Old PST safety

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Joe
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Old PST safety

Post by Joe »

Hi. I was given a PST as a birthday present and I think this was 17 years ago now. It could be slightly less (it was either my 21st birthday or a mid-20s birthday). It's strange the things that stick in your memory and those that fade! I have used it on and off over the years but not for quite sometime more recently. However, I am starting to use it again and have a young daughter who will be keen to see the views if she sees me using it. So my question is: given its age is there any risk posed to eyesight by possible degradation of the filters in the etalon?

Thank you for any advice.


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Re: Old PST safety

Post by marktownley »

Hi Joe.

The PST will be perfectly safe.

There's a possibility the ITF filter on it has rusted, but this will only degrade the view but there will be no issues with safety.

Mark


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Re: Old PST safety

Post by Joe »

Thanks for the reply Mark. From browsing the forum I can see you know your etalon engineering. I think it's time I did a bit of reading to understand them myself. I've never been very interested in the engineering side of things just the astronomy.


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Re: Old PST safety

Post by marktownley »

There's a lot to see on the sun at the moment, so when you look through the pst you should see plenty, if not it's probably either not tuned properly or the ITF is rusted. What does the objective look like?


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Re: Old PST safety

Post by Joe »

Hi Mark. Thanks for the further comments. I hadn't seen you'd replied again until yesterday. I've attached a few pics of the objective here:

https://photos.app.goo.gl/rGUrBJ9xHsZLqX5y7

I've yet to find time to properly read about these issues but I appear to have the older (?) orange objective. From what I can see it's probably rusted as it's somewhat opaque and from the odd picture I've seen of a non-rusted PST objective you should be able to see down the tube clearly, which I cannot. Who knows about the ITF but I see it's easy enough to check, so that's for another day.

However, the views appear pretty good still. I was just out earlier and caught the incredible prominence on view earlier (it may have gone now I could see it changing substantially over the course of 10-15 minutes), and I could see all the fine structure in it very clearly, when seeing and clouds allow, and it appeared pretty bright too. Really very stunning and motivating for finding time when the clouds and work allow to get out. I can very clearly see all the usual features too, such as plage, the larger-scale solar structure/granulation and of course sun spots. However, there does appear to be a diffuse dull red glow around the solar disc, which may be due to rusting on one or both of the objective/ITF, but equally it was cloudy so I need to test on a fully clear day when I can sure there's no thin veil of cloud causing this.

If it's affected I assume the options are: 1) live with it (I'm the kind of person that would probably be bugged by the thought of it being sub-optimal, although the views are still stunning at the moment), 2) sell it as is (I saw a rusted PST went for £200 on ebay recently, presumably to someone who planned to fix it or use it in another project), 3) replace the objective and if necessary the ITF (I'd be hesitant unless I can be confident I can do these safely myself!), 4) can Meade/another telescope company replace these things? I'd assume even if they can it'll probably cost more than the scope did!

Thanks for any advice.


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Re: Old PST safety

Post by EGRAY_OBSERVATORY »

It might help to diagnose any issue, if you are able to take an image through the PST - either with an imaging camera or Afocal with an ordinary camera/iPhone etc. through an EP ??

Cheers
Terry


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Re: Old PST safety

Post by marktownley »

The objective on it is most definitely rusted. If the views are fine then that is good and is safe to use. You could replace the gold ota assembly inc objective, that will unscrew from the etalon assembly.


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Re: Old PST safety

Post by Merlin66 »

I agree with Mark, just enjoy what you have, and when you’re ready to move along the learning curve you can consider various options for the future. Unfortunately all are expensive!!!


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Re: Old PST safety

Post by torsinadoc »

I purchased a couple of PSTs last year to play with a Ha spectrum tube. One really good and the other not. The latter has a clear objective and ITF. Do you live in the US? I can sell it for parts if your interested. DM me if interested


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Re: Old PST safety

Post by Joe »

marktownley wrote: Sat Feb 05, 2022 5:41 am The objective on it is most definitely rusted. If the views are fine then that is good and is safe to use. You could replace the gold ota assembly inc objective, that will unscrew from the etalon assembly.
Thanks Mark. I have a few more questions if you'd be kind enough to answer: 1) Do you know if the ITF is well rusted would that always be very obvious in the views, or can a well-rusted ITF still produce decent views? 2) I can't immediately see where you can buy new otas for the PST online so do you know where this can be done?

I will likely stick with it as it is for now though as suggested by Merlin66 and just enjoy the still very impressive views. If I didn't know about the rusting I wouldn't have thought twice about the views being degraded, so the effect is probably fairly small, but it would be interesting to compare.


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Re: Old PST safety

Post by Joe »

torsinadoc wrote: Sat Feb 05, 2022 9:28 am I purchased a couple of PSTs last year to play with a Ha spectrum tube. One really good and the other not. The latter has a clear objective and ITF. Do you live in the US? I can sell it for parts if your interested. DM me if interested
Thanks for the offer but I'm in the ever cloudy U.K.


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Re: Old PST safety

Post by marktownley »

Joe wrote: Sat Feb 05, 2022 9:17 pm Thanks Mark. I have a few more questions if you'd be kind enough to answer: 1) Do you know if the ITF is well rusted would that always be very obvious in the views, or can a well-rusted ITF still produce decent views? 2) I can't immediately see where you can buy new otas for the PST online so do you know where this can be done?

I will likely stick with it as it is for now though as suggested by Merlin66 and just enjoy the still very impressive views. If I didn't know about the rusting I wouldn't have thought twice about the views being degraded, so the effect is probably fairly small, but it would be interesting to compare.
Hi Joe.

Unscrew the ep holder from the black box. You should see any rusting of the ITF on the base filter. Replacements can be bought from Maier in the states, or Beloptik in Europe. Rusting normally identifies itself as a red glow around the sun and or lack of contrast. If ultimately you do change the objective I have a spare one if needed.

Mark


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