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alanjgreen

Lunt Blocking Filter - Check yours, you won't regret it!

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I am writing this post as I have just received and fitted a free replacement lens supplied by Lunt that has fixed my Blocking Filter and revolutionised my views...

 

The Story

I had begun to get a feeling whilst using my solar scope that it was getting more and more difficult to (1) get an initial view that I was happy with (2) almost impossible to increase magnification and get a sharp image (3) the sweet spot was shrinking :( 

I removed the Blocking filter and looked down the long extension tube to see a grimy looking front lens inside :(

I searched on the internet and found a picture of a new one and saw that the front lens was supposed to be clear. I set about cleaning it with Baader Wonder Fluid and the cleaning cloth which got rid of at least 80% of it, but a thin film remained (see pic).

b1200-2.jpg.91c9f5de89576e6731505aa1156d1a9d.jpg

After more internet searching, I found a post on cloudynights that showed the exact same problem being suffered by other folks and stated that Lunt were happy to send out free replacement lenses!

https://www.cloudynights.com/topic/534161-lunt-60-mm-double-stacked-solar-scope-blocking-filter-issue/

https://www.cloudynights.com/topic/433046-polishing-optical-acrylic-lens-element-in-a-lunt-s/

 

So, I took some photos of the scope, blocking filter and sales invoice and emailed Lunt USA on Monday this week.

On Tuesday (the next day!), Bresser Germany emailed me to say that Lunt had asked them to send me a free replacement lens (Great!)

The Lens arrived this morning (just 4 days after emailing Lunt!) and I fitted it into the Blocking filter following the supplied instructions, then headed out to view the sun...

Here is the glass as received...

lens.jpg.3cd151e6188cd4a5db9220bfda4fd77b.jpg

Here are the supplied instructions...

bresser.jpg.58d37ca8699584ea073275dcba86fa48.jpg

Here is the blocking filter after I fitted the replacement glass (Looking very transparent) ...

clean.jpg.8218ba4f3b0f46599983be5dd31343b4.jpg

WOW, WHAT A REVELATION!

(1) The image is so much brighter :)

(2) The sweet spot is so much bigger :)

(3) Higher magnification is no longer an issue and some lovely surface detail revealed itself ... :) :) :)  

I would encourage all Lunt Solar Scope owners to go check the front lens of their blocking filter for any signs of fungus or growth and if you find some then don't hesitate to email Lunt USA for a replacement.

Happy Solar Viewing,

Alan

Edited by alanjgreen
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What a timely post for me..... I've just determined that the blocking filter lens is my issue. I've emailed Lunt and I'll see what they say :) 

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wonderfull story, ive got to take my hat off to lunt for that great service. charl.

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Had the same problem with mine a while ago ( search on here should have found it )

Sent the BF to Bresser and returned within 2 weeks fixed FOC excellent service from Lunt.

Dave

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21 minutes ago, alanjgreen said:

I had begun to get a feeling whilst using my solar scope that it was getting more and more difficult to (1) get an initial view that I was happy with (2) almost impossible to increase magnification and get a sharp image (3) the sweet spot was shrinking :( 

So is this a degenerative issue then Alan? Is it going to happen again in the future I wonder, or if it was a batch issue, for example?

Edited by parallaxerr

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18 minutes ago, parallaxerr said:

So is this a degenerative issue then Alan? Is it going to happen again in the future I wonder, or if it was a batch issue, for example?

I don't know. My scope is 5 years old in September so its taken a while for the growth to occur. Could just be failed coatings?

Lunt seem happy to it fix for free and it took less than 5 minutes to change the glass so I wont be losing any sleep over it going forward :)

Edited by alanjgreen
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This filter (ITF) and those of the Coronado equivalent are prone to failure over time. Fortunately the more expensive components, the etalon and the blocking filter seem to enjoy a much longer life.

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Thanks for your post, Alan

I went and checked my B1200 filter and it is also showing a lot of grime and worse still, there are two "growths" on opposite sides of the ERF glass

that other people are reporting,  one much larger than the other.  ☹️

I will contact Lunt, hopefully they will  be willing to send a new filter glass to Australia

My scope isn't even a year old yet it is stored inside the house in clean and dry conditions and the B1200 doesn't leave the scope

so am mot sure how all the grimy film over the filter glass got there ???

 

IMAG0412sm.thumb.jpg.89bf947f5b82c02122b939bf44911a53.jpg

 

 

cheers

Dave

 

 

Edited by Davenn

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Unfortunately the design of the ITF filter (the one we're talking about) in both the Coronado and the Lunt can result in failure. Sometimes this can be months or years.....it doesn't depend on usage as much as the possibility of moisture ingress through the failure of the side epoxy seal. Best advise I can offer is to keep the blocking filter diagonal in a seal Tupperware container with a silica gel pack when not in actual use. No guarantees....

(Easier to see this failure in a blocking filter diagonal but difficult to pick up on the PST blocker which is usually securely glued to the Black Box (Thank you Meade!).)

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I checked mine this afternoon and there's a spot developing on the BG filter. Its 6 years old, so it's had it's use. Ive contacted Lunt to see what they can offer.

 

20180702_161552.jpg

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1 hour ago, Zakalwe said:

I checked mine this afternoon and there's a spot developing on the BG filter. Its 6 years old, so it's had it's use. Ive contacted Lunt to see what they can offer.

Shouldn't think that would have much effect on the view mine was nearly 80% obscured.

Dave

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On 29/06/2018 at 12:10, alanjgreen said:

I don't know. My scope is 5 years old in September so its taken a while for the growth to occur. Could just be failed coatings?

Lunt seem happy to it fix for free and it took less than 5 minutes to change the glass so I wont be losing any sleep over it going forward :)

Great service from Lunt, and good stuff to get the scope back performing as it should.

Is this effectively a lifetime warranty then? Any idea what sort of age blocking filter they will replace? Good on Lunt anyway.

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Just now, Stu said:

Is this effectively a lifetime warranty then? Any idea what sort of age blocking filter they will replace? Good on Lunt anyway.

They didn't ask how old mine was, just fixed it FOC.

Dave

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Indeed you are correct.

The original Lunt ITF filter was replaced recently with an RG glass filter. This unfortunately still seems susceptible to deterioration.....

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My Lunt 60 is 8 years old now and the BF is in pristine condition, maybe its not age so much as moisture entering slowly, Lunt has advised me to have a look at it last year when I inquired about regular maintenance.

I have had nothing short of excellent service from Lunt every time I called them when I bought the scope. 

Edited by Sunshine

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I've just purchased a second hand Lunt 35 so will be checking the blocking filter when it arrives, now safe in the knowledge that Lunt will sort out any issue with it.

Great post, and I'm pleased you got to the bottom of things and such a good result, well done to you and Lunt :)  

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Hmmm... Mine (Lunt 50) is alright. (I hate it when people say that! lol) ?
The little dab of "glue" has shrunk away from the filter housing but...

I do find myself (occasionally) wondering WHY such things happen? 
Why are these things (plastic or glass) somehow hygroscopic(!)?!?!?
Amused that the more intrepid give them a "quick polish" on their
pants... like some fast bowler trying to encourage reverse swing! lol ?

N.B. Removed small surface spot on mine using my usual technique.
But NOT recommending any of above (or "my own way") to anyone! ?

Edited by Macavity

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On 02/07/2018 at 17:43, Davey-T said:

Shouldn't think that would have much effect on the view mine was nearly 80% obscured.

Dave

Hi Dave,


I agree that's it not that bad. however, it's not going to improve, only deteriorate further over time. Lunt have been in touch today to ask for my mailing details so they can send a replacement. Superb service!

 

On an aside, I'm not buying the ingress of moisture theory. Mine has developed the spot well away from the edges and with no visible path of damage to an edge.  Who knows what is causing it?  :confused:

 

 

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I'd be interested to know if the 'gunk' on the inner side of the blue green glass also finds its way onto the other little red filter on the other side of the diagonal? To that end I'm sending ours off to Germany for a service and check.

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Sara,

Normally it's just the front filter element which is affected.....

The rear blocking/ sort filter doesn't seem to have any long term issues.

 

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11 hours ago, swag72 said:

I'd be interested to know if the 'gunk' on the inner side of the blue green glass also finds its way onto the other little red filter on the other side of the diagonal? To that end I'm sending ours off to Germany for a service and check.

 

8 hours ago, Merlin66 said:

Sara,

Normally it's just the front filter element which is affected.....

The rear blocking/ sort filter doesn't seem to have any long term issues.

 

 

Hi Sara and Merlin

I have discovered the opposite. I took off that orange rear back plate of the BF and was very surprised to find the tinted mirror on the inner side of that orange plate

was quite film covered. But even worse, the output filter glass was shockingly film covered on it's inside surface !!

I have cleaned that mirror and the inside surface of the output filter.

 

I suspect that MOST of the poor seeing and imaging I have suffered lately and blamed on poor atmospheric seeing, has really been the yucky film layers on all 3 surfaces ...

1) outside of the blue input filter glass

2) the mirror

3) the inside of the output filter glass

 

Now, hats off and major kudos to LUNT.  After emailing them and including the pic of the blue filter glass showing the 2 growing spots.

Thy emailed back asking for the serial# of my LS60THa and a snail mail mailing address

They have already dispatched a new filter glass !!

 

With all the crap companies out there these days, here is one who still believes in good customer service !!

Well Done Lunt

 

Dave

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Dave,

That’s a little surprising.....

I’ve been involved in solar and solar mods for over ten years, as yet I’ve only seen one final/ sort filter with any signs of deterioration.

I’d like to see any images you may have of the issue.....

99.9% of the problems I see are associated with the front filter within the BF assembly.

 

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Here's my failed ITF thread in my PST mod. I suspect it had always been failed since purchased used. The difference spending £75 on a new filter made was huge. In the scheme of things £75 is not a lot for perhaps 5-10 years' use.

 

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One positive thing I have learned is... It is possible to get GREAT results
with (Lunt) solar scopes... But it CAN take a *long* time to get to this... ?
I suppose we pay for being at the (b)leading edge of technology etc. etc. 

After a significant time spent sweating under the  SUN... "clocking" stuff 
etc. I felt myself crying for "straight-thru" (non-diagonal) Lunt scope! lol
Getting "optical alignment right" is crucial? Not claiming any expertise...
Just saying don't "give up"! Solar Astronomy is (quite) FUN & dynamic! 

Lunts can be upgraded (Frankenscopes) with due attention to safety...
I concede that the best images I have seen are Quark + (ED) 120 etc. ?

Edited by Macavity

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