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Coronado PST 12 years old. Still OK to use?

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8 replies to this topic

#1 galazie

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Posted 27 February 2021 - 09:43 PM

Today I took out my Coronado PST, after may be a few years, to have a look at the Sun, as the morning sky was so clear. 

 

The image was OK. I saw a small prom and some surface activities. Is the sun still in a low period? - I heard that since a few years.

 

But I just wonder. I bought the PST in 2009 (and used it almost every day in the first couple of years). Now it is 12 years already. Is there some sort of expiry date for a PST? How do we know if it still works well and safe? Do the filters deteriorate over time and make it unsafe for our eyes? Or if the image still looks good, that means the filtration is still working well and safe?

 

thank you.

 

 

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#2 MalVeauX

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Posted 27 February 2021 - 09:50 PM

Heya,

 

Yes, its the solar minimum still. We are at least transitioned into cycle 25, but still on the minimum side of the curve. There's a solid AR with sunspot on the limb right now.

 

Your scope is safe to use. The only thing that may happen over time is degradation of your ITF filter and it will cause the image to be very dim and lose contrast. If you can see the disc features, then its still ok. If it's just a dim low definition ball, then the ITF is likely degraded and needs to be replaced. It's still safe, just dim and low contrast. BelOptik sells a replacement that is perfect for life and is easy to install.

 

If you have an ancient PST, the ITF is actually the front element of your scope and it doesn't even have an ITF in the eyepiece chamber. The front lens element will be a rusty orange/red color.

 

A newer PST has a blue color front element and the ITF is located as a filter in the eyepiece chamber, the stem coming up from the black box. If you unthread the top chamber where your eyepiece goes, you'll see a small 5mm red filter, this is your blocking filter. The next chamber down after you take the top eyepiece chamber off, is where the ITF is and it will be much larger.

 

JonIassacs_PST_ITF_02142020.jpg

 

Very best,


Edited by MalVeauX, 27 February 2021 - 10:19 PM.

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#3 galazie

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Posted 27 February 2021 - 10:41 PM

Thanks, MalVeauX

 

Not sure if my PST (photos attached) is ancient or newer.

 

I tried unscrewing the eyepiece chamber but could not. Either unscrewable or too tight.

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#4 MalVeauX

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Posted 27 February 2021 - 10:45 PM

Hi,

 

Your PST is a newer one. The front element is blue.

 

So, if you point it at the sun, tune it to be on band (dark filaments, bright plage) and you see these features and prominences, then you're set.

 

If you tune through the whole sequence, with the eyepiece focused, and you can't get any features and its very dim and low contrast, then it's most probably the ITF.

 

All the threaded joints of the PST are glued/locktite. Meade won't even answer a phonecall or email, so they won't repair this (they used to). So its a self repair job.

 

Very best,



#5 galazie

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Posted 27 February 2021 - 11:00 PM

Hi MalVeuX,

 

Yes, dark filaments, bright plage, and prominences are still there to be seen :) (I am just interested in prominences). So all sounds OK.

 

 

Thanks very much for help.


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#6 DAVIDG

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Posted 27 February 2021 - 11:13 PM

 You can view the ITF  filter by taken the side cover off You need to shiny a bright light on it to see if it has clouded over of not. If it is the original Meade filter then the odds are pretty high that is has clouded over.  Taking the side cover off will also allow you to view the penta prism which many times has drifted out of aligned because of the type of glue used.  Aligning the penta prism and replacing the ITF if it has clouded over will make a noticeable difference in the image sharpness and contrast.

 

                 - Dave 


Edited by DAVIDG, 28 February 2021 - 09:11 AM.

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#7 photomagica

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Posted 28 February 2021 - 12:07 AM

I'm using and older PST - bought used - age unknown. ITF has been replaced and the prism realigned. It works great.

There have been some nice prominences in the past couple of weeks. Good ones today.

Hope you really enjoy yours.

Bill


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#8 SpaceConqueror3

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Posted 28 February 2021 - 12:11 AM

As a data point, mine is 9+ yrs old and still cranking along superlatively...


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#9 dswtan

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Posted 28 February 2021 - 12:21 AM

This is the replacement ITF that you want. There are instructions buried here somewhere on CN. I did mine last year, and while the original was not bad, it was low contrast and this improved things considerably. It was quite easy, and I'm not that handy. The PST is vintage 2012 and this needed doing. It was not heavily used, so just time had deteriorated things in a moderate climate. 

 

https://maierphotoni...ssfilter-1.aspx

 

Note you cannot see the ITF directly from the outside -- it is well-buried in the eyepiece section, covered by other filters. You can't easily see if yours is clouded or not without dismantling, in my experience. 

 

BTW, Maier are not joking that you should take care not to smudge the surface -- it is super delicate, not like say regular photo filters that you (and I) are used to!


Edited by dswtan, 28 February 2021 - 12:27 AM.

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