Question about National Geographic NG70CA (225 x 70mm) Telescope

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I recently moved to Florida and left behind the 20mm 4mm and diagonal mirror are they available to purchase

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These come in 3 sizes-- .975, 1.25, an 2 inch sizes.

Measure the hole-- and buy the correct size. Here are two retailers-

http://shop.telescope-warehouse.com/

http://www.agenaastro.com/

Posted on Aug 19, 2010

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My left side mirror does not move in cold weather. any advice?


My best advice is to move to Florida , however if this is not in your plans then most likely the cold is making the mirror contract, causing it to bind . A replacement mirror unit will solve your issue.

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A lens is missing


This telescope uses 1.25 inch eyepieces. Comes originally with a 20mm and a 4mm (probably cheap modified acromats) The 4mm would exceed the maximum practical magnification. 50x per inch. Many eyepieces available on Ebay and telescope vendors. If the 20mm is missing, buy a 20mm Plossl. I prefer other designs focal lengths under 12.5mm because of the eye relief. Agenaastro makes great, inexpensive ($55). I like the Sterling Plossls from Smartastronomy too Eyepieces for planetary viewing I suggest the 5.2mm for your high power or a TMB planetary (Astronomics has them for $50 Get the 5 or 6mm

Clear Skies!

Oct 04, 2012 | Bushnell NorthStar 78-8831 (525 x 76mm)...

1 Answer

I have the whole telescope assemble except I'm having trouble with the lense and eye piece. I have the 78-9970 refractor scope and I don't understand where to put the 4mm lense (and the other...


Put the diagonal into the rear focuser-- then put the eyepiece into the diagonal. DO NOT use the 2 x barlow if you have one. AND the 4mm may also be too much magnification for this size telescope.

So-- put the eyepiece with the largest number written on it into the diagonal and practice focusing on a distant object during the daytime. DO NOT POINT the scope at the sun! You will be instantly blinded!

Jul 01, 2011 | Bushnell Voyager 78-9970 Telescope

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What type of screw is needed to connect the bracket to the back of my 32inch emerson tv?


You would use vesa screws 4mm x 10mm - for non-recessed vesa mounting holes.
4mm x 20mm + approx 1ccubewi_0.pngm spacer - for recessed vesa mounting holes

Mar 28, 2011 | Emerson LC320EM9 32 in. LCD HDTV

2 Answers

I bought a jason mercury model 407 which needs an eye piece.can some tell me where to order it and part number?


This scope has a ,965 in. diagonal (measure the diameter of the diagonal opening.) max power is about 120x
I would get a 20mm for low power e.g. http://cgi.ebay.com/Meade-Telescope-965-20mm-Eyepiece-New-Inexpensive-/270719705992?pt=LH_DefaultDomain_0&hash=item3f0826e388

and a 9mm for higher power http://cgi.ebay.com/9MM-965-inch-Meade-telescope-eyepiece-NEW-/230597193693?pt=LH_DefaultDomain_0&hash=item35b0a9efdd

These are cheap eyepieces but it is a cheap scope. I would not put a lot of money into it.

If you get interested in astronomy, purchase a quality Celestron, Meade or Orion (for example) reflector scope.

Mar 19, 2011 | Optics

1 Answer

I have a edu science 70mm Astro-Gazer. I lost the manual and forgot how to use it. I have 4mm and 20mm lens and I can see moon via 20mm lense. But how can I use 4mm or 3X part to magnify the view ? Thanks!


That little scope will NEVER be able to use the 4mm with the 3xbarlow, just too mmuch magnification. The maximum possible magnification for ANY telescope is about 50 times aperture.

Your scope is about 3 inches so 150 power is the maximum.

Read my tips on my profile page.

Sep 22, 2010 | Edu-Science (10166) Telescope

1 Answer

My Meade Polaris 60EQ-D Telescope is missing the diagonal mirror.


Here is Meade's manual web page. Find your telescope on the page:
http://www.meade.com/manuals/index.html

Aug 09, 2009 | Meade Polaris 60EQ-D (36 x 60mm) Telescope

1 Answer

I dont know how to use my barlow lens


I use a barlow lens quite a bit with my telescope. It is usually inserted before the diagonal if you use one or before the eyepiece if you don't. The barlow lens for your telescope will double the power of the eyepiece used.

However, despite what the manufacturer claims for your telescope things will look quite poorly if you try to view at 180 power. Generally you'll get the best images by using 50x for each inch of your objective lens. For example, your telescope has a 50mm lens. That's roughly 2 inches. 2 inches times 50x gives you a maximum useful power of 100x. Depending on the viewing conditions you may be able to exceed this or not even reach it. Things will look blurry and dim when you try to use too much power.

Your power or magnification is calculated by dividing your telescope focal length which is 360 mm by the eyepiece focal length. You have two eyepieces with focal lengths of 4mm and 20mm. If we divide 360mm by 20mm we get 18 power. If you add a barlow to that you get 36 power. Dividing 360mm by 4mm (no barlow) we get 90 power. That would be your maximum useful power.

Therefore, you should be able to used the 20mm eyepiece with or without the barlow but the 4mm should only be used without the barlow.

I hope all of the math wasn't confusing.

-jodair

Feb 12, 2009 | Edu-Science (10166) Telescope

3 Answers

Bushnell 18-1560 Telescope


Hello,
What you have is called a refractor-type telescope with the primary lenses (the Objective) at the top of the tube and the only other lenses in the system are your selection of eyepieces, probably a barlow lens (2X magnification of any eyepiece used), and a diagonal (in line mirror so that you cand see into the telescope from the side.). As the focal lenth of the eyepiece decreases, so does the distance away from the Objective Lens. I believe that you are using the telescope with a diagonal mirror which makes the optical path longer. The fact that your longer focal lenght eyepiece can focus and not your short one would be only if you didn't have the diagonal or the eyepiece all the way in tight to allow the focus mechanism (rack and pinioin) to get compressed enough to focus. Look at the Moon, if the image gets smaller then bigger as you focus, but not sharp, then I would have to tell you that your eyepeice lenses are not in the right order. Someoner may have taken it apart and didn.t put them back in the correct order. The lenese could just be very dirty also. Barrow a short focal lenght eyepice from a friend and see if it works in your system. Then you will know for sure.

May 15, 2007 | Bushnell Deep Space 18-1560 (150 x 53mm)...

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