161 replies to this topic

[Psion]

One picture of the Moon from Canon 5D (full frame)

 

[meade4ever]

Beautiful image, it is amazing how sharp is it.

This telescope can provide top pictures

[SandyHouTex]

One picture of the Moon from Canon 5D (full frame)

 

 

Excellent pic.

[Astrojensen]

It's a nice picture, but it doesn't show nowhere near what an 8" scope can do near the diffraction limit, so I won't call it amazing. This photo shows less than I can see visually in my 63mm Zeiss Telemator (the double crater near the alpine valley is just a spot, while I can distinctly see two craters in the Zeiss; I can't see Clavius JA in the photo, but it's well visible in the Zeiss, etc.). 

 

 

 

Clear skies!
Thomas, Denmark

[Psion]

The picture cannot show more than 63mm a telescope, but a difference is in a  magnification 300x in the Zerochromat and the Zeiss. I made a picture (one shot) under a bad condition (seeing 5/10) and I cannot resolve in the eyepiece a more detail than 2km.

Edited by Psion, 05 October 2014 - 04:22 AM.

[Astrojensen]

 

The picture cannot show more than 63mm a telescope, but a difference is in a  magnification 300x in the Zerochromat and the Zeiss. I made a picture (one shot) under a bad condition (seeing 5/10) and I cannot resolve in the eyepiece a more detail than 2km.

I'm not really sure I understand all what you're saying here. The picture was taken under bad conditions, that I can understand. 

 

 

Clear skies!

Thomas, Denmark

[Psion]

You cannot compare one shot a picture and view through an eyepiece. 

[Astrojensen]

 

You cannot compare one shot a picture and view through an eyepiece.

Totally agreed and that's what I wanted to say in my post above. It's a nice picture, but it doesn't say much about the quality of the scope. 

 

 

Clear skies!
Thomas, Denmark

[Psion]

Yes, exactly. You can see only how big is rather good FOV

Edited by Psion, 05 October 2014 - 07:48 AM.

[jrbarnett]

Yes, exactly. You can see only how big is rather good FOV

Oh please oh please oh please, get us a high mag image of Plato!

 

Thanks!

 

- Jim

[Psion]

The image of Plato (or any planet) is not about the quality of the telescope, but about the skills of a photographer and seeing condition.

[Simoes Pedro]

Various dialyte designs have been around for well over 100 years, it's true. However, this is a very modern take on the concept, and is completely original.

 

The quoted Strehl ratio is polychromatic for the visual range. 490nm, 560nm and 620nm. It's on the web site.

 

The performance in the violet is not as good as for the visual range, but you can't have everything. For imaging, I have always said that you need to use filters - again it's all on the web site. Nothing is hidden, and there are no 'bugaboos' to be found.

 

This design is not intended to replace 3 and 4 element apos, and the price is not the same, either.

Actually there might be some "bugaboos".

 

Ray trace is not on standard wavelengths. 

 

Ray trace data is at 490, 560 and 620 nm. Should show F and C lines with focus at either e or D lines. C can be replaced with more realistic Sodium 632nm.

 

Also mentions telescope is diffraction limited over field of view, which actually is meaningless when not accompanied  of wavelengths and field sizes in degrees or mm.

 

I also do not get the comparison with the 8 inch f12 achromat. The folded optical path of the zerochromat is about 5000 mm (from your drawings) that is equivalent to a 8 inch f25 scope not f12. So the meaningful comparison is against a f25.

Edited by Simoes Pedro, 14 October 2014 - 09:45 AM.

[wiseone]

No, there are no 'bugaboos', actually.

 

I am primarily interested in visual performance, and scotopic vision cuts off at 640nm, so 632nm is pretty useless. Even 620nm is debatable. 

 

If you have read through this thread, you will see that the visual performance is exactly what I have said, and is crisp and sharp right to the edge of a 0.75 degree field of view. The Moon image taken by Psion is rather good, and shows very little chromatic aberration, particularly considering that he did not use filters. I have always recommended that filters be employed for imaging, as the performance at the blue end of the spectrum is less good than in the visual region.

 

The field of view has always been stated to be 0.75 degrees, and the wavelengths are 490nm, 560nm and 620nm. Not standard maybe, but realistic.

[Simoes Pedro]

No, there are no 'bugaboos', actually.

 

I am primarily interested in visual performance, and scotopic vision cuts off at 640nm, so 632nm is pretty useless. Even 620nm is debatable. 

 

If you have read through this thread, you will see that the visual performance is exactly what I have said, and is crisp and sharp right to the edge of a 0.75 degree field of view. The Moon image taken by Psion is rather good, and shows very little chromatic aberration, particularly considering that he did not use filters. I have always recommended that filters be employed for imaging, as the performance at the blue end of the spectrum is less good than in the visual region.

 

The field of view has always been stated to be 0.75 degrees, and the wavelengths are 490nm, 560nm and 620nm. Not standard maybe, but realistic.

 

What I have learned today:

 

1) The telescope is not intended for planets. Only Scotopic vison matters.

2) The F line (486 nm) is not in the scotopic domain but 490nm is.

2) Diffraction limit = "crisp and sharp".

 

My deepest apologies.

Edited by Simoes Pedro, 14 October 2014 - 10:42 AM.

[wiseone]

For visual use, only scotopic vision is necessary.

 

If you want to image, use filters.

 

Retrofocal dialytes can be any f ratio you want in any given physical length. 

 

The Zerochromat 8 inch refractor is f12. The tube length has nothing to do with the overall f ratio.

 

It's crisp and sharp across the entire field of view, and diffraction-limited for the given wavelengths across the given field of view.

 

wiseone

[Psion]

Diffraction limit is an urban story - I saw a lot of not very good telescopes, but everyone of them reach a diffraction limit.

 

You can see a brighter object also in Mesopic vision and blue of red is not so important like a green.

 

[gatorengineer]

I think this thread has uncovered the critical need for a new accessory to ship with the Zeroachromat -- a Troll repellent holder.  It sure does seem to draw them.

 

Let me summarize what I see with the Zerochromat

 

It has much better color correction than an Achro.  Its a new and innovative unobstructed design with spots diagrams are relatively easily read by consumers who see them for more than pretty colors.  

 

For some reason I dont see spot diagrams on most refractor vendor web pages.....

 

A D&G F12 with a motorized moonlight professionally tubed up, would be at least the same price for an Achro, and would weigh AT LEAST twice as much, and require roughly 3x the mount.

 

Chromacorrs arent commercially available that I am aware of anymore...... perhaps if you have a really oddball lens....  so that D&G wouldnt have as good of color correction (perhaps we can acknowledge that)

 

There is nothing unobstructed in its price range that can touch it, commercially made.  an 8" Chief at this size would be possible but that is an ATM project, not a commercial product.

 

Some folks like the contrasty view of unobstructed scopes.  Thats why i have a 4" refractor...(a scope thats regularly bashed in the refractor forums for its color correction)

 

If I didnt have an MN86, I would be all over this scope, but again my MN86 weighs 50% more and isnt unobstructed....

 

Kudos to the optician who gave the hobby another choice, and congrats to the folks that have them.....

[GlennLeDrew]

It must be stated tbat the Moon and planets are more than bright enough to activate photopic vision. The colors on planets are somewhat subtle, and on the Moon *very* subtle. But even if one argues against the fact of sufficient brightness due to the subtleness of the hues, the biggest clue comes simply from the *prominent* chromatic aberration they can reveal. False color is not amplified; it can be seen only when the intensity of the subject is in the photopic--or at least mesopic--regime.

 

And it bears mentioning that the eye can work over the range of photopic to scotopic simultaneously. A dim galaxy can be seen in the same field along with a colorful star.

[Psion]

I understand Peter, a lot of people cannot believe that the Zerochromat is a very good telescope. Yes, it isn't TMB, but six years is the same situation - "everybody knows everything" about an optical parameters and more than producer, without touch the telescope....

[Astrojensen]

 

I understand Peter, a lot of people cannot believe that the Zerochromat is a very good telescope. Yes, it isn't TMB, but six years is the same situation - "everybody knows everything" about an optical parameters and more than producer, without touch the telescope....

Believe me, when I'm saying, that I'm ITCHING to really put this scope through its paces. I've been offered it for a very good price, but I am not in a financial position to purchase it. If I could, everyone here would know about it already. 

 

 

Clear skies!
Thomas, Denmark

[Mark Harry]

I zoomed the pic above, and saw detail that 'reflects' pretty darn good detail.(as well as the thread/pic allows here)
   The mantra I usually adopt, if I like what I see, it's good enough. Personally, I would prefer to take a good look through a Zero.
New design twist, another viable choice.
M.

[De Lorme]

How well does it bring in DSO like M13?  De Lorme

[Psion]

M13 is fantastic in the eyepiece (Panoptic 35mm or 24mm), you can recognize pinpoint stars from center to edge.

[AlphaGJohn]

Dialytes have been a concept that goes back to Dollond who is credited with inventing the achromat, he wanted to produce larger OGs but was limited by the quality of flint glass,which could not be made in large pieces at that time, although,much larger pieces could be made from crown glass. He conceived the idea of placing small flint lenses about half way down the focal length,producing the first ideas about dialytes. However he could not find a method of calculating the radius of curvature of the flint element.

 

One more note about why the dialyte design has not been popular (aside from folks generally doing what othrer folks do): Not only do modern methods allow determination of unusual curvatures, but Peter also has access to a much wider variety of indexes of refraction in his lens elements than Dolland would have imagined (or could have plugged into his calculations). The thing about the "Zero" is that the fancy glass it uses are of small diameters compared to what would be required in a conventional APO of the same light gathering power. Price comparisons to reflectors are clearly going to come up in favor of the reflector of similar or somewhat larger apertures, but we're hanging out on the refractor forum so it's already established that we're ignoring some of those quite sensible points. Here we have a commercial refractor with fine performance at a price point for a 200mm instrument (with the performance in question) that is impressive--to say nothing of the thing's astoundingly utilitarian size & weight. I'm on record as wanting one and while I admit readily that this isn't for everyone, I'm delighted to see some reports of its actual use. Please keep them coming. I may never actually be able to buy one but I sure enjoy hearing some practical results--just wish I could contribute to them.

 

So, do I begin lobbying my wife now or wait until she's gotten over the Lunt H-a scope's purchase? Anyone want to buy my ATM 10" RC? 

 

One other minor item, I think the request for a hi-mag shot of Plato was referring to the lunar crator--l at least, would love to see that photo myself.

 

Wishing you all fewer clouds and more time under the sky,

 

John

[ATM57]

 

I observe the Moon today and I can't see any CA in magnification 550x (Zeiss MARK V bino-head, Nagler).

 

I agree. chromatic correction is beautiful. the Contrast for mid range size feature is also amazing, even compared to a good C14

 

-- benoit

 

Now that the honeymoon is over... Any new updates/observations?

 

Scopejunkie