Lunt LS60THa Filter Clouding

[sharpiel]

Hello all.

I have a Lunt 60 Ha scope. Two years ago I sent the blue glass from the diagonal back to Lunt under warranty for cleaning/replacement as it had clouded over.

This week after a (2 year) hiatus I inspected the diagonal to find the issue had returned.

1. If I were to refer this issue to Lunt again how would I address it via email? Is the blue glass the blocking filter or would I describe it by another name?

2. I’m aware that in years past there were threads here describing this issue and ways to do a DIY clean (CRT from Bunnings is in my mind). Despite archival searches I haven’t located a thread. Can anyone direct me to one?

3. Has anyone who has done a DIY clean any advise/warnings to share which may help me?

Photo attached

[AstroJunk]

3. Yes indeed.

CLR is your friend. Scrape off that bit of sealant that fixes the ring, screw it off and drop the little blue disk into a plastic tub of CLR for a few hours or overnight and wipe it down between your fingers under a running tap. If is doesn't come up completely clean, repeat...

I have a couple of blue disks - one is permanently stored in CLR and dried off when needed!

BTW, don't bother gluing that ring back in - it's fine just finger tight.

[GUS.K]

If you have no luck with it, I've got a spare BG filter you can have.

[Merlin66]

Les,
Lunt will offer a further replacement...
I do agree that CLR does seem to reduce the fogging.

[sharpiel]

Thanks Ken, Jonathan and Ivan. Seems to me my best option is to seek a replacement from Lunt (seems to be a manufacturing issue?) and keep one in reserve as Jonathan does.

How would I refer to it for the purposes of speaking with Lunt. Ivan called it a BG filter. Is this the correct nomenclature for Lunt? Ivan I will keep you in mind if I have issues with Lunt. Thank you for your offer.

[AstroJunk]

https://luntsolarsystems.com/shop/solar-products/hydrogen-alpha/lunt-replacement-parts/blue-glass-for-lunt-blocking-filters/

They rather cheekily sell them as replacement parts!

To get a perfect finish, Cerium Oxide is the polishing compound that opticians used and is cheap on ebay. Use it like a paste on a cloth to clean it after getting most residue off with CLR. It's worth learning to do as they will continually go bad :mad2:

[GUS.K]

Les, it's simply called the BG (blue glass filter). It's not an ITF ( induced transmission filter) which the Coronado scopes have.

[PeterM]

I think Bintel stock them. Not sure of the cost but I bet it's cheaper than postage both ways.

[sharpiel]

Thanks Gus. Does anyone know what function it serves in the Ha train? In other words what would be the repercussions if it were permanently removed?

[Merlin66]

Les,
Just call it the BG filter as Gus suggests.
The filter uses glass which is susceptible to moisture ingress. This is a known problem. It was Lunt’s decision to use this glass.
Polishing the glass will not remove the effects of moisture deterioration.
The Lunt designed blocking filter assembly definitely needs the BG filter to perform 100% safely.

[sharpiel]

Awesome. Thx everyone. Ironically my partner and I had just bought a new laptop and were setting up to start imaging the sun when I noticed the (recurrent) BG issue.

Much disappointment. Will contact Bintel first as suggested and source further if required. I knew I’d find knowledgeable answers here. 👍👍

[John W]

I just received a replacement BG filter for my Lunt diagonal under warranty.

But it took over 2 months to get here after leaving Lunt in the US - so be prepared to wait. Try cleaning first.

This you tube video shows you how to replace the BG filter. <https://www.youtube.com/watch?v=ylWnC3pLQ7o>



Cheers, John W

[Derek Klepp]

Les I clean mine all the time .In my case into CLR for a few minutes clean and rinse off with distilled water.Repeat if necessary.In humid environments it clouds over quicker.
Derek

[Star Catcher]

Agree Derek! I discovered this fix several years ago when my filter fogged up. It never fails to clean the filter back to its pristine condition and as you say, it might take a second go.

Abrasive materials or polishing creams must not be used.

Ted

[sharpiel]

CLR and distilled water it is then!

[sharpiel]

Btw is the BG critically directional? In other words does it matter which face is facing inwards/outwards?

[Star Catcher]

No.

Ted

[sharpiel]

Thx mate :thumbsup: