Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Lunt 60 mm double stacked solar scope blocking filter issue

solar
  • Please log in to reply
34 replies to this topic

#26 Bob3137

Bob3137

    Explorer 1

  • -----
  • Posts: 85
  • Joined: 19 Dec 2015

Posted 22 July 2017 - 10:39 PM

I have had my Lunt 60 PT for about 6 months and love it. I suspect the issues that are cropping up on the recently purchased new scopes may be from them just rushing to get as many out as possible for the upcoming eclipse. I still believe they are a top notch company that stands behind their product and will take care of whatever issues come up.



#27 davidmcgo

davidmcgo

    Mercury-Atlas

  • *****
  • Posts: 2959
  • Joined: 09 Oct 2004
  • Loc: San Diego, CA

Posted 11 August 2017 - 05:47 PM

Actually these issues seem to be more on units that are ~5 years or so old.

 

I noticed on Schott's page for Near IR cutoff filters  which is what the ITF element is, they show two distinct groups, ones with high steepness of the cutoff, and another with corrosion resistance under humidity.

 

http://www.us.schott...239396-5#group1

 

For cutting the IR band out of the Etalon for safety, I suspect that the sharp cutoff is the need which implies some tendancy for the glass to corrode under humidity.  So storing with fresh desiccant between uses might be a good idea.

 

Dave



#28 Bowmoreman

Bowmoreman

    Clear enough skies

  • *****
  • Posts: 9651
  • Joined: 11 Sep 2006
  • Loc: Wimberley, TX

Posted 14 August 2017 - 10:19 PM

Actually these issues seem to be more on units that are ~5 years or so old.

 

I noticed on Schott's page for Near IR cutoff filters  which is what the ITF element is, they show two distinct groups, ones with high steepness of the cutoff, and another with corrosion resistance under humidity.

 

http://www.us.schott...239396-5#group1

 

For cutting the IR band out of the Etalon for safety, I suspect that the sharp cutoff is the need which implies some tendancy for the glass to corrode under humidity.  So storing with fresh desiccant between uses might be a good idea.

 

Dave

I suspect you are correct; though mine was stored with dessicant. That said, it was stored out in my observatory which was also subject to 100F and humid in summer, and -20F and decidedly NOT humid in winter the last few years...



#29 ASTROTRUCK

ASTROTRUCK

    Viking 1

  • -----
  • Posts: 581
  • Joined: 02 Jan 2010

Posted 15 August 2017 - 10:58 AM

greetings guys - i have a meade 60 coronado about 4-5 years - so far my blocking filter is clear  BUT i did check the meier site in case i need to change the filter as,  if i return it to meade it takes as much as a year for replacement - mine was the first lot made in mexico so i have fingers & toes crossed BUT again looking closer  there is a dab of glue holding the filter in place to the ring so replacement is impossible - thank you very much meade mexico & i cant buy a lunt blocking filter as not allowed to mix & match.

to not lose a year would have to buy a lunt etelon & bf.

 

I DO have an issue with the lunt etelons - my refactor is 900mm fl so to view & tune at the same time is impossible as too long to reach the tuning ring  - i made a long rod that goes the length of the scope to the tuner so i can rotate the tuning ring - the meade coronado etelon ring is loose but THE LUNT IS VERY STIFF SO THE ROD WONT ROTATE THE TUNER  ON THE LUNT ETELONS.

 

what a conundrum

to meade or not to meade - to lunt or not to lunt

 

clear skies for the eclipse guys

 



#30 davidmcgo

davidmcgo

    Mercury-Atlas

  • *****
  • Posts: 2959
  • Joined: 09 Oct 2004
  • Loc: San Diego, CA

Posted 28 August 2017 - 09:24 PM

Interestingly, my replacement ITF showed some haze on the edge when I pulled it out Sunday.  Was fine a month or so ago.  So I pulled it out and the hazy area polished right off with the Meguire's PlastX, in a single application.  May just need to be a periodic task.

 

Dave


  • Live_Steam_Mad likes this

#31 DaveN

DaveN

    Vostok 1

  • -----
  • Posts: 127
  • Joined: 06 Nov 2010
  • Loc: Sydney, NSW, Australia

Posted 29 June 2018 - 07:30 PM

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.jpg

 

 

regards

Dave



#32 BYoesle

BYoesle

    Fly Me to the Moon

  • *****
  • Posts: 6536
  • Joined: 12 Jun 2004
  • Loc: Washington USA

Posted 30 June 2018 - 10:44 AM

Just to be clear with regard to terminology. The first filter now used in Lunt blocking filter's is not an ITF (Induced Transmission Filter). ITF's are used in Coronado blocking filters, and also early Lunt blocking filters. This filter is designed to block mid and far IR passed to the blocking filter component know as the "order selection filter" centered on the H alpha emission, and which importantly blocks the nearby etalon harmonic peaks. This order selection filter is a much more expensive and special-purpose filter in the system, and therefore is well served by very protective pre-filtering from the ERF and ITF or is analog.

 

ITF's are filters with metallic silver and dielectric coatings usually sandwiched with an RG630 substrate. They have to have an epoxy edge seal to keep atmospheric moisture from invading the filter layers and degrading the metallic silver. Due to thermal cycling and heat loading, expansion and contraction of the substrate eventually can cause microscopic cracks in the epoxy seal, allowing atmospheric moisture to invade the filter, which gives rise to the infamous "rust" phenomena, which usually starts at the edge of the filter and moves inward toward the cneter. To help mitigate and prevent premature failure of the ITF, one should always have an IR blocking ERF (full or sub aperture) ahead of the ITF to reduce thermal cycling and loading. A Lunt, BelOptiK, or Baader DERF are all equipped with this IR blocking feature. The DayStar and possibly the Coronado ERF have no such IR coating on their ERF's.  Of course, if the ITF has already developed sealant cracks, anything which can reduce atmospheric moisture exposure, such as storing in sealed container with a desiccant, is helpful to prolong ITF life.

 

The current Lunt blocking filters, and the SolarScope filters use soda-lime glass filters as a replacement for the ITF's mid to long IR blocking. These are either BG filters, KG filters, or a combination of both, and some may even have a short IR blocking applied as well (BelOptik). The deterioration of these filters comes mostly from UV and moisture exposure, and therefore an RG630 substrate ERF, and limiting moisture exposure, are again helpful in prolonging the filter's life. The deterioration generally does not start at the edge as with a true ITF, and happens any place where moisture and UV concentrations combine to 

 

While you could use an ITF to replace one of these filters, it is usually more expensive, and sort of defeats the purpose of using the alternative BG or KG filter to begin with.

 

 


  • Live_Steam_Mad and ONCEWASER like this

#33 euklides69

euklides69

    Sputnik

  • -----
  • Posts: 45
  • Joined: 18 Feb 2007
  • Loc: Chicago, IL

Posted 10 June 2019 - 06:26 PM

I have B1200 purchased in 2008.  In 2014 IR cut filter started to be blurry showing large mineral spots. I called Lunt and they send me the new IR cut filter.
The new one worked well until now.  I just realized the it started to develop blurry film and show similar types spots like the ones back in 2014.

Is it well known returning issue? 
Does it mean that, I have to call Lunt (each 4 or 5 years)  and beg for a new IR cut filter ?

Chris



#34 jwestervelt

jwestervelt

    Viking 1

  • -----
  • Posts: 554
  • Joined: 01 Sep 2012
  • Loc: Phoenix, Arizona

Posted 10 June 2019 - 06:52 PM

Some have said that the "growths" on the BG filters are actually fungus.  When I was talking to the Lunt folks in person, they stated that they'd gladly send a new filter out should it become clouded, but that many people just gently wipe them with some CLR and they go back to being "good as new".  I was initially concerned, thinking that the BG filter had some sort of coating, but was told that its filtering is inherent to the glass and that they are uncoated pieces.  Maybe others can chime in on this.



#35 vincentv

vincentv

    Vostok 1

  • *****
  • Posts: 138
  • Joined: 16 Apr 2017
  • Loc: Costa Rica

Posted 11 June 2019 - 11:34 AM

I have successfully cleaned the glass with plast-x as was recommended by others. If the problem keeps appearing it means you are storing the scope with too much humidity. Out here in the tropics it would begin after ~4months. I have moved to sealed cases and desiccants to deal with it.


Edited by vincentv, 11 June 2019 - 11:35 AM.



CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: solar



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics