Quote:

---

That is the $10,000 question.

---

Well, I will refer to Mark Wagner at Solar Spectrum, who I believe quoted another authority: "our blocking filters are guaranteed for the lifetime of the filter, when it fails – that was it's lifetime."

My DayStar filter went for almost 15 years before it's blockers failed, and it was about $400 to have them replaced around 1990. The average lifetime for DayStar blockers was stated to be somewhere around 10 years, and DayStar now warranties their filters for 10 years. The replacement cost is now $750.

There has been no information I'm aware of coming from Meade Coronado as to how, or even if, they have "fixed" the problem of the rapid ITF failure of the blocking filter. Coronado had warrantied their filters for five years. My original blocker and it's replacement both failed within 3 years, so the replacement cost was/is the cost of shipping, and the time of repair (very fast with Coronado Tuscon, apparently very much longer with Meade Coronado). I'm not sure if the new blockers from Meade Coronado are warranted for the old Coronado 5 year period, or the general Meade 1 year period -- I'm concerned if the latter.

Solar Spectrum, in cooperation with Baader, has gone to an IR blocking ERF for it's rear etalon based system (similar to DayStar), hoping to increase the lifetime of the blocking filters by reducing thermal load cycling. They apparently have not had any significant failures yet. I could find no warranty or other information on what it would cost to replace the blockers when they fail, but I imagine it would be similar to DayStar's costs.

Solar Scope has been around a few of years as well, and I am unaware of any reported blocking filter failures. One would think the blockers are similar in general design and implementation to the Coronado (and Lunt) blocking filters -- but their web site states they use a "multi-cavity interference filter" for additional blocking. Email from Ken at Solar Scope seemed to indicate he uses vey high quality/expensive filter coatings to avoid degradation. I have found no warranty information on Solar Scope filter systems.

Finally, Lunt has also adopted the IR blocking ERF, and increased the thermal cycling tolerances for it's blocking filter's ITF. I haven't seen any specific waranty period, but Lunt states that when used with their ERF they will "guarantee to our customers that none of our filters will fail during normal use." Even if they were to last "only" 10 years, I'd be very happy, as the replacement cost of the Lunt blocker's ITF is currently only about $90 on eBay.

--------------------
Bob Yoesle

You are a child of the universe,
no less than the trees and the stars...
And whether or not it is clear to you,
no doubt the universe is unfolding as it should.

Desiderata

Post Extras:

Quote:

---

I am still not clear if the blocking filters are failing because of an on going chemical reaction (oxidation I guess) that slowly but surely makes the filter fail; or if this reaction is speeded up by the heat from a less than perfect ERF.

---

From what I can determine, it might be both. The better the coatings, the less frequent the failure, and the less the thermal loading, the less frequent the failure. It might be that filter maker / designers approach the blocker from two distinct philosophies:

1. Use blockers with less robust (soft) coatings, which due to thermal loading, will fail more often but are cheaper to make and replace. (Extend the life of the blocking filter by using a better ERF to reduce thermal loading.)

2. Use blockers with more robust (hard?) coatings, which will tolerate thermal loading for a (much?) longer period of time, but which will be more expensive to make and/or replace if/when they eventually fail.

--------------------
Bob Yoesle

You are a child of the universe,
no less than the trees and the stars...
And whether or not it is clear to you,
no doubt the universe is unfolding as it should.

Desiderata

Post Extras:

Quote:

---

SNIP

Quote:

---

I am still not clear if the blocking filters are failing because of an on going chemical reaction (oxidation I guess) that slowly but surely makes the filter fail; or if this reaction is speeded up by the heat from a less than perfect ERF.

---

From what I can determine, it might be both. The better the coatings, the less frequent the failure, and the less the thermal loading, the less frequent the failure. It might be that filter maker / designers approach the blocker from two distinct philosophies:

1. Use blockers with less robust (soft) coatings, which due to thermal loading, will fail more often but are cheaper to make and replace. (Extend the life of the blocking filter by using a better ERF to reduce thermal loading.)

2. Use blockers with more robust (hard?) coatings, which will tolerate thermal loading for a (much?) longer period of time, but which will be more expensive to make and/or replace if/when they eventually fail.

---

I guess I need to reword my question. I sorta thought it was both as I posted earlier.

What I was trying to get at was which is more important. My club has a rather old PST, which has mainly been used for outreach events and shows no signs of "rust". It is stored in a climate controled building in the control room of the local planetarium and maybe used 5 times a year or so.

On the other hand some PST owners seem to have problems with this issue and I wonder if it is because they are storing them in a steam room of the local gym or because they use them every day next to a toxic salt flat or what ever.

So what I want to know is if I limit my solar observing will my solar stuff last longer, or is climate controlled storage more important, or maybe there is some other factor I should also consider.

--------------------
Meade ETX 90, Meade AR5, Orion ED80, Atlas GT, 8 in Newt, Coronado DS SM40, Garrett 10.5X70, Sigma SD10, SD14, Canon 1D2, Xti, Nikon CP4500, C-14

Post Extras:

Quote:

---

1. Use blockers with less robust (soft) coatings, which due to thermal loading, will fail more often but are cheaper to make and replace. (Extend the life of the blocking filter by using a better ERF to reduce thermal loading.)

2. Use blockers with more robust (hard?) coatings, which will tolerate thermal loading for a (much?) longer period of time, but which will be more expensive to make and/or replace if/when they eventually fail.

---

Post Extras:

Quote:

---

I would think that you would give a lifetime warranty in order to sway more customers to your product knowing that you will have to absorb some replacement costs down the road. Good Business.

---

Post Extras:

Quote:

---

Quote:

---

I would think that you would give a lifetime warranty in order to sway more customers to your product knowing that you will have to absorb some replacement costs down the road. Good Business.

---

This is so true.

Too often I see a huge disconnect between peeps who understand technical stuff and peeps who understand how to run a business that makes stuff.

I would bet that the number of claims under a life time warranty is a tiny fraction of the number of units produced; but the good will by such a policy may sway a huge number of buyers.

---

I'm not so sure and I'm not even talking "lifetime". There are several things that immediately come to mind like the 20 year warranty on a mattress. Who keeps one that long? Who is going to ship it back to the manufacturer for their appraisal that the mattress failed due to manufacturing defects? Automobiles with 10 year warranties. A warranty like that is only valid if you take your car back to the dealer continuously which adds up to a heck of an additional profit to the dealership and their $80+ per hour service techs. I tend to look at any lifetime warranty as no incentive at all since my feeling is that (a) the company will not remain in business during the entire period of my lifetime (when I was much younger than I am now :-) ), (b) usually there are too many catches involved in the fine print which most people don't read and (c) that the company will be bought out by another which will not honor the lifetime provision any longer. The latter may or may not be legal...don't know, I'm not a lawyer.

--------------------
Clear Skies- Lenny

NexStar11 GPS on APT Wedge
Takahashi FS-78 piggybacked
Orion Mak 127 on AS-GT GEM
Lunt LS60THa/B1200
8" f/8 Homemade DOB
SBIG ST-8XE DMK21AU04 NexImage cameras
Dogpatch II Observatory
Celestron Beta Tester
Moderator- NexStar GPS Group
http://www.lenny-shaffer.com/

Post Extras:

Quote:

---

The problem comes in the Far IR blocking filter which requires silver. It is the silver we see degrade. All the pictures I have seen and my two examples started from the edge. This implies O2 or H20 ingress. I know DayStar and Solar Spectrum are using MDM filters with two layers of metal. Andy tells me that Lunt is using a DMD filter that only has one layer of metal. I have not gotten my textbook out to learn the practical difference.

The other filters seem to do fine.

---

Hi Colin, thanks for the info! You seem to be very well versed on the technical details of these types of filter systems: The ITF either has two layers of dielectric sandwiching a metallic layer, or two metallic layers sandwiching a dielectric.

This does not seem to explain why one type can last several years to over a decade (seems the two metallic layers used by DayStar and Solar Spectrum would deteriorate as easily, or even more quickly), and the other only a couple of years.

I have been told by some in the industry it can only be the quality of the coatings. Others cite, as you do, that the problem begins at the periphery and works inwards, possibly indicating the "sealant" (I don't even know if there really is such a thing) used around the edge of the ITF is defective, or more susceptable to the thermal cycling, developeing minute cracks, and thereby allowing atmospheric moisture to invade the silver layer and prematurely degrade the filter.

And then we have Solar Scope, which uses a "multi-cavity" blocker system -- I have no idea what that means ('dammit Jim I'm a doctor, not an optical engineer')* -- but it seems to have had no problems so far. Any ideas?

And when you state "other filters seem to do fine," are you referring to the air-spaced etalons, which don't use the metallic silver layer(s) the blocker does, and are also variously stated as being "hard coated" and therefore should last "indefinitely"?

Finally, Mark Wagner has also stated the silver-based blockers can be either "soft-coated" or "hard-coated" with the latter being almost or as expensive as the etalon itself. Do you know why, and how this would affect filter longevity, and possibly be worth it in the long run?



* actually I'm a paramedic, and when it comes to cavities, I see a dentist

--------------------
Bob Yoesle

You are a child of the universe,
no less than the trees and the stars...
And whether or not it is clear to you,
no doubt the universe is unfolding as it should.

Desiderata

Post Extras:

Quote:

---

In the case of Meade/Coronado, are they honoring the original 5 year warranty issued by Tucson/Coronado, for example in the case of a rusty PST?

---

Post Extras: