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PST mod Telescope question.
Posted: Sat Dec 19, 2015 2:39 pm
by aboy
I there.
I just have a silly question here.
For a PST mod I know it's better a F/10 refractor scope. But, I was reading about the lunt 100 specifications and I find out that is like the Explorer Scientific 102.
My question here is:
It is possible to use the ES 102 on the PST modification as well?
Here are the specifications on both scopes:
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LS100THa scope Specifications (Single Stack)
Optical Aperture: 102 mm
Etalon: Internal <0.7 Angstrom
Tuning: Internal Pressure Tune (Doppler True Tuning)
Focal Length: 714 mm
F Ratio: F/7
Focuser: 2″ Feather-Touch focuser with 10:1 reduction
Tube diameter: 121 mm
Tube length with blocking filter: 634 mm
Storage: Aluminum finished hard case with fitted foam
Weight: 12.2 lb
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ES-ED102mm Essential Series Aluminum Air-Spaced Triplet Refractor
Item Number ES-ED10207-01
Optical Aperture: 102 mm
Focal Length 714mm
Focal Ratio f/7
Limiting
Magnitude 12.5
Resolution 1.14 arcsec
Tube Length
w/ Dew Shield 30.5"; 774mm
Tube Length
w/out Dew Shield 23.75"; 603mm
Diameter 119mm
Weight 9.6 lb; 4.4 kg
Thanks for all your time guys.
Re: PST mod Telescope question.
Posted: Sat Dec 19, 2015 9:09 pm
by Merlin66
You could use the 102/714 with the PST Mod, but it would be restricted to an effective aperture of 71mm (714/10).
Alternatively you could replace the front barlow element of the PST assembly with a -140mm barlow to give the full 102mm.
Re: PST mod Telescope question.
Posted: Sat Dec 19, 2015 11:42 pm
by aboy
Merlin66 wrote:You could use the 102/714 with the PST Mod, but it would be restricted to an effective aperture of 71mm (714/10).
Alternatively you could replace the front barlow element of the PST assembly with a -140mm barlow to give the full 102mm.
How I can replace the Barlow ?
Re: PST mod Telescope question.
Posted: Sun Dec 20, 2015 12:02 am
by Merlin66
The front barlow lens of the PST assembly can be easily removed and replaced with a 25mm -140mm barlow - if you can find one from Thorlabs/ Edmund Optics.
Re: PST mod Telescope question.
Posted: Sun Dec 20, 2015 12:41 am
by Valery
Merlin66 wrote:The front barlow lens of the PST assembly can be easily removed and replaced with a 25mm -140mm barlow - if you can find one from Thorlabs/ Edmund Optics.
It can't work as designed in the PST or close. Two lenses - barlow negative and a second positive (refocusing objective) works as a whole system and they
have no spherical aberration, no coma and astigmatism. If one change one lens with unknown radii, then absolutely no warranty that these aberrations will be fixed in a new system. More so, we can state, that they will not be fixed.
Better to change F/7 cone to F/10 with regular Barlow lens or with a special barlow lens. The PST etalon block better be work with it's native lens system.
Valery.
Re: PST mod Telescope question.
Posted: Sun Dec 20, 2015 1:00 am
by Merlin66
Valery,
I hear you, but many amateurs have already successfully changed the front barlow element in PST mods.
Re: PST mod Telescope question.
Posted: Mon Dec 21, 2015 2:05 pm
by Valery
Merlin66 wrote:Valery,
I hear you, but many amateurs have already successfully changed the front barlow element in PST mods.
But I never saw crystal clear razor sharp images taken with PST etalon with randomly chosen lenses.
So, the "success", I suspect, is limited.
Valery.
Re: PST mod Telescope question.
Posted: Mon Dec 21, 2015 6:05 pm
by aboy
Well. Thank you guys for all the answers.
Re: PST mod Telescope question.
Posted: Mon Dec 21, 2015 9:27 pm
by marktownley
It's all about compromises this modding; unless you're using bespoke designed optics for a project there will always be a price to pay in terms of image quality. I modded a 70mm f6 refractor to use with a PST mod, I was pleased with the results. At the end of the day it's a way of getting a result without spending big bucks.
Re: PST mod Telescope question.
Posted: Wed Dec 23, 2015 12:30 pm
by aboy
marktownley wrote:It's all about compromises this modding; unless you're using bespoke designed optics for a project there will always be a price to pay in terms of image quality. I modded a 70mm f6 refractor to use with a PST mod, I was pleased with the results. At the end of the day it's a way of getting a result without spending big bucks.
Well, Like you say.
I do want the mod for HD pictures, and I hear you guys that my Astrotelescope 102 f/11 will do the job. But, I always was wonder if I can get the ES102ED Working for this mod as well.
Thanks you guys for your the answers.