Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Anybody love Stellarvue dielectric diagonals?

  • Please log in to reply
11 replies to this topic

#1 jeffmac

jeffmac

    Viking 1

  • -----
  • topic starter
  • Posts: 713
  • Joined: 01 Aug 2014
  • Loc: Triad area, NC

Posted 25 June 2019 - 10:29 PM


What's the general consensus on Stellarvue's dielectric diagonals? Anyone compare one with the Astro-physics Maxbright or Tele Vue's Everbrite?

#2 Rich V.

Rich V.

    Fly Me to the Moon

  • *****
  • Posts: 6366
  • Joined: 02 Jan 2005
  • Loc: Lake Tahoe area, Nevada

Posted 26 June 2019 - 10:09 AM

My SV 2" diagonal, while the mirror itself puts up a good image, does not have nearly as good internal baffling as my AP Maxbright.  One look inside and you'll see the extra effort and quality put into the AP design. 

 

Though "baffled" with ridges inside the nosepiece, the ridges were shiny anodized instead of anti-reflective flat black.  I had to apply flat black paint to the grooved interior surface of the nosepiece of the SV as it was introducing some veiling glare from off-axis light under circumstances where a bright object was located outside of the scope's FOV.  Not a frequent issue but there just the same.

 

My SV diagonal is 12 years old now, though they still look the same, perhaps they do a better job of anti-reflection blackening of the interior these days...   question.gif

 

Rich



#3 Binojunky

Binojunky

    Fly Me to the Moon

  • *****
  • Posts: 5455
  • Joined: 25 Dec 2010

Posted 26 June 2019 - 10:12 AM

I have the 2' and did have the 1.25, at the price point they sell for they are for me anyway fine,and they cost a lot less than the two others the OP mentioned,D


Edited by Binojunky, 26 June 2019 - 10:13 AM.


#4 Rich V.

Rich V.

    Fly Me to the Moon

  • *****
  • Posts: 6366
  • Joined: 02 Jan 2005
  • Loc: Lake Tahoe area, Nevada

Posted 26 June 2019 - 10:26 AM

I should point out that my SV 2" dielectric clamps securely into my FT and AP compression ring visual backs just like my Maxbright does.  The eyepiece holder compression ring is equally secure so I never worry even with a heavy 21E held in the diagonal.



#5 Jeff Bennett

Jeff Bennett

    Vostok 1

  • *****
  • Posts: 162
  • Joined: 30 Oct 2005
  • Loc: Clayton, California

Posted 26 June 2019 - 10:48 AM

I picked up a Stellarvue 2-inch dielectric diagonal recently with the purchase of a used scope. This diagonal is a very recent one with the twist-lock 2-inch eyepiece holder mechanism. I just took a look, and the interior surfaces are all nicely blackened.

I also have an AP MaxBright and two Everbrights, and while I have not done a detailed comparison, the SV seems pretty comparable optically. Build quality is also quite nice albeit a notch below the AP and TV models.

Jeff

#6 peleuba

peleuba

    Surveyor 1

  • *****
  • Posts: 1668
  • Joined: 01 Dec 2004
  • Loc: North of Baltimore, MD

Posted 27 June 2019 - 01:52 PM

What's the general consensus on Stellarvue's dielectric diagonals? Anyone compare one with the Astro-physics Maxbright or Tele Vue's Everbrite?

 

The real benefit of (true) dielectrics is the ability for the surface to resist abrasion when being cleaned.  

 

Applying a dielectric coating is stressful to the substrate - especially at the edges.  Its why the A-P Maxbrite and TV Everbrite are slightly oversized - so the error at the edges does not impact the center of the reflective surface.

 

And regarding actual surface area in use, light from stars/planets/DSO's, when at focus, does not use much of the mirror's surface area to reflect the light to the eyepiece.  The diagonal is quite close to the focal plane of the telescope and the light cone is narrow.  So, an honest 1/10 wave diagonal will have something like 1/40 wave surface error for the small portion that's actually in use.

 

Also, a mirror diagonal generally only suffers from two aberrations that may affect the view:  Scatter and Astigmatism.  A high quality mirror diagonal will have minimal scatter and zero astig.  It will also contribute no spherical aberration unlike a prism.

 

I don't have any thoughts on the SV diagonal.  I use Maxbrites with my refactors and an Everbrite with my SCT - both dielectric.


Edited by peleuba, 27 June 2019 - 01:52 PM.

  • Paul G and Jon Isaacs like this

#7 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 77208
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 27 June 2019 - 07:29 PM

Just a quick tidbit:

 

 TeleVue diagonal bodies machined from a single piece of aluminum.  The nosepiece cannot rotate in the diagonal.

 

Jon


  • Binojunky likes this

#8 SDTopensied

SDTopensied

    Viking 1

  • *****
  • Posts: 771
  • Joined: 25 Apr 2011
  • Loc: Atlanta

Posted 28 June 2019 - 02:30 PM

I have both and did a comparison recently out of curiosity, using the two diagonals, a set of TeleVue Naglers, and a 6" Maksutov-Cassegrain.  I was at home observing a first quarter moon, Jupiter, and a few brighter DSO's that are visible from my suburban home in the Atlanta area.

 

I was quite surprised to find that the views through the StellarVue diagonal were more pleasing to my eye than the TeleVue diagonal.  I was not expecting that at all.  Objects through the StellarVue were brighter and had better contrast.  The latter was very unexpected!

 

-Steve



#9 jeffmac

jeffmac

    Viking 1

  • -----
  • topic starter
  • Posts: 713
  • Joined: 01 Aug 2014
  • Loc: Triad area, NC

Posted 28 June 2019 - 03:25 PM

An enhanced mirror diagonal will eventually lose some of it's reflectivity. How about a dielectrically coated diagonal?



#10 peleuba

peleuba

    Surveyor 1

  • *****
  • Posts: 1668
  • Joined: 01 Dec 2004
  • Loc: North of Baltimore, MD

Posted 02 July 2019 - 01:59 PM

An enhanced mirror diagonal will eventually lose some of it's reflectivity. How about a dielectrically coated diagonal?

 

If a true dielectric, then no, it should retain its reflectivity.  This is the reason to go with a dielectric surface - durability and retention of reflectivity over the long haul.

 

I say "true" dielectric as at the price point of some of the imported diagonals that are labeled "dielectric" I cannot believe its in the same class as an A-P Maxbrite or TV Everbrite as not all dialectric coatings are created equal.  



#11 peleuba

peleuba

    Surveyor 1

  • *****
  • Posts: 1668
  • Joined: 01 Dec 2004
  • Loc: North of Baltimore, MD

Posted 02 July 2019 - 02:00 PM

I have both and did a comparison recently out of curiosity, using the two diagonals, a set of TeleVue Naglers, and a 6" Maksutov-Cassegrain.  I was at home observing a first quarter moon, Jupiter, and a few brighter DSO's that are visible from my suburban home in the Atlanta area.

 

I was quite surprised to find that the views through the StellarVue diagonal were more pleasing to my eye than the TeleVue diagonal.  I was not expecting that at all.  Objects through the StellarVue were brighter and had better contrast.  The latter was very unexpected!

 

-Steve

 

Interesting.  Were the diagonals both clean?  How was the color rendition - did one offer a warmer view then the other?



#12 Orion68

Orion68

    Vostok 1

  • *****
  • Posts: 107
  • Joined: 18 Jan 2014

Posted 10 July 2019 - 08:06 PM

Never tried one but I have owned three of their telescopes and liked them all.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics