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Hi all,

I've just re entered the astronomy hobby. I have a Celestron PowerSeeker 80EQ refractor with a motor drive. It has great clarity but the eye pieces have plastic lenses, I would like to go with coated glass lenses and filters. When I bought the 80EQ it came with a 20mm, a 4mm and a 3X barlow. I would prefer a 2X barlow and a better range of eye pieces. I do understand the magnification formulas. Could anyone direct me to a reasonable source for a kit, I have to restrict myself from buying the best and overstocking myself with more than I need, (a personal challenge).

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Upgrading your EPs will be an enormous improvement. Generally the rough maximum magnification you can expect from a telescope is double the aperture in millimeters, in your case about x160. Much above this and the quality of viewing will defeat further magnification. So really a 5.5mm eyepiece is probably the top. EPs vary in price from about $20 up to nearly $1000 for really premium glass, so an idea of your budget would be useful.

This difference in price is largely due to the complexity of design as well as the quality of polishing, coating etc. Plossl EPs are very good value at the lower end of the market, with a wide range available at about $30 upwards, however they tend to have quite short eye relief especially at higher magnifications. The Vixen NPL series is excellent for the price: http://www.vixenoptics.com/Vixen-Telescope-eyepieces-s/115.htm

Although again with short eye relief, othographic EPs are very good for higher magnifications, for example the Baader Classic Orthos: http://agenaastro.com/baader-classic-ortho-eyepiece-6mm-2954106.html

Another type of design is the Paradigm (also sold in Europe as the BST Explorer or Starguider etc.) which gives much more comfortable eye relief: https://www.astronomytechnologies.com/astro-tech-paradigm-dual-ed-eyepieces_c17.aspx

The Antares x2 Barlows are very good for the price: http://agenaastro.com/antares-1-25-2x-barlow-lens-twist-lock-adapter-t-thread-ub2stl.html

For reference, this gives you a basic idea of some different EP designs:

eyepiece.gif

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Hi tripod tipper, if you are new to the hobby I would not go for expensive glass. I used the eyepieces in the Celestron 1.25 inch eyepiece and filter kit for a long time with my first telescope (Firstscope 114 f8 reflector) and also my CPC 1100. If you don't wear glasses you will be able to see a lot with these while you refine your observing skills and determine the kinds of objects (planets, deepsky etc.) you are more interested in. You will be in a much better position to determine which accessories (or scope) you may want after some months or longer of observing. 

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Thanks beka,

Thank you for the response. I do wear glasses. I have always had reflectors, this time I bought an 80EQ from Celestron. it's been a long while since I've been in astronomy. The eyepieces I got with the kit only had a 3X barlow, a 20mm and a 4mm, no filters. I found them to be plastic lenses, I did purchase coated midrange eyepieces to widen the usefulness, a 15mm, a 9mm, a 6mm, a 5.5mm to add to it. I also purchased filters that didn't come with the scope, a 15 deep yellow, 58 green, an  80A blue, an oxygen-III nebula and a moon filter. I figure if I do go bigger, I will have what I need. I did spend more than I would have aloud myself (please don't tell my wife), however I now can re familiarize myself with the ranges of observation.

Thanks again

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16 hours ago, tripod tipper said:

Thanks beka,

Thank you for the response. I do wear glasses. I have always had reflectors, this time I bought an 80EQ from Celestron. it's been a long while since I've been in astronomy. The eyepieces I got with the kit only had a 3X barlow, a 20mm and a 4mm, no filters. I found them to be plastic lenses, I did purchase coated midrange eyepieces to widen the usefulness, a 15mm, a 9mm, a 6mm, a 5.5mm to add to it. I also purchased filters that didn't come with the scope, a 15 deep yellow, 58 green, an  80A blue, an oxygen-III nebula and a moon filter. I figure if I do go bigger, I will have what I need. I did spend more than I would have aloud myself (please don't tell my wife), however I now can re familiarize myself with the ranges of observation.

Thanks again

Hi tripod tipper, sorry I misread your original post and though you were just entering the hobby rather than re-entering. Good luck with your new collection!

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13 hours ago, Dave In Vermont said:

To go with Patrick's post, here's another EP chart for you to peruse:

EP's Schematic PNG.png

 

Enjoy!

Dave

Hi Dave, nice chart but I don't understand the key.

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They are the different types of glass used in construction:

Key to the glass types:

    names                                       examples

A)  Phosphate Crown
B)  Borosilicate Crown                          BK7
C)  Hard Crown                                  K5
    Zinc Crown
D)  Soft Crown
(C, D: Crown)
E)  Crown Flint
    Telescope Flint
    Short Flint
F)  Extra Light Flint (or E and F)              LLF6
G)  Light Flint                                 LF5
H)  Dense Flint                                 F2
I)  Extra Dense Flint (or I and J)              SF8
J)  Double Extra Dense Flint                    SF10, SF6

K)  Light Barium Crown
L)  Medium Barium Crown                         BaK4
(K, L: Barium Crown)
M)  Light Barium Flint                          BaLF4
N)  Barium Flint (or Q and R)                   BaF N10
O)  Dense Barium Flint
    Borate Flint

P)  Dense Phosphate Crown
Q)  Dense Barium Crown (or L and M)             SK2
R)  Extra Dense Barium Crown                    SSK N5

S)  Lanthanum Crown
T)  Lanthanum Flint                             EK-325
U)  Dense Lanthanum Flint
    Phosphate Flint
V)  Dense Lanthanum Crown

W)  Fluorite Crown                              FK51
X)  Titanium Crown
Y)  Extra Light Titanium Flint
Z)  Light Titanium Flint
AA) Medium Titanium Flint
BB) Dense Titanium Flint
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7 minutes ago, Putaendo Patrick said:

They are the different types of glass used in construction:


Key to the glass types:

    names                                       examples

A)  Phosphate Crown
B)  Borosilicate Crown                          BK7
C)  Hard Crown                                  K5
    Zinc Crown
D)  Soft Crown
(C, D: Crown)
E)  Crown Flint
    Telescope Flint
    Short Flint
F)  Extra Light Flint (or E and F)              LLF6
G)  Light Flint                                 LF5
H)  Dense Flint                                 F2
I)  Extra Dense Flint (or I and J)              SF8
J)  Double Extra Dense Flint                    SF10, SF6

K)  Light Barium Crown
L)  Medium Barium Crown                         BaK4
(K, L: Barium Crown)
M)  Light Barium Flint                          BaLF4
N)  Barium Flint (or Q and R)                   BaF N10
O)  Dense Barium Flint
    Borate Flint

P)  Dense Phosphate Crown
Q)  Dense Barium Crown (or L and M)             SK2
R)  Extra Dense Barium Crown                    SSK N5

S)  Lanthanum Crown
T)  Lanthanum Flint                             EK-325
U)  Dense Lanthanum Flint
    Phosphate Flint
V)  Dense Lanthanum Crown

W)  Fluorite Crown                              FK51
X)  Titanium Crown
Y)  Extra Light Titanium Flint
Z)  Light Titanium Flint
AA) Medium Titanium Flint
BB) Dense Titanium Flint

Thanks Putaendo, I understood that they were different kinds of glass but I do not fully understand the numbers on the axes. I imagine the vertical one is refractive index but I have no clue what the horizontal is. 

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  • 2 weeks later...
13 hours ago, DannyLee said:

to be honest, who cares what the glass used is? Unless you actually make your own,  The point is does the eyepiece work or not?

I know I have no idea and no interest in such details

 

Dan

To some (like myself) in the hobby, its as much about the equipment as the astronomy itself. Like in other hobbies (cars, watches and so on) it is an appreciation of the the precision manufacturing processes and skilled workmanship that is involved in the creation of these products. On the practical side, the types of glass are sometimes mentioned in the specifications of equipment like ED of FPL so if you know these, you are more informed about what you are buying.

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It's not the glass thats used that matters, it's the combination of glass types that is key together with the quality of figuring, polishing, coating, mounting and baffling. Get any of these wrong and optical performance suffers.

It's also rather difficult to work out exactly what glass types are used in eyepieces, and some scopes, because the manufacturer / brand regards this as proprietary so won't reveal them other than in general terms.

 

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Hey,

I thank you all! In middle school, I learned much about optical science. The grafts and pic's in this thread are actually re acquainting me with the optical sequencing of the telescope and microscope. At the age I am now and from suffering a depilating cranial event, I'm just glad the technology has progressed to a point that I can enjoy the benefits. I try to make sense of it, it just want to look again at the spectacular scenes of our galaxy. BTW, optics were mastered several decades ago. I remember looking at a photograph of New York City from 50 miles away and at an altitude of 40,000 feet. Absolutely crystal clear. In my opinion, the progression of optics is already settled. There are no proprietary solutions. Just enjoy the view!!!

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I was just re reading this thread, BTW, I did find proprietary combinations to be true, (I stand corrected). coatings and lenses do add an element of precision and ads to the cost. I am an obsessive person, I read everything I can about astronomy as I have for many of my past hobbies. There's just something about knowledge that an obsessed person as myself finds satisfying even in the indulgence of this science. Please keep the info coming! When it's cloudy I research and learn.

Thanks,

Dennis

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