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

[tooth_dr 4,693]

I took photos of mine this morning, is it worth contacting Lunt?

 

[AdeKing 959]

I contacted Bresser Europe regarding my blue filter on Friday, had response asking for my mailing address yesterday with another email this morning confirming that a replacement would be shipped today.

I'll post an image of mine later, it looks worse than some, but better than others in this thread.  

The views it gives are pretty good, but I'll be interested to see if the new filter makes a difference.

I'm really impressed with the level of service from Bresser Europe.

Regards,

Ade

[Davey-T 15,440]

5 minutes ago, AdeKing said:

I'm really impressed with the level of service from Bresser Europe.

So was I  

Dave

[symmetal 582]

3 hours ago, tooth_dr said:

I took photos of mine this morning, is it worth contacting Lunt?

No harm in sending the picture to Lunt or Bresser Europe. They may say wait until it gets worse or just send a replacement anyway, as it will need replacement in the future.

I'll have a go at aggresively cleaning the old filter when I get the replacement (there are several suggestions on CN) to see if the deposit can be removed.

Alan

[tooth_dr 4,693]

Thanks Alan. It’s strange alright. My solar scope is never stored outside, it lives in my living room apart from when it’s being used. And it really doesn’t get used too much!

[symmetal 582]

11 minutes ago, tooth_dr said:

Thanks Alan. It’s strange alright. My solar scope is never stored outside, it lives in my living room apart from when it’s being used. And it really doesn’t get used too much!

Same here. I'll try keeping the diagonal in an air tight food container with a couple of FLOs little desiccant bags when not in use, to see if it is moisture related but I'm not convinced.

Alan

[Davey-T 15,440]

Mine's always stored in it's case with desiccant bags and obviously only used in sunshine so never been damp.

A job to tell from the picture but there was only a small clear bit remaining on it.

Dave

[Altocumulus 48]

The good and the bad....Ignore the dust bunnies, they're on the cloth and were removed before assembly of the new piece. I had a silicon sliver helping to hold the plate in place - the video on Lunt showing how to replace, didn't.

 

As I don't have any, I've just left it without. Tighten then untighten 1/4 turn. I used kitchen scissors easily enough.

The other side of the 'bad' filter was worse! It all I'd say it was pretty much 95%+ tarnished....

[tooth_dr 4,693]

Bresser replied - new blue being shipped tomorrow.  Impressive service

[Altocumulus 48]

At this rate they'll be running out stock - again

[symmetal 582]

2 hours ago, Davey-T said:

Mine's always stored in it's case with desiccant bags and obviously only used in sunshine so never been damp.

A job to tell from the picture but there was only a small clear bit remaining on it.

Dave

Thanks Dave. Was only clutching as straws with the damp theory. I suppose the glass does get quite hot in use so maybe the temperature extremes are causing problems somehow. I did clean yesterday, the rear of the output side filter with Baader fluid so thought leaving it with desiccant would remove any water traces that might be lurking. Removing the orange plate doesn't cause any alignment problems as the mirror is held in its recessed location in the housing by the pressure from the foam pad on the orange back plate. The edges of the mirrored surface are quite scratched as the mirror presses directly onto metal but the mirror is larger than it needs to be so the scratches aren't in the optical path.

7 minutes ago, tooth_dr said:

Bresser replied - new blue being shipped tomorrow.  Impressive service

Yes. They must be wondering what has caused this sudden request for filters. Hopefully mine arrives tomorrow.

[Oddsocks 730]

2 hours ago, Davey-T said:

Mine's always stored in it's case with desiccant bags and obviously only used in sunshine so never been damp.

I had the same issue Dave, my filter became completely obscured in a matter of months. I did wonder if the problem was from something in the case outgassing, possibly vapour from the glues used in the case construction or foam lining, possibly even the paint on the OTA.

Bresser sent me a replacement filter very quickly, arriving just two days after requesting it, and I now keep the diagonal in a sealed food container with desiccant bags, completely away from the Lunt case and scope.

William.

 

Edited May 21 by Oddsocks
Added photo

[AdeKing 959]

I contacted Telescope House about mine first then remembered that someone on this thread had had a very slow response from them. 

On the phone they mentioned something about the blue filter containing silver which oxidises. Not sure whether this is right. 

Ade

 

[Oddsocks 730]

33 minutes ago, AdeKing said:

On the phone they mentioned something about the blue filter containing silver which oxidises.

If that is correct Ade it might indicate that keeping the diagonal in the Lunt case as being a possible issue as many foam rubbers outgas Sulphur naturally as they age and Sulphur reacts readily with Silver.

[Live_Steam_Mad 28]

1 hour ago, Oddsocks said:

If that is correct Ade it might indicate that keeping the diagonal in the Lunt case as being a possible issue as many foam rubbers outgas Sulphur naturally as they age and Sulphur reacts readily with Silver.

There's no silver in the blue filter. Lunt confirmed a while back that the blue filter is Schott BG38 Blue Glass. There is no coating on either side of the blue filter. The thickness of it determines the transmission at 656.28nm, the transmission is quite low already. The glass appears to be chemically unstable (in some conditions?). It's Meade who use ITF filters with Silver as the middle layer. The thread holding the filter is tapped at an angle to prevent filter reflections. One f our local Astro club members has a B600 with way higher transmission than either of my two B600's.

Regards,

Alistair G.

[jam1e1 255]

thanks for advice ive got a new filter coming too- glad i checked it.

Does anyone know if white light filter diagonals have a similar issue? hope not.....

[AdeKing 959]

3 hours ago, Live_Steam_Mad said:

There's no silver in the blue filter. Lunt confirmed a while back that the blue filter is Schott BG38 Blue Glass. There is no coating on either side of the blue filter. The thickness of it determines the transmission at 656.28nm, the transmission is quite low already. The glass appears to be chemically unstable (in some conditions?). It's Meade who use ITF filters with Silver as the middle layer. The thread holding the filter is tapped at an angle to prevent filter reflections. One f our local Astro club members has a B600 with way higher transmission than either of my two B600's.

Regards,

Alistair G.

Thanks for clearing that up Alistair. 

[Altocumulus 48]

I've had further info from Faye.

 

The silicon sliver is only put there to prevent any undue slippage during shipping - it's not necessary to replace.

[jam1e1 255]

got my new blue filter in the post on friday, fitted ok so all back to normal now gladly! 

[nigelg 57]

Received an email this afternoon from Bresser, they have run out of the filters and not expecting the next batch for about 2 weeks

 

Nigel

[symmetal 582]

After getting a replacement blue glass filter from Bresser, I thought I'd have a go at possibly cleaning the old cloudy one. The CN thread said some people had success with CLR (calcium, lime, rust) cleaner. I had some Viakal limescale remover spray, so I thought I'd give it a try. I sprayed some into a small glass and dropped the filter in to soak. Came back half an hour later, rinsed it off, wiped it dry and was surprised that it now looks like new and is very clear (but still blue ). So worth keeping now as a backup in case the replacement shows signs of deposits appearing.

If you were going to just throw your cloudy filter away it's worth giving it a try (but at your own risk). 

Alan 

[AdeKing 959]

Thanks Alan I think I might give it a go as now the new filter is fitted there is nothing to lose. 

I'll dig out the Viakal

Edited June 1 by AdeKing
Spelling

[Altocumulus 48]

I (coughs) quickly cleaned mine with some spectacle spray - so I have it as a back-up spare - to be fair there's a small amount of something stuck on the glass - but the worst of it cleaned off I guess sufficiently well for it to function as a spare.

[symmetal 582]

7 hours ago, Altocumulus said:

I (coughs) quickly cleaned mine with some spectacle spray - so I have it as a back-up spare - to be fair there's a small amount of something stuck on the glass - but the worst of it cleaned off I guess sufficiently well for it to function as a spare.

As it's non-coated glass there's no real harm in using a more aggressive cleaner if you wish. 

Alan

[Nigella Bryant 629]

I had the same problem with the blue filter going cloudy. TH replaced it for £30 and took only 7 days. I thought, really great service.