getting a 70ish
power application here. And I set up the Konus right next to the
pentax and zoomed in on the same rock about 3 miles away. The
Konus gets me "nearer" but the Pentax is a lot clearer.. So what
I want here I 'clear and near'.... Can this be done with the Pentax PF80.
I would consider trading up for a PF100. Again this is strictly for
land viewing (and maybe the occasional peep at the moon and planets).
Would an XW 5-7 lens do it, or maybe the PF 6.5-19.5 zoom...Am kinda
new at the techie end of optics here.

Thanks
jim in gold bar
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Old Wednesday 27th October 2010, 22:45   #2
RJM
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I doubt your 80ED Pentax is very good beyond 80x. Buy a telescope like a Celestron 5" or 6" SCT. You'll need more aperture to keep a larger exit pupil >1mm. The eyepiece you have now is a perfect match. With these you should be able to get up to ~100x before heat shimmer destroys the image.

These scopes are shorter/lighter than a comparable refractor so need less mount too and are fairly cheap at ~$500. You can also use it with a binoviewer so can use both eyes for better acuity.
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Old Wednesday 27th October 2010, 23:11   #3
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I have seen the Celestron 6" SCT scopes go for or advertised for $280 + shipping with just about everything you need including eyepiece on Astromart.
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Old Wednesday 27th October 2010, 23:46   #4
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Hi Jim,

Welcome to the forum.

With your 8-24mm zoom you are getting 20x-60x magnification.

The focal length of the PF-80ED is 500mm, so if you divide that by the eyepiece focal length you will get the resulting magnification.

The 6.5-19.5mm XF zoom would yield 26x-78x, but would give you less field of view, and has less eye relief than the 8-24mm. I would not consider this eyepiece an upgrade.

The XW7 would give you 71x and as much field of view as the 8-24mm zoom has at 60x.

I have a Televue 2.5x Powermate that is similar to a barlow. It yields 89x with a 14mm eyepiece and 125x with a 10mm eyepiece. This is pushing the limits with the PF-80ED and requires the right atmospheric conditions to be usable, especially at the ranges that you are talking about.

Mike
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Old Thursday 28th October 2010, 08:31   #5
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There is the Celestron Regal F-ED with 100mm lens, and I think that admit 1.25" astronomical eyepiece...
Al
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Old Thursday 28th October 2010, 08:48   #6
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`I have a Televue 2.5x Powermate that is similar to a barlow.`

i doubt that would work in the pentax scope??
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Old Thursday 28th October 2010, 09:45   #7
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If you are not bothered by reverse image and keep the scope in about the same area and don't need WP. I would get an Orion 100ED , I have a 80ED and there is quite a bit of difference between the 80 and the 100. You have to have a good tripod though. This is the 80ED on the tripod
http://www.birdforum.net/attachment....5&d=1275354058

Last edited by mooreorless : Thursday 28th October 2010 at 09:59. Reason: add picture
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Old Thursday 28th October 2010, 12:51   #8
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Quote:
Originally Posted by woodhornbirder View Post
i doubt that would work in the pentax scope??
No need to doubt, it works just fine.

Mike
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Old Thursday 28th October 2010, 17:47   #9
jimbcac
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looooong pentax PF80

Well guys thanks....
I guess I shouldha done some more reading on this forum before blowing
big bucks on the PF80. However I have been looking at medium
size Astro telescopes. HOWEVER in my own defense the mantra
seemed to be "for land use a spotting scope- for space use a telescope"
guess there are exceptions to every rule.
Anyway I guess I would STILL like to get the absolute best I can
out of the PF80 SOOOOOOO the question still sort of remains
would a single lens in say the 5-8mm range get the most "clear
and near" that this scope is will do. I want to try the best I can do
with what I have (well I might have to buy another lens :)
before heading off into telescope land..

Thanks to you all this is great..

jim in gold bar
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Old Thursday 28th October 2010, 17:57   #10
jimbcac
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For instance

I have read very good things about the Baader Hyperion eyepieces.
Albeit they are not as hardy as the pentax. however they are a LOT
cheaper. So would the Baader 8ish eyepiece... Or am I better off
just putting the PF80 on ebay and buying a telescope... and
yes things being upside down WOULD bother me...

Thanks again
jim in gold bar
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Old Thursday 28th October 2010, 21:12   #11
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Hi Jim, I forgot to say welcome to Birdforum. That is reversed left and right not upside down with refractors and CAT scopes. I have Baader Hyperion 5mm eyepiece and like it a lot.
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Old Friday 29th October 2010, 01:43   #12
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No harm in trying but don't get your hopes up. The hurdles to overcome will be vibration, the sub-1mm exit pupil at mags over 80x and the atmospheric turbulence at that distance. You will need a sturdy vibration isolated mount to minimize the shakes.
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Old Friday 29th October 2010, 20:05   #13
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Jim, Here is a link that might help some.
http://www.cloudynights.com/ubbarchi...l/fpart/1/vc/1
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Old Friday 29th October 2010, 20:57   #14
jimbcac
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Reading a car license plate at 50 miles

Steve..
That was a very interesting and long thread.....However
after plowing through it I realize that what I want to do is harder then
I thought it would be. After reading bird viewing forums about looking at
duck bills at 7000 yards, I figured what I wanted would be a snap.

I am in a valley. I am looking up at mountains, however learning about
heat haze and atmospheric stuff....Well gosh.
The answer I wanted was to purchase X brand and model of
scope with Y eyepiece and shaaaazzzam you got it.

The answer I got was that it does not work out quite that easy.
So guess I will take the Ol PF80 out on the back deck and watch
Wallace falls shoot over the mountain for a while..

What I WANT is to see a large boulder that I will guess is about
15' tall and about 3-4 miles away. It was very cool watching the snow
melt off of it the other day. however I want to see the MOSS GROWING
on the rock....So I guess it is back to the drawing board, because
the answer is...

that there is not a simple answer here,
only; as with most things -
some sort of compromise that one must find the best of, and
make work, as best it will...as best as one can.

Thanks folks
jim in gold bar
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Old Friday 29th October 2010, 22:07   #15
jimbcac
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views from my deck

Today while looking at my rock I saw three mountain sheep - which
I never understood why they are called that. Mountain goats look
more like sheep,,and mountain sheep..well anyway While waiting
for those pesky clouds to roll away I moved my scope a bit down
the side of the mountain. They used to mine copper/gold/silver
up here, and you can make out the scree from old mine shafts. So
from time to time I check it out. Sometimes - now that gold is $1,300
per ounce - and it is worth while poking around these old mines - I see
folks up there. But today no folks, just sheep. White ones.
I used
to just sit on my deck. Having a powerful optic piece has really opened
up my world. I do not worry about watching birds. My wife feeds em.
They come to me. Wife watched far too many Disney movies as a child,
butterflys land on her head....sigh...And those mice sewing sewing sewing, really annoying....
The Eagles, will be here in December.
We had a pair would come every day to a hemlock tree about 100' from
the house..this year I GOT em...Those birds will be so gosh darn
observed that they might just turn pink...observed from a discrete distance of course....:)
The bear are found in my front yard, the deer in the woods on the property,
rabbits, raccoons, squirrels, owls,..all can now fall, under the cleaver
of advanced optics..........who needs to hunt, when you can just look
at em???????Maybe even take pictures!!!!!!!!

jim in gold bar (well actually about 3 miles north east of town)
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Old Friday 29th October 2010, 22:17   #16
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Hi Jim, Sorry that thread was so long. I thought it would be good for you to read that one. I have a lookout on top of a small mountain that I watch and it is 2.8 miles away. When it is clear out I have used the Orion 100ED to look up there. I was able to be able to identify a person at 72x, well I could of if I had know them. There is also a high tension power line 5 miles away on the same mountain that I have watched some and I have taken pictures of these places. So I guess you and I both are sort of alike.
BTW I measured these distances with Google Earth
Jim I have some pictures I took if you are interested, these are prime focus with the Orion 100ED and a Pentax 6Mp DSLR. PM me I will send them to your home email. If you don't want to that is ok.

Quote:
Originally Posted by jimbcac View Post
Steve..
That was a very interesting and long thread.....However
after plowing through it I realize that what I want to do is harder then
I thought it would be. After reading bird viewing forums about looking at
duck bills at 7000 yards, I figured what I wanted would be a snap.

I am in a valley. I am looking up at mountains, however learning about
heat haze and atmospheric stuff....Well gosh.
The answer I wanted was to purchase X brand and model of
scope with Y eyepiece and shaaaazzzam you got it.

The answer I got was that it does not work out quite that easy.
So guess I will take the Ol PF80 out on the back deck and watch
Wallace falls shoot over the mountain for a while..

What I WANT is to see a large boulder that I will guess is about
15' tall and about 3-4 miles away. It was very cool watching the snow
melt off of it the other day. however I want to see the MOSS GROWING
on the rock....So I guess it is back to the drawing board, because
the answer is...

that there is not a simple answer here,
only; as with most things -
some sort of compromise that one must find the best of, and
make work, as best it will...as best as one can.

Thanks folks
jim in gold bar
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Old Sunday 31st October 2010, 12:23   #17
DRodrigues
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Jim,
Have a look at http://www.pt-ducks.com/cr-telescopes.htm
Some of your questions have answer there.
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Old Monday 1st November 2010, 01:17   #18
mooreorless
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Orion 100ED

Pictures of Orion 100ED on Bogen 501head & Bogen 3236 mount
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Old Tuesday 10th May 2016, 17:38   #19
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Quote:
Originally Posted by jmepler View Post
No need to doubt, it works just fine.

Mike
Does it work in the PF80ED-A without any of the tweaks required for other barlows, or are those tweaks always necessary?

Thanks!
Pedro
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Old Wednesday 11th May 2016, 20:58   #20
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I have the straight version of the scope, but it worked fine for me with no modifications.
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Old Wednesday 14th September 2016, 02:35   #21
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In case it helps anyone, I've tested the Powermate 2.5x with the PF80ED-A and it works just fine!

The chrome barrel doesn't go all the way in, but still I'm able to reach focus in all focal lengths using the Powermate with the smc PENTAX Zoom XL 8-24mm.
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Old Wednesday 14th September 2016, 09:11   #22
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Hi,

thanks for sharing your results. Could you comment on what is the usable maximum magnification of this combination - or is it good up to 160x (I would be impressed).

Joachim
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Old Thursday 15th September 2016, 17:37   #23
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Well, light loss is noticeable, but I'm still surprised that it works!

When the zoom is at 8mm with the powermate it gives around 161x, and you can see eye-floaters, but it's not a surprise since the exit pupil in that case is less than 0.5mm. As it can be read in Televue's eye piece calculator:

Quote:
An exit pupil greater than 7.5-mm may be too big for a telescope with central obstruction (most reflectors). Exit pupils of less than 0.4-mm are small enough to allow eye-floaters to interfere and also indicates an eyepiece with too high a power for useful viewing.
I find that when setting the zoom to higher values than 8mm (9, 10, 12) the scope is pretty usable, but I guess it depends on many factors (the individual unit, atmospheric conditions, eyesight, etc), so I can't recommend with 100% confidence to buy the powermate.

For instance, the other day I looked at the moon and was surprised to see how good it looked even at 161x!
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Old Thursday 15th September 2016, 21:13   #24
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Hi,

thanks for the impressions - it seems you have got a very nice example - congratulations.
And yes, you're right - that does not means tha another example will perform the same - not even the same one with different seeing or another observer (like some person with exceptional eyesight who gets beyond the resolution limit of the 80mm objective at that magnification).

Joachim
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Old Monday 21st November 2016, 14:56   #25
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Regarding reading number plates at 5 miles.
This type of observation was easy with my 120mm refractor, but at 3 a.m. on good nights.
A clock tower clock about 5 ft diameter. But the clock was lit from behind.
The minute ticks were maybe an inch wide and 2 inches high or smaller.

My 6 inch Maksutov might have also done this on really steady days in September, but not in England.
Islands 5 mile distance were amazingly clear. There seemed to be no haze reduction at all at sea level. The air in Britain is too polluted for this.

The 70 inch aperture Big eye satellites were able to resolve better than 4 inches at 200 to 250 miles. Maybe using adaptive optics.
A 6 inch Maksutov type optics could lock on the specular reflection from a car door handle at 90 miles so I was told by someone involved with this type of optics.

Aircraft at 80,000 ft can photograph golf balls on the ground.

P.S.
The magnification on the 120mm f/8.3 refractor was 250x. 330x was tried but no gain.
The 6 inch Maksutov was used at 95x, but I would need to increase this to 150x or 200x.

I have read a hotel name sign at 11 miles with a Japan Celestron 20x80 but cannot remember how large the letters were.

With car number plate letters some are difficult, some easy, depending on crowding.
The light levels are critical for long distance viewing

P.P.S.
Horace Dall showed me photos he took with his 110mm aperture f/30 camera obscura objective corrected for 4 colours.
Some were of church gutters 17 miles away, which were clearly visible with detail.

Also photos of Mercury with an equivalent focal length of 1,100 metres taken with his 16 inch Dall Kirkham. He used his atmospheric dispersion corrector, which I think he invented.

Seeing the daytime scene in his darkened attic on the large round white table presented by his camera obscura in beautiful colour was an experience like no other. There was a table microscope to show very fine detail.

The views of the planet Mars at 400x with his own made 8 inch Maksutov through his specially selected and ground attic plate glass window, was another experience that had to be seen to be believed.

I think that an 80mm Pentax spotting scope may be a little small to read number plates at 5 miles.
Someone I think described seeing 0.22 inch holes at 1 mile with a 100 Pentax spotting scope.

Last edited by Binastro : Monday 21st November 2016 at 17:37.
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