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Equipment Discussions >> Reflectors

Pages: 1
BDS316
Carpal Tunnel


Reged: 09/16/09

Loc: Sol 3
Protostar question new
      #5554266 - 12/04/12 04:50 PM

This past April at NEAF, Protostar announced that they were coming out with drop-in replacement secondary mirror mounts and holders for 8 and 10 inch Synta (Orion) Dobs.

There is no mention of this on their online catalog and I just called their tech support line to inquire and found that it is disconnected, and no answer on their toll free order line either.

What's up with this?

thanks


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starman345
Wait, I'm Thinking
*****

Reged: 07/06/10

Loc: New Brunswick, Canada
Re: Protostar question new [Re: BDS316]
      #5554277 - 12/04/12 04:58 PM

I bought some Protostar products last spring and found Bryan to be very good, prompt and helpful but lately, there seems to be some reports of orders not being filled and no correspondence. If they are having problems I hope they can overcome them, they make good products.

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stratocaster
sage
*****

Reged: 10/27/11

Re: Protostar question new [Re: BDS316]
      #5554318 - 12/04/12 05:23 PM

I haven't heard anything either. I've been wanting to get the 2.48" replacement diagonals myself.

The last I'm aware of is that there was a move to a new location and changing of the phone numbers. There was some downtime as the provider messed up the service for a few days, but then all was fixed. But for the last 6 months or so there have been no responses to e-mails and no one answering the phones.


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BDS316
Carpal Tunnel


Reged: 09/16/09

Loc: Sol 3
Re: Protostar question new [Re: stratocaster]
      #5554487 - 12/04/12 07:22 PM

Does anyone else offer the same/similar product, ie a drop in replacement secondary mirror assembly for the 8 and 10 inch econodobs?

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stratocaster
sage
*****

Reged: 10/27/11

Re: Protostar question new [Re: BDS316]
      #5554691 - 12/04/12 09:41 PM

I called Antares Optics about a week or two ago. They will make sizes to order; however, it's about twice the price as the standard sizes. And whether it's a 1/10 wave or 1/30 wave will be somewhat of a *BLEEP* shoot as the mirrors in the standard sizes are produced in large volumes and differentiated by wavefront error during evaluation. Custom sizes necessitate a much smaller production run, so there's a lot smaller sample size to possibly get a 1/20 or 1/30 wave mirror, if that's what one is looking for.

Also of consideration is a replacement spider and secondary holder. Astrosystems appears to be one of the vendors of choice, but I'm not sure how seamlessly one of their spiders/holders can be used.

And I don't know how seamlessly a 2.6" secondary can be used on the existing holder. In my case I have a GSO secondary holder with the shroud. I'm not sure if the shroud can be removed and the new mirror can be fastened to the holder. And, during my discussions with Antares, the 2.6" may be border-line from a weight perspective for fastening to the secondary using just silicon. Though I know many have not had issues.

I believe JasonD has mounted a 2.6" secondary on his 10" Orion dob. If he drops in he may have some comments.

These are all reasons why I liked the idea of a direct drop-in replacement spider/secondary. Would have been nice and clean.


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uniondrone
Carpal Tunnel
*****

Reged: 12/05/09

Loc: Streetlight Archipelago
Re: Protostar question new [Re: BDS316]
      #5554743 - 12/04/12 10:10 PM

Quote:

This past April at NEAF, Protostar announced that they were coming out with drop-in replacement secondary mirror mounts and holders for 8 and 10 inch Synta (Orion) Dobs.

There is no mention of this on their online catalog and I just called their tech support line to inquire and found that it is disconnected, and no answer on their toll free order line either.

What's up with this?

thanks




I spoke with someone at protostar a few months back about the drop-in secondary holder and mirror. They said that it would be some time before they would be ready to offer it, but they were willing to put me on the "contact list" for when it is available. I followed up with them about two months ago and got no response. My guess is that they will get around to it when they are good and ready... which means if you're in a hurry, don't count on getting this from them.


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Mirzam
Post Laureate
*****

Reged: 04/01/08

Loc: Lovettsville, VA
Re: Protostar question new [Re: stratocaster]
      #5555217 - 12/05/12 07:33 AM

The Antares secondaries will not be a %^$# shoot because they are analyzed by interferometry. You will know what you are getting.

Astrosystems also makes custom spider/secondary holders at reasonable prices and delivery times. I would still buy the secondary itself from either Protostar or Antares Optics.

JimC


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tomharri
sage
*****

Reged: 09/19/08

Loc: USA
Re: Protostar question new [Re: Mirzam]
      #5555238 - 12/05/12 07:56 AM

I got flocking from Protostar 6 weeks ago from their new location.....

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stratocaster
sage
*****

Reged: 10/27/11

Re: Protostar question new [Re: Mirzam]
      #5555513 - 12/05/12 11:19 AM

Quote:

The Antares secondaries will not be a %^$# shoot because they are analyzed by interferometry. You will know what you are getting.




Agreed. Perhaps a clarification is needed on my point. You will definitely know what you're getting. But my point was if you want a 1/20 or 1/30 wave secondary, since the number of mirrors manufactured for custom sizes is so small there may not be a 1/20 wave or 1/30 wave mirror in the bunch.

As it was explained to me, they make a large run of secondaries, then test them. Depending on the test results the mirrors are differentiated into the 1/10, 1/20, and 1/30 categories and priced accordingly. If the number of mirrors manufactured is small there may or may not be 1/20+ wave mirrors in the batch.


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FirstSight
Duke of Deneb
*****

Reged: 12/26/05

Loc: Raleigh, NC
Re: Protostar question new [Re: stratocaster]
      #5555662 - 12/05/12 01:09 PM

Quote:

As it was explained to me, they make a large run of secondaries, then test them. Depending on the test results the mirrors are differentiated into the 1/10, 1/20, and 1/30 categories and priced accordingly. If the number of mirrors manufactured is small there may or may not be 1/20+ wave mirrors in the batch.




You're speaking of Antares secondaries, but I had a similar conversation with Bryan Geer of Protostar when I was deciding between a Pyrex vs Quartz secondary mirror upgrade for my Orion 12XTi to complement the refiguring of my primary mirror. He said essentially the same thing you reported above about the variability in quality of any given batch of pyrex secondaries; the very best-of-batch matched the optical quality of the quartz secondaries, but although all the pyrex secondaries matched specified minimums, it was a bit of a crapshoot whether you'd get one of the best-of-batch or merely average-but still above specified minimum. I note that Protostar doesn't differentiate the batch results the way Antares does e.g. offering 1/30, 1/15/ or 1/10 wave mins at different prices, but the principle about production batch variability is the same. By contrast, the quartz secondaries were much more uniformly consistent (he called them "reference flats").

I hope Bryan and Protostar can quickly work out whatever customer interface issues people have been experiencing lately; Protostar's products are absolutely first-rate, and Bryan was very patient and responsive the three times I've purchased products from them: secondary mirror + heated spider/secondary holder; flocking paper; hand-adjustable knobs to replace the original Allen-wrench adjustable screws the Protostar secondary holder originally came with (not sure if more recent versions now come with this standard or whether it's still an upgrade).


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catboat
professor emeritus
*****

Reged: 12/01/09

Loc: Maine
Re: Protostar question new [Re: stratocaster]
      #5555796 - 12/05/12 02:51 PM

Quote:

the mirrors in the standard sizes are produced in large volumes and differentiated by wavefront error during evaluation.





Stratocaster,
Can you confirm that the PV errors for the secondary mirrors listed on the Antares website are for the wavefront? and not the surface?

On the Antares page "more about secondary mirrors", they discuss the difference between PV at surface and wavefront. From what they say there, you'd expect their secondaries to be listed with PV errors at the wavefront:

link

To quote from the above link: But a mirror that's accurate to 1/20 wave causes the error to double at the wavefront - where the light comes to a focus. So the true error of a 1/20 wave mirror in actual use is really 1/10 wave. Therefore, manufacturers prefer to tout their measure of surface accuracy. [my bold]

So far, so good. But when I examine the specs that Antares lists for their secondaries, I see no clarification of the issue except: you can be assured the stated surface flatness is indeed what you're getting and paying for.

link 2

I've wondered about this for several years. My guess is that that the stated PV is indeed at the surface, despite what they imply in the first link. But I've never confirmed that -- or ordered one of their mirrors.

Protostar makes it clear on their website that the stated maximum PV error of Protostar secondaries is at the wavefront.


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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: Protostar question new [Re: catboat]
      #5555810 - 12/05/12 02:59 PM

Quote:

On the Antares page "more about secondary mirrors", they discuss the difference between PV at surface and wavefront. From what they say there, you'd expect their secondaries to be listed with PV errors at the wavefront:




Flats are always referenced to surface error. In use at 45 degrees the typical error is about 1.4x the surface error, not 2x as for a primary mirror.

If they say "surface flatness" that's what they mean. The first link hasn't got a whole lot to do with secondaries as they mostly seem to be talking about primaries, and it appears they just pasted most of the ancillary text from here:

http://www.lcas-astronomy.org/articles/display.php?filename=scope5&catego...

Best,
Mark


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catboat
professor emeritus
*****

Reged: 12/01/09

Loc: Maine
Re: Protostar question new [Re: mark cowan]
      #5555887 - 12/05/12 03:48 PM

Mark,

Thanks for the clarification -- and for the icas link that the Antares "more about" info comes from.

When I first saw those PV figures like 1/30 wave at Antares, I assumed they meant surface. But checking the "more about" page and seeing the write-up how manufacturers "tout" PV surface made me wonder if that 1/30 could actually be wavefront PV. Then I wondered if I was being misled to believe wavefront…
So it's good to know that it's surface and not ambiguous for more knowledgeable folk.

BTW, I just re-checked the Protostar site (I've bought from them in the past and have been entirely satisfied with quality). They specify wavefront -- or seem to -- for their quartz secondaries.
Surface flatness is a minimum quality of 0.1 wave peak-to-valley on the wavefront
But Protostar is the only vendor I've come across that does this for secondaries -- and it may be the case only for their quartz secondaries.


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stratocaster
sage
*****

Reged: 10/27/11

Re: Protostar question new [Re: catboat]
      #5556037 - 12/05/12 05:22 PM

Quote:


Stratocaster,
Can you confirm that the PV errors for the secondary mirrors listed on the Antares website are for the wavefront? and not the surface?




I may have been a bit fast and loose with the terminology.


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catboat
professor emeritus
*****

Reged: 12/01/09

Loc: Maine
Re: Protostar question [Re: stratocaster]
      #5556118 - 12/05/12 06:17 PM

Thanks, stratocaster. No problem. It was an opportunity to get my questions answered.

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mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: Protostar question new [Re: catboat]
      #5556211 - 12/05/12 07:02 PM

Quote:

BTW, I just re-checked the Protostar site (I've bought from them in the past and have been entirely satisfied with quality). They specify wavefront -- or seem to -- for their quartz secondaries.
Surface flatness is a minimum quality of 0.1 wave peak-to-valley on the wavefront
But Protostar is the only vendor I've come across that does this for secondaries -- and it may be the case only for their quartz secondaries.




I've bought from them too - and that looks like a misstatement for the quartz secondaries. The Zygo report was better than .1 wave PV surface, IIRC.

Best
Mark


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Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: Protostar question new [Re: BDS316]
      #5556444 - 12/05/12 09:17 PM Attachment (26 downloads)

ya know there's not much travel in the protostar stalk bolt

I would use a drawing like the attached pdf and redo the stalk and collimaiton bolts so you can add a new secondary mirror with out adding holes to your tube.

1800 destiny sells just the stalk and stems and compression strings.

hd sells bolt standard or metric that's at least 1-1/2in long.


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