View Full Version here: : Megrez problems

03-06-2005, 10:44 AM
For those interested, the megrez is being sent back to William Optics in Taiwan (shipping paid for by William Optics) for repair/replacement. Both WO and Frontier Optics said they tested the telescope and that its performance was fine, so I guess this would suggest that something may have happened during shipping.

I just have to wait and see how they assess the problem and what the outcome is.



03-06-2005, 10:53 AM
Hi Dan , as I said in my e-mail , i find this hard to beleave.
The transportation case that you had it in seams quite substantial.
If any thing were to happen it would be more in bad collimation and not the optical abberation we saw.
A few of the first Celestrons had this problem with lens cells working there way loose in transport and the doublets moving in relation to each other but were easialy rectified.
Also the Orions were prone to bad collimation and don't have any way of adjusting the cell easaly .
Your collimation was spot on .
We checked for loose optics which you didn't have so it is a mistery.
Did you send it back to Frointier first and did they recheck it before forwarding it on to WO.


03-06-2005, 11:07 AM
No, Frontier Optics said to directly contact WO. So it is going directly back to the factory in Taiwan. I see your point regarding the packaging.

03-06-2005, 02:27 PM
Hope all goes well for you Dan,I would send It back too!I expect a high end apo to star test well on both sides of focus! there is no Ifs or buts.

Louie :mad2:

03-06-2005, 05:23 PM
Thanks Louie. I have been told that William Yang himself will be looking at it next week when it arrives. Communications with William Optics so far have been excellent.

03-06-2005, 05:42 PM
I have read that some ED designs can produce weird star test results without there actually being anything wrong with the scope.

My ed80 has sharp rings inside of focus and mush on the outside. This I hear is due to the different colours refracting at slightly different points away from focus. In focus images are great and thats the important thing.

03-06-2005, 06:43 PM
Geoff that does not explain why others of the same design have near perfect star test.

Louie :confused:

03-06-2005, 10:44 PM
What is the problem with the scope ?

Quite a few of the early megrez 80's had issues with the objective cell being too tight and pinching the optics, but I thought this was resolved long ago.

Cs-John B

04-06-2005, 03:29 AM
Dan i really hope everything works out and quickly for you to , its the biggest fear when buying equipment that the optics may be amiss but hopefully WO will look after you .

04-06-2005, 08:02 AM
What he has got is mush both sides of focus.
But outside is better than the in , but both have excessive flarring like heat abberation.
We allowed it to cool down inverted but even by the end of the night this flareing didn't change at all, not one bit.
The inside focus has a couple of out side rings that can be seen but the inner rings on the star are surrounded by large amounts of blue and flareing and are quite ill deformed.
Out side is some what better but not what you would expect.
Focused stars (sirius) were surrounded by a lot of blue.

Now this is as compared to my C80Ed and if you have a looky at the review I did a while back the star tests are there of it. Inside , out side and focused stars images are excellent for a ED doublet.

He also can't crank the mag up as much as mine with out it washing out.
One would expect to be able to do the 60x / inch on a good night .
The night was not perfect but was able to get this and more.

So it appears there has to be some thing major wrong.

I have an old chinese acromate that has a better star test with less blue.
I thought the idea of the Ed triplet and doublets is to reduce the distance all the colors come to focus especially in the blue green area and different designs and glass work at different wavelenths better , but there all trying to get all the spectrum focused at the same focal plane.

I am very interested in finding out what is wrong.
What i should have done but plane forgot to do is take a snap shot of the star tests done that night , but every one present observed the testing.
I was to busy fondling my new Nagler :D

P.S. we swapped diagonals and used various eyepieces as well.


04-06-2005, 08:25 AM
For any one reading this tread and thinking what are they talking about here is a link and a good explanation on star testing your optics.

Just remeber reflectors and refractors show different star tests due to the obstruction.


Quoted TMB Optical
The first and most important thing to remember about star testing a telescope is to never expect your telescope will star test perfect, as it will not. The test itself is just too sensitive to wavefront aberrations. W. T. Welford studied the sensitivity of the star test (see "Optical Shop Testing" pages 397 - 426), and found that under ideal testing conditions, the star test is sensitive to 1/20 wave for slowly varying aberrations (such as third order spherical), 1/60 wave for rapidly varying aberrations (like a sharp zone on the optical wavefront). These are wavefront measurements, not surface errors. Amateur optics that exceed 1/8 wave on the wavefront, or a better measure, a RMS wavefront of 1/40 wave are rare indeed, and are fully suited for high quality planetary work.

Most amateurs and authors of star test manuals make the mistake of using too little power during testing. If you use a low magnification, such as only 20x per inch of aperture, you are desensitizing the test. Much better still is to use 50x or slightly more magnification per inch of aperture (200+ power for a 4" telescope). The next mistake is the commonly heard recommendation of using a 2nd or 3rd magnitude star. This may be fine for large apertures of over 12", but in the most common telescope sizes, a bright star is a much better choice (Vega, Capella, Altar or Deneb are good choices). A bright star will show zonal aberrations much clearer than a dimmer star, and will allow other optical defects to be much easier to see. Use a well corrected eyepiece (Nagler, Radian, Plossl or Ortho) and don't use a diagonal or barlow in your tests (unless it is known without question, to be of very high quality). A prism diagonal will add overcorrected color and spherical aberration, therefore it is not recommended.

Give the scope a full two hours of cool-down time (or more if the scope has a long thermal equilibrium time or you live in a cold area), and make sure it is a night of good seeing, say 7 or better on a scale of 10. Testing under worse conditions can hide aberrations, and the poor seeing can mimic surface roughness on the optics. Atmospheric turbulence can also cause softening of the contrast in the ring pattern, outside of focus. This is due to focusing on the upper level turbulence. Just another reason to test on nights of good seeing. The higher the test star is in the sky during testing, the better. Using filters in the peak visual wavelengths such as a Wratten number 58 filter (dark green) or number 15 (dark yellow) will help in your testing, especially with refractors, because of their chromatic and spherochromatic aberration components, which can make the star test look worse than the optic really is. Focus on the star, and then focus out 5 or 6 rings on either side of focus (inside and outside). The most important area of the optic is the edge, ideally the outer most thick ring should appear identical on both sides of focus. That means the thickness, brightness, texture and hardness/softness should be the same. If they are just slightly different, the optic is a good one. A gross difference, however, is a bad sign.

Next, rack out 10 or more rings and look for any bright, thin rings (dim on the other side of focus) inside the diffraction pattern. These are zones, and can be common in mass produced and homemade optics. Then bring the focus down to 1 or 2 rings on either side of focus. Here you are compressing the aberrations down close to focus, and very few optics will pass the one ring test. Again, don't expect perfection. You are looking for perfect symmetry here, the breakout of the Airy disk to the first ring, with identical focus travel on each side of focus.

Now bring the scope to best focus. What you want to see is a well defined, round Airy disk, with no more than 2 or 3 diffraction rings around it. This is the real meat and potatoes of optical performance, that is, how dim are the first and second diffraction rings at best focus? If they are dim (a perfect optic would have 7% of the total energy in the first ring, 3% in the second), then you know the optics are good. You can also do the "snap" test, which is a subjective way to test optics, but still a good general test. If the star (or planet) snaps into focus without any ambiguity of focus, the optic is probably a good one. The same holds for high power viewing. A good optic can stand high magnification on a night of good seeing, and a poor one will get mushy at high powers.

Other aberrations such as astigmatism will show itself as oval images, just outside of focus, that shifts to a 90-degree angle oval on the other side of focus. The contrast of the ring pattern on both sides of focus is a good indicator of smooth optics. This is important for detecting low contrast details on the planets, because telescopes can have quasi-perfect symmetry in the star test, but if the surfaces are rough, the images will not show high contrast. Anything that deviates from a clean, round Airy disk at best focus, assuming the telescope is collimated, no tube currents or temperature boundary layer problems above the mirror, fully cooled down (optically at null), and is tested during excellent seeing, is a sign of an optical aberration.

Even if your telescope doesn't pass the star test with flying colors, please don't stop enjoying your telescope, and don't worry about the star test too much, unless it shows very obvious errors. Again, no optic can pass the star test perfectly. What really counts is how it performs in focus. If your telescope shows highly detailed lunar and planetary images, you have a very fine optic.

Happy star testing!

04-06-2005, 11:27 AM
And thats the bottom line!sending out bad objectives in high end gear ,now remember Dan's already forlked his money out,he should be compensated from these big Prks!
This kind of thing will just keep happening because the law lets them and where not willing to fight back.

Louie :tasdevil:

05-06-2005, 08:41 AM
OK , got to Star test Strickers new scopes last night .
Both the Orion ED80 and the C11.
Won't go into the C11 much because in all fairness it never really cooled down enough to do a serious evaluation on the optics.The only thing able to really be seen was it was very slightly out of collimation , but again I would like to do it again on a night of better seeing and a cooled scope.
Now onto the Orion ED80 with reference to the Megrez 80 problems and the Celestron ED80 I have used as a bench mark.

The Orion ED 80 tests for all purposes showed the same star test pattern as the C80. (see Review onC80)
Not very surprising as the optics are reportedly of the same origin , just in different packages.

The only thing to note was a slight bit of over correction in the out focus star test, seen as a slightly brighter second outer ring than it should have been.
The inner focus was spot on and collimation was also very good with round well defined rings.
All tests including the focused bright stars showed very little blue surrounding them, about the same as the C80 , but less than the Megrez.
Heat was not a problem and test patterns showed very little heat aberrations.

Hands on viewing proved the optics to be good and we pushed the scope up to over 180x on Jupiter with reasonable results considering the night was not perfect with some high wispy clouds about.

Any way the moral to the story is, never assume your optics are good just because of a name , always do a star test so you know that your getting what you paid for.
Bad one do slip through even premium brands.
One comforting thing is , it sounds like Williams are looking after Dan .


16-07-2005, 01:31 PM
Did this issue get resolved ?

17-07-2005, 10:02 AM
We got the AVI's star images done last night and am extracting good frames to send back to Dan first.
I will let Dan give to go ahead before doing a post on the results.


26-07-2005, 04:53 PM
Any further updates here??

27-07-2005, 04:07 PM
The Megrez was returned by WO who suggested the optics were perfect. This came as somewhat of a surprise to myself and the other guys who had the opportunity to look through this telescope.

I star tested the returned scope the other week thanks to mark (mark h) and andrew (astro_south). I haven't resized the images yet so I can't attach them, but mark or andrew might be able to comment on what we saw in better detail than I can?

The main problem I think is that there is considerably more false colour than you would expect from an ED triplet.

Anyhow, the scopes main use is low power widefield views, and for this it works fine.



02-08-2005, 03:04 PM
I am really sorry to say that, but I would not call William a high end brand.
I heard similar problems from other owners of the EDT and of the ED/SD series. The only 3 really good telescope Williams ever sold are the 80/480 super-apo, the 80/600 super-apo and the FLT 110/715 FluoroStar. All 3 optics are not made by Williams. Both 80's are TMB and the FLT is a TEC. I am not surprised by your experience.

02-08-2005, 07:09 PM
Who is TEC / TMB? (Manufacturers obviously)

Any more info Stephan? :help3:

02-08-2005, 09:46 PM
Hi Stu,

TMB Optical is a US based company owned by Thomas M Back, they started business in 1990. They specialise in Apochromatic Refractors of the highest standard. They no longer produce telescope optics of their own. They have the lens elements made a by a Zeiss subcontractor in Russia and their telescope tubes and other components are made in Germany.


TEC stands for Telescope Engineering Company. They are based in Colorado and build high quality Apochromatic Refrcators and Maksutov's.


Both top quality products.

CS-John B

03-08-2005, 09:31 AM
Star test images from Megrez .
These 5 are with out a barlow using a ToUcam.
Going from no2 outside focus focused to no6 inside focus.
Frames extracted and the best ones picked.

The conditions were quite good as seen from Andrews Newtonian and his 100mm f5 Achromate at 4/5, and there was a first 1/4 moon .
We allowed the scope to cool down inverted and no obstruction in the focuser for 1hr and Dan had the scope case open all afternoon so that the scope was not insulated.

It was initially obvious that there was some improvement from before visually .

Visually we used a Radian and orthoscopics eyepieces with and with out an Orion 3 element 2x APO barlow and a 4x Powermate

Imaging we used the 2x Barlow as well as just the imager.

Overall the central part of the star tests was steadier than before but still showed the same heat like distortions and haze masking the inner rings.
At first you would say that this is heat distortion except that on both nights it showed no improvement over the whole night. 4hours plus.

You would assume there to be some improvement over 4 hours if it was heat.
The temperate drop on both nights was not extreme and the nights were fairly mild for winter.
So the objective should have been able to come to temperature .

You can see the centre is a wash with a blue and green haze and the focused star has a blue halo surrounding it .
The focused star a tad worse than my Celestron 80Ed or Tony's Orion Ed.
My star test pics can be seen at the review section for comparison and show a very well defined ring system.

Even Andrews old F5 Achromate showed a better star test.

No mater how far in or out of focus we racked the Megrez it just would not show a well defined diffraction rings or show the central star and you can see the outer was better than the inner focus.

The last thing we did was cranked up the power on the moon to 90x per inch ---280x , and was surprised to see a fairly well defined view with little atmospheric heat distortion.
This was quite a good result .
Jupiter would not take this magnification and 112x was it's limit .
This had me thinking that may be the star test was acceptable ????

This had me thinking all the way home , so when I got home that night I pulled out the Celestron with the same power and no cool down and it was still a better image.
90x per inch is pretty dam good for a refractor thou and as Dan points out low power views are very good..
This is what i bought my ED for low power imaging and not high power planetary use.

As I have said before , mechanically the Megrez is first class but optically there is some thing amiss.
If this is a heat issue life is to short to wait for the triplet to come to temperate.

Williams did offer Dan the choice of spending even more money and buying the Florite APO.
From what I have read on the forums this appears to bve the model of choice for imaging but comes at a much higher price.

I am just hopping that some one at the Queensland Astrofest will have another Megrez triplet or another brand of triplet APO there that I can have a looky through just for a comparison as this has got me baffled.


03-08-2005, 09:37 AM
This lot with the APO barlow.
Notice the distortions at 180degs to each other????????????

The powermate was the same and is obvious that the Megrez did not like the higher powerfor the star tests.

03-08-2005, 11:23 AM

I have to say those star test images are not good. But as you rightly allude to, the important issue is not how it star tests out of focus, but the quality of the in focus images, we don't do a lot of observing out of focus :) However, for a supposedly premium triplet it should star test a lot better than that IMO.

CS-John B

03-08-2005, 12:55 PM
Thanks for posting the star test images Mark!!!


03-08-2005, 01:13 PM
I have never had such a difficult time star testing an optical system before , but then i have never had a APO triplet to test before.
No mater how much we racked the focuser or waited for cool down it just didn't want to play ball.
A real mixed bag.

I had my cheapy 20x80mm triplet binoculars(not an APO) apart a week ago re blackening the interior of the barrels and fixing a few little annoyances and did a star test image from one of the individual barrels with the original eyepiece and prisms removed and an old 3x barlow and a12.5mm orthoscopic held in place , like a telescope system.
Any way it was easy to produce a very nice star test pattern inside and out side focus and colour was obvious but not what you would expect from an f4ish triplet lens assemble at that magnification. 80x approximately
Worse colour than the Megrez but not as bad as an f5 Acromatic refractor.

I will attempt to get a TouCam image from them after Astrofest and compare to the other refractor tests done to date.
I also will be doing a Bino review before I destroy them between them and a pair of Celestron(Vixen) 11x 80's .

I love pulling things like this apart and there only fairly new.
Putting them back together was not as much fun due to the very simplistic prism mounts.
I tried different wide field eyepieces to see how they work and have toyed with the idea of using the objectives and making a neck friendly 45deg binocular , with interchangable eyepieces.
By my avaitar you see why. :rofl: :D