PST Mod and TEC140

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Montana
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PST Mod and TEC140

Post by Montana » Mon Aug 31, 2020 6:18 pm

Hello guys,

Thanks with all your help so far. If I were to use the PST mod on the TEC140 what else would I need? I know that it should be used on an F10 scope and the TEC140 is F7. I already have a front ERF at 125cm from my Quark days, so I think this makes the TEC140 F7.84 with this ERF.

To make it F10 before the PST mod I would a need a 1.3x telecentric is that right? is that possible. Or could I use my 3x telecentric before it which would make it F23.5 does this matter?

Many thanks for your help.
Alexandra



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Re: PST Mod and TEC140

Post by marktownley » Mon Aug 31, 2020 8:04 pm

Hi Alexandra.

You don't need telecentrics for PST mods, rather a barlow. The Magnimate from Astroboot should get you close to the f10 beam you need. Just mount it on one of these https://www.365astronomy.com/Filter-Ada ... hread.html then mount that in the 2" nosepeice of the etalon module.

My only thought is will you have enough infocus as i'm guessing you're not going to be cutting the TEC tube shorter ;)

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Re: PST Mod and TEC140

Post by Merlin66 » Tue Sep 01, 2020 8:04 am

Alexandra,
Even with the ERF the PST mod would act as an aperture stop and bring the TEC to a100mm f10 system.


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Re: PST Mod and TEC140

Post by Montana » Tue Sep 01, 2020 9:53 am

Thanks guys, so basically no then! oh well, will stick with the Solarscope at 100mm :( such a bummer that the Quark didn't last longer than 3 months, I got my best ever images with it :(

Alexandra



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Re: PST Mod and TEC140

Post by marktownley » Tue Sep 01, 2020 6:13 pm

Montana wrote:
Tue Sep 01, 2020 9:53 am
Thanks guys, so basically no then! oh well, will stick with the Solarscope at 100mm :( such a bummer that the Quark didn't last longer than 3 months, I got my best ever images with it :(

Alexandra
No, definitely not a no. You have a the 125mm free aperture DERF, so, as long as you make the beam entering the etalon f10 by doing what I suggested you will have a 125mm (f10) PST mod.


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Re: PST Mod and TEC140

Post by Montana » Wed Sep 02, 2020 1:21 pm

? but Merlin says not, he says the PST mod would stop it down to 100mm. So I am better off with the 100mm Solarscope?

I don't quite understand.

Alexandra



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Re: PST Mod and TEC140

Post by GreatAttractor » Thu Sep 03, 2020 3:41 pm

As I understand, Merlin meant the configuration without any Barlows; in that case, the f/7 beam from your 140 mm, f = 980 mm 'scope would be only used by the PST as an f/10 beam (because of clipping), having f = 980 mm and D eff. = 98 mm.


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Re: PST Mod and TEC140

Post by marktownley » Thu Sep 03, 2020 8:48 pm

Montana wrote:
Wed Sep 02, 2020 1:21 pm
? but Merlin says not, he says the PST mod would stop it down to 100mm.
ONLY if it is used in the native f7 beam of the TEC (or the f7.84 beam with a 125mm ERF), if you put a barlow before the PST etalon assembly and you get it to f10 that way then you will be using the full 125mm aperture.


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Re: PST Mod and TEC140

Post by AndiesHandyHandies » Fri Sep 04, 2020 9:17 am

Hi

You can put in new collimator and re-focus lenses to use the full aperture.

I have got a pair of 150mm and -150mm for my Meade 127mm F7.5 triplet. Yet to try it. Just x the FNo by 20 for your scope.

The lenses fit in a plastic Celestron/Skywatcher Moon filters.

I have removed the lenses out of the PST for my current Mod. Now its a 'Combo'.
One moved forward to reach focus on Maks and to not need to chop bits off refractors.
And the other sudpended after the PST in a Blue Lightning 48mm to 28.5mm adapter. That and the T2 to 28.5mm adapter are great for PST Mods for bodging together bits and holding empty cheap Chinese filters with 20mm aperture as baffles as ideal for the PST 20mm clear aperture. Sold by Agena Astro. They also do 1.25" extension tubes.

https://www.ebay.co.uk/itm/Astronomy-Te ... 2749.l2649

So I can just make a new nosepiece for the require position for the 127mm and swap the Moon filter over with the collimator lens in after.

Cheers. Andrew.



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Re: PST Mod and TEC140

Post by marktownley » Sun Sep 06, 2020 4:59 pm

AndiesHandyHandies wrote:
Fri Sep 04, 2020 9:17 am
Hi

You can put in new collimator and re-focus lenses to use the full aperture.

I have got a pair of 150mm and -150mm for my Meade 127mm F7.5 triplet. Yet to try it. Just x the FNo by 20 for your scope.

The lenses fit in a plastic Celestron/Skywatcher Moon filters.

I have removed the lenses out of the PST for my current Mod. Now its a 'Combo'.
One moved forward to reach focus on Maks and to not need to chop bits off refractors.
And the other sudpended after the PST in a Blue Lightning 48mm to 28.5mm adapter. That and the T2 to 28.5mm adapter are great for PST Mods for bodging together bits and holding empty cheap Chinese filters with 20mm aperture as baffles as ideal for the PST 20mm clear aperture. Sold by Agena Astro. They also do 1.25" extension tubes.

https://www.ebay.co.uk/itm/Astronomy-Te ... 2749.l2649

So I can just make a new nosepiece for the require position for the 127mm and swap the Moon filter over with the collimator lens in after.

Cheers. Andrew.
Yup, that's another way of doing it, but would mean getting the 160mm DERF (with adaptor plate) to run full aperture (140mm). I did this with a 'f6' pst mod I ran a couple of years ago.


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