How to calculate max. TFOV of scope
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carlogambino
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How to calculate max. TFOV of scope
How to calculate max TFOV of scope? I know it is dependent on f/ratio, but how to exactly calculate? (e.g my f/13 4" Mak has a max. TFOV of 1.3 degrees). I dont think AFOV of ep and magnification matter in this case, since we are talking about max. TFOV without vig/obvious secondary obstruction, not magnification here.
you will need to measure the inside diameter of your mak's baffle tube, eg c5 baffle tube i.d. is 25mm, c8 is 38mm, c9.25 is 48mm.
tfov = field stop/scope's focal length * 1 radian
Treating the central baffle as the limiting field stop:
C5 at F10: 25/1250*57.3 = 1.15 degrees
C8 at F10: 38/2032*57.3 = 1.08 degrees
C5 at F6.3: 25/787.5*57.3 = 1.8 degrees (e.g. pentax xl 21mm)
C8 at F6.3: 38/1280*57.3 = 1.7 degrees (e.g. pentax xw 30mm)
tfov = field stop/scope's focal length * 1 radian
Treating the central baffle as the limiting field stop:
C5 at F10: 25/1250*57.3 = 1.15 degrees
C8 at F10: 38/2032*57.3 = 1.08 degrees
C5 at F6.3: 25/787.5*57.3 = 1.8 degrees (e.g. pentax xl 21mm)
C8 at F6.3: 38/1280*57.3 = 1.7 degrees (e.g. pentax xw 30mm)
Last edited by ariefm71 on Fri Dec 17, 2004 12:07 am, edited 2 times in total.
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weixing
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Hi,
True Field Of View = Eyepiece Apparent Field of View / Magnification
But this will be an estimate only, because the focal length of telescope and eyepiece and the Apparent Field of View of eyepieces may vary a bit with each eyepiece. The more accurate method is to measure the time a star travel across the centre of your field of view.
Have a nice day.
Don't need to be so "deep" lah!!tfov = field stop/scope's focal length * 1 radian
True Field Of View = Eyepiece Apparent Field of View / Magnification
But this will be an estimate only, because the focal length of telescope and eyepiece and the Apparent Field of View of eyepieces may vary a bit with each eyepiece. The more accurate method is to measure the time a star travel across the centre of your field of view.
Have a nice day.
Yang Weixing
"The universe is composed mainly of hydrogen and ignorance."
"The universe is composed mainly of hydrogen and ignorance." The question is related to compound scope (sct/mct) tfov. This formula can not be used to calculate the max tfov for such scopes. The limiting factor is the diameter of the primary mirror baffle tube.True Field Of View = Eyepiece Apparent Field of View / Magnification
Carlo, i bet your Nexstar 4 baffle i.d. is 30mm, since you said the max tfov is 1.3*. Use a caliper to measure.
cls,
arief
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weixing
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Hi,
To Kayheem: You have try the 1rpd 30mm 80 degree with C5 @ f10... may be you can measure the TFoV that this combination give.
Have a nice day.
Oops... :oops: never see that he want to find the max TFoV for his scope.How to calculate max TFOV of scope?
By the way, I think the max TFoV for C5 should be greater than that.C5 at F10: 25/1250*57.3 = 1.15 degrees
To Kayheem: You have try the 1rpd 30mm 80 degree with C5 @ f10... may be you can measure the TFoV that this combination give.
Have a nice day.
Yang Weixing
"The universe is composed mainly of hydrogen and ignorance."
"The universe is composed mainly of hydrogen and ignorance." -
carlogambino
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