ES 127 CF FCD100 issue.

[Pingster]

I have two 80mm APOs. A TS Photoline and a new ES 80mm with new FCD 100 glass. I often bino view thru them with 24pans and the image is crystal clear, especially the ES80mm which looks super clear errect image daytime.

Motivated by the new ES80 CF. I decided to get the 127mm Carbon Fiber with FCD 100 glass. Looking inti the lens you get that wow feeling. This is a lot of glass. 

The good thing is it works with binoviewers without barlow/oca and it even works with errect view diaginals without barlows.

But to my suprise the image at the same mag as my 80mm's is softer/more blurry! Rember this is daytime viewing. I am totally shocked as the double in aperture should give almost twice as much resolution... so the view should be super crisp!

The scope could be out of colominating? Its hard to believe collomination problem can make the scope give views worse than an 80mm!

With refractors... bigger objective surely mean better daytime views? Sharper, more resolution?

[Ben the Ignorant]

Hi, I also have the 80mm TS triplet; it's super-clean. I can push it to 240x if the air doesn't jostle too much, and if the target is very bright, but 200x is more reasonable. I never looked through an Explore apo, but i wish i had. Anyway, a 127mm triplet should be very crisp, but the reason why it's not will be revealed by a nighttime star test, or an artificial star test.

Yes, your 127 could be miscollimated, and it does make the image much softer if the misalignment is large. I did recollimate my 80 triplet a couple of times (because I opened it to paint the lens edges black, and another little mod). I also realigned a 80mm doublet achromat that was horribly blurry at first, but it does very well now.

Wait for the star test, it speaks for itself.

[Peter Drew]

Don't forget that daytime viewing at this time of year is going to be subject to turbulence due to the warmth, a 127mm aperture is going to be affected far more than a 80mm even at the same magnification. Do star test it though just in case it needs collimating.

[Pingster]

The daytime turbulance came to mind.  But i also use a 12in dob during the day and it looks better than all my APOs. Ill do a star test and report back. 

[Pingster]

Today i did a artificial star test with the 127 to find out why the daytime views are less sharp than the 80mm i have.

Artificial star, a tiny pin prick in card, with LED lamp. +20m from telescope.

The photos are naturally more blurred than thru the eyepiece.

When moving the drawtube towards the objective... to focus.... then going thr focus i get the image where the centre middle core is right. 

What the pictures dont show is that moving towards focus, the ceoncentric rings are much more defined and sharper than when moving the drawtube backwards out of focus.

When moving the drawtube away from the objective and i get the image where the middle core is dark, and the rings are slightly less sharp defined.

So inside and outside of focus the star test is not identical? What does that mean? Can an expert chime in. Should i reject this scope?

Because i bought it mostly for daytime viewing, was supposed to blow my 80mm out of the water but it dies not.

Under the stars last night, the seeing was not great. There centre FOV shape, but 75 to 85% from centre the stars where not great. Slightly smeared.

Used 24mm TV Panotics.

[Ben the Ignorant]

Your star test is excellent, do not reject this scope! Having slightly sharper rings inside of focus is normal, and what matters most is your scope...

1...has no astigmatism, or the circles would be ellipses, and oriented differently on each side

2...has no roughness, or the rings would not be even in brightness and thickness; the polish is very good

3...no false color, or the disks would not be plain white

4...has only a barely-there zone at 1/3 of the radius, a circular region where the optics are a little too shallow or slightby humped. You can see a darker circle in the top image, and its brighter counterpart in the other. These imperfections are called "cosmetic" because they only make the star test look a little less perfect, but they don't change the image quality.

The star test is hypersensitive, so seeing traces of less-than perfection is nothing to worry for. Compare your star test with this one:

http://r2.astro-foren.com/index.php/de/9-beitraege/01-aeltere-berichte-auf-rohr-aiax-de-alles-ueber-apos/726-a078a-toa-130-1000-14023-ortho-apo-spitzen-qualitaet-wrohr

(no need to translate, just compare the pics). It's nearly the same, even the Tak has a zone but still has a Strehl (optical quality) ratio of 0.99 (99% of theoretical perfection). Its inside focus rings are somewhat sharper, and at excessive power the central core of a star is a bit skewed. Between 0.95 and 0.99 Strehl a refractor is excellent, they are decadent below 0.80 but your ES is way higher than that.

Keep it, and try daytime observation when it rains (yes!), or when it's heavily overcast, turbulence will be dampened a lot. Also, avoid looking over paved roads and such, they radiate lots of heat waves that blur the view, especially in larger scopes.

[Pingster]

Just a quick reply, i shall update this post tonight when i have time.

Ben thank you so much for your expert reply. I compared it to my 80mm on the same star tesr and they both came out almost exactly the same as you said... that its normal for in focus to be better and the dark centre etc. And as you saidf the star test was almost perfect white, the blue is caused by the phone camera. Thank you so much!

And under far better conditions, a cool day i compared them both for 3hrs and yes the 127mm is twice as good as the 80mm.

Ive used a APM 100mm gaint bino and both these scops thrash it to bits. Very happy.

[John]

Thats not a perfect star test but it's good enough for very satisfactory viewing I'd have thought. The only scopes that I've used that have identical intra and extra focal star images are my Tak 100 and LZOS 130 and those cost a fair bit more than the ES 127 of course.

Very many scopes do exhibit a little spherical over or under correction. Looking though the star test archives on a couple of sites (eg: Astro foren the German site) shows most of the tests showing one of these abberations to some extent but that does not stop the scope being pretty useful.

I usually star test at 150x - 200x and use stars well up in the sky. Of course the scopes have to be well cooled (triplets can take some time !) and the seeing conditions need to be good to get reliable results.

Test it under the stars on some tight doubles and see how it fares.

 

 

[Stu]

I think it would be interesting to re test both scopes at higher power so you can actually see the diffraction rings, I think you will see a lot more useful info then. About x120 to x130 for the 80mm and x200 for the 127mm

[Pingster]

The defration rings are very round and much more clear at the eyepiece and i did it at x175 the highest mag i could. 

The phone pics did not perfectly capture the test. 

[Stu]

1 hour ago, Pingster said:

The defration rings are very round and much more clear at the eyepiece and i did it at x175 the highest mag i could. 

The phone pics did not perfectly capture the test. 

Sorry, a little confused. Your original post said the pics were taken using 24mm Panoptic, so at a low mag? Do you have the high mag pics?

[Pingster]

Oh my first use was during the day and i used 24mm pans and 40mm TV plossles. But the star test was done with a TV x2 powermate and 11mm TV eyepieces. ☺

The optics of the 127mm and 80mm CF FCD 100 are both extremely good. Infact in daytime use the es 80mm is sharper than my TS80mm APO, which suprosed me. However night time the TS80mm shows a tiny... and i mean a extreme tiny but more.

The only thing i dont like about the ES scopes is.

1. Cheap feel of the focuser knobs... the silver paint is already coming off the knob.

2. The draw tube is riduclosly short at 50mm.

3. The view shifts on focusing.

4. Overly cheap steps taken. Ie the view finder braket with its plastic knobs and rought finish. And various metal parts with rough finish that look like they belong on an old car rather than a telescope.

But saying that theres not many or any scopes in the same class of price & aperture that is in light weight carbon fiber.

I am most likely going to change the focuser to a feather touch. As using the quark and focusing with the 127 is a nightmare. But at the same time the rack and pinon focser holds the mrk5 bino with quark and 24mm pans perfectly. The draw tube moves flawlessly up and down with all that weight and never slips. Will a feather touch handle all that weight as well?

[Stu]

6 minutes ago, Pingster said:

Oh my first use was during the day and i used 24mm pans and 40mm TV plossles. But the star test was donw with a TV x2 powermate and 11mm TV eyepieces. ☺

The other thing to try is not defocusing too much

[Pingster]

To get the phone to capture the star test i had to defocus wider than usual. Becuase a smaller defocus was so bright all the phone captured was a completely white disc. Completely washed out. The bigger the disc the eaiser it was to capture the star test rings. 

Heres a few of my first attemps. 

What the camera does not capture is infocus the rings are perfectly circular and run all the way into the core with distinct separation. Out of focus the rings are slightly less defined but still perfectly concentric and looks very simular to photos of a Tak star trst to my newb eyes. 

[John]

Looks a good star test. It's easy to get paranoid about these things but using the scope on some challenging objects is the best way to show up any issues I think.

If the optics are good then, seeing conditions allowing, close doubles will split, CA will be more or less absent, and high powers will be more useable than you thought possible on planets.

It's the latter two factors that I've really noticed with my Tak and LZOS refractors, not that ultra high power is the be all and end all of course but you do notice that quality optics just hold their form better when pushed 

All the reviews I've read on your scope are very postive from an optical performance point of view and ES seem to quality check their products well so "relax and enjoy", as they say