Astromart Reviews - William Optics FLT110mm f7 TMB designed ...

Astromart Reviews - William Optics FLT110mm f7 TMB designed triplet and matching field flattener
One can see a few •icks?in the outer ring of the pattern. This may have been caused by the producer clamping
the lens on 3 points during production, or even from lens cell effects. Given the effect is so minor and does not
really give the impression of pinched optics, I did not bother to dig deeper into possible causes. For the
perfectionists amongst us, this may lead (being careful here) to bumps or tiny spikes in the halo around stars
when using image histogram stretching with DDP processing on long exposure images. But if you would use a
DSLR or one of the blooming CCD most likely they will give more artefacts around stars on their own already.
All images are the result of a stack of a few AVI movies in prime focus of the FLT110, made with a DMK 21AF04
firewire camera.
For the visual observations, we used similar eyepieces from TMB, and both equipped with a 1.8x TMB ED Barlow
to obtain higher magnifications. The three of us had a very hard time to detect differences between the Orion
Nebula trapezium stars and immediate vicinity.
Both scopes show clean sharp stars with nice hints of real colour. One observer noticed a slight contrast
advantage for the TMB 105, but not by all that much. I did not detect significant contrast differences on the
nebula, nor any difference in the sharpness and clarity of the Trapezium stars.
Saturn under good seeing was very nice in both scopes, with no differences to be noticed on the Cassini division,
nor in the belts on the planet. We knew about the slight optical imperfections upfront, so we really looked very
carefully to spot effects from it, but without success. Saturn was slightly brighter in the FLT110, showing 0.5cm
more aperture. I did have the impression the equatorial belt on Saturn may have been slightly darker and give
the idea of a bit more contrast in the TMB 105, but I wouldn• place a bet on it, as it can be related to the slightly
brighter overall image. Both telescopes showed the subtle colour hues on Saturn.
All this really makes evident how critical a star test can be. Everything shows, even marks that have in practice
little influence on the end image.
The clever design of the TMB 105mm dew shield (seen on the picture with Jorg) did prove its use in the field.
Thanks to the tiny front baffle in the dew shield, the TMB 105mm remained dew free during the night with lots of
moisture in the air. The FLT110 has no such front baffle and needed a Kendrick dew heater after a few hours.
Jorg Versluys is seen carrying both the TMB 105mm and the WO FLT110. Notice the heavier looks of the TMB
105, but it is not really that much heavier than the FLT110.
http://www.astromart.com/articles/article.asp?article_id=523 (6 of 19)1/6/2007 10:54:28 AM