What size barlow or Powermate do you use
Posted 22 January 2013 - 09:07 PM
Posted 23 January 2013 - 01:54 PM
1 - To be able to get long focal length eyepices to high magnifications to take advantage of their typically more comfortable eye relief and larger eye lenses
2 - Wanted Telecentric design so eye relief does not get extended too much as this makes already long eye relief long focal length eyepieces more prone to blackouts. Also, some wide fields (and TV Plossls) need a telecentric so they won't vignette.
3 - Wanted 2" so I could insert a 1.25"-to-2" Helical focusing insert ( e.g., like this ) so could do fine focusing of the 1.25" eyepiece used (some scopes I have only have a 1-speed focuser).
Posted 30 January 2013 - 05:05 PM
Which is best of Tele Vue Powermate and Barlow?
Posted 31 January 2013 - 11:36 AM
Properly designed Barlows do wonderful things: They amplify power, slow the telescope's f/# (improving
eyepiece sharpness), and give designers the opportunity to compensate for eyepiece aberrations.
Tele Vue Barlows use multi-coated high index glasses for optimum aberration correction, exceptional contrast
with virtually no light loss. Observed performance is aberration free, even when tested with f/4 scopes. They
even improve our competitor's eyepieces and telescopes!
For astro-imagers, the above chart indicates the magnification for each Barlow (2x, 2x Big & 3x) as a function of distance from
the Barlow top surface to the imaging surface (CCD or film).
Posted 31 January 2013 - 06:32 PM
Posted 31 January 2013 - 07:28 PM
Posted 01 February 2013 - 04:27 PM
I have a 2" focuser on my Reflector so I use a 2" Powermate.
When I use my older SPC102 Refractor it has a 1.25in focuser so I also have a 2x Ultima and 2.8x Klee barlow for use with that.
Posted 01 February 2013 - 04:53 PM
Posted 01 February 2013 - 06:14 PM
Posted 01 February 2013 - 08:36 PM
Had the 2.5x and 4x powermates which are now gone, retained the Celestron 2x Ultima and Antares 1.6 , ...
Yup the 2x Ultima is a keeper
Posted 02 February 2013 - 06:44 AM
Curious what size Powermates or barlows people use (1.25" or 2" or both); and if you use a 2", why?
I have several Barlows, all are 1.25 inch. I have a good selection of eyepieces that are well corrected in fast scopes and I don't wear glasses when observing so Barlowing a 2 inch eyepiece would only transform a heavy, bulky eyepiece into an even heavier, even bulkier eyepiece with shorter focal length. I hope David's friend has a 20mm Type 5 rather than a 20mm Type 2 Nagler...
I use a Barlow when when I need focal lengths shorter than 3.5mm. This is mostly double star stuff. I do have an Celestron Ultima but I prefer the 2 element Celestron Shorty, it's simple and does the job I need it to do. There are advantages to the Telecentrics but not at short focal lengths.
Posted 02 February 2013 - 10:46 AM
However, once in every great while, when there's a full moon (literally) I'll have fun stacking the 2.5x into the 2x to go to insane magnifications with my 12" reflector (f.l. 1500mm) using a 5mmT6 Nagler. This creates an effective 1mm eyepiece yielding 1500x magnification and the sensation of looking through the window of a spacecraft orbiting the lunar surface from about 160 miles up. Yes, the view is softer than desirably acceptable for normal observing, yet more than amply good for the purpose at hand of indulging a fantasy thrill ride above the array of clearly discernable lunar craters, mountains, and lava plains as they pass underneath. The upside to the softness of detail is that internal eye floaters which would likely be annoyingly, perhaps prohibitively intrusive at such a tiny exit pupil (0.2mm) are no problem, and neither is the accompanying dimunition of light on an object so bright as the moon. Unfortunately, for a variety of reasons, this same trick doesn't work well enough to create an acceptable spacecraft "fly-by" look at Jupiter; it registers as little more than a blurry blip that whizzes through the FOV too quickly to catch whether any even gross detail is visible.