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Corroded ITF PST Mod

Moonshane

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moriniboy

moriniboy

Posted
Posted

I need an ITF for the PST which I'm taking to the US eclipse in August.

It would be easy to adapt a Baader 35nm to use in the PST but if it goes wrong (i.e. breaks due to heat) then my eye is at risk, therefore not an option.

I'm assuming that the ITF is a lot thicker compared to the Baader for a reason - thermal shock prevention perhaps?

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Merlin66

Merlin66

Posted
Posted

Guys,

Stop! 

If you want to replace an ITF in a Coronado instrument then you can use the OEM supplier Maier. This is a direct change over....

If you want to replace an ITF on a PST Mod etc where an up front (or reduced size) ERF is fitted, then based on experience there are other options.

Baader 35nm - identical coatings to the D-ERF

Oliver's KG3 UV/IR - similar base material to I believe Lunt and others but coated.

None of these filters will "break due to heat" WHEN USED PROPERLY - BEHIND A FRONT ERF.

 

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moriniboy

moriniboy

Posted
Posted

Taking this one step further (and currently relating to PST's only) as the Baader H-alpha 35nm has the same coatings as their D-ERF it could be used as a front erf.

This is a photo of a 2" filter placed in front of a standard PST blue objective as an example of how it would fit (I don't have a 2" 35nm to hand). It is a loose fit but could be secured very easily.

The internal standard (rusty) ITF could then be disposed of.

Note the above is untested by me and just for forum discussion as I have just bought a new ITF from Maier, but it might help others in this situation.

 

P1000563.JPG

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moriniboy

moriniboy

Posted
Posted

The Baader 2" 35nm filter got delivered yesterday and I have used a long and short Baader Hyperion tuning ring to construct a basic filter cell.

Also used 3 pieces of thin flocking (not the DC Fix type as it was too thick) to centralise and provide resistance against falling out. In reality it can be screwed in the PST objective and you can hopefully see the thread marks on the attached photo.

All has gone well with a first test.

 

P1070143.JPG

P1070144.JPG

P1070145.JPG

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  • 2 weeks later...
Paul73

Paul73

Posted
Posted
On 5 April 2017 at 10:48, Mark at Beaufort said:

Moriniboy they look terrible - can you see anything through them? I assume the PST is the top photo? How easy is it to remove the ITF from a PST scope?

Hi Mark

If your PST is made by the same chap as mine, he did a good job and the bottom half of the eypiece tube (the one with the ITF) won't budge without without the help of a large hammer. A quick check is to unscrew the main OTA & Etalon, remove the top half of the eypiece tube with the blocking filter and look though it whilst aiming the eypiece tube towards a desk lamp. You can get a pretty good idea from that if you need any extra exploration. I'd have another go at removing the whole eyepiece tube at this stage. You can release the glass disc of the filter from the top. But from the bottom is much safer. Mine wouldn't shift, so I used a chisel (very carefully ?) to get the retaining ring moving. Make sure that you do this flat otherwise the ring and the ITF will fall out...

Pleased to report that mine is clear as a bell and old. I've got number 95217!

Paul

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spaceboy

spaceboy

Posted
Posted

I have to thank Shane for bringing this issue to my attention. I have to admit when I bought my PST mod I was a little dubious to the quality of the views when compared to my lunt. My first thoughts were that it may benefit from a stage 2 but having read several threads on various solar chat forums suggesting that the costs over improvements are negligible (sounds about right for anything astronomy) that I put it down to the higher mags achieved in the PST/TAL and some poor seeing that, to be fair has been plaguing my night time observing also.

Anyway long story short ...... after clear blue skies yesterday I set about splitting the blocking filter ITF assembly and .......

filt.thumb.jpg.a3298c2826e31e74d8f69f59bd2f42b8.jpg

I wish I could say I'm PSST at the idea of having to shell out on a new ITF filter but TBH I'm looking forward to swapping it out and reaping the benefits. The 100mm aperture potential has already been revealed at the eyepiece so the added contrast a rust free filter should offer is an exciting thought :) 

Sorry to yet again come across as a PST hater but at least prior to Meade you could easily identify a rust problem but now they hide the ERF away from view. I understand the reasons for doing it as the ITF is better protected from the elements but clearly this tread has pointed out that ITF are a common failing point in solar scopes and should be easier for customers to identify potential issues. Who knows how long some PST's sit on shelves before sold and someone new to solar observing may be none the wiser to substandard views offered by a hidden rust problem. OK ITF can fail as easily in Lunt but you can clearly see what your buying by simply removing the diagonal.

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Paul73

Paul73

Posted
Posted

I think that this thread may cause a spike in sales for these guys! Shane should be on commission!

After checking the ITF yesterday. I was unable to resist the urge to tinker....... I was completely unable to remove the Etalon/Tuner from the main OTA tube (gold bit). Any advice on this will be greatly appreciated. But, more importantly, on removing the front/objective lense, I discovered a bloom on the inside of the lense! Given that this is just a normal lump of glass, I'll give it a light clean. This does lead me to worry about what might be going on further down the tube.....

Fortunatally the Double Stack unit is as clear as a bell??. This is just as well because it is about to be sold to pay for a D-ERF.

Paul

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Solar B

Solar B

Posted
Posted

Yes definitely oxidation and they do form pretty patterns or blooms ?

 

Re selling your DS to fund an ERF I'm not sure that I'd recommend doing that , could you not find someway of mounting a 35NM

internally ? (as a cost effective option) PST mods can be good but do lack the finesse of a DS , I know as I was amongst the first to

successfully complete a stage 1 mod in Dec 06.

 

Brian 

 

 

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Paul73

Paul73

Posted
Posted
21 hours ago, Solar B said:

Yes definitely oxidation and they do form pretty patterns or blooms ?

 

Re selling your DS to fund an ERF I'm not sure that I'd recommend doing that , could you not find someway of mounting a 35NM

internally ? (as a cost effective option) PST mods can be good but do lack the finesse of a DS , I know as I was amongst the first to

successfully complete a stage 1 mod in Dec 06

All good points. But, I need the peace of mind that would come with a proper 75mm D-ERF. I won't be using a driven mount, which would further decrease the risk. But a future owner may be living in hotter climes with a panchant for tracking for hours. I'd happily pop a 35nm on the front to revive a PST. It is there for all to see and would not be receiving concentrated solar energy.

re. Selling the DS. Yes. I'd miss the subtle detail that the drop in bandwidth gives. But I find that the image scale in a PST doesn't allow me to study that detail properly.

Paul

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Mark at Beaufort

Mark at Beaufort

Posted
Posted
On 25/04/2017 at 17:29, Paul73 said:

Hi Mark

If your PST is made by the same chap as mine, he did a good job and the bottom half of the eypiece tube (the one with the ITF) won't budge without without the help of a large hammer. A quick check is to unscrew the main OTA & Etalon, remove the top half of the eypiece tube with the blocking filter and look though it whilst aiming the eypiece tube towards a desk lamp. You can get a pretty good idea from that if you need any extra exploration. I'd have another go at removing the whole eyepiece tube at this stage. You can release the glass disc of the filter from the top. But from the bottom is much safer. Mine wouldn't shift, so I used a chisel (very carefully ?) to get the retaining ring moving. Make sure that you do this flat otherwise the ring and the ITF will fall out...

Pleased to report that mine is clear as a bell and old. I've got number 95217!

Paul

Sorry Paul I must have missed your reply on this. My reference is 97155 which I bought new in 2005.

I recently went to a star party and used someone's double stack which I thought was brilliant.

 

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Paul73

Paul73

Posted
Posted
2 hours ago, Mark at Beaufort said:

Sorry Paul I must have missed your reply on this. My reference is 97155 which I bought new in 2005.

I recently went to a star party and used someone's double stack which I thought was brilliant.

 

Blimey. Mine is anceint! I guess that this proves that the ITF's can last.

Yes. The double stacks are great. But, at north of £700 new.......

Paul

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Solar B

Solar B

Posted
Posted

Understood Paul and can see what your saying about the image scale .... however I'm still pro the DS (have to be honest)

 

so trying to save yours ... you need not set your sights as high as a D-ERF ! ... a C-ERF would do or even an old AE one like

 

i used to use and how's about placing a wanted Ad ?

 

Brian 

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