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Interesting BF Rusts, Filters, and other Solar Scope Phenom

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#1 LarryAlvarez

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Posted 09 August 2014 - 08:32 PM

I thought it would be neat to start a thread with interesting filters, rusts, and other solar scope oddities seen over the years.  Feel free to add your images to this thread, I'd like to see what others might have experienced over the years rust wise or just anything out of the ordinary.  The more interesting the better!  Below is what a Coronado Calcium K-line ITF looks like when it rusts. Its blue rust on one side, green on the other.

:)

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  • Calcium_BF10.jpg
  • Calcium_BF102.jpg


#2 LarryAlvarez

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Posted 09 August 2014 - 08:33 PM

Here is a classical H-alpha rusted ITF from a BF15's front barrel. It sort of looks like the Helix Nebula.

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  • BF15_rusted_sun2.jpg
  • BF15_rusted_sun1.jpg

Edited by LarryAlvarez, 09 August 2014 - 08:33 PM.


#3 LarryAlvarez

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Posted 09 August 2014 - 08:37 PM

I have had several filters over the years, one of the most prized was an odd rose colored 60mm filter I found.  Normally etalons look gold when looked at from the back.  This one was rose colored, really nice.  Personally its the only one I've seen like this but I'm wondering if anyone else has one.   :question:

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  • coronado90-60.jpg

Edited by LarryAlvarez, 09 August 2014 - 08:38 PM.


#4 Bill Cowles

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Posted 09 August 2014 - 10:05 PM

I have had several filters over the years, one of the most prized was an odd rose colored 60mm filter I found.  Normally etalons look gold when looked at from the back.  This one was rose colored, really nice.  Personally its the only one I've seen like this but I'm wondering if anyone else has one.   :question:

 

Yes yours is more red than mine. This was a shot to compare the 60mm Coronado to my newer 50mm Lunt. I will have to check my 60, as I hardley use it anymore, to see if it as gotten more red. :)  

 

Bill13450.jpg



#5 Bill Cowles

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Posted 09 August 2014 - 10:16 PM

How do you add images? :crazy:

 

Bill



#6 LarryAlvarez

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Posted 09 August 2014 - 11:35 PM

In the lower right hand corner of the reply window there is an option that says "More Reply Options".  You can use this to access the attachment option.   :)



#7 BYoesle

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Posted 10 August 2014 - 10:17 AM

This is a rusted ITF on a Coronado BF30.  Note how the deterioration starts at the periphery and moves inwards toward the center.  These types of filters are a laminate, which are generally sealed around the edge with an epoxy.  When used as part of a solar filter system, thermal stress and cycling causes the filter to expand and contract, which can crack the epoxy and allow atmospheric moisture to invade the filter, causing the inward deterioration.  Dielectric coated ERF's, which block IR (heat) from reaching the ITF, can help to prolong the life of these types of filters.

 

 

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  • BF30rust2.jpg


#8 BYoesle

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Posted 10 August 2014 - 10:21 AM

Here are some CaK PST filter system components.  The first is the "number 2" filter on the primary filter stack with similar deterioration, followed by a completely rusted ITF seen through the penta prism:

 

Note:  The H alpha PST's ITF is also susceptible to similar deterioration... so any used PST should always be evaluated for this issue.

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  • CaK PST main IMGP3108.jpg
  • CaK PST ITF IMGP3115.jpg

Edited by BYoesle, 10 August 2014 - 12:38 PM.


#9 BYoesle

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Posted 10 August 2014 - 10:27 AM

An interesting white light filter from the 1960's or early 70's (can't remember now ;-) was the Criterion S4, which used a mirrored barlow lens and internal dark welders glass filter to dim the sun to a safe viewing level:

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  • Criterion S4.jpg


#10 LarryAlvarez

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Posted 10 August 2014 - 11:55 AM

I have a catalog circa 1964 that has that filter in it.  Attached below is one page.  Pretty advanced for it time.

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  • criterions4.jpg

Edited by LarryAlvarez, 10 August 2014 - 11:55 AM.


#11 BYoesle

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Posted 10 August 2014 - 12:33 PM

Awesome Larry, thanks - and check those prices!

 

:)



#12 LarryAlvarez

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Posted 10 August 2014 - 12:56 PM

I know, right!  That's a pretty good deal, wish I had a time machine.  I have a question about your blocking filter, the BF30.  I have heard that they are making them now where they require a diagonal on the back end.  When they fixed yours did they convert it to the 2 part type or is it just a single unit?  I had an old Nearstar, 2nd gen I think that had a really odd blocking filter.  It only consisted of a Mirror that you could tilt with a small thumb screw in the back end.  I think there were some early BF30's that had something similar.  Below is a picture of my NearStar's blocking filter.

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  • backofscope.JPG

Edited by LarryAlvarez, 10 August 2014 - 12:56 PM.


#13 BYoesle

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Posted 10 August 2014 - 04:11 PM

Hi Larry,

 

Nope; when Meade Coronado replaced the ITF (the second replacement - the first replacement from Tuscon Coronado failed after two years) it was a straight through as well.  It does have some additional sealing measures, such as the gasket seen in the right picture.  I have always used this repaired BF30 with a Baader DERF, and try and keep it vacuum sealed when not in use.  So far so good.  :fingerscrossed:

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  • Before & After w arrow.jpg


#14 Philip Levine

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Posted 10 August 2014 - 07:27 PM

Hi Larry, Bob,

The dreaded "rust" problem.  Some say if rust is going to happen, it will happen, and nothing can prevent it. 

It may not prevent rust, but I added a couple of desiccant tins to the case containing my Coronado h-alpha filter/blocking diagonal.  Also added a Baader UV IR cut filter to the blocking filter diagonal.

Here's hoping...

Phil

 



#15 LarryAlvarez

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Posted 11 August 2014 - 08:56 AM

Here's an interesting pic.  It shows a difference in a couple Coronado ITF's.  I had one with the traditional turq color on both sides and a new one that was only that color from one side.  I wasn't 100% sure because both edges were blackend but I suspect the new one had red glass on one side.  

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  • Coronado_ITF_2versions.jpg


#16 LarryAlvarez

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Posted 11 August 2014 - 09:00 AM

Hi Larry, Bob,

The dreaded "rust" problem.  Some say if rust is going to happen, it will happen, and nothing can prevent it. 

It may not prevent rust, but I added a couple of desiccant tins to the case containing my Coronado h-alpha filter/blocking diagonal.  Also added a Baader UV IR cut filter to the blocking filter diagonal.

Here's hoping...

Phil

 

About 5 years ago I saw an ad on the Baader website that had a hardcoated replacement for the ITF.  I tried to order one at that time but could never get it.  It soon disappeared.  It would be cool if they did come out with one that worked as well as the Coronado type.   I think the longest I've been able to make one last is about 5 years and even then it was only 25% rusted.   I use mine now until they hit about 65% to 75% rust over.  They seem to work well for imaging still.



#17 Bill Cowles

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Posted 11 August 2014 - 03:13 PM

13440.jpg My non red 60mm filter next to my 50mm Lunt.

 

Bill


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#18 LarryAlvarez

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Posted 11 August 2014 - 06:36 PM

Wow, that is pretty cool.  Not really red but not really gold either.  Looks magenta prehaps.  I just noticed another change in filter manufacturing.  The rear obstruction on the older Lunt filters appear to be made of rubber.  Is that rubber on your 60 Bill or a black felt?  On the newer Coronado filters they appear to be using the same aluminum obstruction that the front has.  

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#19 Bill Cowles

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Posted 11 August 2014 - 08:09 PM

Wow, that is pretty cool.  Not really red but not really gold either.  Looks magenta prehaps.  I just noticed another change in filter manufacturing.  The rear obstruction on the older Lunt filters appear to be made of rubber.  Is that rubber on your 60 Bill or a black felt?  On the newer Coronado filters they appear to be using the same aluminum obstruction that the front has.  

 

Wow is right, it is rubber and since the last time I looked at the rear, part of the obstruction is melted. I wonder if this was caused in using this with a Lunt blocking filter and not the Coronado blocking filter. I have stacked the 60 on my Lunt, which should be OK, but I could have used it on my TV Genesis with the Lunt blocking filter. Would this notch in the rear obstruction effect anything?

13520.jpg

Bill



#20 Bill Cowles

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Posted 11 August 2014 - 08:23 PM

Here is a closeup of the rear obstruction. Looks like I can now join the club of solar filter problems. :crazy:

13540.jpg

Bill



#21 Bill Cowles

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Posted 11 August 2014 - 08:27 PM

This was 3 years ago and about the last time I used the 60mm filter and it's on my TV Genesis with a Lunt blocking filter, I was told this is a no/no. Could this be the cause of the melted rear Obstruction?

13550.jpg

Bill



#22 sullij1

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Posted 11 August 2014 - 08:48 PM

Great topic guys!


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#23 LarryAlvarez

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Posted 13 August 2014 - 07:23 AM

Wow, I can't say I've ever seen one that was melted.  That melted part seems so pinpoint accurate almost like the return beam was focused there.  That sort of seems impossible with the optics in the path but I know that Lunt rear blocking filters are way differently built than Coronado and that a Coronado will work on a Lunt scope but I don't think its design will safely work the other way around.  I could be wrong though as I'm not very savvy on how they design or test these things.  Just by looking at them though, it appears that the first element in a Coronado BF seems to reflect back the beam while Lunt's blocking filters use something like a KG glass to absorb it.  If you've ever had both a Coronado and Lunt scope you know that on a Lunt system they usually put an ERF (red glass with strong IR blocking coating on it) way up in front prior to the etalon.  Coronado does not do this, they only have redglass, #29 red I think, so it passes a lot of IR through the etalon.  As your scope is setup in the image I would expect the IR to reach the blocking filter and be absorbed by it but it would put a tremendous amount of stress on your Lunt BF as they are designed to have ERF's further up in the system to remove some of that IR.  It seems impossible but its a hard arguement when you see the image.  The only thing it could be is IR being reflected back from one of the internal elements. 



#24 LarryAlvarez

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Posted 13 August 2014 - 07:28 AM

Does anyone own one of these?  They were announed right before Coronado Prime closed but I don't know if they ever say the light of day.  I wanted to get one but never got the chance.  I had heard they were demo'd at Neaf at one point a long time ago.  The curious thing about it is that the front element is on a T-max.  This, in my opinion might have the same effect as the t-max on an h-alpha system and help tune in the prom details.  One of the main issues today with current calcium filters is that its harder to see proms.  This was not so on my old Coronado 70 Cak scope but with new calcium filters it is somewhat difficult to image them.  

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  • cak60.jpg


#25 Bill Cowles

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Posted 13 August 2014 - 10:51 PM

Wow, I can't say I've ever seen one that was melted.  That melted part seems so pinpoint accurate almost like the return beam was focused there.  That sort of seems impossible with the optics in the path but I know that Lunt rear blocking filters are way differently built than Coronado and that a Coronado will work on a Lunt scope but I don't think its design will safely work the other way around.  I could be wrong though as I'm not very savvy on how they design or test these things.  Just by looking at them though, it appears that the first element in a Coronado BF seems to reflect back the beam while Lunt's blocking filters use something like a KG glass to absorb it.  If you've ever had both a Coronado and Lunt scope you know that on a Lunt system they usually put an ERF (red glass with strong IR blocking coating on it) way up in front prior to the etalon.  Coronado does not do this, they only have redglass, #29 red I think, so it passes a lot of IR through the etalon.  As your scope is setup in the image I would expect the IR to reach the blocking filter and be absorbed by it but it would put a tremendous amount of stress on your Lunt BF as they are designed to have ERF's further up in the system to remove some of that IR.  It seems impossible but its a hard arguement when you see the image.  The only thing it could be is IR being reflected back from one of the internal elements. 

Larry, you are correct about stress on the Lunt, sometime later I had a friend and Lunt owner looking at my blocking filter. He said you have a cracked blocking filter and on close inspection, he was correct. I had to send to Lunt where it was repaired. Lesson learned , don't mismatch Solar equipment. Your sure know the operations of Solar equipment and the pitfalls and problems that can happen when you don't use equipment properly, or know what you are doing. :waytogo:

 

Bill


Edited by Bill Cowles, 13 August 2014 - 10:52 PM.

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