Skywatcher v Orion Optics

[osbourne one-nil]

This has probably been asked before but would there much noticeable difference between a 6" Skywatcher DS Newtonian and an Orion Optics VX6 (or the 8" equivalents)? 

I find myself in a need to....how to put it....unexpectedly find some money 13 years after I last had to find some money. This means that as much as I love my Takahashi 100DF and Vixen NA140, I feel uncomfortable keeping them when, for a fraction of their used cost, I could buy myself something which would actually be better in someways. I can't let my T-Rex mount go as I'd find it difficult to replace ever, but it does mean I could still mount a large-aperture but affordable Newt very nicely. The reason I'm thinking about a 6" is the shorter tube length would make pointing at the zenith easier, and an f5 wouldn't cause problems with coma to the same degree as an f4.5. 

Anyway, would the VX6 be noticeably better? I suspect not, but I'm still drawn towards it!

[Rob]

Ahh.. yes the old battle ground here. Ive owned an SPX 8" f6, and now own a SW 200pDS f5. In some respects I wished I'd never let the SPX go!. The views were amazing. So this comes back to the v's challenge.

Ok bottom line ... OO mirrors are really good. SW mirrors are very good. OO mechanics are poor. SW mechanics are really good. 

If you buy a OO telescope expect to replace the focuser and tube rings, plus the finder. If you buy SW its usable out the box - upgrades are a nice to have. That said you could always grab the 6" ota deal on FLO right now and pop a OO mirror in there?.

My 2p....

Rob

[osbourne one-nil]

Thanks Rob - that's very interesting as I imagined the OO would be better in every respect; I know the mirrors are good, but I thought by now they'd have sorted the mechanics and the focuser etc would be bang on. I've had OO stuff in the past and haven't been impressed. If Skywatcher really is good out of the box, and the mirrors are perfectly acceptable, then I think it's a no brainer. They even fo an 8" f6!

[CraigT82]

I'm in a similar boat myself, just had to sell off a load of astro gear due to a blown turbo on my car

I guess the higher spec OO mirrors (1/10th PV) may be noticeably better at high mags on very good nights, never looked through one myself. The synta mirros are good... probably as good as you'll ever need in the UK some might say?  Of course you could by the skywatcher now, and if the feeling really grabs you you could send the mirrors off to Nichol ro someone like that for refiguring to a higher spec.

My SW 200p f6 has a cracking mirror in my opinion, and when collimated and cooled properly serves up sharp planetary views, I've had up to over 300x once or twice without going soft (I've also seen excellent jupiter images that a former owner of my scope captured).  I imagine that I'll send the mirrors off for a hilux coating sometime in the future but that's about it!

EDIT: Just thought I should add... my SW scopes have required a few modifications in order the get the best from the mirrors (flocking, cooling fan, upgraded focuser to allow accurate colimation etc...) so the OO VX versions might be a better bet in DIY isn't your thing as I believe they'll be better out of the box.

[scarp15]

14 minutes ago, Rob said:

Ahh.. yes the old battle ground here. Ive owned an SPX 8" f6, and now own a SW 200pDS f5. In some respects I wished I'd never let the SPX go!. The views were amazing. So this comes back to the v's challenge.

Ok bottom line ... OO mirrors are really good. SW mirrors are very good. OO mechanics are poor. SW mechanics are really good. 

If you buy a OO telescope expect to replace the focuser and tube rings, plus the finder. If you buy SW its usable out the box - upgrades are a nice to have. That said you could always grab the 6" ota deal on FLO right now and pop a OO mirror in there?.

My 2p....

Rob

That may or may not have been the case with the SPX range, I could not comment, but it is not the case with the current VX range. Mechanically very good, 10:1 ratio crayford focuser is smooth very good quality no need to replace. 9 point mirror cell is superb. Option for quality angled 50mm finder. The tube is light and not as bulky as Skywatcher, guaranteed high quality mirror set with hilux coatings. I have the VX8L on a dobsonian mount and consider it to be a great all rounder, a scope that I enjoy using as often as possible.

[John]

I have a high regard for Skywatcher mirrors from the examples I've owned from 6" to 10".

The main appeal of my Orion Optics F/5.3 12" dobsonian is that it's overall weight is the same as a Skywatcher / Meade 10" dob so it's a lot lighter and easier to move about than a 12" from either of the Chinese companies. I had a 12" Meade Lightbridge for a while but it was just to heavy for me to use frequently. My OO dob is my most used scope.

The optics on mine at F/5.3 are a little easier to collimate than the F/4.9 of SW / Meade and at around 1/9th wave PV seem a little better at higher powers than those manufacturers scopes. The Hilux coatings might give the OO scope a slight edge too but probably not as much as OO claim ! The central obstruction of my scope is 21% of the primary diameter which is a decently small size.

I'd not have paid the £1K+ price for my OO that they want new in all honesty - I got the tube for £250 and the mount custom made by an SGL member so my 12" dob cost not a lot really.

 

[osbourne one-nil]

My mount would take either, no problem. It could probably take a fast 10" too if I could ignore the coma (which I probably could initially). As I'm definitely a faint fuzzy man, I don't think I'd get much value out of a 1/10th mirror and really I'm after the best value for money at the moment - sounds like that could be the Skywatcher. 

[John]

11 minutes ago, osbourne one-nil said:

My mount would take either, no problem. It could probably take a fast 10" too if I could ignore the coma (which I probably could initially). As I'm definitely a faint fuzzy man, I don't think I'd get much value out of a 1/10th mirror and really I'm after the best value for money at the moment - sounds like that could be the Skywatcher. 

I tend to agree - for DSO's I doubt higher quality optics make any difference. Dark skies and aperture are the key things I think.

 

[riklaunim]

There was some controversy over OO optics so keep that in mind that what they claim may not be true.

[John]

22 minutes ago, riklaunim said:

There was some controversy over OO optics so keep that in mind that what they claim may not be true.

Do you mean the supplied optical Zygo tests are not accurate ?

 

[Stu]

26 minutes ago, riklaunim said:

There was some controversy over OO optics so keep that in mind that what they claim may not be true.

I'm sure Orion Optics certificates are correct, but they show the best case for the mirror I think in terms of the particular cross section chosen. They also don't necessarily quantify the smoothness of the mirror. Mirror makers such as Nichol and Zambutto focus on smoothness and keeping micro ripple to a minimum and this produces the best contrast. You can have two mirrors measuring a certain accuracy, one which is rough (i.e. Has ripple within the quoted wave limits) and the other smooth, the smooth one will show much better contrast. I now reckon this is actually just as important on DSOs as on high power planetary observations.

[Chris]

6 minutes ago, Stu said:

I'm sure Orion Optics certificates are correct, but they show the best case for the mirror I think in terms of the particular cross section chosen. They also don't necessarily quantify the smoothness of the mirror. Mirror makers such as Nichol and Zambutto focus on smoothness and keeping micro ripple to a minimum and this produces the best contrast. You can have two mirrors measuring a certain accuracy, one which is rough (i.e. Has ripple within the quoted wave limits) and the other smooth, the smooth one will show much better contrast. I now reckon this is actually just as important on DSOs as on high power planetary observations.

Interesting point obout the smoothness of the mirror and contrast, I hadn't ever really thought about that before but it makes sense.

[John]

That's a good point Stu makes about smoothness. Is there an accepted measure for smoothness in a primary ?

Or is it just a matter of reputation of the manufacturer ?

 

[CraigT82]

I believe the Strehl ratio can 'quantify' the smoothness of a mirror, at least better than the wavefront error can.  The wavefront error is the quality of a given point on the mirror, whereas the Strehl quantifies the quality of the whole mirror.

[Stu]

Have a read of Zambutto's website, specifically their seven criteria. Some excellent explanations there which really helped me understand more about this stuff.

http://zambutomirrors.com/zambutoopticalca.html

[Stu]

16 minutes ago, CraigT82 said:

I believe the Strehl ratio can 'quantify' the smoothness of a mirror, at least better than the wavefront error can.  The wavefront error is the quality of a given point on the mirror, whereas the Strehl quantifies the quality of the whole mirror.

Strehl is certainly a better measure than pv but I don't understand fully if it relates to or covers smoothness. Hopefully someone will know

[YKSE]

Here's a link to edmoundoptics about US standard about scratch-dig:

http://www.edmundoptics.com/resources/application-notes/optics/understanding-surface-quality-specifications/

20-10 is considered as high precision quality, and Zambuto's at least 10-5 mirrors are a little better than that

[Mark at Beaufort]

I have owned a 10" Skywatcher Dob and the 6" PDS Skywatcher Newtonian and both were very good. Since then I have obtained an Orion VX8 which is very light and manageable. I changed the secondary and primary collimation screws which has made an improvement. To be honest viewing DSOs is not much different in the VX8 to the 10" Dobsonian. The most recent version of the VX range has a better focuser and they have improved the secondary collimation screws. The cost of a new Orion VX6 or VX8 is high in comparison to the Skywatcher range if that is important. You might be lucky and be able to purchase a secondary hand Orion because they do turn up.

My main DSO scope is now a 12" Dob although I like to use my Orion VX8 as a quick grab and go on my SkyTee Alt/Az mount.

[riklaunim]

3 hours ago, John said:

Do you mean the supplied optical Zygo tests are not accurate ?

Sending the same test with different telescopes, bad mirror send back and forth between them and a customer (ending in court), Maksutov OTAs dropping declared PV after external tests. Friend of mine had some of their high end astrographs and it wasn't quick and easy either

So take all those PV, Strechl ratios and more with a big dose of marketing salt. In general if the SW or OO telescope works, gives good views (especially high magnification lunar/planetary) then it works correctly and is diffraction limited - no matter how accurate it is - you won't be able to distinguish that difference. In terms of mechanical design things may differ a lot.

[Starflyer]

10 hours ago, osbourne one-nil said:

Thanks Rob - that's very interesting as I imagined the OO would be better in every respect; I know the mirrors are good, but I thought by now they'd have sorted the mechanics and the focuser etc would be bang on. I've had OO stuff in the past and haven't been impressed. If Skywatcher really is good out of the box, and the mirrors are perfectly acceptable, then I think it's a no brainer. They even fo an 8" f6!

I have a recent OO VX10, the focuser is better than the Moonlite CR2 I used previously, the 9 point mirror cell is far superior to Skywatcher cells, the tube is light yet stiff enough and it holds collimation extremely well.

I'm not easily pleased, I've chopped and changed kit over the years but I'd say that this is my perfect imaging scope.

 

Cheers,

Ian

 

[jam1e1]

just bought a OO VX12 pv1/10, whilst havent had chance to really test out yet, focuser is top notch and collimation easier with better bolts - agree with positive comments above. I'd say the tube ring tighteners could have been bigger , apart from that all good so far

[cs1cjc]

The ability of interferometry to pick up small scale errors is limited by the number of points sampled.  I know that Orion UK have had problems in the past and they can be difficult to deal with, but I have no reason to believe that their measurements are deliberately inaccurate.  They are certainly capable of producing mirrors of the highest quality with a good hard wearing coating, so far as I can tell.  Their production is always being improved.

A couple of articles on mirror smoothness are as follows:

• Zambuto_on_Primary_Ripple;
• Bartels_on_Rating_Mirrors.

[niallk]

From what I've read, Mr Rohr's OO mirror tests in recent years appeared to validate the Zygo report data, and lots of reports of excellent views through OO mirrors.

Different manufacturers can be testing at different wavelengths eg 632nm (OO) vs 550nm (OMI). There seems to be a real lack of an accepted or standardised way of quoting the quality of a mirror...

[osbourne one-nil]

Thanks to all for your replies. I'm currently siding with a Skywatcher as I'm not sure the added benefits an OO scope brings are of value to me at the moment. I'm not after high power views and the weather here (and other lifestyle aspects) mean use will be relatively brief and infrequent. Weight's not an issue either with a T-Rex mount...it might be like putting budget tyres on an Aston Martin, but under most conditions, those budget tyres will be good enough. 

 

[Alkaid]

I'm on the fence...

I don't believe that generally there is a huge difference between OO and Skywatcher (Synta) mirrors.  I think that Synta have got really good at mass producing 'good' mirrors and like many mass produced batches you will get one or two mirrors in there which are absolutely superb, a load of them that are 'good' and one or two that are poor.   It isn't a lottery though, far from it...generally if you buy a SW scope you will get a decent mirror.

What you get with OO that you don't get with SW is certified optics - you are paying for the certainty that you will get what you want.  No lottery.  I got my VX6L 2nd hand and it is very good indeed.  As I type this, the cert is at home in a draw, but I remember it being something like 0.98 strehl. I'll have to dig it out and have another look.  Personally speaking, I quite like the fact that I use a scope with that certified mirror (like I said, it's the 'knowing' what you've actually got which is nice).  Star test is excellent.  Views are very sharp (they have to be for me, I am a moon/planet man).

Having said that, I don't think that DSO views would be any different to any other 6" scope which meets diffraction limited criteria.  On the moon and planets, my scope would pull out ahead of the 6" SW when there is excellent seeing.  Then again, I have no doubt that an 8" SW dob with the normal 'good' mirror would beat my 6" certified VX6L when observing the moon & planets.

If you want the certification...you must have the OO.   If you are not too bothered about certification, get a SW.  At the end of the day, there is a very small chance that you will get a poor mirror and every chance that you will get a good one, as they really seem to have nailed their manufacture process.  Even if you got a duff mirror, you could return the scope to the dealer and get a replacement scope on those grounds alone.  There...I've probably just talked myself into buying an 8" SW!