127mm Triplet Refractor
of .8X and f/6.3 Focal Reducers
Skies were overcast with thin
clouds so I decided to take some test images of M3 using the following
two focal reducers I had on hand for other telescopes:
Reducers attached to modified
Canon XSi (450D) in stock focuser:
Photos below show the position
of focuser at focus with no reducer and with the focal
Televue 0.8X Photo Reducer
Celestron f/6.3 Reducer / Corrector:
Test Images M3
One minute exposures were stacked in Deep Sky Stacker with a level
stretch and resize being the only processing. No Flat or Dark
calibration was done and all images are full frame.
Images below were taken with the
f/7.5 Astro-Tech 127mm Triplet that has a focal length of 952mm
1. AT 127mm - No Reducer................................................................................................f/7.5
2. AT 127mm with Televue 0.8X
Photo Reducer / Corrector for 400-600mm focal lengths...f/6.0
3. AT 127mm with Celestron f/6.3
Reducer / Corrector for Schmidt-Cassegrains..................f/4.7
(providing f/5.2 with spacer I use)
1. No Reducer:
2. Televue 0.8X Photo Reducer
3. Celestron f/6.3 Reducer
The Televue 0.8X reducer causes
stars to become elongated at around 70% into the Field of View.
This is not unexpected since this version of the focal reducer
is not meant for the longer focal length of the Astro-Tech 127mm.
I would expect the Televue 800-1000mm version of this reducer
to perform better but don't have one to test.
I was surprised by how well the
Celestron f/6.3 Reducer / Corrector did since it is not designed
for refractor telescopes. There is some noticeable star distortion
in the corners of the Field of View that would be easy to improve
with image processing software. I plan to do longer exposure deep
sky imaging with this 5 inch triplet using the Celestron corrector
at f/4.7 to test this configuration further.
After taking images at both prime
and with the Celestron f/6.3 reducer/corrector, I made measurements
and found that the scope is operating at f/5.2 with the f/6.3
Previous Astro-Tech 127mm pages:
Photos of the Astro-Tech
127mm Triplet Refractor along with specifications can be seen
On April 28, 2008 took first deep
sky images with the Astro Tech 127mm Triplet using a modified
Canon 450D camera and images of M51, M13 and the Virgo Core of
Galaxies can be seen HERE.
I am now using both the Astro-Tech
127mm and the Orion ED 80 for imaging on the Atlas EQ-G mount
using an ADM side-by-side system and a photo of the setup can
be seen HERE.
Lunar images using the Astro-Tech
127mm at prime and also with a Televue 2X Big Barlow along with
star testing results and video can be seen HERE.