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Homemade Image Intensified Eyepeice

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Homemade Image Intensified Eyepeice

Postby athornett » Tue Jan 26, 2010 9:13 pm

Hi folks,

We have successfully made an image intensified eyepeice from a £50 35 year old ex-military three stage image intensifier from eBay. How we did it can be found here: [url=http://www.imageintensifier.org.uk]www.imageintensifier.org.uk[/url]

Below are the results of a recent comparison with Ethos eyepieces.

Andy & Damian (Rosliston Astronomy Club)

Observations from Lichfield, UK, 17/1/2010, 2030-2230

For these observations we used a Takahashi TSA102s Super
Triplet Apochromat on a William Optics EZTouch Alt-Az Mount
with a Manfrotto 058B Triaut tripod (this combination had visibly
less vibration on the grass than on the concrete patio); a True
Technology Supa-Slim Manual 2" filter wheel with 2" Lumicon
filters (OIII, UHC, 25% Neutral Density); Televue 2" Everbright
Dielectric Star Diagonal; and the following eyepieces: 31mm
Televue Nagler T5 and 17mm Televue Ethos, and, for Mars,
6mm Televue Ethos and Takahashi 5mm LE and 3.6mm Hi-LE eyepieces. In addition,
we also used our homemade image intensifying eyepiece made with a 35 year old
generation one three-stage image intensifier (gives images at the focuser and
enables the observer to retain the experience of apparently looking through the
scope unlike an integrating video camera).

The night was cold and seeing and transparency were close to best for this area
in our experience. However, light pollution still meant that only three stars
were visible in Ursa Minor (including the Pole Star). The Milky Way was visible
as a very faint band.

Mars
Mars was well placed in the sky and a lovely orange-red colour. The disc
suffered from some colour fringing in the telescope, noticeable above 130x
magnification. The high quality of this scope suggests that the fringing was not
due to the optics but rather to atmospheric distortion. On other nights we have
observed the same effect with 12" and 16" Meade Lightbridge Dobsonian
telescopes, and usually blamed poor collimation. Tonight's observations suggest
that this aberration is (at least in part) due to our observing location.
Surface features on Mars were difficult to make out. We could just make out the
polar region and vague surface features and these were later confirmed with
Stellarium. This was not something beginners will easily see, nor would most
scopes in our view be capable of resolving these features from an observing
location like ours - remembering this is one of our better nights!
It seemed to us that books and magazine articles make it sound as though these
aspects of Mars are easy to observe and that this risks putting people off the
hobby. We would value comments from folks who are able to see more of Mars than
ourselves.

M42
M42 was magnificant through the 17mm Ethos or 31mm Nagler and UHC filter. Far
more detail was visible in the outlying areas of the nebula with the
UHC filter than with an OIlI filter or without filter (a filter wheel really
helped us with these comparisons). The image intensifer eyepiece provided an
image as impressive as the UHC plus Ethos and the nebula was seen at least as
easily through the image intensifier. However, the image of the nebula through
the image intensifier was subject to more aberrations such as smearing giving
the appearance of it being more elongated towards the edge. Our view was that
most casual observers would not object to this as it did not detract from the
"Wow!" nature of the intensified image and the need to use averted
vision was removed.

Double Cluster in Perseus
For the Double Cluster in Perseus the winning combination was the 31mm Nagler
without filters. The view was awesome with this eyepiece and, for us, defined
the meaning of the Nagler Spacewalk experience. We found ourselves easily lost
in the glorious view of jewels hanging in the sky and you had to move your head
to even get close to seeing the edge of the field of view. The image intensifer
gave a muted view compared to the Nagler with this object and using higher
powers did nothing to improve the view.

M81 and M82
The image intensifer came into its own with M81 & M82 in Ursa
Major. The cigar galaxy was visible using averted vision with the Ethos
eyepieces as a slash without any detail within it. With the image
intensifier, the slash was easily visible without the need for special
techniques. The two starburst regions just above and below the centre of the
galaxy on long exposure images could be seen as brighter spots and the dark dust
lane between them was also visible.

Conclusions
The 31mm Nagler demonstrated why it is so well loved by amateur astronomers. It
defined the Spacewalk experience and gave stunning views of the Double Cluster.
With galaxies and nebulae, it helped with object location and views showed
objects with a wide vista of their surrounding sky. Images of M42 were
dramatically improved by the UHC filter but not by the OIII filter. However, the
accolade of the evening went to the £50 homemade image intensifer eyepiece. We
had a novice observer with us who summed up its various views with a series of
shouts of "Wow!" – we had to agree.

Andy & Damian
athornett
 
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