Astronomy/built-in barlow

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Expert: Tom Whiting - 10/29/2009


Question
Dear Mr. Whiting:

I recently purched a Celestron Powerseeker 127 EQ. The label on the scope says that it has a 1000mm focal lenght but the tube is only 18" long. I later found out that the reason for this is that it has a built-in Barlow lens. Normally this scope without the barlow would be a fast f/5 500mm wide field scope. Does the addition of the built-in barlow denigrade the image to a significant degree? Or, given the aperature, i.e., 5" and the shor focal lenght would this be insignificant?

Thanks

Randy

Answer
Hi Randy,
Sorry, but I'm not up on the newer scopes with the built-in barlows, built-in eyepieces, permanently fixed primary mirrors, and built-in front cover lenses...wouldn't have one;  How would one ever clean, let alone collimate them?  What do you do if the factory 'built-in' part gets shifted slightly?  Send it back to China for re-collimation?
Paul Wagner is our telescope expert, having built both reflectors and refractors, so please
ask this question of him.
Clear Skies,
Tom Whiting
Erie, PA

Astronomy

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Tom Whiting

Expertise

Astronomy has been my hobby/pasttime for over 50 years.  Currently own 3 telescopes, the largest of which is a 30 inch Newtonian truss Dob that is portable.I taught Astronomy/Meteorology at the University Level for 13 years before retiring in 1995. Being retired and home most of the time, I am able to answer all questions relatively quickly, unless it's a new moon weekend with good observing conditions.  No astrology questions please, or questions about alleged UFO picture identifications.

Experience

Experience: Astronomy has been my hobby and study for over 50 years. We currently now own a 30 inch portable telescope (Updated - Pennsylvania`s largest portable telescope). It can be seen on our website at:http://www.velocity.net/~bwhiting and also attend several regional starparties during the year, and have been on 5 total solar eclipse expeditions.

Organizations: President, Erie County Mobile Observers Group for over 15 years.

Publications: Wrote the "Over Erie Skies" newspaper article in our local newspaper for 11 years (1975-86).

Education: Masters Degree- Taught at the University level for 13 years. Retired 20 years -USAF Pilot - KC-135 with 180 combat missions;  Also Eagle Scout, Philmont staff 2 Yrs, Order of Arrow Lodge Chief, Ham Radio (inactive).

Awards: two discoveries: The mini-coathanger asterism in Ursa Minor (the little dipper) And the mini-ladle- another asterism in the bowl of Ursa Minor. Clients: Currently President of the ECMOG as mentioned above.

Education/Credentials
BS  Metallurgical Engineering Grove City College, PAMaster's Degree, Gannon University, Erie, PA Also retired USAF pilot, 20 years.

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