A few months back I made a post about a few of the binoculars I have been collecting, and mentioned I was thinking of picking up a pair of Celestron SkyMasters for some sky type viewing. (I never did get them).
Shortly after the post was made I found a Mead Etx 60 Telescope at a thrift store for about 30$. I have not really tested its auto find functions yet as it was purchased in the middle of winter, but the other steering type functions do work though the remote. Right after I purchased it I printed up some instructions and dropped it off at my fathers house and asked him to figure out how to use it, (He's retired) and has some time on his hands.
Then just last weekend I found this one for a similar cost that I'm pretty excited about. Its a Tasco 11TR. It came in the original packaging and looked to be in great condition. It could not have been used very much at all.
After I brought it home I was happy to find all the parts were included and assembled it from its packaging. That same evening I took it out to the backyard and was pleasantly surprised with the views I was seeing, but it seemed a little stiff. The next morning I dis-assembled the mount and cleaned and re-lubed all the moving parts.
Here it is now, looking almost new:
For the last two days much of my spare time has been spent either reading or watching youtube videos on how I can best use this scope. At first there was a big learning curve and I had some trouble understanding a lot of what was said. Now I'm able to understand a little more of what I'm either watching or reading.
To help get me started and understand some terminology better, I took some notes from various sources including this site. This is all the information I have so far compiled pertaining to this telescope and the eye pieces that were included.
The notes I have taken can be seen below, and I'm also wondering if everything I collected is correct?
One more question: Can any one tell me anything about the two F type eye pieces I have listed below? They must have been extra as they were not in the manuals part list. Note: Two more eye pieces came with the set, but they were duplicates in power and seemed to be of lesser quality.
Telescope: Tasco 11TR
Year Made: 1985
Type: Newtonian Reflector
“114.3 x 900”
4 1/2" / 114.3mm Objective Diameter
900 Focal Length
45x – 228.6X (With the Eye Pieces listed below)
(The Focal Length "114.3" X 2 = Highest Power With A Clear Image "228.6X")
This Telescope Should Be Used Below 228.6X, Most people would Use a 9mm eyepiece that equates to 100X for comfortable max magnification in a “114.3 x 900” configuration.
H20mm Japan Z = 45x
F12.5mm = 72x
F4mm = 225x
SR4mm = 225x
1.5X Erecting Eyepiece (Flips Image): 20mm = 67.6x, 12.5mm = 108x, 4mm = 337.5x
2x Barlow: 20mm = 90x, 12.5mm = 144x, 4mm = 500x
3x Barlow: 20mm = 135x, 12.5mm = 216x, 4mm = 675x
H= Means it is a hygens design (H=Hygens), simple design of 2 plano convex lens. The 2 lens are facing the same way.
SR= Means It is a Super Ramsden design (R=Ramsden), Similar to the Hygens design but one of the lens faces the other way
There are 3 or 4 eyepieces to be avoided that are fairly common. Ones to avoid include eyepieces with the following markings: H25mm, H20mm, H12.5mm and SR4mm. Eyepieces with H markings (Huygens optical configuration) are not of very good quality, the apparent fields of view are on the smaller side. Huygens eyepieces with smaller focal lengths tend to be worse than those with larger focal lengths. Most users that attempt to use an SR4mm eyepiece will also find it of little practical use.
You basically need one eyepiece to produce a good low power magnification (in the range of 25x - 50x) and the other one should produce a good higher magnification (in the range of 90x - 120x). These magnifications will be the ones most commonly used in most any telescope.
Edited by Mbinoc, 19 March 2019 - 08:58 PM.