Budget RC announced at NEAF

[seeker372011]

http://www.astronomics.com/main/category.asp/catalog_name/Astronomics/category_name/U5QNWB3RKWWL8N3EL99F9DX9A0/Page/1

sorry if this is old news But I just got the email from Astronomics


Narayan

[matt]

Looks good...although the tech specs fail to mention the extent of secondary obstruction.

Looks large, though. Over 30%.

I would like a smaller secondary housing/CO.

[netwolf]

Matt i think the larger secondary is to provide for larger CCD's and to help produce a flatter field. Still the price is not Budget, at these prices the Meade LX200-ACF OTA's would be better choice. The 8" is almost 3000USD the Meade 8" is the same price (from opt) as the 6" RC. I guess time and testing will indicate weather they are worth it. But I would sure like to check what the factory price is direct from China.

Regards
Fahim

[matt]

I'd be happy to pay the extra $$$ to get optics which are guaranteed to be at least 1/12th wave.

You wouldn't get anywhere near that with the LX200-ACF...so it's not like you're comparing apples with apples:)

If you place no stock in the wavefront values of optics, by all means opt for the Meade product.

Not that I'm Meade "bashing". It's just that you get what you pay for....and I'm sure the ACF does a fine job.

Cheers.

[netwolf]

Matt, I had not read the 1/12th optics bit so in light of that you are right then they are worth more. It will all come down to performance tests once these come out. Until then we can only wait and speculate.

[Gama]

Be happy to buy 1/12 wave WHAT ?.. RMS, Peak to valley, Wave at Kuma Beach Surf club!!.. Doesnt specify, so your paying $$ for WHAT ???. I dont know.. This can make the whopping difference.

Also as said, "You get what you pay for", so you must be getting a Premium scope for such low pricing..Hmmm, doesnt sort of make sense.

Jeeees guys, its good to get hyped up, but the ship hasnt docked yet, so lets not start unloading cargo..

I would like to know the real surface accuracy and also optical alignment and its ability to keep it during the night, yada yada..
This is why (And i hate to say it) the RC's do cost money. Maybe Peter Ward may explain a tad as he would have the figures tatood in his brain.
The secondary is most likely to be 50%, as thats what the cheaper RC optics use to get around costs on manufacturing.
Im not selling my pin hole telescope yet... Now excuse me while i move back into the shadows..

Theo

[matt]

Hi Theo.

Appreciate the input.

I can assure you I'm not getting hyped up...but I don't think there's any harm in enjoying our hobby and revelling for just a moment in the thrill of 'affordable' new gear with possibly great optics being released.

When I say 1/12th wave, I'm assuming they are referring to the same measure as Celestron refers to when they guarantee their SCTs to be at least 1/4 wave and GSO when it refers to its mirrors being 1/12th wave.

When I say 'you get what you pay for'...that wasn't to imply the pricing of this new scope is in any way a guide to the quality of the optics. Certainly...a premium RC scope attracts a premium price.

But that is not to say prices are the only guide to an instrument's 'quality'. Look at what has happened with the Dob/ Newtonian market and companies such as GS and Synta. No...they are not what you might describe as premium products, but they are still very good and priced in a manner which would have been unthinkable 10-20 years ago.

I guess it's all relative, isn't it? Let's not shoot it all down in flames before we've had a chance to have a better look. As Fahim says, the proof of the pudding will be in how it performs once it's released.:)

[avandonk]

Sounds like the GSO RC's. It won't be perfect but at least it will be affordable. One could have lots of fun fixing the shortcomings and then put endless drivel on 'how to' on many sites!

What did a 16" DOB cost a couple of years ago?

Bert

[matt]

Very true, Bert.

[Gama]

Matt, you had me ready to go out and pick up Aluminium cans to get the extra money to buy one !. Well, maybe not too ready..
I knew what you were trying to say Matt, just jiggling some chains....
There is something i do say to people, "If your going out to buy a fruit, make sure you dont buy a lemon" because it leaves a sour taste..
Most of us wouldnt have known or know much about wave surface details.
So the reason for the post.

Theo

[matt]

No worries, Theo.

But I happen to like lemons...and buy them often when I go fruit and veg shopping:lol:

Cheers.

[Gama]

Well, just dont let me catch you selling them !.

Anyways, heres a link for those that wish to understand women ... Oh wait, there no such link !.
But there is a link to optical wave accuracy here http://www.telescope-optics.net/aberrations.htm .

Theo

[netwolf]

Any news on who is bringing these out in Australia and for how much?

[Satchmo]

I would guess that that they mean 1/12 RMS surface accuracy as they claim 1/16 RMS surface for their Newtonian mirrors which are far easier to make than the highly aspheric RC's.

You can see the Newt specs here:

http://www.gs-telescope.com/content.asp?id=95

1/12 RMS equates roughly to 1/3 PV wavefront, and 1/16 RMS is 1/4 PV wavefront. If these tests are done at 632mm HeNe laser wavelenghth then increase those figures by about 20% for wavelength at peak visual sensitivity.
I don't see the point of talking about surface accuracy on a mirror as it can only produce an optical wavefront upon reflection.

[Satchmo]

These scopes are clearly not the GSO RC's.

They show light baffled tubes, Feather Touch focusser and Quartz optics with 99% enhanced coatings.

Looks like there are more than one new player in the budget RC market.

[netwolf]

Some pictures from Neaf in this thread on CN
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/2353510/page/0/view/collapsed/sb/5/o/all/fpart/2/vc/1
Also Stargazr mentions he has found it to be 1/12 (dont know what) overall. Not sure what he means by running a Roddiers over it. What is a Roddiers?

Regards
Fahim

[Satchmo]

He's referring to a piece of software that applies Roddiers Transform : a way of measuring wavefront accuracy working backwards from an Airy Pattern photograph.

I note from the Astronomics website that these optics are completely machine figured and that 12, 14" and 16" models will be forthcoming...

[jase]

Help me out here... looking at the GSO parabolic mirror sets, they list the 16" (AD015) as a 1800mm FL @ F/4.5. Huh? only 1800mm? Great for Nebulae, but very far from a galaxy hunter. Sheez, don't think I'd bother. If I was to purchase a 16" RC, I'd want it to at least 3000mm FL. A fast focal ratio is great, but imaging at slow focal ratios isn't a bad thing with the sensitivity of today's CCD camera. Am I missing something...Mark?

[netwolf]

I think the 16" is referring to the the 16" dob not an RC. At least thats what is being indicated in the linked thread.

[duncan]

hi Sachmo.
i hope you are right. But even if you are not lets all hope and pray that these measurements are all equal across the board
that to me seems the most important thing. lets get a standard measurement across the board. Then maybe ametures can make a viable decision.
C'mon all you manufacturers getn your act together!!!!!!!!!!!!!!!!!!:thumbsup :

[jase]

Ah yes. Thanks for clarifying Fahim. Next time I'll read the fine print. Was thinking they were hyperbolic. Got a little confused.

[Satchmo]

I guess its alll a trade off. Some people might feel the 4X greater photographic speed @F4.5 was more appealing .

And Fahim is right , these are Newt optics. I was simply indicating that "1/12 wave' probably meant surface RMS rather than wavefront if their Newt mirror specs were anything to go buy.

[Satchmo]

Most of the amateur market thrive on cut-throat cheap prices on their optics. Thorough testing , certification , and paperwork on optics can cost a lot, in the case of these cheaper optics as much as the optics themselves. I'll bet that if the mass production makers were to pull the occassional mirrors randomly off the production line , officially certify them and charge occordingly few people would buy them. The majority of people seem to be happy to buy cheap if they think they can get away with it. This may be a fair gamble with smaller mirrors.

On the subject of wavefront quality on these RC's , I don't think wavfront quality on a heavily obstructed instrument is as important as the quality of the tube assembly , how well it can be collimated and mainintained and the mounting. For example the final `focal plane ' Strehl on 1/4 wavefront 40% obstructed scope is 0.68 and a 1/10 wavefront 40% obstructed scope is 0.73 . Not much difference really.

The following text from the Star Instruments web site ( supply the optics for RC Optical telescopes) indicate that they think 1/4 wave system is good enough for prime focus photograpghic systems...

" OPTICAL QUALITY

STAR INSTRUMENTS guarantees a minimum of 1/4 wave front, 1/20 wave r.m.s. on all systems.
STAR INSTRUMENTS continues to be concerned with the false advertising claims being made by amateur optical suppliers who claim 1/10 to 1/20 wave optics. These claims tend to confuse the amateur astronomer into believing you must have 1/10 wave optics "

I think the new Chinese entrants on the market will be capable of that. Its weather the mechanics of the tube assemblies do the job properly that will make or break them in the ameteur market . Its fair to say also that the low prices will attract many more people to the RC market who may be less experienced and have lesser standards than someone who remorgaged their house to take their astrophotography to the next level...

[CoombellKid]

I dont think it quite works like that in the mass produced market. They will
independantly test their mirrors randomly and peg the results to anything
coming along behind. Checking on occassion to see if they're still producing
their stated wave front.

I think a 16" (AD015) as a 1800mm FL @ F/4.5 would make a great galaxy
hunter for a visual observer :thumbsup:, and I'll add... with not a great deal of funds.

regards,CS

[Roger Davis]

For en"light"enment and for information go read:

http://www.galaxyoptics.com/ImageQualityDiscussion.html

[Satchmo]

Ah Roger, don't go complicating the thread by opening another technical `can o'worms' :-)

[Terry B]

Just need to find out who the Chinese manufacturer is and buy direct from them:P without a label. Then it probably will be affordable.;)

[Starkler]

Who oh who can one talk to to get a high quality small newtonian mirror?:shrug:

[Satchmo]

I was referring to the smaller Taiwanese Dob scopes.They very adequately fill a niche for 'bang for buck'. 10 years ago the completely USA made dobs by Meade , Coulter and Celestron showed optics with far more inconsistency in quality than the Tawanese jobs IMO.

If you want a `Zambuto' there are no free lunches there :)

[Starkler]

Mark my question was meant to be taken literally and is prob off topic for this thread.
The only maker I know of happy to produce high quality sub 10" mirrors is Royce in the usa.

[Doomsayer]

It will be interesting to see how these cheap RCs turn out over time. I am building two carbon truss RCs based around cheaper pyrex Star Instruments 12.5"f6.7 optics. Star Instruments are one of the suppliers for the RCOS instruments, as many here will be aware. My dealings with the optician there impressed upon me that one of the most important aspects of the RC figuring process is the mirror material. They cannot guarantee high accuracy with pyrex because of its relatively uncontrolled thermal behaviour in the optics prodn lab - whereas with the zero expansion material they can reliaby produce very high accuacy mirrors.
I have also learnt that large to very large secondary obstructions and oversize baffling are a fact of life with the RC design in practise. Bringing the f ratio down below f8 or 9 increases field curvature and adds to the secondary obstruction in general. I am looking at around %55 secondary baffle obstruction with my f6.6 optics. The high magnfication factor of the secondary adds another degree of difficulty with the RC. I still expect the Corrected Dall Kirkham designs will prove to be better large flat field performers at the the budget end of the cassegrain astrograph market.
cheers
guy

[Satchmo]

Guy , I'd have to disagree with that one. Fine annealed Pyrex, not too thick ratio is perfectly capable of taking on a relaible 1/10 PV wavefront figure. As long as the optics are within half a degree C of the surrounding air they will give a reliable reading for the optician and of course the figure is the same regardless of ambient temperature. Using Sital would make the opticians job easier ,as less equalising time between figuring runs. I thought the low cost Star Instruments RC sets were Pyrex ?

Anthony ( Bird) Wesleys latest Jupiter is pretty good testimony of the optical quality achievable with Pyrex..
http://www.iceinspace.com.au/forum/attachment_browse.php?a=42799



You'll need enhanced coatings on those optics : the total light transmission will only be around 55% otherwise ( 30% light loss is due to the large obstruction).

[Doomsayer]

Yes they are pyrex.
I am only repeating what the optician at Star Instruments said. They have no plans to use pyrex or its equivalent in the future -possibly another alternate zero expansion material - I note that all sizes of their cheaper pyrex optics are now sold out. Both mirror sets I have had 98% coatings done in the US.