CHAPTER 1. DISCOVER YOUR ALPY 600
If you want to take an image with a camera, you
need to add the objective lens, to focus the parallel
beams onto the CCD sensor. This is built into the Alpy
600 body:
On the next picture, you can see the objective lens,
part of the Alpy 600 body:
The eye contains its own objective lens - the
crystalline lens. Then, it accomodates any
beam coming from the infinite !
1.7
Different slits
The Alpy 600 is a versatile instrument. As described
in section1.6, a spectroscope requires a point light
source to properly work - the smaller the source, the
better is the resolution. Alpy 600 contains several slits,
to fit to several usages. Table 1.3 shows some of them.
To work with an extended source (which is the case
in most everyday situations), use the standard slit -
25µm wide. It is optimized for visual usage, and for
bench measurements. The resulting spectrum is a wide
band (top line of table 1.3).
In some conditions, it is better to only have a small
hole : this way, the spectrum is always at the same
position in the image - but it is more difficult to see
visually. To a certain extent, this is a way to reproduce
in the lab what will be seen with stars (second line).
There is another useful case : working in slitess
mode. This is applicable to stars, which are point-like.
The advantage is that you’ll see a bigger star field, and
you’ll be able to find easily the star you’re looking for.
To do that, you can totally remove the slit from the
Alpy 600, but it is better to keep in position the “3mm
hole” : this way, you’ll limit the optical aberrations at
the field edges - and you’ll not lose the slit (third line).
Sometimes a wide slit is useful. For instance, when
you have no guiding module but want to eliminate
most of the sky background, or when you want to
collect the full star light if the star image is bigger
than 25µm. In this case, you can use the 300µm slit
(last line).
The Alpy 600 also includes 50µm and 100µm slits.
Changing the slit position
The slit position is easy to change. It is mounted
with two screws. Remove the outer one, and just loosen
the central one. Choose the slit you want, and put its
notch in front of the outer screw’s hole. Put back the
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Summary of Contents for Alpy 600
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