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Cant Get Clear Round Image from SolarmaxIII,Any Help?

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#1 melllince

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Posted 27 May 2019 - 07:48 AM

Hi all,newbie here.

 

I have just phased a Coronado Solarmax III 70mm BF15 DS from OPT,and recived today.Follow the manuals,I try to get clear sharp round image,but when I try to get focus,I got that from the eyepiece(show in bottom).In right-down and left-up corner,It looks as many solar disk stack closely,looks like a comet.

I have tried with all three tuners,focus again and again,change eyepieces,no success.

Want to know which part of the telescope cause this,Anyone can help me?

 

Sorry for my poor English.

 

taken by cellphone from the eyepiece:

solarmax_20190527180845.png



#2 BYoesle

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Posted 27 May 2019 - 10:26 AM

One of your etalons has suffered damage from a sharp blow or fall and is "decontacted." One or more of the etalon spacers has become loose and the filter is therefore not only off-band, the etalon plates (mirrors) are no longer parallel and you have a multitude of off-band images similar to two mirrors facing each other at an amusement park "fun house." Hopefully it is only one of the etalons and not both.

 

Regardless, the scope will need to be returned for repair or replacement. If you got it like this, it is on them to do this repair or replacement at no cost.

 

You should contact OPT immediately to discuss the situation.


Edited by BYoesle, 27 May 2019 - 11:01 AM.


#3 Eikonal

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Posted 27 May 2019 - 10:47 AM

Seems like someone has beaten me to it ;-)

Anyway: with a bit of explanation...

 

Hello,

 

the Hydrogen-Alpha solar filter is a Fabry-Pérot-Etalon, followed by a blocking filter to restrict the range of wavelenths.

The Etalon consists of two extremely well-figured and highly refelective plane mirrors facing each other.

Normally, hardly any light would through (except maybe a millionth of the incident light - just thing of stacking up two mirrors and looking through).

Now, when the two mirror surfaces are exactly parallel, light bounces between them so often, with a tiny bit getting through each time, that they suddently become transparent again.

But (and this is the clever bit) they only do this for a wavelength that inferferes constructively between a ray that has just arrived at the second mirror and ones that have bounced back and forth between the mirrors several times.

This means the separation has to be an integer multiple of half the wavelength you want to transmit, which makes for a highly selective filter.

 

For this to work, however, the plates have to be very parallel, indeed. Think of fractions of a second of arc.

If they are not, you get some sort of infinity-mirror-effect of fainter and fainter solar images fading to the side where the mirrors are separated a bit more than at the others.

 

I am sorry to be the bearer of bad news:

This does look like a faulty etalon.

Most likely, the plates of the main filter are not parallel, which means that the etalon needs re-adjustment. For a cemented etalon, most likely, the etalon is in need of repair.

 

My conjecture would be twofold, depending on the kind of adjustment possible: 

- First of all, it is likely that the etalon has come apart very slightly on the side where the image trail points to (Has the instrument received any bad bumps recently?)

- Secondly, if the etalon is a cemented one, then it needs repair. If the etalon, however, has a screw that presses down on each spacer, then the one where the images trail to might need some minute tightening.

 

If you have never done this before or have not passed, say, a lab class in experimental physics on university level (or are not an avid amateur optician), I would recommend that you seek assistance from the manufacturer.

 

Hope this can be fixed easily.

All the Best,

Kai. 


Edited by Eikonal, 27 May 2019 - 10:51 AM.


#4 BYoesle

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Posted 27 May 2019 - 11:14 AM

Hi Kai,

 

A very good explanation. However, the Coronado SolarMax telescopes use air-spaced etalons with fixed spacers around the periphery of the filter as well as a central spacer. If decontacting occurs there is no way for the user to adjust this away. It has to be returned, the etalon plates disassembled, and then the process of re-contacting the spacers via optical contacting can occur. If one or more of the etalon spacers has become damaged or is missing, all the spacers will need to be replaced and the etalon reassembled with a completely new set of spacers to ensure the required parallelism of the etalon plates.

 

If not covered under warranty - e.g. user dropped or otherwise caused the decontacting - this repair will generally be in the hundreds of dollars price range.



#5 MalVeauX

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Posted 27 May 2019 - 11:25 AM

Agreed with the others. Send it back. That's not at all how it should look. That's not user error or anything you can fix.

 

Very best,



#6 melllince

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Posted 27 May 2019 - 08:46 PM

Thank you all,I will contact them at once.



#7 melllince

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Posted 16 June 2019 - 03:49 AM

Report here.I finaly got the secend scopt through OPT service three days ago.This time the scope is perfectlol.gif .


  • BYoesle, marktownley, rigel123 and 1 other like this

#8 SkipW

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Posted Yesterday, 05:17 PM

Good deal. Thanks for the update!




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