How much visible difference between different quality optics is there?

[Skills]

PV Explained

I understand that atmospheric conditions have a major role in what you can see, but all else being equal: does the visual difference in reality match the images here?

cheers

Adrian

[johninderby]

I'd have to say yes. For planetary observing top quality optics do deliver sharper images with more contrast. Smoother mirrors have less light scatter and this has a great effect on contrast. On DSOs however the difference isn't so noticeable as contrast isn't so important.

John

[Ben Ritchie]

There's a comprehensive discussion here

Optical Standards

The conclusions you reach from this page should be:-

PV 1/4λ Wavefront mirrors are very satisfactory for most users at a reasonable price.

PV 1/10λ Wavefront mirrors offer a slight improvement over 1/4λ, - but at an increase in costs.

but to me that page (http://www.orionoptics.co.uk/OPTICS/pvexplained.html) looks to overstate the case - personally I don't think you'd ever see that in practice under UK skies. There's also a comment on the utility of P-V as a measure here:

Rating Mirrors - amateur telescope making

[John]

Under ideal conditions better quality optics do show themselves but the Orion Optics link overstates the case I feel. But then they are trying to sell their higher quality optics I guess

[Ben Ritchie]

If we take the picture of Saturn as representative then I'd guess it would be a rare night in the UK that allowed the 1/8 optics to be distinguished from the 1/6 - and I suspect that on many UK nights you would be unable to tell any of them apart.

[Carbon Brush]

No my own estimates.. YES.

If you can try different types of eyepieces in a scope, you will see all sorts of things from internal reflections to fuzzy edges to astigmatism.

I recently did a side by side WO80 Megrez and SW102. I can only describe the difference on a terrestrial target as clear day to foggy day. Though with the SW102 alone, most would think it performed OK.

Though as you increase the price tag, the quality increases slowly. doubling the price does not necessarily give double the performance. But we all tend to find the price/performance mix that we are happy with.

I think you will get lots of replies to your post!

[Ben Ritchie]

I wouldn't disagree, my only real objection here is the (IMO strong) impression from the OO page that if you don't pony up for 1/8th or better the 1/10th optics then you're getting a poor 'scope with fuzzy optics. The missing context here is what view the 1/10th optics give under Pickering 5 seeing, or even Pickering 7 (which is a pretty reasonable night for these parts).

[Capricorn]

If the optics were not better why would TMB scopes (and many others) have a good name and people save to get them. One US brand has a several year waiting list for theirs. We would save the money and buy a cheap achro instead and get "same" performance.

[Ben Ritchie]

As an owner of one of those brands with a "several year waiting list" i'd honestly say that on 90-95% of nights you couldn't really tell it apart from a considerably cheaper telescope. On the remaining few it's a bit special though. To me it's worth it for those few nights, because they're the ones that really stick in the memory, but from any kind of value for money perspective it's not sensible under UK conditions.

[johninderby]

The image on the OO website for 1/10 PV may only show what's possible under perfect seeing conditions, but it's been my experience that yes you can get views like that when the seeings right. One thing I have found with OOs better optics is that they will take more magnification than Meade or SkyWatcher newts, and that's something that can really make a lot of difference under less than perfect seeing conditions.

I've found that while the best OO optics aren't going to make a lot of difference for DSOs, they do make for an all-round scope that's great on lunar / planetary as well.

And yes it's not a good idea to do the value for money calculations, that will just depress you.

John

[JimStan]

I think that most of us would just DIE to be able to see Saturn as good as that 1/6 PV illustration! I have probably only experienced it a couple of times in my lifetime, myself.

Real life viewing opportunities are much less apt to be that rewarding, and the money spent on 1/10 PV optics could probably be more wisely spent purchasing accessories for your scope, such as filters, cameras, etc. etc.

JMHO

Jim S.

[Skills]

I wouldn't disagree, my only real objection here is the (IMO strong) impression from the OO page that if you don't pony up for 1/8th or better the 1/10th optics then you're getting a poor 'scope with fuzzy optics. The missing context here is what view the 1/10th optics give under Pickering 5 seeing, or even Pickering 7 (which is a pretty reasonable night for these parts).

This was certainly an impression I thought that page was giving (not that I believed it).

Most people will I'm sure agree that better optics = better image but I'm interested to know how much better. Where would the average skywatcher 8" newt optics rate? Somewhere between 1/4 and 1/6 I would imagine. Suppose I was to directly compare a standard, average skywatcher newt with an OO 1/10 hilux newt on a night of superior seeing at 250x magnification (or higher). Using the images from the link what difference would I see?

edit: I'd have thought something like image 1 to image 2, never having used a superior optics scope though...

[johninderby]

The average SkyWatcher is about 1/4 to 1/4.5 PV, and a really exceptional one may reach nearly 1/5 PV. The OO ratings are given as better than so a 1/10 PV would usually be around 1/11 actual PV.

As to image comparison, if the seeing is good the SkyWatcher would be a bit better than image one and the OO about image 3. Although my 14" OO can give views similar to image 4 on really good nights. Don't forget that the OO Hilux coatings give better reflectivity which also has an effect.

The SkyWatcher newt optics are as good as it gets in a mass produced scope. I wouldn't hesitate to recommend one as you can't beat them for value for money. Unfortunately the closer you try to get to optical perfection the more rapidly the price increases.

John

[Ags]

I was reading that wavefront errors are additive. Excellent seeing would add 1/10 error, a central obstruction of 35% would add 1/4 error and then the optics add their error. I haven't been able to find another source to confirm this unfortunately. If true high quality optics will only make a moderate difference in a faster reflector.

I've been looking at the OO mirrors too. They charge small change to upgrade a 1/6 OO newt to 1/10 - less than the price of an eyepiece. If you are buying from OO there is no reason not to get the best possible mirror.

[Ags]

I was reading that wavefront errors are additive. Excellent seeing would add 1/10 error, a central obstruction of 35% would add 1/4 error and then the optics add their error. I haven't been able to find another source to confirm this unfortunately. If true high quality optics will only make a moderate difference in a faster reflector.

[RikM]

I think the size of the image on the OO site is what makes the apparent impact of the better PV much more obvious that it might appear to the eye. Even at 240x in my Dob, planets are still quite small.

1/4 PV vs. 1/10 PV at realistic image size?

[Ags]

I think the size of the image on the OO site is what makes the apparent impact of the better PV much more obvious that it might appear to the eye. Even at 240x in my Dob, planets are still quite small.

1/4 PV vs. 1/10 PV at realistic image size?

Excellent point! I think others pointed out that 1/10 PV is only noticeable at high mags - your pic shows one reason why.

[johninderby]

I think the size of the image on the OO site is what makes the apparent impact of the better PV much more obvious that it might appear to the eye. Even at 240x in my Dob, planets are still quite small.

1/4 PV vs. 1/10 PV at realistic image size?

The big problem with this comparson is that with the 1/10 PV OO optics you can use much more magnification, and hence the image scale is bigger so the comparison is more like this. It's this ability to take higher magnifictions that makes such a difference.

John

[RikM]

The big problem with this comparson is that with the 1/10 PV OO optics you can use much more magnification, and hence the image scale is bigger so the comparison is more like this. It's this ability to take higher magnifictions that makes such a difference.

John

So it's a bit like comparing a small scope to big scope? If the seeing is good, the bigger scope allows better angular resolution, brighter image and higher magnification, hence more detail.

[Ags]

My head is exploding!

[johninderby]

So it's a bit like comparing a small scope to big scope? If the seeing is good, the bigger scope allows better angular resolution, brighter image and higher magnification, hence more detail.

That's probably the best way to put it.

I have observed Saturn at 600x with the 14" when seeing is really good. And while conditions aren't that good too often, when they are it's a real WOW moment that makes it all worth while.

John

[Steve]

Seeing conditions play a huge role, particularly where planetary observing is concerned. I have observed Jupiter through a number of telescopes, including a 7-inch Maksutov, but have generally been dissapointed. I look for structure in the weatherbands but usually see only hints of detail.

Then one night at Kelling I observed Jupiter through a 4-inch ED doublet. It took my breath away! The view was magnificent with plenty of contrast and detail. The telescope was good but I feel sure the view that night had more to do with the exceptionally clear and still atmosphere.

The unspoken truth is most of us rarely experience the full potential of our telescopes, whether it be reflector, refractor or catadioptric.

[JamesM]

I have been fortunate to have observed the same object at the same time of night using the same eyepiece on three 12" dobsonians of which one was from Orion Optics with Hilux coatings. I couldn't tell you what the wavefront were for the other scopes (though the Orion was 1/8th PV) so I can't comment on that aspect of their relative performances but that Hilux coating to my eyes made a noticeable difference especially on DSO's. Whether it is worth the extra money only people can decide for themselves but this coating would be something that I would not question paying extra for.

James

[Peter Drew]

Last Wednesday night I did a side by side shootout on Jupiter with a 16"SCT, an excellent 12" F8.5 Newtonian and a 5" F15 APO triplet. The 16" was easily the best, followed closely by the Newtonian, the 5" I have to say was disappointing by comparison. Each scope was using approx 250x magnification.

[derekm]

Th OO page says it shows a visual representation of the differences. Is this a rather grey description, as in "artists impression"?