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

Issue with my Coronado PST: shift towards green

Solar Refractor Optics Imaging Filters DSLR
  • Please log in to reply
26 replies to this topic

#1 c12marin

c12marin

    Lift Off

  • -----
  • topic starter
  • Posts: 10
  • Joined: 18 Apr 2021
  • Loc: Barcelona

Posted 06 May 2021 - 10:09 AM

Hi folks 

 

 

I'm having trouble imaging with a Coronado PST and a DLSR APS-C. The thing is the telescope allows more light to enter than it should and also there is a shift towards green in the left upper quadrant. A friend of mine told me that filters are likely to be misplaced (PSTs are said to be very sensitive to the position of their filters) help.gif

 

Has anyone run into the same problem?

 

Thanks in advance thanx.gif

 

Chris

Attached Thumbnails

  • Solar disk with my PST.jpeg


#2 Tapio

Tapio

    Skylab

  • -----
  • Posts: 4,302
  • Joined: 24 Sep 2006
  • Loc: Tampere, Finland

Posted 06 May 2021 - 10:49 AM

Hope it's not shifted.
You have tried to tune tilt (ring)?
Are visual views the same?
  • c12marin likes this

#3 vincentv

vincentv

    Mariner 2

  • *****
  • Posts: 288
  • Joined: 16 Apr 2017
  • Loc: Costa Rica

Posted 06 May 2021 - 11:17 AM

If you see green visually STOP using it. That would imply a serious problem in 1 of the filters.

 

-Can the camera reach focus? In other words, is the limb sharp?

-If the above is "yes", can the camera see solar features? I.e. is it on band?

 

There's a chance that the green is simply a camera artifact. Color cameras apply processing techniques to figure out the color. Monochromatic light could be throwing it off.

 

I have never heard of a PST with filter position problems. It's always the ITF getting damaged and occasionally the etalon is decontacted.


  • c12marin likes this

#4 c12marin

c12marin

    Lift Off

  • -----
  • topic starter
  • Posts: 10
  • Joined: 18 Apr 2021
  • Loc: Barcelona

Posted 06 May 2021 - 12:45 PM

Hope it's not shifted.
You have tried to tune tilt (ring)?
Are visual views the same?

 

If you see green visually STOP using it. That would imply a serious problem in 1 of the filters.

 

-Can the camera reach focus? In other words, is the limb sharp?

-If the above is "yes", can the camera see solar features? I.e. is it on band?

 

There's a chance that the green is simply a camera artifact. Color cameras apply processing techniques to figure out the color. Monochromatic light could be throwing it off.

 

I have never heard of a PST with filter position problems. It's always the ITF getting damaged and occasionally the etalon is decontacted.

Unfortunately, green also appears in visual views but is not easily perceivable. For now, it’s a slight shift to green which appears in the left upper corner of the eyepiece. It becomes particularly evident when using a DSLR APS-C. I'm also afraid of using it with a mono camera since the Etalon may be damaged in the process.

Let's hope it's worth fixing jump.gif 



#5 jwestervelt

jwestervelt

    Viking 1

  • *****
  • Posts: 748
  • Joined: 01 Sep 2012
  • Loc: Phoenix, Arizona

Posted 06 May 2021 - 01:18 PM

The etalon is a comb filter. 

The fact that you are visibly getting something other than red indicates that your blocking filter is missing or damaged.  This is actually a bigger problem than a broken etalon when it comes to safety.


  • c12marin likes this

#6 jeffcrilly2

jeffcrilly2

    Explorer 1

  • -----
  • Posts: 81
  • Joined: 25 Jun 2011

Posted 06 May 2021 - 04:15 PM

I had an older PST, and had it repaired by Meade ... it had the "rust" problem and I had basically written it off... until I checked with Meade and the repair was actually pretty reasonable... I think it was $100-200.. like $150 maybe?  This was a while ago.   (which reminds me I need to get it out for an upcoming trip.)

Anyhow.. check with Meade if they have a fix for this.

 

-Jeff


  • Vlad likes this

#7 vincentv

vincentv

    Mariner 2

  • *****
  • Posts: 288
  • Joined: 16 Apr 2017
  • Loc: Costa Rica

Posted 06 May 2021 - 08:22 PM

The PST has 3 filters: etalon, ITF, and trim filter. Troubleshooting is not impossible but it will take some patience and methodical thinking.

 

 

I'm also afraid of using it with a mono camera since the Etalon may be damaged in the process.

To figure out what is causing trouble you'll have to use cameras. Using your eyes is too risky. The camera can not possibly damage the etalon, in fact, it can't damage the scope. Let us know the answer to the 2 question I posted before.

A mono camera can pick up halpha details much easier. It can help make the diagnosis simpler.

 

A third question: How does the objective lens look, is it mostly transparent with a blue coating? Red/pink/green and not all that transparent?


  • c12marin likes this

#8 DAVIDG

DAVIDG

    Voyager 1

  • *****
  • Posts: 10,237
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 06 May 2021 - 10:28 PM

  Did  you buy the PST new or used ? Having repaired a couple of PST if your Etalon was decontacted you would get multiple images of the Sun.  You have no hint of H-alpha detail in your image as your way off band. The only way I  can think of  why you would see green is that your missing the blocking filter 

 

                  - Dave 


  • c12marin likes this

#9 c12marin

c12marin

    Lift Off

  • -----
  • topic starter
  • Posts: 10
  • Joined: 18 Apr 2021
  • Loc: Barcelona

Posted 07 May 2021 - 04:18 AM

The PST has 3 filters: etalon, ITF, and trim filter. Troubleshooting is not impossible but it will take some patience and methodical thinking.

 

To figure out what is causing trouble you'll have to use cameras. Using your eyes is too risky. The camera can not possibly damage the etalon, in fact, it can't damage the scope. Let us know the answer to the 2 question I posted before.

A mono camera can pick up halpha details much easier. It can help make the diagnosis simpler.

 

A third question: How does the objective lens look, is it mostly transparent with a blue coating? Red/pink/green and not all that transparent?

 

 

By the time you're done making adapters, buying additional filters and a few rounds of trial&error you'll have spent almost as much as the quark. PST mods drastically dropped in popularity when the quark came out.

By the way, I've also noticed that the PST lets through more light than it should. Just a little more, it’s still acceptable but PSTs are usually darker.

 

In answer to question #2: Due to bad weather and the low magnetic activity of the sun, I haven’t had a chance to photograph solar features yet. I got a sunspot just digiscoping with the tiny sensor of my Chinese mobile phone. However, last time I didn't manage to get a sharp image of the solar disk with an ASI 120 mm-s (mono). Perhaps I was too close or it was due to atmospheric dispersion. 

 

Regarding the third query, please take a look at the attached image. In my judgment, the objective lens looks milky pink and clean.  

 

Thanks for your help pal smile.png

Attached Thumbnails

  • PST_objective.png


#10 c12marin

c12marin

    Lift Off

  • -----
  • topic starter
  • Posts: 10
  • Joined: 18 Apr 2021
  • Loc: Barcelona

Posted 07 May 2021 - 06:32 AM

  Did  you buy the PST new or used ? Having repaired a couple of PST if your Etalon was decontacted you would get multiple images of the Sun.  You have no hint of H-alpha detail in your image as your way off band. The only way I  can think of  why you would see green is that your missing the blocking filter 

 

                  - Dave 

Used for some $400. The problem is likely to be the blocking filter. I hope this won't be too expensive to fix wacko.png



#11 EVS

EVS

    Sputnik

  • *****
  • Posts: 42
  • Joined: 17 Jan 2009

Posted 07 May 2021 - 07:20 AM

Here’s a good start. 
 

https://www.cloudyni...-alpha-filters/


  • c12marin likes this

#12 DAVIDG

DAVIDG

    Voyager 1

  • *****
  • Posts: 10,237
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 07 May 2021 - 07:56 AM

  What is the serial number ? That will indicate if  unit is  the older version with the ITF coating on the objective that can  deteriorate ie "rust" or the newer version were the ITF coating was placed on a filter that is  below the blocking filter. The IF filter can also "rust". The deterioration of ITF coating would cause the image to be dimmer not brighter so something else is going one. I would check if the blocking filter is installed. The blocking filter is one that you see when you remove the eyepiece and look into the tube. It is about 5mm in the diameter. and dark red in color. I have never seen a blocking filter go bad. The filter that does go bad is the ITF but again that causes a dimmer image and doesn't cause the image to show green. 

   The other possibility is the Etalon decontacted and some one removed  it and either it is not installed or that  they only installed one of the two pieces. That would cause a brighter image and one that might show green. If the Etalon is damaged it would cost more then 1/2 the cost of new telescope to replace.

 

                   - Dave 


  • BYoesle and c12marin like this

#13 briansalomon1

briansalomon1

    Messenger

  • *****
  • Posts: 401
  • Joined: 21 Jul 2018
  • Loc: Oxnard CA

Posted 07 May 2021 - 09:03 AM

Here’s a good start. 
 

https://www.cloudyni...-alpha-filters/

My experience with a decontacted etalon was that the solar disk will come to focus with a sharp limb but won't show any detail at all. If the etalon is decontacted it's likely (but not certain) there are loose parts inside. If there are, you can hold the etalon in a very quiet place and slowly rotate it and listening closely you may be able to hear the parts moving inside.

 

If you hear parts rattling around, the etalon is finished.

 

As EVS points out, components in the Coronado blocking filters are prone to deterioration of the coatings and/or substrates. The old timers believe this is the result of thermal cycling and/or moisture. Many users use desiccant packets to control moisture and depending on the heat load the blocking filter is seeing, some people add an ERF of some type but your scope should function as designed without it.

 

The etalon and the ITF are the two components that commonly fail in H-alpha scopes. Some of the Coronado scopes had the ITF built into the objective.

 

On most of the Coronado and Lunt blocking filters, (Lunt uses a blue glass filter) the ITF is the 1st glass component the light hits on the blocking filter diagonal.

 

Since you don't have other known good components to swap out with, you should familiarize yourself with what a good ITF should look like on your scope. They don't all look the same. The link EVS posted is a good place to begin looking at those components.

 

(Thanks to bob71741 for pointing out that the ITF is a more complex filter than the blue glass found in Lunt blocking filters)


Edited by briansalomon1, 07 May 2021 - 01:37 PM.

  • jwestervelt and c12marin like this

#14 jwestervelt

jwestervelt

    Viking 1

  • *****
  • Posts: 748
  • Joined: 01 Sep 2012
  • Loc: Phoenix, Arizona

Posted 07 May 2021 - 11:54 AM

If I had to venture a guess, I'm going to say that this is your blocking filter.

The etalon isn't going to block enough of the green light to prevent visual detection or camera detection even when it IS working properly.

The blocking filter's job is to simply select the correct peak coming from the etalon and reject all of the other peaks (harmonics).

The good news is that the blocking filters are usually much cheaper, especially if it is just fixing the "rust" issue.  It's like a $10 part in the case of the Lunt devices.

The bad news is that from a safety standpoint, you could easily be risking your eyes looking through the thing.  The rust is often greenish in the photos that I have seen, however the light coming through the blocking filter and etalon combo SHOULD be monochromatic... so even if the light were hitting your camera sensor or eyeball, reflecting back to the "rust" and back-illuminating it, you still should not perceive green since there should be no green light making it to the end of your optical train. This, of course, is not the case if external light is coming in through your eyepiece and either reflecting off the coatings and presenting a "green" image to your eyeball or camera... in which case this is not a major safety issue.

The really bad news is that the part that "rusts" is an IR blocking filter, if I recall correctly.  The filter(s) tasked with bandpass of the etalon harmonic shouldn't fail, but it is the part that should be blocking green and blue light.  I'm very suspicious of your blocking filter, and if you've ever taken the unit apart, I would check it again to make sure that 1) the filter wasn't accidentally removed and left out at some point and 2) that the filter wasn't knocked loose or something.  I think these are usually part of the diagonal, so I would suspect that there would be no image at all if this filter was missing or out of place, but I am not terribly familiar with the Coronado design, so maybe someone else can chime in.


Edited by jwestervelt, 07 May 2021 - 11:57 AM.

  • c12marin likes this

#15 jwestervelt

jwestervelt

    Viking 1

  • *****
  • Posts: 748
  • Joined: 01 Sep 2012
  • Loc: Phoenix, Arizona

Posted 07 May 2021 - 12:04 PM

Now for the devil's advocate stance...

there might not even be an issue.

You appear to be using a DSLR... a color one at that.  These WILL show some activation of the green and blue photo sites.  In fact, it is often advantageous to use the green channel and throw out the other two since you have twice as many photo sites dedicated to green.

As for your eyeballs?  Sometimes you can perceive greens and even whites when looking at h-alpha solar because the image, especially on single-stacked devices, is bright enough that your eyes get saturated.  There is a bit of a burn-in effect when doing visual and, despite having a bright image, you still have to use diverted viewing to see some of the fainter features, and you also learn not to keep your eyes fixed on one part of the image too long so you don't develop a temporary burnt-in image of the limb or other prominent features.

Out of curiosity, do you have the raw image from the camera available, or just a .jpeg at this point?


Edited by jwestervelt, 07 May 2021 - 12:06 PM.

  • BYoesle and c12marin like this

#16 c12marin

c12marin

    Lift Off

  • -----
  • topic starter
  • Posts: 10
  • Joined: 18 Apr 2021
  • Loc: Barcelona

Posted 08 May 2021 - 04:48 AM

  What is the serial number ? That will indicate if  unit is  the older version with the ITF coating on the objective that can  deteriorate ie "rust" or the newer version were the ITF coating was placed on a filter that is  below the blocking filter. The IF filter can also "rust". The deterioration of ITF coating would cause the image to be dimmer not brighter so something else is going one. I would check if the blocking filter is installed. The blocking filter is one that you see when you remove the eyepiece and look into the tube. It is about 5mm in the diameter. and dark red in color. I have never seen a blocking filter go bad. The filter that does go bad is the ITF but again that causes a dimmer image and doesn't cause the image to show green. 

   The other possibility is the Etalon decontacted and some one removed  it and either it is not installed or that  they only installed one of the two pieces. That would cause a brighter image and one that might show green. If the Etalon is damaged it would cost more then 1/2 the cost of new telescope to replace.

 

                   - Dave 

Hi, Dave:

 

The serial number is 97068. Both the objective lens and the Etalon seem in order (check the attached pic in this message and the one from yesterday). I'm going to take a look at the blocking filter waytogo.gif

 

**By the way, CN has removed one of my previous posts due to a safety concern. So take the norms into account and avoid the topic of reengineering solar scopes.**

Attached Thumbnails

  • 823e766a-e68c-4dd4-89ad-0d86cc366254.jpg


#17 c12marin

c12marin

    Lift Off

  • -----
  • topic starter
  • Posts: 10
  • Joined: 18 Apr 2021
  • Loc: Barcelona

Posted 08 May 2021 - 05:03 AM

My experience with a decontacted etalon was that the solar disk will come to focus with a sharp limb but won't show any detail at all. If the etalon is decontacted it's likely (but not certain) there are loose parts inside. If there are, you can hold the etalon in a very quiet place and slowly rotate it and listening closely you may be able to hear the parts moving inside.

 

If you hear parts rattling around, the etalon is finished.

 

As EVS points out, components in the Coronado blocking filters are prone to deterioration of the coatings and/or substrates. The old timers believe this is the result of thermal cycling and/or moisture. Many users use desiccant packets to control moisture and depending on the heat load the blocking filter is seeing, some people add an ERF of some type but your scope should function as designed without it.

 

The etalon and the ITF are the two components that commonly fail in H-alpha scopes. Some of the Coronado scopes had the ITF built into the objective.

 

On most of the Coronado and Lunt blocking filters, (Lunt uses a blue glass filter) the ITF is the 1st glass component the light hits on the blocking filter diagonal.

 

Since you don't have other known good components to swap out with, you should familiarize yourself with what a good ITF should look like on your scope. They don't all look the same. The link EVS posted is a good place to begin looking at those components.

 

(Thanks to bob71741 for pointing out that the ITF is a more complex filter than the blue glass found in Lunt blocking filters)

Hello, Brian:

 

I would rather bet on the ITF itself assuming that is applied on the blocking filter. Although a fellow solar astronomer who has checked the PST in situ told me the problem is likely to be a filter out of its usual position. Others have told me there is no way for a PST to shows green images in visual (except for retinal saturation). I wasn't aware of that shift towards green until I lent the telescope to a friend who has both versions, single and double stacking  Etalon. On Tuesday he's going to bring me back the PST and I'm going to check it myself before bringing it to the technical service. 


Edited by c12marin, 08 May 2021 - 05:04 AM.


#18 BYoesle

BYoesle

    Fly Me to the Moon

  • *****
  • Posts: 7,139
  • Joined: 12 Jun 2004
  • Loc: Washington USA

Posted 08 May 2021 - 06:01 AM

Hi Chris,

 

In addition to what DAVIDG stated, the direct sunlight falling on your objective indeed makes it look a bit cloudy (rusted) to me and likely is the version that had an ITF coating there, and if so it needs to be replaced. As the second owner and its age you're likely out of luck in having MEADE replace it under warranty. There should be a RG630 (red) filter somewhere in there, and if there is I doubt you're seeing any real green, and I would tend to agree with jwestevelt you're having a DSLR color shift issue with your image, and / or an oversaturation of the retina. Your image is too poor to come to any judgement as to whether you're even on or close to being on-band. PSTs are also notorious for having pentaprism sag and this may be a contributing issue to the poor image. A decontacted etalon would result in an almost infinite set of images going off in one direction, so this does not appear to be the case. If the trim filter is missing you'll have basically a bright red continuum image from the light passing through the RG630 filter, but this would not be safe to view through due to near IR leakage. The ITF coating even when rusted will still block far IR, but give you a cloudier image.

 

Unless you really know what you're doing and familiar with the variations on the PST design an location of the ITF/coating and filters, you'll need to get the scope to someone who does have better familiarity and be able to give you concrete answers. Purchasing used solar equipment is an iffy proposition, and you should always have a no questions asked ability to return the equipment to the seller if it does not perform as expected.

 

Good luck, and I hope your friends evaluation will shed some more light on the issue. I would not look through this scope until you have informed answers and solutions put in place.


  • briansalomon1 and c12marin like this

#19 c12marin

c12marin

    Lift Off

  • -----
  • topic starter
  • Posts: 10
  • Joined: 18 Apr 2021
  • Loc: Barcelona

Posted 09 May 2021 - 12:15 PM

If I had to venture a guess, I'm going to say that this is your blocking filter.

The etalon isn't going to block enough of the green light to prevent visual detection or camera detection even when it IS working properly.

The blocking filter's job is to simply select the correct peak coming from the etalon and reject all of the other peaks (harmonics).

The good news is that the blocking filters are usually much cheaper, especially if it is just fixing the "rust" issue.  It's like a $10 part in the case of the Lunt devices.

The bad news is that from a safety standpoint, you could easily be risking your eyes looking through the thing.  The rust is often greenish in the photos that I have seen, however the light coming through the blocking filter and etalon combo SHOULD be monochromatic... so even if the light were hitting your camera sensor or eyeball, reflecting back to the "rust" and back-illuminating it, you still should not perceive green since there should be no green light making it to the end of your optical train. This, of course, is not the case if external light is coming in through your eyepiece and either reflecting off the coatings and presenting a "green" image to your eyeball or camera... in which case this is not a major safety issue.

The really bad news is that the part that "rusts" is an IR blocking filter, if I recall correctly.  The filter(s) tasked with bandpass of the etalon harmonic shouldn't fail, but it is the part that should be blocking green and blue light.  I'm very suspicious of your blocking filter, and if you've ever taken the unit apart, I would check it again to make sure that 1) the filter wasn't accidentally removed and left out at some point and 2) that the filter wasn't knocked loose or something.  I think these are usually part of the diagonal, so I would suspect that there would be no image at all if this filter was missing or out of place, but I am not terribly familiar with the Coronado design, so maybe someone else can chime in.

Hi, jwestervelt wavey.gif

 

Just $10 for fixing anything at Meade/Coronado/Lunt would be a bargain. It seems too cheap to be true, particularly when the PST is by far out of warranty. On Wednesday I'll bring the telescope to the technical service. I thought the issue was just a matter of one or more of the filters shifted out of their proper position. The thing is I will surely sell the PST to get money for the Quark and cannot until this issue is fixed. 

Thank you very much for your help smile.png



#20 DAVIDG

DAVIDG

    Voyager 1

  • *****
  • Posts: 10,237
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 09 May 2021 - 01:11 PM

  Blocking filter  is at least $100 if not much more. An ITF from Maiers is $75.   Here is a link to  an old thread that listed the PST serial numbers and one that were built with the original design that had the "rust" issues on the objective.  There are also pictures of what a "rusted" objective can look like. 

https://www.cloudyni...st-serial-list/

With yours having a serial number of 97068,  it fits in the list  of  the older models that had the "rust" on the objective  From your image it looks to have the problem and wasn't sent back to Meade to be repaired.  Meade is in bankruptcy  so it  is unclear if they could repair your instrument. 

   Having seen a number  of PST with fully "rusted" objective it doesn't cause the image to show green or be brighter, it causes the image to be dimmer. So I still believe something else is going on with yours. It looks to me that someone has disassembled the Etalon assembly. When you rotate the tuning ring you should see the Etalon tilting. The tilt is only a few degrees but you should see it move. If not something could be wrong with the how the Etalon was placed back in the assembly. 

    When your looking through the scope and you turn the tuning ring what do see happening to the image of the Sun ?

 

                  - Dave 


  • BYoesle likes this

#21 jwestervelt

jwestervelt

    Viking 1

  • *****
  • Posts: 748
  • Joined: 01 Sep 2012
  • Loc: Phoenix, Arizona

Posted 09 May 2021 - 01:21 PM

Hi, jwestervelt wavey.gif

 

Just $10 for fixing anything at Meade/Coronado/Lunt would be a bargain. It seems too cheap to be true, particularly when the PST is by far out of warranty. On Wednesday I'll bring the telescope to the technical service. I thought the issue was just a matter of one or more of the filters shifted out of their proper position. The thing is I will surely sell the PST to get money for the Quark and cannot until this issue is fixed. 

Thank you very much for your help smile.png

https://luntsolarsys...ocking-filters/

It is cheaper than $10 now.

To be clear, there are multiple filters in the blocking filter of most solar scopes.  The element that "rusts", at least on the Lunt, is the one I linked.  The big money is tied up on the filter that is on the diagonal and downstream of it.  Yes, replacing the whole blocking filter is a multi-hundred-dollar affair in most cases, but luckily some elements can be field-replaced by the owner.

Also, if your problem turns out to be the "rusting" issue, it might be worth looking in to storing the scope in an airtight container with a decent desiccant pack.



#22 DAVIDG

DAVIDG

    Voyager 1

  • *****
  • Posts: 10,237
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 09 May 2021 - 02:50 PM

https://luntsolarsys...ocking-filters/

It is cheaper than $10 now.

To be clear, there are multiple filters in the blocking filter of most solar scopes.  The element that "rusts", at least on the Lunt, is the one I linked.  The big money is tied up on the filter that is on the diagonal and downstream of it.  Yes, replacing the whole blocking filter is a multi-hundred-dollar affair in most cases, but luckily some elements can be field-replaced by the owner.

Also, if your problem turns out to be the "rusting" issue, it might be worth looking in to storing the scope in an airtight container with a decent desiccant pack.

  The filter referenced for the Lunt and the one in the PST are very different in design and functionality The Lunt filter is a simple blue glass long pass filter. The blocking filter in a PST is a  narrow band interference filter with  a band pass of about 10 angstroms to isolate the H-alpha transmission from the Etalon.  The ITF coating to remove the IR was first applied in between the elements in the objective lens and since it was not sealed the coating deteriorated ie "rusted". Meade's solution was to replace the objective and move the ITF coating to smaller filter that is placed at the very bottom of the eyepiece tube. The ITF filter is NOT the one you see when you look down into the eyepiece tube. That small red filter is the blocking filter. You need to remove the side cover or fully unscrew the eyepiece tube to examine the ITF filter  and the ones  provided by Meade also rusts at the same frequency that the coating on  the objectives did.  The  ITF filters sold by Maiers and Beloptik are made differently and last much longer. My Maiers ITF is 10 years old and shows no sign of deterioration.

 

                        - Dave 


Edited by DAVIDG, 10 May 2021 - 08:32 AM.

  • BYoesle and briansalomon1 like this

#23 BYoesle

BYoesle

    Fly Me to the Moon

  • *****
  • Posts: 7,139
  • Joined: 12 Jun 2004
  • Loc: Washington USA

Posted 10 May 2021 - 08:45 AM

Agreed, MEADE will not likely be able to replace the objective or want to add an ITF where the later models had it. It would be possible to use a different but similar diameter and focal ratio objective to replace the rusted OEM objective, used with a good quality 2 inch UV/IR filter. Then a Maier ITF or BelOptik replacement could be employed as the first element in the eyepiece tube or at its base. As Dave noted, the blocking filter is a different animal for a much more precise job of near CWL out-of-band harmonic blocking, and indeed is pretty expensive.

 

The only possible alternative here is to purchase another Coronado blocking filter to obtain this element. Some people have also removed the pentaprism focuser and make a straight through adaptation by adding a small R&P or helical focuser to the back of the box (or eliminate it completely), and then your can use the aforementioned focuser and new blocking filter upgrade.

 

If the etalon itself is the issue, then you're pretty much out of luck.


  • briansalomon1 likes this

#24 DAVIDG

DAVIDG

    Voyager 1

  • *****
  • Posts: 10,237
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 10 May 2021 - 09:56 AM

 I know that Ed Jones up the ATM forum  took his objective and disassembled it  and removed the rusted ITF coating between the elements  and then added a ITF filter.  I have recontacted  Etalons on my disk at home. It isn't difficult once you know the procedure and I posted it here before.  The fact that the OP did not say he was seeing multiple solar images is a good indication that the Etalon is not decontacted. I have always seen multiple images on the decontacted Etalon I have repaired. 

   The solar image that was posted shows no H-alpha detail so it is clearly not on band. I'm wondering if someone in the past has disassembled the tuning  mechanism and over tightened something or moved the screw that determines the range of motion so the Etalon is either not tilting or the range of tilt is not correct so that  it is not coming on band.

 

                    - Dave 


Edited by DAVIDG, 10 May 2021 - 09:56 AM.


#25 vincentv

vincentv

    Mariner 2

  • *****
  • Posts: 288
  • Joined: 16 Apr 2017
  • Loc: Costa Rica

Posted 10 May 2021 - 11:53 AM

I understand Meade doesn't have the customer service level of Lunt, but the situation is not THAT bad.

Here's a link a thread from late last year. Meade accepted the PST for repair (I would like to know how long it took though):

https://www.cloudyni...1-pst-rust-fix/

 

There's little reason not to update older scopes. The way Meade/Coronado updated the design means that older scopes can be easily retrofitted with the current productions parts.




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, Refractor, Optics, Imaging, Filters, DSLR



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics