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What makes an old Achromat better than a modern ED scope at low magnification

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27 replies to this topic

#26 deSitter

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Posted 17 April 2024 - 08:46 AM

An FPL-51 doublet is about 3.6 x better than an Achro, a FPL-53 doublet is more than 5 times better, a Fluorite doublet is better than that.

 

Jon

Yeah I think I got as usual the 51 and 53 confused. Thanks,

 

-drl


 

#27 Jon Isaacs

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Posted 17 April 2024 - 09:22 AM

Well I don't think you live in Dublin by some heavy industry Jon. If you do your welcome to come round and see how sharp my eyes are wink.gif

Last night the 'off gassing' of the neighbouring industry meant I was 50X max on Hercules, but managed 120 near Virgo.

 

But why am I always explaining myself?

 

Why am I always receiving private messages that concur with what I am experiencing, and yet people are too scared to post publicly for fear of ridicule.

It's hardly a triumph to win an argument, when there is a silent majority (or minority). A lot of people are too scared to contribute to these discussions, for fear of a few stalwarts shooting them down. Where's the enjoyment in that. I can tell you no one would stand for such a show of disrespect in Ireland.

 

I am asking you questions and trying to understand what is going on. You have said some acromats are better than your ED scopes. What are those ED scopes?  "Explaining yourself" is part of any discussion.  

 

If you had not included the Pronto, I would have suggested a common explanation for longer focal length scopes to provide more stable images:  The objective is further from the observer, further from the ground so thermal effects are lessened.  But with the Pronto in the equation, that no longer applies.  It is difficult to understand why a Pronto would be superior to a TeleVue 76.. 

 

I have answered many questions you have asked in many threads to the best of my ability. There is no disrespect in that.

 

Jon


 

#28 Sean Cunneen

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Posted 17 April 2024 - 10:12 AM

Locking this thread as there is a duplicate posted in refractors...


 


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