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Equal exit pupil brightness in larger/smaller refractors

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#51 gnowellsct

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Posted 28 June 2020 - 04:30 PM

  Don't junk the scope, and/or drop out of the hobby, just spend more time at the eyepiece.  And, ask the folks on CN when you're not seeing what you think you should.

Go get 'em Bob!     grin.gif


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#52 Bomber Bob

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Posted 28 June 2020 - 05:42 PM

:funny:

 

Hey!   I'm down-sizing my Collection... though, that one is tempting...


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#53 Wildetelescope

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Posted 28 June 2020 - 09:01 PM

But the guy who is out accumulating observing hours (and drawing experience) with a 60 mm is going to see a lot more details over time than the guy who is too tired to set up the 15".

 

My 1978 Tasco (Towa) 80mm F15 was my planetary scope for about 10 years, until I bought my 1988 D&G 5" F10.  Conservative estimate of observing hours... at least 3000.  So, I trained my brain to look for very tiny details.  Imagine!  My first views of Mars / Jupiter / Saturn in that D&G.  Eye-popping.  The Towa had a good lens (the Model 339 was their flagship refractor back then), and I upgraded it to 1.25" accessories, and bought Meade Research Grade Orthos for it (still have that set 40 yrs later).

 

Anywho, I didn't want to go too far off-topic, but I did want to share what I've found at the eyepiece for 50+ years now.  

 

In observing, you can only go as high as the object, your scope, your seeing, and your eyes allow.  If your view is too dim, too fuzzy, too susceptible to floaters, then you have to back off the magnification.  If you're new to the hobby, keep in mind that posts by experienced observers at different locations may see more than you do.  Don't junk the scope, and/or drop out of the hobby, just spend more time at the eyepiece.  And, ask the folks on CN when you're not seeing what you think you should.

I have a slightly earlier version of that F15 Towa.  The optics on my sample are also very nice.  I have had it up to 250x on Jupiter with only a little dimming of the image.  Detail was still as sharp as it was at lower magnifications.  I was quite surprised.  Frankly it held up better at those magnifications better than my Eon 80 mm F6 ED doublet.  I tend to favor the longer focal length format in any event.  

 

I agree with Bob on the importance of observing experience.   When I first started, frankly I could look through ANY scope and be impressed with the view.   Saturn has Rings, check.  Jupiter has two bands and a spot, check.  It is always frustrating when starting out to hear voices of experience say that observing is something you need to train your eyes and your brain to do, but it is really true.  Once you do that with the scope(and eye pieces) that you have, then you are ready to start looking for something better.  

 

With respect to the topic, most nights I personally find exit pupils from 0.5-1 most satisfying.   On really stable nights, which for me are few and far between, I will run things higher, because I like the increased image scale.  Most of my refractors will handle at least 65-70X per inch on a very calm night.  My eyesight craps out before the scopes do(floaters, etc..:-).  If I am out with my 4 inch and the night is still, I have no problem with pushing things, but if I know ahead of time that I really want more magnification I will pull out a bigger aperture refractor,  Cat or Mak.  The right tool for the job, and like my father the carpenter, I have been blessed to be able to assemble a pretty good tool set over the years.   Astronomy is a hobby of patience, in all its aspects:-) 

 

Cheers!

 

JMD




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