Getting bigger views of jupiter

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aleetk
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Getting bigger views of jupiter

Post by aleetk »

Hi! I own a Powerseeker 80eq which is a 3 inch telescope and the eyepieces that I have are the 20mm, 15mm and 6mm. I have tried all the eyepieces. Even when viewing jupiter using the 6mm eyepiece which gives about 150x magnification, the planet still appears quite small. Is there any other way of viewing jupiter at a larger magnification? I saw this youtube video http://www.youtube.com/watch?v=akm-DQeb63Q. This person is also using a 80mm refractor and he stated that he just stacked a 2x barlow with a 2.5x barlow together with a neximage webcam. 2 multiplied by 2.5 gives you 5x and since my telescope's focal length is 900mm. It's 900/5 which gives 180x magnification. Is this possible since the highest useful magnification for a 3 inch telescope is about 150x? The view of jupiter in that video is way bigger then what I see at 150x and if it is possible to view jupiter at even higher magnification, I would like to know because I want to try and photograph jupiter. Please advice. Thanks!
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Mariner
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Re: Getting bigger views of jupiter

Post by Mariner »

Short of poking your eye out with the eyepiece, I guess barlowing is the only way to go.
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orly_andico
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Re: Getting bigger views of jupiter

Post by orly_andico »

beyond a certain point all you will get is "empty magnification"

for a 3" = 76mm telescope, the maximum magnification - assuming premium optics - is 50X per inch or 2X per millimeter.

So that's just about 150X.

if you stack barlows and such, the image will get bigger, but there will be no additional detail. And the image will be super-dim. And your mount's every shake and wiggle will be magnified to unheard-of levels.

just for fun, i tried using a 2.5mm eyepiece in my 90mm refractor, giving 240X. the image was very dim and not at all satisfying.

basically if you want more magnification, you need to use a bigger scope, like say an 8" which should let you crank up the magnification to 400X or so on a good night.

the guy in that youtube is using a camera, hence he can use tricks like Registax wavelet filtering to sharpen the image and tease out more detail. your eye can't do that.....
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Gary
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Re: Getting bigger views of jupiter

Post by Gary »

Hi Aleetk. Welcome to the forum!
aleetk wrote: This person is also using a 80mm refractor ...
I think that youtuber is using a higher priced and quality triplet apochromatic 80mm lens (Explore Scientifc 80ED): http://www.optcorp.com/product.aspx?pid=12194&tb=2

This may be partly the reason he/she may be able to push the magnification higher per inch of aperture compared to an achromatic refractor of the same aperture.

For lunar and planetary imaging, assuming the same budget and sky condition, a SCT/MCT/Newtonian should give a better final processed image.
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aleetk
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Re: Getting bigger views of jupiter

Post by aleetk »

Thanks guys for all your inputs. I'm still a newbie to astronomy. I intend to buy a bigger and better telescope but not till I learn the basics first.

Cheers!
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cloud_cover
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Re: Getting bigger views of jupiter

Post by cloud_cover »

Hi aleetk! Welcome to Singastro!
First of all, let me point out that the youtube video user was doing video imaging, not visual (as in putting his eye to an eyepiece). In the youtube setup, there was no eyepiece and the camera was at "prime focus". By stacking 2 barlows and getting effectively 5x magnification, he was essentially converting his telescope into a 2400mm telephoto lens. This is completely different from you using an eyepiece to physically look at jupiter. In his case, his eye never went close to the telescope.
Regarding Barlows: Barlows can be used on any eyepiece to increase the magnification. Barlows can also be stacked to multiply the effect of their magnification. In fact, a Barlow is a useful lens to have as it effectively doubles your eyepiece collection. There are lots of people who espouse using only 2 or 3 eyepieces with a Barlow on a wide variety of telescopes. (of course then on the flip side, there are those with hundreds of eyepieces)
Regarding magnification, as a rule of thumb the highest useful magnification for a telescope is 50x/inch, or about 160x in your particular case. There are 2 reasons for this:
1. Beyond a certain magnification vs. aperture, the telescope cannot resolve the image clearly. If you tried to use your scope at, say, 300x, what you will get is a blur and dark image. Not very pleasing.
2. Beyond 50x/inch aperture, the exit pupil of the image (that is, the size of the image at the eyepiece) falls below 0.5mm, at which point floaters and defects in your own eyes will become distractingly obvious. I'm sure you've seen these things when using your 6mm eyepiece :) Some people are more affected, some are less.
Again, another consideration about the 50x/inch is the quality of the optics. Like all rules of thumb, this is a generalization and is meant to apply to optics of a relatively good quality. Less well-made optics have more abberations, resulting in an image that is less clear at higher magnifications because errors in the lenses cause the some of the incoming light to be smeared. Better quality optics produce clearer images at higher magnifications and some particularly premium telescopes can exceed the 50x/inch rule, at least as far as image sharpness.
So as for your question on what can you do to make the image bigger: You can apply a 2x Barlow on your 6mm eyepiece but the tradeoff may be a less pleasing image. Or you can "borrow" someone else's bigger telescope during one of our sidewalk sessions :) Still, 160x on Jupiter is a fine magnification and is enough to take in most of the features.
Enjoy the view! :)
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MooEy
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Re: Getting bigger views of jupiter

Post by MooEy »

err..even with a huge telescope, jupiter can still look puny when it is far away. the guy who took the video prolly pick a period during jupiter's opposition to take that.

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superiorstream
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Re: Getting bigger views of jupiter

Post by superiorstream »

Hi,All
The following facts should be considered
1)On those scopes availible to us armature,refractor in general give a more contrasty view than
reflector--take for example--I find the great red spot shows up better on a 127 meade apo than on
a 8 ins meade SCT and as you will see,contrast is very necessary to visual observing.
2)Our sky give 'waving' image due to various layer of air has different refraction index.Thus,
subjecting a image to high magnification doesnt mean seeing more.Moreover,high magnification
means spreading the light over a larger area--thats optics--and hence a DIMMER image.For example
,a long time ago,I had only the 4ins refractor--FL102S.I view the moon with it with a 2.5mm LV ep
but finds the image too dim and no matter how I adjust.; no improvement.
3)Barlowing will increase the magnification,but in general with the increasing of each layer of optics
multiple reflection and optical distortion is increased.Thus stacking of barlow is NOT recommended.
Rather,if want x4 barlow,use the televue 4x barlow or if need 5x,use their 5x barlow.
4)Those high contrast,beautiful images you see in books and forums of Jupiter are PROCESSED image
acquired using tracking mount,expensive CCD,and processed by expensive high speed notebooks
using expensive software.You cant see such high contrast steady image in the eyepiece of generally
available telescope.
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orly_andico
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Re: Getting bigger views of jupiter

Post by orly_andico »

actually things need not be too expensive to take good photos of Jupiter.

and registax software isn't expensive (free 30 day trial in fact). a good webcam like a Microsoft Lifecam Cinema HD will produce really great photos of Jupiter.

this is a photo i took during last year's double transit.. using a cheap and old Meade DSI Pro camera and the free Registax software. No barlow, either.

Image

the raw images didn't look this good... but a lot of processing and i got something half-decent.

the Meade DSI has huge pixels and low resolution (only VGA). If that had been a Lifecam Cinema HD the image would be over twice as large and in color too..
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