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Rust on either Lunt or Coronado

Posted: Wed Nov 14, 2018 3:29 am
by RKBerta
I have a 60mm Coronado Ha filter and both a BF15 and BF30 blocking filter also Coronado. It is used on a TV 85 APO refractor. I did have Meade replace the BF 15 filter because of rust but the BF30 is holding up thus far. All equipment was US produced before Coronado moved facility to Mexico.

I am contemplating upgrading to either a Lunt 100 or 152 with double stacking. Is rust also an issue on some Lunts or have either Coronado or Lunt solved it?

Also....since it seems moisture is a cause of the rust....guess getting between the two elements, I have been using a moisture absorbing device in the case to suck up any moisture. Have others found that to be useful or not?

Re: Rust on either Lunt or Coronado

Posted: Wed Nov 14, 2018 9:59 am
by Merlin66
Failure of the ITF filter in both the Lunt and Coronado is still a common occurrence.
I know know if it really helps but I do store my BF in sealed containers with Silica Gel.......

Re: Rust on either Lunt or Coronado

Posted: Wed Nov 14, 2018 6:10 pm
by 4average
https://www.cloudynights.com/topic/4330 ... ?p=5592771

Lunt no longer uses ITF in its blocking

Re: Rust on either Lunt or Coronado

Posted: Wed Nov 14, 2018 10:47 pm
by Merlin66
I agree, but the Lunt replacement BG element is also subject to failures....
B1200_failure_iis.jpg
B1200_failure_iis.jpg (163.58 KiB) Viewed 4501 times
Lunt-blocking-filter-problem_12-09-25_12r.jpg
Lunt-blocking-filter-problem_12-09-25_12r.jpg (195.12 KiB) Viewed 4501 times
IMG_9852_lunt b1200.jpg
IMG_9852_lunt b1200.jpg (102.82 KiB) Viewed 4501 times

Re: Rust on either Lunt or Coronado

Posted: Sun Nov 18, 2018 7:56 pm
by RKBerta
Thanks all for feedback. Sad that this evidently is still an issue after all these years with both C and L products. Hopefully using a desiccant pack in my case will help. Luckily where I live humidity isn't a big issue like it was where I lived before.

Re: Rust on either Lunt or Coronado

Posted: Mon Nov 19, 2018 1:21 am
by mdwmark
That's not a humidity problem on the images. Humidity usually fails from the outside in. This is something different.
Mark W.

Posted: Mon Nov 19, 2018 3:16 pm
by Bob Yoesle
As shown in Ken's pics, and as in the above Cloudy Nights link, the Lunt issue now appears to be "glass disease:"

https://en.wikipedia.org/wiki/Glass_disease

See the Stage 1 and Sage 2 descriptions.

It is known the Lunt uses BG glass (verses an ITF), which is a simple soda lime glass. It seems the KG glasses are susceptible to UV exposure deterioration, and perhaps this UV exposure is some sort of accelerator for glass disease, especially the concentrated exposure near focus. The solution would seem to be coatings to protect the surface from both moisture and UV penetration. I note that Oliver uses a UV/IR blocking coating on his KG3 BelOptik glass filters...

Lunt seems to be well aware of the issue and will send you a new BG element for free as a replacement if the problem develops.

During the winter and in high humidity months I store my blocking filters in a sealed food storage vacuum bag with a desiccant, and have employed UV/IR blocking filters and DERF's ahead of every ITF. So far no problems with ITF failure after 10 years. Prior to using these methods I had 2 failures within two years. It would be interesting to see if these methods would have an effect on the standard BG filter used by Lunt.

Re: Rust on either Lunt or Coronado

Posted: Fri Nov 23, 2018 3:30 am
by Christopher
The wonder fluid is great stuff. I’ve been using it for years. I can’t attest to it being a cure for the aforementioned glass disease one way or the other. But I use it to clean all my optics. It does claim to protect from fungus etc. I get it from Alpine Astro here in the states.