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Home > Forums > ASTRONOMY > Beginning Astronomy? > Message #836488

Re: barlow basics

Posted by Ed Blankenship on 11/5/2017 3:51 PM in response to Re: barlow basics   (41 hits)
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Chris Kelly said:

Its a 6" Newtonian : 100 cm from primary to secondary and 152 cm from secondary to eyepiece... I have a good 25 mm eyepiece and an OK 23 mm that I use primarily. I also have a 4 mm & 10 mm that aren't very functional in my area ( 1 hour west of Philly).
I foresee a trip into lesser radiant areas for better viewing. .............. Thanks for the input. I think it is f5.


Hi again Chris,

I suspect you meant to say "... 100 cm from primary to secondary and 152 mm from secondary to eyepiece...", so that would make the total focal length 1000mm + about 152mm more for approx 1150mm. So with your 25mm eyepiece, 1150mm/25mm gives about 46 power and with a 2x barlow, you would get about 90 power. I recommend you start with a 2x barlow (purchased used here on AstroMart) and use the 1st or 3rd quarter Moon as a first subject. You should see the difference clearly in power on a crater near the light/dark boundary (terminus or terminator).

Good luck - Ed

Thread:

Subject Posted By Date/Time Hits 
barlow basics Chris Kelly 10/28/2017 5:52 AM 82
Re: barlow basics Ed Blankenship 11/1/2017 9:04 PM 63
Re: barlow basics Ed Blankenship 11/1/2017 9:31 PM 48
Re: barlow basics Chris Kelly 11/2/2017 9:57 AM 60
Re: barlow basics Ed Blankenship 11/5/2017 3:51 PM 41
Re: barlow basics Ed Blankenship 11/5/2017 3:58 PM 36
Re: barlow basics Ed Blankenship 11/5/2017 4:31 PM 44
Re: barlow basics Chris Kelly 11/11/2017 8:19 AM 39
Re: barlow basics Thomas Dey 11/11/2017 4:45 PM 43
Re: barlow basics Chris Kelly 11/13/2017 6:44 AM 34

All times are in (GMT-8:00) Pacific Standard Time Zone  
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