Pst mod and takahashi

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Pst mod and takahashi

Post by EboO »

Hi all,

I'm new here but found some usefull informations.
I have a pst and want to modify it to use with my refractor.
First is to buy the 2" adapter and still use the unit, but after i want to use the FP alone with my fc-100df and a blocking filter (bf10 or bf15).
Will it be possible to focus with this configuration without modify tube ? I plan to use a 1.25x glasspath before FP.
And which rings use after the FP and which length please ?

Many thanks !


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Re: Pst mod and takahashi

Post by marktownley »

Welcome to the forum!

I don't think it will come to focus without cutting the tube, and let's be honest that's something you wouldn't want to do with a Tak ;)

You can find out anyway, point the scope at the sun, hold a piece of paper behind and find the focal point, with the other hand and a ruler find where 200mm of in focus is, if it is inside the tube then you need to cut it.


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Re: Pst mod and takahashi

Post by AndiesHandyHandies »

Hi

Seperate the first collimating lens and place it on the front of a few 2" or T2 extension tubes. To get it inside the focusser.
I use the adapters from Swizerland to get a 48mm thread at the front.

You need a 25mm cell. I ended finding a cheap 1.25" Barlow from Astroboot which had a 25mm lens and used that.
The cheap PLASTIC Celestron or Skywatcher have a 25mm cell as they were for the US market. Tend to melt used at the business end. But OK for internal use.

If you have access to thread cutting lathe facilities you can make a custom cell.

Its only a singlet lens so you will get a bit of expansion of the beam. But the PST body will fit just after the standard 2" focusser.

Cheers. Andrew.


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Re: Pst mod and takahashi

Post by EboO »

Hi,

I'll look for focal point on paper, but i don't have glasspath yet so it do a false measure no ?

Andieshandyhandies you suggest to disassembled FP am i right ? I don't know if i have the capacity 😬

And to be sure : i can use pst mod stage 1 (black unit and 2" adapter) with my taka ?


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Re: Pst mod and takahashi

Post by faber »

Hi Eboo,
Qhy don’t think about a LUNT 50 mod?
I have a Takahashi fc 100 dl and I’m using it without tube modification, but only with m72-m68 Baader adapter.
Full of fun and if you want you can use another BF and is fully reversible. Bit more costly than PST but very easy to use.
Regards


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Re: Pst mod and takahashi

Post by EboO »

Hi faber,

it's easier you're right but pricier too :(
Perhaps i need to mind this solution if pst mod 2 is impossible.


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Re: Pst mod and takahashi

Post by marktownley »

EboO wrote: Tue Feb 21, 2023 6:25 am Andieshandyhandies you suggest to disassembled FP am i right ? I don't know if i have the capacity 😬
I would suggest you don't attempt a PST mod then :)


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Re: Pst mod and takahashi

Post by EboO »

marktownley wrote: Tue Feb 21, 2023 4:15 pm
EboO wrote: Tue Feb 21, 2023 6:25 am Andieshandyhandies you suggest to disassembled FP am i right ? I don't know if i have the capacity 😬
I would suggest you don't attempt a PST mod then :)
I already unassembled pst, FP is unscrewed but there's still the lenses before and after. That's that i fear to unscrew.


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Re: Pst mod and takahashi

Post by EboO »

I wait sun to do the measure with paper.

I'm curious : is it possible to use a barlow/powermate x3 after the FP or the diagonal ?


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Re: Pst mod and takahashi

Post by marktownley »

Use the barlow / pm after the blocking filter.


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Re: Pst mod and takahashi

Post by EboO »

Thanks, is there a preference between powermate and barlow for sun observation ?


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Re: Pst mod and takahashi

Post by marktownley »

Just get the sampling right on the camera chip, I think that is more important.


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Re: Pst mod and takahashi

Post by EboO »

Yes, you're right !


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Re: Pst mod and takahashi

Post by AndiesHandyHandies »

EboO wrote: Tue Feb 21, 2023 6:25 am Hi,

I'll look for focal point on paper, but i don't have glasspath yet so it do a false measure no ?

Andieshandyhandies you suggest to disassembled FP am i right ? I don't know if i have the capacity 😬

And to be sure : i can use pst mod stage 1 (black unit and 2" adapter) with my taka ?
Hi

The two collimating lenses in my PST are in a holder with a screw off cover.

I took both out so I can use other lenses to customise and get full aperture on my F7.5 Meade Triplet.
Both in seperate new holders.
Other wise with native etalon set up stops down to 95mm F10. Does work OK.

I had to do that to get far enough into the back of my Maksutovs where you could not saw the back off at all.

Cheers. Andrew.


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Re: Pst mod and takahashi

Post by EboO »

Hi Andrew,

Do you use a specific tool to unscrew lenses ?


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Re: Pst mod and takahashi

Post by EboO »

I have an other reflexion : a quark would be easier to use but worth it face to a pst mod ?


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Re: Pst mod and takahashi

Post by marktownley »

EboO wrote: Fri Feb 24, 2023 2:52 pm Hi Andrew,

Do you use a specific tool to unscrew lenses ?
A lens spanner or a metal ruler will work


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Re: Pst mod and takahashi

Post by EboO »

Hi all,

I'm waiting for my 2" adapter and glasspath.
Can i use a powermate for max magnification with a 4" refractor ? Or is it too much ?
Actually i failed to focus with a pst, Pentax xw 7mm and 2x Tv barlow.


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Re: Pst mod and takahashi

Post by EboO »

Hi,

I received my pst adaptor and glasspath, i tried without GP and i can't focus. Like expected...
So now i want to try with GP but i can't adapt it on pst adaptor. Is there a ring to screw GP on M42 or M48 please ? I don't find anything.


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Re: Pst mod and takahashi

Post by AndiesHandyHandies »

EboO wrote: Fri Feb 24, 2023 2:52 pm Hi Andrew,

Do you use a specific tool to unscrew lenses ?
Pair of dividers or vernier guage for small parts.

Cheers, Andrew.


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Re: Pst mod and takahashi

Post by AndiesHandyHandies »

Hi

First picture is of the PST Collimating lens in the 1.25" front on a t2 2" nosepiece.
The first part is a cheap barlow holder which had a 25mm lens in it.

ImageP1060957 by Andrew Huskinson, on Flickr

The second picture is of the PST body used. It has a Swiss adapter on the front to T2 thread the first part screws in to.

ImageP1060958 by Andrew Huskinson, on Flickr

The third picture is the rear adapter for the PST to a 2" holder.

ImageP1060959 by Andrew Huskinson, on Flickr

I think this had a stop in it but it was vignetting the full beam so I had it turned it out. Manufacturers guess.

The fourth picture is of the rear filter holder and the 45deg bino-viewers I use, off ebay. A copy of am Olympus model I think.

The re-collimating lens is in a PLASTIC Celestron.SW Moon filter holder. Tends to melt up front for the collimator!. In a bluelightning 48mm to 28.5 mm adapter. On the back a 1.25" KG3 screwed back to back in the adapter, a red 25A to block the blue-green light leakage from the etalon. There is a loose photographic CPL in the body. Felt pads on the back of the 25A with a cheap 20mm aperture filter holder front and a random rubber ring at the back. I then have a tilter made of a T2 passthrough holder for a 28.5mm filter with another one turned down and 3 push-pull bolts which then fits inside a turned out T2 extension tube.

The most interesting bit is the bino-viewers. These give the best view of the Sun up to imager standards.

The advantage of the PST Mod2 is that the suns image is not greatly magnified. The best eyepieces are the PZO (Polish Zeiss Ortho) silver body which are selected from normal production for the best flat field.

Cheers. Andrew.


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Re: Pst mod and takahashi

Post by EboO »

AndiesHandyHandies wrote: Thu Mar 23, 2023 10:46 pm
EboO wrote: Hi Andrew,

Do you use a specific tool to unscrew lenses ?
Pair of dividers or vernier guage for small parts.

Cheers, Andrew.
Please have you got a picture ? I'm not aware of this solution :?


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Re: Pst mod and takahashi

Post by AndiesHandyHandies »

Hi

For the rings holding filters in and similar and they are not tight these are enough. Do not slip though!

My friend Rod bought me a sticky black sheet used to stop phones sliding about on dashboards.
Very useful for getting stuck extension tubes and so on off. Press down firmly on the pad and turn.

Cheers. Andrew.


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Re: Pst mod and takahashi

Post by EboO »

I tought it would exist some rings, but no. So i need to try some exotic solution and i'm not really easy with this perspective.


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Re: Pst mod and takahashi

Post by EboO »

I found this : https://www.pierro-astro.com/materiel-a ... der_detail
It's the only solution i found, no other way to have M34 to M42.


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Re: Pst mod and takahashi

Post by EboO »

Hi,

I found another solution : place the GP between two rings (M48-M28).
Which solution would be the best ?


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Re: Pst mod and takahashi

Post by marktownley »

What are you going to use for an ERF?


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Re: Pst mod and takahashi

Post by EboO »

I have a Baader D-erf in a cell.


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Re: Pst mod and takahashi

Post by EboO »

Great news it works fine with GP, i'm so happy !
If clouds are kind enough to go away this week-end then i'll try with Tv barlow 2x.
But i'm a bit lost : bf10 would give me a larger diameter and a more confortable observation am i right ?


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Re: Pst mod and takahashi

Post by marktownley »

Glad to hear it is working!


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Re: Pst mod and takahashi

Post by EboO »

Hi,

It works fine up to 5mm eyepiece but after it's impossible to have a fine observation.
Would a bf10 help to have better observation ?


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Re: Pst mod and takahashi

Post by marktownley »

A bigger BF always helps. BF10 is a good combination with a PST mod. I wonder if you might be pushing the magnification a bit already with the 5mm eyepiece?


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Re: Pst mod and takahashi

Post by EboO »

I'm looking for one in classified.
Yes i think too 5mm is a bit too much, observation is more confortable with a 10mm eyepiece.
Now i need to try photos, it would be wonderfull.


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Re: Pst mod and takahashi

Post by EboO »

I tried yesterday both visual and photo, visual is nice and easier. Sweet spot made a great feature : i look all around the sun and proeminences appeares suddenly, it's fun :)
About photo it's harder : with pst alone i have many reflections, with barlow 2x it's easier and no reflections. In both cases it's hard to have a fine focus. Have you got tips ?


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Re: Pst mod and takahashi

Post by marktownley »

Post an image of what you're experiencing, it will make it easier to diagnose a solution.


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Re: Pst mod and takahashi

Post by EboO »

Yes, take in account i'm a newbie.
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Re: Pst mod and takahashi

Post by EboO »

Hi all,

I have a dilema : i was about to buy a BF10 or a BF15 for photo but an other opportunity has appear. A Lunt 50 with pressure tuner would be available in classified un an astronomy club near to me. Worth it to switch to Lunt or i keep my PST mod ?
If taking Lunt option i'll try the mod suggested by faber, FP is a little bigger am i right ? So sweet spot too ?


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Re: Pst mod and takahashi

Post by marktownley »

Just looks like focusing and tuning to me.

A lunt 50 is only really for full disks, If you can buy it then do so, i'd focus on mastering the PST mod first.


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Re: Pst mod and takahashi

Post by EboO »

Ok, thanks for advice.
A Lunt 50 mod isn't really interesting ? Does a DS lunt and pst is possible ? I suppose no because of the f ratio difference.


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