Coronado PST shows no detail. Hope can fix but if not, it was a joy to have while it lasted

[Tej]

Hi guys


My PST is showing no details on the sun, just a solid red disk..I don't even see prominences projecting out. So I am assuming one of the filters is failing. I understand there are two filters, an ITF and a blocking filter? Would any of you have an idea if the issue maybe one of those filters? I understand I can replace (it appears that this should be an easy self DIY job). If you think however, I should send it off for servicing, who would you recommend? Thanks.  I had a look at this thread:  https://stargazerslounge.com/topic/350236-pst-milky-filter/?tab=comments#comment-3815864 . But I am unsure if Gajjer's issue is the same as mine? 

If on the other hand, you think my PST has no chance, then may I indulge a tribute!


I have had the PST for about 6-7 years now, so I guess perhaps it was getting on with age. In it's prime, it was a really lovely thing that I would take around in my backpack with a computerised Nexstar 8se alt az mount (so convenient, as it has a flat base to just plunk onto a table top) and entertain friends and guests with views through it. And what wonderful views they were for such a small aperture. Filaments, sunspots, prominences and spiculation were all clearly visible and surprisingly vivid through my Baader Zoom eyepiece. The failure of the PST happened last year and I thought, well I enjoyed it while it lasted, and this is the end. But as a regular volunteer at Royal Greenwich Museum's Public Solar viewing events, I get to frequently enjoy the views of the sun in HA throughout the summer on their 60mm and 90mm Solar Max solarscopes, so I always have my HA solar viewing fix every summer.


But of course all that changed, in this almost apocalyptic world that we live in now! And aside from worrying about how am I getting baked beans, brown flour and eggs, I am also feeling starved of my solar viewing in HA (even though the sun was so quiet, at least seeing the spiculation makes my day). So hence I am investigating if my PST could possibly get a new lease of life that I can enjoy looking through from home. And it seems, there is a possibility, having browsed some threads here. My fingers are crossed...!


Thanks

[Merlin66]

I would certainly remove the eyepiece holder and check the ITF filter.

I’d say that’s the most likely cause of your issues.

 

[jonathan]

I had corrosion on my blue glass element (I think this is just another name for the ITF) in my Lunt, the problem has been solved on new blue glass elements so if you purchase one (Lunt sell them on their website) it should not happen again.  Simple way to check this is to look at your blue glass element (it will be blue in colour, not red or anything else) to see if you can see any surface corrosion, it might be on the inside or outside surface (or both).  In some cases the corrosion can be removed fully using alcohol and a microfibres cloth / normal glasses or camera lens cloth, in my case it left a stain which still affected the views.

I've never dismantled a PST however I might be doing so soon as I'll need to check the society's PST for just this issue after going through the process with my own solar scope.  I'm sure there will be instructions online for this somewhere, it shouldn't be difficult or dangerous to do.

Edited June 10, 2020 by jonathan

[Merlin66]

Jonathan,

The ITF filter in the PST is completely different from the Lunt.

Looking at the PST ITF it has a bright mirror finish (if OK), if deteriorated it looks like rusty rings. It cannot be cleaned, must be replaced.

Maier Photonics supply a drop in replacement.

Edited June 10, 2020 by Merlin66

[Craney]

This is the little beastie for a PST...

First picture is the upturned eyepiece 'holder'  which has been unscrewed from the main body of the PST.   ITF is sat at the base of this.

   

Second picture is with the ITF removed, showing great 'rustiness'.

On advice of @Merlin66  I ordered a replacement filter from Maier Photonics from the States.  Took about 3 weeks to arrive.   Job done, works a treat.

 

Sean.

[Tej]

Thank you all so much for such thorough replies.  You have made me feel very optimistic in reviving the life of my PST now!  I will check the filters tomorrow and see what I can assess from that first thing and then give an update.  Thanks again!

[Tej]

9 hours ago, Craney said:

This is the little beastie for a PST...

First picture is the upturned eyepiece 'holder'  which has been unscrewed from the main body of the PST.   ITF is sat at the base of this.

   

Second picture is with the ITF removed, showing great 'rustiness'.

On advice of @Merlin66  I ordered a replacement filter from Maier Photonics from the States.  Took about 3 weeks to arrive.   Job done, works a treat.

 

Sean.

Well this is embarrassing, I am stuck on the first hurdle...I can't unscrew the eyepiece holder!  Should I apply brute force or is it possible that I may have a different version of the PST to you?....I see that your eyepiece holder is next to the frequency adjustment ring, whereas my eyepiece holder is at the rear end.

Thanks

 

 

[Craney]

Hi @Tej

Re: my picture ....ah yes, it looks that way, but once I had removed the eyepiece holder, I placed it on the flat top surface of the PST  near to the etalon grip to take a picture of it.   

So do not be worried. They are the same design.

Now, that eyepiece holder. Well I must have been lucky with my PST  because it screwed off with medium stiff resistance.  Maybe the previous owner had tinkered around with it.

You can see the screw thread in my picture.   So it is designed to come off.

I may be wrong here , but I think  that during the manufacturing process the assemblers  use to put a bit of Loc-tite on the thread and that is stopping you from easily removing it.   

Probably to deter you from taking it off and force you into returning the unit for a costly replacement of the ITF.  

If you read around the issue on-line,  people have had trouble removing this piece of the telescope.  It seems a lottery as to how much Loc-tite is on there.   Obviously, it is your scope and you take the risk if you are going to go for it.  All I can suggest is that you use some kind of rubber tape wrench to grip the tube ( to even out the turning force and not distort the  tube barrel )  and be careful not to break the eyepiece retaining screw on the top.  It's only made of plastic on mine.

Probably best to read around the issue and learn from other people successes etc....

This was useful when I changed my ITF.

https://www.tanstaafl.co.uk/2014/08/coronado-pst-eyepiece-holder-disassembly/

Good Luck.

 

Sean.

 

[Craney]

To give you some idea of my ITF problems...  here is a before and after shot of a Solar disc.

   

 

... and the last one is from a bout a week ago.... with proms.    As you can see I had a nasty scratch/smear/gremlin on the ITF which made observing / imaging very difficult, not to mention

frustrating.

The disc is a lot brighter now and I can image at a faster frame rate.

 

Sean.

Edited June 10, 2020 by Craney

[Rusted]

The eyepiece unit is best unscrewed with a "Boa" type of oil filter remover.
This has a tough rubber strap to avoid cosmetic damage.
I clamped the black metal body down [with protective padding] before applying torque to the eyepiece unit.

[Tej]

Well, thank you, @Craney for wishing me luck and educating me about Loctite.   Luck is not with me, sadly, as I couldn't budge it one but.  I tried using machine oil at the rim joint inside and outside but no go.  Clamped into a vice and used a pliers to rotate the barrel and again no budging.  Looks like the Loctite is doing its job.

 

So perhaps I need to buy a heatgun?  What's the holder made of? 

[Tej]

1 hour ago, Rusted said:

The eyepiece unit is best unscrewed with a "Boa" type of oil filter remover.
This has a tough rubber strap to avoid cosmetic damage.
I clamped the black metal body down [with protective padding] before applying torque to the eyepiece unit.

Oh sorry, I just noticed this after my previous post.  I'm trying to visualise how that strange looking contraption works and how you use it on the pst!

[Merlin66]

The "loop" shown at the right goes over the eyepiece holder and made tight by pulling the rubber strap through the handle - towards the left. The serrated teeth when turning, bite into the rubber strap to provide the force to, hopefully, release the eyepiece holder - without damage.

 

[Rusted]

A heat gun risks serious damage to the optical components within.
Red Loctite takes quite a bit of heat 550° to break down.
That's well up to top heat setting on some guns.

[Merlin66]

The eyepiece holder is actually in two sections.

The top section (with the blocking filter) may be easier to remove.

on the newer PST you can access the ITF at the bottom of the eyepiece tube when the top is removed.

 

[Rusted]

[Montana]

Tej,

I had exactly the same problem. don't use oil. Use the rubber boa, I had never heard of one either but found one in a local hardware store. It comes with full instructions on the packet  I had tonnes of loctite on mine and sadly had to enlist the help of the hubby as I was not strong enough to do it. What I found a huge help was using a hairdryer. Let it blow on the area (not too close - like you would to your hair) for 5 minutes. When it was nice a hot the hubby went for it and it just shifted straight away. 

Alexandra

[Tej]

@Rusted

OK this looks similar to what you have. 

https://www.amazon.co.uk/gp/product/B00096JDJY/ref=ox_sc_act_title_2?smid=A3P5ROKL5A1OLE&psc=1

 

I'll try open with that first.   Failing that, there appears to be another option to use Brake fluid which can reduce the resistance of Loctite without damaging the metals.  I am assuming the holder is metal because it seems that Loctite is mostly applicable to metals.

 

[Tej]

@Montana , oh great, thanks for the hairdryer tip,  I got no hubby or a strong missus but I do have a bench vice clamp so I can get some heavy duty assistance using that!

[Rusted]

37 minutes ago, Tej said:

@Montana , oh great, thanks for the hairdryer tip,  I got no hubby or a strong missus but I do have a bench vice clamp so I can get some heavy duty assistance using that!

A vice crushes opposite sides of any round thing into an oval.
Which greatly increases the friction!

Can't recommend a "missus" or a "hubby" either.
Not just for unscrewing a PST component.
Though I have heard rumours that "they" have other uses.

 

[Dr_Ju_ju]

I hate to say it, but if you have a 3d printer you can print one of the 'Boa Constrictor' opener in a few hours.... 

[Rusted]

5 minutes ago, Dr_Ju_ju said:

I hate to say it, but if you have a 3d printer you can print one of the 'Boa Constrictor' opener in a few hours.... 

Probably improve the design where the strap falls out of the side of the slot if you crank it with a four foot length of scaffolding pipe...

Edited June 12, 2020 by Rusted

[Dr_Ju_ju]

3 minutes ago, Rusted said:

four foot length of scaffolding pipe...

🤣 That may be a little excessive, but yes, it's relatively easy to manipulate the design..... 

[Tej]

1kg of 3D printing material is about £25.  How much would be needed for 3D printing a Boa Constrictor?

 

But anyway, happing buying the tool and looks useful to have for other applications in the home.

 

There is a Baby Boa and a medium Boa.  @Rusted , which one do you have? Thanks

 

Medium:

https://www.amazon.co.uk/gp/product/B017W7WE2K/ref=ox_sc_act_title_1?smid=A3P5ROKL5A1OLE&psc=1

 

Baby:

https://www.amazon.co.uk/Baby-Boa-Strap-Wrench-Colour/dp/B00096JDJY/ref=pd_sbs_60_1/257-9923441-8984720?_encoding=UTF8&pd_rd_i=B00096JDJY&pd_rd_r=ce2b361c-72d2-4ef1-83c5-54e4ec02c239&pd_rd_w=FsaRo&pd_rd_wg=EU9nK&pf_rd_p=2773aa8e-42c5-4dbe-bda8-5cdf226aa078&pf_rd_r=BH5CR9HZ4TQF7AKARA11&psc=1&refRID=BH5CR9HZ4TQF7AKARA11

 

Edited June 12, 2020 by Tej

[Dr_Ju_ju]

I've just printed one with 40 M of filament, which is a small fraction of a 1Kg reel....