Tasco #58T/302058

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  • Member since
    May, 2005
Tasco #58T/302058
Posted by Anonymous on Thursday, January 25, 2007 4:08 PM

I am moving house in a couple of months and I have decided to start using my telescope. My specification is:

Objective Diameter: 600mm (2.36")
Focal Length: 700mm
Eyepieces: 12.5mm, 4mm
Barlow: 3x
Erecting Eyepiece: 1.5X
Maximum Magnification: 525X
Accessories: Diaganal, 5X24mm Finderscope

I would like to know what does the Barlow and Erecting eyepieces do?
What will I be able to see with this specification?
What does the finderscope do?

 



 

 

 

 

 

  • Member since
    January, 2004
Posted by tkerr on Thursday, January 25, 2007 4:57 PM
 CliveKoopa wrote:

I am moving house in a couple of months and I have decided to start using my telescope. My specification is:

Objective Diameter: 600mm (2.36")
Focal Length: 700mm
Eyepieces: 12.5mm, 4mm
Barlow: 3x
Erecting Eyepiece: 1.5X
Maximum Magnification: 525X
Accessories: Diaganal, 5X24mm Finderscope

I would like to know what does the Barlow and Erecting eyepieces do?
What will I be able to see with this specification?
What does the finderscope do?

I am sure you meant 60mm objective diameter (aperture) rather than 600mm.Smile,Wink, & Grin [swg] that would be nice however.

And I can assure you that you will not achieve 525x magnification with that telescope. 

50x to 60x per inch of aperture. Or 2x per millimeter.  Generally magnification is also restricted to about 300x to 350x magnification maximum even in much larger telescopes by the Earths atmosphere. However, larger aperture is still better even at equal magnifications.  More aperture equals higher resolving power.  

Divide the focal length of the telescope by the focal length of the eyepiece to calculate the magnification you will be using

for example this telescope has a 700mm focal length and has a 12.5mm EP and a 4mm EP

700 / 12.5 = 56x magnification

700 / 4 = 175x magnification. (exceeding the limits of the telescopes aperture) 

Include the 3xBarlow into those equations then with the 12.5mm EP you would have 168x magnification (again exceeding the limits of the aperture.) With the 4mm EP and 3xBarlow you would get 525x magnification, which is by far exceeding the limitation of a 60mm telescope.  You wouldn't see anything but a black or at best a dark faint blur.  Just because the combination of eyepieces, Barlow and telescopes focal length equal to a certain number doesn't mean you can use it.  

If that is what they are telling you then it is time to look elsewhere to shop for your telescope.  Did you read my long post on getting started into amateur astronomy? I seriously recommend you review that before you continue any further. Scroll down to the part about magnification.  Please read through it. That will give you a greater understanding of what to look for. 

http://www.astronomy.com/ASY/CS/forums/291288/ShowPost.aspx
 

What does a barlow do? 

A barlow lens multiplies the focal length of the telescope effectively multiplying the magnification with whatever eyepiece you are using it with. If it is a 3xBarlow then it will multiply the magnification by 3.  If you are using a eyepiece the will yeild 100x magnification with your telescope, then when you include a 3xbarlow you would double the effective magnification to 300x. Far beyond the capabilities of that telescope

An errecting eyepiece corrects the orientation of the image so it appears in the eyepiece as it would if you were to look at it with the naked eye. Generally used for terrestrial observing such as birdwatching.

When you look through a telescope otherwise, the object will be be oriented quite differently than you are used to.  For example without getting too deep into the details of how optics work,  a Reflector will project the image sort of inverted and reversed.  A refractor will project the image inverted and reversed if you were to use the eyepiece straight through. If you were to use the eyepiece with a star diagonal it would only appear reversed. However, you can also get a correct image star diagonal.  IMHO those work better than errecting image eyepieces. Especially those included with entry level telescopes.

 

What does the finderscope do?

It is essentially a small version of a refractor telescope in most circumstances. It is used to aim the telescope in the general area of the object you are looking for. You have to first align it to the telescope so they will be looking at the same thing.

Some objects are bright enough to be seen in the finderscope. However, many times you will only be able to use it to aim on a star or formation of stars (Astrism) to get you in close proximity of the object you are hunting.  

 

What can you expect to see? 

To be totaly honest, I get the feeling it won't be as much as you would like. Unless you are in pristine clear very dark skies not much other than the moon. You will be able to identify and locate the larger planets and some other deep sky objects. But the amount of detail will be very little and very plain.  The planets will be very small and pretty much featureless. You should still be able to see and distinguish the rings around Saturn and some of the darker banding around Jupiter. You will be able to see some of the brighter and or large deep sky objects. The Orion Nebula, The Andromeda Galaxy and a few other smaller but brighter galaxies, open clusters and a few of the more dense globular clusters. However, they will leave a lot up to your imagination than you will actually be able to view.  You will be limited to a maximum useful magnification of only around 120x. The planets such as Saturn and Jupiter don't really start resolving much detail until you reach 200x and higher. 

 

Have A Nice __________ 

 

Have A Nice ...
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Equipment: Orion XT10 Classic, Celestron C6 R-GT (CG5 GT mount), C80ED Canon EOS 350D, Canon EOS 50D, Meade DSI II Color CCD, Phillips SPC900NC

  • Member since
    May, 2005
Posted by Anonymous on Friday, January 26, 2007 4:24 PM

Thank you, that has been very helpful. A few questions on some of what you said:

Why will the detail be small and plain? Is there anyway I can improve the quality?

Where can I find light pollution filters to make the sky look darker so I can see much more? 

 

  • Member since
    January, 2004
Posted by tkerr on Friday, January 26, 2007 5:32 PM
 CliveKoopa wrote:

Why will the detail be small and plain? Is there anyway I can improve the quality?

 

The light grasp and resolviong power of the telescope is very limited. The only way to improve what I am discussing is to increase the aperture. More aperture = more light grasp and increased resolving power.  More aperture also = the ability to increase to higher magnifications.  

resolving power: A measure of the ability of a lens or optical system to form separate and distinct images of two objects with small angular separation.

An optical system cannot form a perfect image of a point (i.e.,point source). Instead, it performs what is essentially a Fourier transform, and the resolving power of an optical system may be expressed in terms of an optical transform (transfer function) called the modulation transfer function (MTF).

The resolving power of an optical system is ultimately limited by (a) the wavelenght involved, and (b) diffraction by the aperture, a larger aperture having greater resolving power than a smaller one.

 

 CliveKoopa wrote:

Where can I find light pollution filters to make the sky look darker so I can see much more? 

 

How much benefit you would get with a 60mm telescope is questionable. Your light grasp is already limited, and with the addition of a light pollution filter of any kind you will be blocking too much light. Although they may be a little help, generally they are a greater benefit with larger aperture telescopes. 

However, You can find them almost anywhere. Telescopes.com sells a variety of them from differnt manufactures. Orion telescopes and Binoculars has their own, Celestron has there own, Meade has some of their own, and if you really want to fork out the bucks there is Lumicon.

 

Have A Nice ________ 

 

 

Have A Nice ...
Find me on Google Plus
Equipment: Orion XT10 Classic, Celestron C6 R-GT (CG5 GT mount), C80ED Canon EOS 350D, Canon EOS 50D, Meade DSI II Color CCD, Phillips SPC900NC

  • Member since
    May, 2005
Posted by Anonymous on Friday, January 26, 2007 5:45 PM
Okay, so how do I increase the arperture?
  • Member since
    May, 2005
Posted by Anonymous on Sunday, January 28, 2007 4:08 PM
Please tell me how do I increase the aperture? I get the feeling from some of what you said that my telescope is crap or at least needs improving a little.
  • Member since
    November, 2006
  • From: Dover DE
Posted by Bill W. on Sunday, January 28, 2007 6:31 PM
Aperature is the physical size of the primary lens or mirror. Unfortunately the only way to increase it is to buy another scope. As many on here will tell you, a scope is not crap if it gets you out there enjoying the hobby. Smaller inexpensive scopes can springboard you to something more signifigant later on. Since they are smaller, theres more of a chance that you'll carry it out on a regular basis and use it. Luggin a 75+ lb monster out regularly can be overwhelming and you may quickly find the hobby unenjoyable. Although a beginner myself, I would suggest stick with this one and learn your way around the night sky. Then when your ready go as big as your pockets will allow Evil [}:)]
Zhumell 10" Dob Meade DSX-90 20x60 Binos Fuji S9000 Ultrazoom If you only look at the path ahead, you may never look up to see the path untraveled.
  • Member since
    November, 2003
Posted by Ripps1 on Sunday, January 28, 2007 7:57 PM

A while back I refurbished a Tasco 70mm scope similar to yours. I had a good time spotting open clusters, the moon, Jupiter, Saturn and other brighter objects with it. 

Replacing the eyepieces supplied with these scopes with a better quality eyepiece makes a lot of difference in image quality and viewing comfort. You might try a 25mm SMA and a 10mm Plossl. These are the eyepieces usually supplied with new higher quality scopes and usually wind up on Astromart for a decent price. Oh, yeah,give the barlow to someone you dislike. Also, before buying an eyepiece, check the barrel diameter of the ones that fit your scope. Most now are 1.25" but some (esp. older Tasco scopes) are .975" diameter.  You'll find .975" a bit harder to find. If yours is, let us know - there are "fixes".

The next improvement is replacing the finder with one of the non-magnifying "Red Dot" type finders.  

Here's a review I found on your scope:

 

http://www.dmottershead.co.uk/page4.html

 

 

GATEWAY ASTRO - a boring but worthwhile site for St. Louis area amateurs. http://groups.yahoo.com/group/gag_astro 15x70 Oberwerk 4.25" StarBlast TV102 C8 18" Obsession w/Sky Commander
  • Member since
    January, 2004
Posted by tkerr on Sunday, January 28, 2007 8:32 PM

 CliveKoopa wrote:
Please tell me how do I increase the aperture? I get the feeling from some of what you said that my telescope is crap or at least needs improving a little.

 

Does your telescope get you outside and allow you to look up at the night sky?

If so than it is good enought to start with. There are many of us who started with less the desirable (crappy/junk) telescopes.  The important thing is that they got us to look up, they increased our curiosity, and when we could we got a larger telescope, or two or three Smile,Wink, & Grin [swg]

Getting your first telescope is only the beginning of your adventure and expenses into this hobby.  

As already pointed out you can not increase the aperture of the telescope. The Optical Tube diameter and length is designed for that specific primary optical component (lens or mirror)  

Continue with the telescope you have, learn your way around the night sky and enjoy it as much as possible. Meanwhile save your money towards a better larger telescope. Learn your limitations and think about your desires when considering what telescope to get next. Too large and or too complicated then it can become a chore. When things become a chore we start to loose interest. This we do not desire. Get something that is practical for you and your desires.

Improving the stability of your mount will help a lot. Trying to view an image that is shaking or vibrating gets anoying.  Look at how it is assembled and secured together. See if there is anyway you can make things more secure and stable. Sometimes simple straps around the tripod to prevent wobbling. or tie a strap from the center of the mount to a weight on the ground to help stabilize it. Some of those mounts and tripods use plastic nuts and bolts that can crack and break, Replacing them can help. Just be carefull not to strip, crack or break anything by making it overly tight.  That is something you often just have to use your imagination and a little ingenuity to accomplish.  

Getting better eyepieces can make a world of difference. New eyepeices could be used with your next telescope, so that is not an investment you could go wrong with.

Other than that, there really isn't much you can do for that telescope.  

 

Have A Nice _________

 

Have A Nice ...
Find me on Google Plus
Equipment: Orion XT10 Classic, Celestron C6 R-GT (CG5 GT mount), C80ED Canon EOS 350D, Canon EOS 50D, Meade DSI II Color CCD, Phillips SPC900NC

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