PDA

View Full Version here: : Mirror Quality & Eyepiece Quality


Eternal
26-04-2007, 11:40 PM
It is my understanding that the mirrors used in the Newtonians produced by Skywatcher and GSO are, as a whole, not as good as the mirrors used in Vixen and Meade Newtonians. If that is the case then will higher quality eyepieces such as those produced by Tele Vue produce a worse image than say the lesser GSO eyepieces because they accentuate the imperfections in the lower quality mirrors?

bojan
27-04-2007, 08:07 AM
Both mirrors (primary and, to the somewhat lesser extent, secondary) and eyepiece quality contribute to the image.
If primary mirror is bad, nothing will help to improve the image.
If eyepiece is not so good, it depend in what way it is bad, but generally, the image will be OK around the optical axis (centre).
Really excellent eyepieces produce pinpoint images of stars all across the field of view.

ghsmith45
27-04-2007, 09:53 AM
But a bad eyepiece will make it worse, so you are better off with a good eyepiece, but even better off with a good eyepiece and a good mirror

wavelandscott
27-04-2007, 10:50 AM
I like to think about the entire optical chain and the cumulative effect that quality has on the entire system.

As a chain it is only as strong as it's weakest link...I think that you should strive for the best quality that you can afford/enjoy in as much of the optical chain as you can. If nothing else, it will hold it's value better than the "budget" offerings.

Concerning your question/comment about the quality of company A versus company B reflector scopes I am not sure that I agree with your statement.

I do not know what (if any) "standard" differences there are in the QC/QA processes and/or tolerances specifications between the brands you have listed. There may very well be but this is unknown to me. I suspect that there is not a material difference. I also suspect that the site of manufacture of the mirrors themselves are likely the same on at least some of the brands you have listed.

I would also speculate (this is just my opinion and without any supporting facts) that even if there was a difference in the "standard" specification and QA/QC programs between the two groups of companies that you listed (and I myself doubt that there is due to efficiences in production) I suspect that most new or "limited experience" observers would not be able to pick out the difference between them.

While I think that this is generally true on the "budget" end, I think that the same holds true on the "premium" end too (but are distinct between the two groups)...

Saying it a different way, I think you get what you pay for...In my opinion, quality of gear falls into "clusters"...concentrated at the budget and premium ends. Unfortunately, the "middle" is fast disappearing...but that is another post...

I say the below with respect to relector scopes only...I am not nearly as confident that the below statements will hold true to other telescope optical designs...

With respect to reflectors, I would expect that all of the brands you listed (assuming properly collimated, cooled and properly set up and less than 12 inches in size) would perform with respect to mirrors and eyepeices generally the same to most users and most people would be hard pressed to pick up any difference between them...

There might be some differences brand to brand in other "build" materials (tubes, focusers etc.) but with respect to mirror performance they would fit in a "normal" and statistically identically place.

As noted above, I believe that it is possible to differentiate between the budget scopes and the premium...

So I think (my opinion) that the mirrors in the brands you have listed would be very similar and hard to differentiate between. There may be some other build/brand features or dealer representation that a particular brand has that has more appeal (tension knobs, fine focuser, crayford focuser, bearings on base versus teflon etc.)

It is a question of degree but, Higher Quality is preferred to Lessor Quality when ever possible...but, anything that gets you out under the stars and looking up is a good thing.

Today even the "budget" end of scopes and accessories are as good or better (and affordable) than anything that was available to hobbyists just a few years ago...it is a golden age for us all.

Just imagine what Messier (or similar) could have done with a 12 inch "budget" scope readily available to us today!

ausastronomer
27-04-2007, 11:07 AM
A $50 eyepiece in a $5,000 telescope gives you a $50 view

A $5,000 eyepiece in a $50 telescope gives you a $50 view

A $500 eyepiece in a $5,000 telescope gives you a million $$$$ view :)

Two things to remember:-

1) An optical system is as bad as the weakest component in it.

2) An optical system is only as good as the weakest component in it.

Stick with decent eyepieces in a decent telescope. That having been said, the 6",8",10" and 12" newtonians (dobs)produced by both GSO and Synta are quite good and worthy of using decent eyepieces in. If anything the GSO mirrors may be consistently a bit better than the Synta mirrors, but they are both very good and close in quality. For mass produced optics they are both outstanding. The Meade mirrors are nothing to write home about, some good ones and some bad ones. They are a long way from premium optics that's for sure. If anything the GSO and Synta mirrors would be "consistently", a touch better then the Meade mirrors IMO. Without a doubt the GSO and Synta dobs have far better designed mirror cells and the entire scope is a far better quality product than the Meade Newts/dobs IMO. Vixen is a slight step up in class but you pay for it. As an entry to the hobby you would be very happy with one of the 6" to 12" dobs from GSO or Synta, exceptional value for money. They are better products than something costing 10 times more money 20 years ago.

I wouldn't jump straight in and buy Pentax or Televue eyepieces, they are very good and very expensive. The Baader Hyperion/Orion Stratus offer a very good level of performance for less than 1/2 the cost. They are the best value for money eyepieces presently available. They are a quantum leap above the starter eyepieces (cheap plossls) normally supplied when you purchase a scope.

CS-John B

74tuc
27-04-2007, 07:37 PM
Hi all,

Just to put in my 2 cents worth.

Re: " A $50 eyepiece in a $5,000 telescope gives you a $50 view

A $5,000 eyepiece in a $50 telescope gives you a $50 view

A $500 eyepiece in a $5,000 telescope gives you a million $$$$ view "

Price may not be a good indicator as to how well a 'scope/eyepiece might perform.
One needs to consider the f# of the optics. A $65 orthoscopic will give one million dollar views with a good F10 newtonian (say $2000). A $1000 Nagler of long focal length may give terrible views with an F4 16" newtonian because of the normal off axis aberrations - the larger the newtonian mirror the greater will be the coma.

Jerry.:)

ausastronomer
27-04-2007, 09:57 PM
Jerry,

I was trying to apply some generalisations that a beginner could follow. I think your making it a bit confusing for someone buying their first telescope and eyepieces.

Regardless of the F-Ratio of the telescope a good quality eyepiece will always outperform a poor quality eyepiece, even in slow systems like F15 Maks or Achromats. In a slow system the difference between a good eyepiece and a bad eyepiece is not as pronounced, but it is readily visible to an experienced observer.

Nothing much has changed in regard to quality either, generally a good eyepiece costs more than a bad one. I own a full set of UO HD orthos, as well as about $6k worth of Naglers and Pentax XW's. The ortho's give excellent image quality on axis, but eye relief is tight and the AFOV narrow at 45 deg. What does the $450 Pentax XW give you over the $100 ortho? 20mm of eye relief and a 70 deg AFOV, in other words a considerably more comfortable and pleasing view. ie. You get what you pay for. I don't know that we need to start confusing the poor guy worrying about visible coma in an F4 system using an 82 deg AFOV eyepiece. Especially considering he isn't likely to buy a 16"/F4 newtonian or a $1,000 Nagler. BTW there are no Naglers that cost $1,000, the most expensive is $929 and that will soon drop with the improving exchange rate. There are 4 that cost over $600 and 17 that cost less than $600.

CS-John B

Starkler
27-04-2007, 10:07 PM
I think good eyepieces in a cheap telescope can give great views!

In general the cheaper packages IMO are more let down more by the eyepieces than the quality of the scope optics.

ballaratdragons
27-04-2007, 10:16 PM
Hi Eternal.

To put it in simple terms, I have a GS 12" Reflector. I have been using series 500 El-Crappo EP's and fairly reasonable GSO EP's and have been happy with the views (well, maybe not happy with the Series 500's).

I am very happy and suprised at the quality of the GSO mirrors! They aren't 'Mark Suchting's or Observatory Grade 'Ritchie Cretian's, but they are fantastic for a mass produced item. Very rarely does anyone complain about the views using GSO mirrors.

I thought I was getting very good views with the EP's I had, but I was presented at Camp last year with a Pentax XW7. WOW!!!!!

Now I know the optics of my GS 12" are great! The premium EP shows just how good these mirrors actually are. I have also had all sorts of Premium EP's in my scope at this years camp and all were fantastic. The EP on it's own can't improve a bad mirror, so the mirror must be good. Feel safe buying a GS mirror.

Just my 87.5 cents worth :thumbsup:

ausastronomer
27-04-2007, 10:49 PM
That's very true as "some" cheap telescopes are quite good, a lot are bad. Unfortunately, it's very difficult for a beginner to know before buying, what's good and what's bad. Generally speaking cheap telescopes are bad, because a lot more money goes into computer control and or a flimsy equatorial, fork or one arm alt/az mount, than goes into the optics. Care to try a 10mm Pentax XW in a Meade DS2114 ATS? This is why I recommended Eternal stick with the Synta or GSO dobs in 6" to 12" Aperture. They are cheap and proven to be excellent optically for mass produced scopes. Combined with good quality eyepieces these scopes give excellent views. You can't say that about all cheap telescopes or even the majority of cheap telescopes.

CS-John B

Miaplacidus
27-04-2007, 11:04 PM
Hi John. I admire you immensely for your astronomical knowledge, and I would listen intently and seriously to anything you have to say on the subject, but my question is: What's the name of your broker? :)

Cheers,

Brian.

Eternal
28-04-2007, 03:30 AM
Thankyou all very much for your responses. I've so far being accumulating a few cheaper GSO/Synta eyepieces for my 8" Newtonian but you have all calmed my fears regarding getting a more expensive eyepiece. Now all I need is the money.:)

Starkler
28-04-2007, 09:59 AM
Cant disagree with any of that. When I said "cheap telescope" I was thinking about cheap semi decent scopes, forgetting about the multitude of ebay and camera store rubbish scopes.

For visual use, you cant go wrong with a synta or gso dob as a first scope.

ausastronomer
28-04-2007, 10:56 AM
Brian,

These cover just about all options I might come across. Also there is a 2" visual Paracorr, 2" 1.6X Antares barlow, a 1.25" 2X Orion Shorty plus and a 1.25" 2.5X Televue Powermate.

Here is the team assembled on my kitchen bench

CS-John B

ausastronomer
28-04-2007, 11:01 AM
And here is the team in the "everything proof" Pelican model 1600 case, with a host of different filters.

CS-John B

matt
28-04-2007, 11:08 AM
:eyepop:

Nice line-up, John.

That's what I call an ep collection!!!!!

wavelandscott
28-04-2007, 12:26 PM
That is it?!?

Only one case full?!?...I thought you might have a few more stashed around...are you sure that that is all of them...

Regardless, Nice set!

Miaplacidus
28-04-2007, 12:44 PM
Dear John,
:jawdrop:
But what have you done with all the 20 mm Meade modified achromatics??? (I give mine away, but I always find more under the couch.)