Orion Optics v Skywatcher!

[saturn5]

what a cut throat industry...shoot or be shot, eh?

Thats life/business in general and to think otherwise is being a tad naive imho.

Since when did the business world play fair? never! do whatever it takes to get as much custom as possible from your competitors by what ever means possible... although there are some companies with a helluve a lot more integrity than others.

[themos]

what a fascinating thread...

[philsail1]

Here's a photo of the two main mirrors side by side - not that you can tell any visual difference between them. The Skywatcher mirror is on the left, out of its cell and ready to go to Orion Optics for testing. (The faint reflections you can see in them, is of the "broken leather" "Artex" finish on my lounge ceiling!)

(click to enlarge)

I measured the diameter of both mirrors. Skywatcher is exactly 203mm across - to the edge of the "silvering" (for want of a better word).

The Orion mirror is exactly 200mm to edge of "silvering."

The Skywatcher feels the heavier of the two - almost as heavy as the Orion's which is still in it's cell.

The "Zygo" Wavefront Analysis report that came with my Orion Scope read:-

(click to enlarge)

Optic Type:- 200mm f4.5

Wavelength - Out:- 632.8 nm

Strehl:- 0.984

PV. Wavefront:- 0.123 wave

RMS:- 0.020 wave

AstMag:- 0.043 wave.

There is also a coloured circular diagram which shows a Wave "range" from:- +0.0578 to -0.0649

I must admit that apart from understanding parts of the explanation Barry from Orion gave me at the time of receiving report, I don't fully understand.

Perhaps some of you scientists out there do!

When I recieve the "Zygo" report from my Skywatcher mirror, it will obviously be interesting to compare details - which I will post on here for your "dissection" and feedback.

Regards,

philsail1

[ngc2403]

Hey Phil,

just wondering what it was that you were unsure of about the report?

The king for me is the Strehl, TMB only quote the strehl for their mirror that is because it is a complex but more complete way of assessing the optical quality of any lens or mirror than say 1/n th wave.

the idea is that it measures how many photons are sent to the correct position by the mirror. 1 is the best and TMB refractors have a strehl of ~0.96 or better. hence the high price.

A more detail explanation is here http://www.telescope-optics.net/Strehl.htm

i don't know the strehl for RCOS, SW, GSO, VIXEN, WO because they don't publish or at least the last time i checked they didn't.

The PV is your max wave front error however this has no effect on the strehl, other than for two small points on the mirror.

RMS is related to strehl by a complex equation but it is related. and is a measure of quality.

I can't remember what the AstMag is but i know how does. guess anyone?

Thats business Paul and its why I am deeply cynical when humans are involved. I also worked ina University once handling funding for reserach projects and you'd hardly believe the guff I had to listen to from scientists when money is up for grabs.

The only human involvement here is the focusing of the SW telescope, if it isn't focused then the mirror report from the Zigo will not work, by which i mean that it probably will not give one.

once the ZIGO is focused Barry, John or Phil can push/click the button to start and it will shoot out a laser pulse off the mirror and back then the ZIGO computer automatically produces the report see above. if they were to try and tamper with it they would need to be care fully they don't break the ZIGO which i hear cost them an arm and a leg and well they need it to make/sell telescopes

ally

[philsail1]

Thanks for your helpful and clear explanations there "ally"

I didn't really understand any of the above "Zygo" report - I do now!

AND - you say that actually focusing plays such a critical part in getting the best from a quality mirror?

It's no wonder that Orion fit their scopes with "Crayford" style focusers.

It will be interesting to see how the old Skywatcher mirror performs in the Zygo test.

Regards,

philsail1

[narrowbandpaul]

John told me that astmag was the astigmatism magnitude in units of wavelength.

Another important factor is the ratio of PV error to RMS.

A number like 6 or above is good

[russ]

It will be interesting to see how the old Skywatcher mirror performs in the Zygo test

If OO give it anymore than 1/2th wave i'll be amazed. My guess is they'll say it's barely useable. Not that i don't trust them to give a fair and accurate test.

[narrowbandpaul]

very cynical of you! ;-)

[philsail1]

Thanks for that Paul. All those numbers (and initials) are starting to make sense now you've given what is classed as a reasonably good number(s) to start with.

Now then Rus!

Regards,

philsail1

[russ]

I'm sorry. I like OO and the OO scopes i've owned. Don't doubt the Zygo reports for a minute on their own scopes. But they gave my Orion USA XT10 such a mauling, i lost faith in their assessment of other makes after that.

Russ

[Milamber]

I think the OO mirror shows much better contrast on the central dot in your pic Phil , not to mention better definiton of the Artex

Arthur

[philsail1]

Ah! I wasn't aware of that Rus.

Arthur - you've got good eyesight! Now I've taken a second look, I think you're right you know (unless it's a digi camera aberration or something).

Well, by Friday I hope to be able to share the results of the test on the Skywatcher mirror. (I think that debates can "rage" on and on about whether I will obtain a true test or not). All I can do at the end of the day is "hope" that it will indeed be an honest test result.

Regards,

philsail1

[ngc2403]

I'm sorry. I like OO and the OO scopes i've owned. Don't doubt the Zygo reports for a minute on their own scopes. But they gave my Orion USA XT10 such a mauling, i lost faith in their assessment of other makes after that.

Russ

?

plz explain what happened?

[mik]

Just had another look at the pics and agree with Arthur

Mick

[ngc2403]

Just had another look at the pics and agree with Arthur

Mick

i looks very interesting but am afraid i know the reason why the contrast in the OO looks better.

the lights in the room are illuminating the ceiling plainly in the skywatcher mirror where as the OO shows a part of the ceiling not illuminated face on hence there are shadows like on the surface of the moon close to the terminator compared with the rest of the illuminated region.

so am afraid it's not going to prove the quality of the mirrors.

[FLO]

Arthur, you're a bad man

[GazOC]

It will be interesting to see how the old Skywatcher mirror performs in the Zygo test

If OO give it anymore than 1/2th wave i'll be amazed. My guess is they'll say it's barely useable. Not that i don't trust them to give a fair and accurate test.

I'm betting the phrase "barely 1/4th wave" crops up somewhere in the report.....;O)

[philsail1]

Hey "ngc243" - how do you know what my lounge ceiling looks like? (Oh! I forgot - you can see it in the reflection of the mirrors!).

Arthur's not a bad old stick really Steve!

Regards,

philsail1

BTW When I removed the Orion Mirror cell from tube, it does look a solid set up - and it is very, very easy to collimate, without tools!

(click to enlarge)

There are three large knurled knobs that act on heavy springs. After adjustment, the mirror can be locked down using the adjacent "allen" headed bolts (but these only have to be hand tightened - as it says on the little slip of paper stuck to back of mirror). And there are three "nine point" mirror support arms too (these are just out of sight behind the cast steel triangular mirror support base. (Don't know how much more support they actually give the mirror - but I suppose they are handy, in that the Orion Mirror looks thinner than its Skywatcher counterpart). I'll post some more pics when I do the next write up on mirror report!

[russ]

?

plz explain what happened?

I wanted to mount my XT10 on an EQ6 when the EQ6 first came out. At the time OO were the only Skywatcher stockist in the UK, they had another company name they operated under. Scopecity or something?

So i talked it over with OO and the conclusion was my Orion XT10 was just about good enough to shave with. I bought an OO DX250 and couldn't tell the views apart. Really felt like i'd been taken for a ride. In hindsight i'm not an experienced optician and i'm sure there were differences between the mirrors. They just weren't apparent to me. But this all comes back to what we said earlier. Is 1/4 wave enough for most observers, even some experienced ones?

Russ

[ngc2403]

hmmm,

i think that perhaps not in normal visual use but if you take your scope to the darkest skies then i would want to be able to take full advantage of them and for that i think you need better than (mass produced) 1/4th wave.

for imaging i think that better mirrors show this on a more regular basic. example the contrast in images when you are imaging things like the double cluster, bright stars. the better telescopes will have darker backgrounds compared with the stars, because more of the light has gone into the star's pixels that the surrounding ones due to mirror error.

Some of you seem to think that the report will have phrases in it like barely usable etc. this i can understand would come from the marketing but the facts will be clear and not up for discusion. (i am sure very one will be talking about it but it will be what the facts show, not what they are)

The best thing for OO to do in this, will be to test and then just release the ZIGO report without a statement because i don't think it will make any difference to some of you what they say, but fact are facts and they will tell the story.

ally

[Milamber]

Arthur, you're a bad man

Damn - you got me bang to rights... it was supposed to be a tongue-in-cheek comment

Arthur

The best thing for OO to do in this, will be to test and then just release the ZIGO report without a statement because i don't think it will make any difference to some of you what they say, but fact are facts and they will tell the story.

ally

I agree - on both counts! I think there are many born Skywatcher owners and you just can't please or sway them.

[russ]

I bow to other people's expertise in these matters. And OO have done me proud (two superb 150's and a 300) over the last few years. So i say things in jest. A report is a report and the figures won't lie......even if they did switch the SW mirror for shaving miror in their toilet....only joking

Russ

[ngc2403]

...even if they did switch the SW mirror for shaving miror in their toilet...

I know i would

[Milamber]

I think Synta already did

[narrowbandpaul]

haha

nice one arthur