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DPAC Test - Orion 110ED

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#1 Jeff B

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Posted 28 February 2020 - 01:30 PM

Another Orion ED doublet, this time the discontinued 110ED, where FPL-51 is the ED element.  So it's got a larger aperture, is faster and uses FPL-51 rather than FPL-53 as in the Orion 80ED and Celestron 100ED doublets.

 

This sample too was obtained randomly on the used market.  It had been languishing in it's case for about a year before I got around to doing a quick DPAC in green.  I was impressed.  So I spent a couple of clear nights with it on the Moon and a star test.  Both were excellent but I could easily see a bit of blue at high power (~165X +/- ) around brighter stars and color disturbances in the intra/extra focal rings.  However, I was surprised by just how nice and sharp the scope was on the Moon at ~165X with my Denk bino-viewer power switch system with very little blue scatter off of bright crater walls and central peak tips.   This is a good sample and rode nicely on both my Losmandy GM8 and older AP 400 (non-goto version).

 

Jeff

Attached Thumbnails

  • 110ED B.jpg
  • 110ED C.jpg

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#2 Jeff B

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Posted 28 February 2020 - 02:04 PM

Now in DPAC.  

 

This is overall another really good lens, which is actually a tad over-corrected in green (I find most are a bit undercorrected or neutral in green). 

 

Comparing the red and, especially, the blue images on each side of focus, you see the spherochromatism at work with lines that bend in the opposite direction.  You will also immediately see in the in focus images (green especially), there is a broad zone in the middle but the figure is pretty smooth.  

 

But there are compromises with this sample as you can clearly see there is a difference in focus of the blue relative to the red and green (which are very close to each other).  Specifically, blue focus falls a bit closer to the lens than does green and red.  You see this, for example with the inside of focus images as more bars in the blue image than in the red and green images.  You also readily see it in the in-focus images with the black bar shadow bisecting the blue image. 

 

So there were indeed some compromises with this larger, faster FPL-51 based lens, specifically, more spherical aberration in blue and a focus difference relative to red and green.  However, IMO, from a visual point of view, they were very good compromises for a ED doublet as lunar views were very sharp with little subjective blue color error.   Plus the lens showed no coma or astigmatism at high power.

 

Build quality is quite nice though a bit porky for the aperture, especially compared to the 100ED. 

 

Lots of images here and as usual, hover the cursor over the images to read its title.

 

Jeff

 

Attached Thumbnails

  • 110ED, Blue, Inside of focus.jpg
  • 110ED, Green, Inside of focus.jpg
  • 110ED, Red, Inside of focus.jpg
  • 110ED, White Larger, Inside of focus.jpg
  • 110ED, Blue, at focus.jpg
  • 110ED, Green, at focus.jpg
  • 110ED, Red, at focus.jpg
  • 110ED, White, Outside of focus.jpg
  • 110ED, Blue, Outside of focus.jpg
  • 110ED, Green, Outside of focus.jpg
  • 110ED, Red, Outside of focus.jpg

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#3 Jeff B

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Posted 28 February 2020 - 04:07 PM

So, I had an idea.  idea.gif

 

While I had this critter set up in DPAC, why not look at the effects of using a prism diagonal.  All of the images above have an AP diagonal in the light path (and yes, I see NO differences in DPAC with it in the light path..none...zero...zilch....nada).   I do have a Baader Zeiss Spec prism diagonal and a 2" eyepiece adapter that screws on over the T2 threads on the diagonal's top so it was an easy swap out for the AP diagonal.

 

I figured this might settle some of, and/or create even more of, the arguments that tend to crop up here concerning the use of prism diagonals with fast ED based scopes. 

 

I focused the rig as best I could to match those DPAC screen positions when using the AP diagonal (got pretty close actually) and redid the white light shots at, and inside of, focus images with the prism in tow.  I then separated out the individual RGB channels of the white light "prism images" for comparison to those with the AP diagonal, specifically looking for correction and focus shifts associated with the extra refractive optics of the prism.

 

And

 

And

 

And

 

I could see not differences at all.

 

So here are the comparison shots with the at focus ones first.

 

Hover the cursor over the images to read the titles.

 

And let the arguments continue......

 

 

Jeff

Attached Thumbnails

  • 110ED, White, at focus.jpg
  • 110ED, Prism, White, at focus.jpg
  • 110ED, Green, at focus.jpg
  • 110ED, Prism, Green, at focus.jpg
  • 110ED, Blue, at focus.jpg
  • 110ED, Prism, Blue, at focus.jpg
  • 110ED, Red, at focus.jpg
  • 110ED, Prism, Red, at focus.jpg

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#4 Jeff B

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Posted 28 February 2020 - 04:10 PM

And now the inside of focus comparisons of the two types of diagonals.

 

Jeff

Attached Thumbnails

  • 110ED, Blue, Inside of focus.jpg
  • 110ED, Prism, Blue, Inside of focus.jpg
  • 110ED, Green, Inside of focus.jpg
  • 110ED, Prism, Green, Inside of focus.jpg
  • 110ED, Red, Inside of focus.jpg
  • 110ED, Prism, Red, Inside of focus.jpg

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#5 m9x18

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Posted 28 February 2020 - 04:21 PM

Jeff, you are so meticulous in your testing methods. Thank you for taking the time and effort to do all this and posting your findings.



#6 peleuba

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Posted 28 February 2020 - 04:23 PM

Jeff, there should be no arguing - wait, no, this is CloudyNights...   The prism is adding overcorrection at all three wavelengths - RGB - that does not exist when using the mirror diagonal.  

 

Dramatic - No; Noticeable - Yes.  In your image it looks like the prism actually helps in Red...   In Red, its slightly undercorrected.  The prism nearly takes it to a null.

 

I am not surprised.  Prisms add correction at some level - always.  Whether this correction helps or hurts depends entirely on the sign of the error in the main objective.  

 

When I have a scope on my test bench performing DPAC or an indoor star test, I don't use any diagonal.  I don't own a prism.  Your test shows something that I've always known to be true with prisms - They ADD correction, no matter what.   

 

Well done.


Edited by peleuba, 28 February 2020 - 04:29 PM.

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#7 Kent10

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Posted 28 February 2020 - 04:34 PM

Thanks very much for this, Jeff.  Very interesting.  I also noticed the prism images aren't as bright.  Is that just the picture or is the transmission noticeably less through the prism?  Do prism diagonals always add  overcorrection?  And I wonder if it is always the same amount.  How much?


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#8 Jeff B

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Posted 28 February 2020 - 06:34 PM

Jeff, there should be no arguing - wait, no, this is CloudyNights...   The prism is adding overcorrection at all three wavelengths - RGB - that does not exist when using the mirror diagonal.  

 

Dramatic - No; Noticeable - Yes.  In your image it looks like the prism actually helps in Red...   In Red, its slightly undercorrected.  The prism nearly takes it to a null.

 

I am not surprised.  Prisms add correction at some level - always.  Whether this correction helps or hurts depends entirely on the sign of the error in the main objective.  

 

When I have a scope on my test bench performing DPAC or an indoor star test, I don't use any diagonal.  I don't own a prism.  Your test shows something that I've always known to be true with prisms - They ADD correction, no matter what.   

 

Well done.

OH YEAH!!!  grin.gif

 

Actually Paul, I'm not so sure I see that as if you look carefully, there are small differences in screen position relative to focus between the AP and Baader diagonals, especially visible with the green inside of focus shots.  Specifically, the shots with the prism diagonal are a hair closer to focus, which will tend to make the lines bulge just a bit more. 

 

With the in focus shots, I had to get really, really, really close to the same position in focus but also where the screen was at laterally to get anything useful from the shadows at focus.  For example, here are some at focus images with the prism diagonal with the screen placed precisely between the bands in the white area.  Wow!  No shadows at all.  I've found even slight changes in the positions of the shadow at focus can give very different looking shape.   Another example is where I took the AP 178 images where I simply panned the shadow from the right hand side to the left hand side without moving the focuser.  You see very different shapes to the zone, inverts of each other.

 

So I am really hesitant to draw any real conclusions here regarding the effects of the prism diagonal.  If there is an effect, and there should be one as the prism is a refractive element, it to me is right at or below my level of detection in my DPAC rig.   This tells me though, it's a really good prism!

 

Now, however, if I was pressed to say there was indeed something there, I'd say a tiny, tiny bit more overcorrection in green and blue and maybe something in red with no changes in focus though. 

 

Jeff

Attached Thumbnails

  • 110ED, Prism B, White, at focus.jpg
  • 110ED, Prism B, Blue, at focus.jpg
  • 110ED, Prism B, Green, at focus.jpg
  • 110ED, Prism B, Red, at focus.jpg
  • AP 178, Green, at Focus, RH Shadow.jpg
  • AP 178, Green, at Focus, LH Shadow.jpg

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#9 precaud

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Posted 28 February 2020 - 06:55 PM

Color balance looking much better in these pics.

 

One thing to be careful of when taking images with and without a component in the chain as comparing them, as in with and without a diaginal. Make sure your camera is in full-manual mode, i.e. you set the aperture and shutter time to be identical for pics of both. Otherwise the camera firmware will try to make up the difference...that's what it was designed to do...



#10 Jeff B

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Posted 28 February 2020 - 07:25 PM

Thanks John.  Yup, learned that the hard way and thanks again for the new white LED and the tips on processing single the white LED shots (!!!!).

 

Jeff



#11 peleuba

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Posted 28 February 2020 - 09:03 PM

I looked again at green specifically.   I see more over correction with the prism.  The two green shots look to be taken at nearly the same spot with virtually same bands visible...   over correction by a small amount. 


Edited by peleuba, 28 February 2020 - 09:04 PM.


#12 scooke

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Posted 28 February 2020 - 10:43 PM

So, I had an idea.  idea.gif

 

While I had this critter set up in DPAC, why not look at the effects of using a prism diagonal.  All of the images above have an AP diagonal in the light path (and yes, I see NO differences in DPAC with it in the light path..none...zero...zilch....nada).   I do have a Baader Zeiss Spec prism diagonal and a 2" eyepiece adapter that screws on over the T2 threads on the diagonal's top so it was an easy swap out for the AP diagonal.

 

I figured this might settle some of, and/or create even more of, the arguments that tend to crop up here concerning the use of prism diagonals with fast ED based scopes. 

 

I focused the rig as best I could to match those DPAC screen positions when using the AP diagonal (got pretty close actually) and redid the white light shots at, and inside of, focus images with the prism in tow.  I then separated out the individual RGB channels of the white light "prism images" for comparison to those with the AP diagonal, specifically looking for correction and focus shifts associated with the extra refractive optics of the prism.

 

And

 

And

 

And

 

I could see not differences at all.

 

So here are the comparison shots with the at focus ones first.

 

Hover the cursor over the images to read the titles.

 

And let the arguments continue......

 

 

Jeff

I did the same experiment in DPAC using AP Maxbright, APM prism, and AT 99% dielectric.  I saw no difference between the AP and APM diagonals.  Same image with or without the diagonal as well.  It took awhile to see it but the bars were not quite as distinct in the AT diagonal.  Just the tiniest bit fuzzier but it was so close.



#13 stevew

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Posted 29 February 2020 - 01:12 AM

I love my Orion 110ED. I have been touting its quality for years, but there does not seem to be too many other owners of this scope on CN.

It gives nice sharp views, and I can see the slight difference in aperture when comparing it to my Stellarvue 102.

The HFK61 lens does give a warmer view of the Moon and Planets than an FPL53 Stellarvue I own, but the excellent optical figure make it a keeper. 

The Orion does show some field curvature at lowest power. Of course my TMB130 triplet is another kettle of fish...

Attached Thumbnails

  • DSC_0750m.jpg
  • post-15477-0-75679200-1476642668.jpg

Edited by stevew, 29 February 2020 - 01:22 AM.

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#14 stevew

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Posted 29 February 2020 - 01:29 AM

So, I had an idea.  idea.gif

 

While I had this critter set up in DPAC, why not look at the effects of using a prism diagonal

 

And

 

And

 

And

 

I could see not differences at all.

 

 

 

Jeff

Thanks Jeff, I always wondered if a high quality prism diagonal would make a difference on the color correction.

Now I don't have to spend the money to find out...



#15 Jeff B

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Posted 29 February 2020 - 05:36 PM

So staring at the images a fresh, I have to agree with Paul, the prism is adding some over correction.

 

So I had another go at some mirror/prism comparison images.  These were shot inside of focus.

 

This time, I was more compulsive than usual in getting the Ronchi screen positions closer to each other and closer to focus overall (as that also increases the sensitivity of the test).  I switched to my 200 LPI grating too, for a bit more resolution.  

 

Another thing I did was to separate out the RGB channels in mono-chrome.  This helps me really see differences better as I, and my computer screen, don't have to deal with any color artifacts we may both have.

 

And it worked well if I say so myself.  The prism is very definitely adding some over-correction (something this lens does not need).  You can especially see this in the "white" and green images as a "belly bulging" of the lines, which on the inside of focus, is overcorrection.  However, I see no real changes in color focus positions relative to each other.  

 

So, this scope (110mm F7, FPL-51 ED doublet) does not, on the test bench anyway, benefit from the use of a high quality prism diagonal over a high quality mirror diagonal.  In fact, the use of the prism diagonal seems to degrade the optical performance a small amount.

 

And, as usual, sensi-Paul was right....fingertap.gif

 

Again, place the cursor over the images to read them (especially important in mono-chrome).

 

First the white light images.

Attached Thumbnails

  • 110ED, Redo, 200 LPI, Mirror, White, Inside  focus.jpg
  • 110ED, Redo, 200 LPI, Prism, White, Inside  focus.jpg

Edited by Jeff B, 29 February 2020 - 05:45 PM.

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#16 Jeff B

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Posted 29 February 2020 - 05:37 PM

In Blue

 

 

Attached Thumbnails

  • 110ED, Redo, 200 LPI, Mirror, Blue, Inside  focus.jpg
  • 110ED, Redo, 200 LPI, Prism, Blue, Inside  focus.jpg

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#17 Jeff B

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Posted 29 February 2020 - 05:39 PM

Now green

 

 

Attached Thumbnails

  • 110ED, Redo, 200 LPI, Mirror, Green, Inside  focus.jpg
  • 110ED, Redo, 200 LPI, Prism, Green, Inside  focus.jpg

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#18 Jeff B

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Posted 29 February 2020 - 05:40 PM

And finally red.

Attached Thumbnails

  • 110ED, Redo, 200 LPI, Mirror, Red, Inside  focus.jpg
  • 110ED, Redo, 200 LPI, Prism, Red, Inside  focus.jpg

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#19 m9x18

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Posted 29 February 2020 - 05:45 PM

Wow Jeff, you and Paul sure do some wonderful tag-teaming in on these lenses. I learn something new every time I read these threads.


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#20 scooke

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Posted 29 February 2020 - 10:30 PM

And finally red.

Thanks for doing this Jeff and thanks Paul for the input.  It's quite obvious with the latest set of images.  It sure wasn't obvious when I tried it myself.


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