16 replies to this topic

[JoshUrban]

Hey folks!

 

  Anyone out there have a Fecker scope?  A good friend of mine just gifted me a '57 Celestar, 4" Newtonian reflector.  It is AWESOME.  I've been observing a lot with it, and made a YouTube review:  https://www.youtube....v=REoEksSRIhM  

 

  I was talking with Lew about his list of these telescopes, and am curious if anyone else has been using one lately.  What a little gem!  Not only is it fun to use, and look like a million bucks, but I've been finding it optically excellent, too.  

 

  Wondering if there's anyone else out there who's using these things...

 

  

[DAVIDG]

 I have three of them, two 4" and one rare 6". Here is  a picture of one of my 4" 

 

                   - Dave 

 

              

[clamchip]

Hi Josh,

great video, and your Edmund video too! two of my favorites!

My Fecker is 472 and by the time it was made they went from green to blue.

Robert

 

[Terra Nova]

They are definitely cool looking! Very mid-century modern. I love the flecked paint.

[DAVIDG]

 I have one of the original brochures and it say that the scopes are available in a number of different paint combinations. My one is the teal green but has a gloss white tube. My other two are the more typical  blue Zolatone splatter finish paint which is still available.

 

                   - Dave 

[clamchip]

Here's a close up of the blue, and notice my tube has yellow, and every time 

I see those yellow specks it reminds of my shirt after eating a Costco hotdog

out in the parking lot !  what ever happened to tilt steering wheels !

Robert

 

 

 

[steve t]

Dave Josh,

Wow, very nice!

Steve T

 

Edit Very red faced, I addressed my email to the wrong person  Apologizes Josh.

Edited by steve t, 25 January 2021 - 09:16 AM.

[pbealo]

I have both a 4" and 6". 

[JoshUrban]

Here's a close up of the blue, and notice my tube has yellow, and every time 

I see those yellow specks it reminds of my shirt after eating a Costco hotdog

out in the parking lot !  what ever happened to tilt steering wheels !

Robert

 

post-50896-0-81947600-1485213387_thumb.jpg

Ha, so true!  Man, love that color scheme!

[JoshUrban]

 I have three of them, two 4" and one rare 6". Here is  a picture of one of my 4" 

 

                   - Dave 

 

         Feckercelestar.jpg     

Beautiful scope, Dave!  Glad to hear you've got a whole stable of 'em.  I get that - what delightful scopes!

[JoshUrban]

Hi Josh,

great video, and your Edmund video too! two of my favorites!

My Fecker is 472 and by the time it was made they went from green to blue.

Robert

 

post-50896-0-30701100-1510277012.jpg

post-50896-0-71413200-1472403134_thumb.jpg

 

Hey there, and thanks!  Glad you enjoyed the vid!  I dig that paint on yours - what a nifty design!  

 

  The Edmund I have is a lot of fun, too.  It's quite a bit longer of an f/ratio (I think it's 10 vs. the 7.5 or 8 that the Celestar is?  Or perhaps the Celestar is 10 and the Edmund is 12?)  I did a side-by-side "shootout", and they were fairly evenly matched on Lunar stuff, but the Fecker pulled ahead on deep sky crispness and nicer star images.  The Edmund's weakness is the single stalk spider, from what I can tell.  (I think the Fecker mirror is better, too.)  

[DAVIDG]

 I have both the Edmund 4.25 f/10 Palomar Junior and the two 4" Feckers which are f/8. The Edmunds use a spherical mirror and at f/10 if it is  true sphere is good to 1/8 wave. There are two problems, one is if the mirror is actually a true clean sphere. Mine was not and I refigured to a parabola. Many "spheres" I have test are not spherical but zoney and just what ever comes off the polishing machine that is the figure. The next problem is the diagonal. Most are far from optically flat. I have about 20 of these Edmund diagonals and only two were 1/4 wave or better, the rest were junk. Fix these problems and you have a killer scope with true 1/8 wave optics  So my advice is to actually bench test the optics, that way you  know exactly what you have. It removes any bias from comparing images and doesn't make general statements that one model of telescope gives a better image then another model of telescope. 

 

           - Dave 

Edited by DAVIDG, 24 January 2021 - 07:42 PM.

[JoshUrban]

 I have both the Edmund 4.25 f/10 Palomar Junior and the two 4" Feckers which are f/8. The Edmunds use a spherical mirror and at f/10 if it is  true sphere is good to 1/8 wave. There are two problems, one is if the mirror is actually a true clean sphere. Mine was not and I refigured to a parabola. Many "spheres" I have test are not spherical but zoney and just what ever comes off the polishing machine that is the figure. The next problem is the diagonal. Most are far form optically flat. I have about 20 of these Edmund diagonals and only two were 1/4 wave or better, the rest were junk. Fix these problems and you have a killer scope with true 1/8 wave optics  So my advice it to actually bench test the optics, that way know exactly what you have. It removes any bias from comparing images and doesn't make general statements that model of telescope gives a better image then another model of telescope. 

 

           - Dave 

Dave, this advice is truly appreciated!  Sounds like a fun project.  By the way, is the Fecker a parabola?  I wasn't sure if it was, or a spherical figure.  

[DAVIDG]

 My green/white Fecker had a mirror that was very close to a  sphere. So one can define that  as  an undercorrected parabola. I refigured it  My Blue/white one is also undercorrected but not has bad as the green/white one was.  My Edmund had a  spherical mirror but with a large hole in the figure. The diagonal was also far from optically flat. 

 

             - Dave 

[steve t]

 I have both the Edmund 4.25 f/10 Palomar Junior and the two 4" Feckers which are f/8. The Edmunds use a spherical mirror and at f/10 if it is  true sphere is good to 1/8 wave. There are two problems, one is if the mirror is actually a true clean sphere. Mine was not and I refigured to a parabola. Many "spheres" I have test are not spherical but zoney and just what ever comes off the polishing machine that is the figure. The next problem is the diagonal. Most are far form optically flat. I have about 20 of these Edmund diagonals and only two were 1/4 wave or better, the rest were junk. Fix these problems and you have a killer scope with true 1/8 wave optics  So my advice it to actually bench test the optics, that way know exactly what you have. It removes any bias from comparing images and doesn't make general statements that model of telescope gives a better image then another model of telescope. 

 

           - Dave 

Hi Dave,

Just curious, how did you calculate the wave front error for the f/10 sphere?

Thanks

Steve T

[DAVIDG]

Hi Dave,

Just curious, how did you calculate the wave front error for the f/10 sphere?

Thanks

Steve T

 I use OSLO raytracing program. The Peak to Valley is calculated at best focus to be 0.138 or  about 1/ 7.5 waves but that is if the mirror is a clean sphere with no zones  or turned edge. Now if you put a little smooth correction on the mirror and don't over corrected it, the wavefront gets  even better BUT again you need a good diagonal mirror as well.  This is one of those "sweet spots" in optical designs that when made correctly you have an excellent optical system that will give amazing images. 

 

               - Dave 

 

Edited by DAVIDG, 25 January 2021 - 09:18 AM.

[steve t]

Thanks Dave