| review: Flip Mirror Filter Changer by True Technology ( appr. € 350,- ) |
This handy piece of hardware enables the photographer to simultaneously mount a ccd camera and an eyepiece to one focuser.
With the built in 45 diagonal flip mirror you can switch from eyepiece view to ccd.
This makes it easy to get a rough focus and a fast centering of the object relative to the ccd frame.
When in eyepiece mode, the little black box is absolute light proof for the ccd so it's possible to shoot the darkframe while watching.
Additionally there is the possibility to insert filters.
So three colour exposures are much easier.
The CCD shall be mounted into the linear beam (without mirror).
The eyepiece then uses the mirror.
This is extremly important because the quality of the mirror is not at all photographic.
The picture looks somehow granulated and not very sharp and a bit darker as well.
However promised by the manufacturer I would not like to use it for visual work.
For me its only use is to center objects on the frame of the ccd camera.
Thats what I bought it for so this is OK.
The eyepiece holder can be shifted a bit with two screws.
So it is possible to bring the reticule center of the eyepiece to the center of the ccd frame when the ccd detector is not centered.
This is the case in my Starlight MX516.
To make the eyepiece parfocal to the ccd I used a special ring with screw.
Now I can find a rough focus with the eyepiece, flip the mirror and the first frame of the ccd is almost perfect in focus.
The standard eyepice filters are screwed to special rectangular supports.
Four of them are included.
(Filters are not included)
With these supports they can be inserted before the mirror only by using gravity.
So they are always on a definite and proper position.
This is important for flat frames of course.
They then are fixed with velcro strip from above.
This system is very primitive but it really works fine.
And it does not take much of back focus - important for all newton reflector users.
The four supports seem to be like one too much for three colour work.
But the manufacturer is recommending to use the fourth one for a *blank* filter of the same thickness like the other threes.
Then you can place the blank one for not filtered frames (black and white or the luminance frame in LRGB).
The obvious advantage is that all frames with all filters will have the same common focus.
This might be important for three colour work at fast moving objects where you have to act quickly.
An example is Jupiter and its fast rotation.
The whole unit takes about 5 cm (2 in) of back focus.
I could easily achieve this by placing the primary mirror 3 cm closer to the secondary + the 2 cm of the focuser I had in *reserve*.
There might be a little of additional vignetting now in 35mm photography but it is not at all visible in the tiny area used by an average ccd detector.
I am very satisfied with that piece.
It is constantly mounted to my photographic newton for centering and focusing and to be ready for three colour work if needed.
But I would not use it for visual work.
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