Star Testing Scope

Hi,
Is there any knowledgeable guys/gals in the Bracknell (Berks) area who
would do a star test on my 80mm refractor for me, I think the optics may be
dodgy
(flaring on a bright star either side of focus). I can drop the scope off,
and collect it a week or so later.

Regards Richard

Have you made sure you have the telescope out long enough for it to reach
'thermal equilibrium'? Do that first to make sure it's not just thermal
currents in the tube ruining the image. Atmospheric turbulence may also be
the culprit (in which case you just have to wait for better weather
conditions!).

If you have a short-tube (f/5) refractor, you might have pinched objects
(pretty common with these). In which case just slightly unscrew the ring
that holds down the objective lens cell and slightly tap the objective lens
gently from the side (make sure scope is upright!) before tightening the
ring (not too tight!).

You might find this site helpfull:

http://www.skywatchertelescope.net/EducationST.html

Regards

Yunus

"Ricardo" wrote in message
news:kMAic.102$44.69@newsfe1-win...
Hi,
Is there any knowledgeable guys/gals in the Bracknell (Berks) area
who
would do a star test on my 80mm refractor for me, I think the optics may
be
dodgy
(flaring on a bright star either side of focus). I can drop the scope off,
and collect it a week or so later.

Regards Richard





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Hi Richard

I live about 20 Mins away from you; in Farnham. If no-one closer shouts-up,
let me know and you can bring it round. Don't know how knowledgable a person
you're looking for confirmation rather than diagnosis should be simple
enough. It wouldn't be a bad idea if we set yours, and and a test scope
(mine or whoever takes a look at yours) side by side so seeing conditions
can be ruled out/confirmed.

Its probably best to do this on a clear-ish evening and we can take a quick
look. You'll be able to take it away with you, save you two trips. How long
have you had the scope? and what make is it? Give me your e-mail address or
phone number and I'll pop you my details.

Regards


Chris



"Ricardo" wrote in message
news:kMAic.102$44.69@newsfe1-win...
Hi,
Is there any knowledgeable guys/gals in the Bracknell (Berks) area
who
would do a star test on my 80mm refractor for me, I think the optics may
be
dodgy
(flaring on a bright star either side of focus). I can drop the scope off,
and collect it a week or so later.

Regards Richard

Hi Chris,
Many thanks for the offer. I'm not snubbing you but I might
give it few days just to see if someone a little bit closer gets in touch.
The scope is a Vixen Custom 80mm that I bought a few years
ago secondhand, through the Astronomy Now readers ads. I think I'm probably
the 3rd owner. Although I've not dropped it I think it could have been in
the past.

Thanks again for the offer,
Regards Richard



Chris Taylor" wrote in message
...

Hi Richard

I live about 20 Mins away from you; in Farnham. If no-one closer
shouts-up,
let me know and you can bring it round. Don't know how knowledgable a
person
you're looking for confirmation rather than diagnosis should be simple
enough. It wouldn't be a bad idea if we set yours, and and a test scope
(mine or whoever takes a look at yours) side by side so seeing conditions
can be ruled out/confirmed.

Its probably best to do this on a clear-ish evening and we can take a
quick
look. You'll be able to take it away with you, save you two trips. How
long
have you had the scope? and what make is it? Give me your e-mail address
or
phone number and I'll pop you my details.

Regards


Chris



"Ricardo" wrote in message
news:kMAic.102$44.69@newsfe1-win...
Hi,
Is there any knowledgeable guys/gals in the Bracknell (Berks) area
who
would do a star test on my 80mm refractor for me, I think the optics may
be
dodgy
(flaring on a bright star either side of focus). I can drop the scope
off,
and collect it a week or so later.

Regards Richard

"Ricardo" wrote in message news:BTVic.172$1f2.131@newsfe1-win...
Hi Chris,
Many thanks for the offer. I'm not snubbing you but I might
give it few days just to see if someone a little bit closer gets in touch.
The scope is a Vixen Custom 80mm that I bought a few years
ago secondhand, through the Astronomy Now readers ads. I think I'm probably
the 3rd owner. Although I've not dropped it I think it could have been in
the past.

The Vixen Custom models are high quality, Japanese made, small
achromatic refractors. My Custom 90 offers nice sharp images in the
right seeing conditions.

If your telescope had been dropped the chances are that the objective
would be broken or badly chipped. So don't lay it flat on anything
where it can roll off, will you? I keep my refractors vertically
resting on their dewshields and always keep an eyepiece in place to
keep dust off the back of the lens.

As the Vixen has a fixed screw-on objective cell the chances of
objective misalignment are tiny. I wouldn't even try to bump it with
the locking ring loosened. The lens should be a good fit in the cell
so there's really nowhere for it to go in this size!

Shake the telescope gently to see if the objective lens rattles
slightly. To make sure the lens ring isn't actually loose allowing the
lens to flop backwards and forwards. Or too tight to allow a tiny
amount of freedom.

It may be that a complete idiot has dismantled the objective and then
replaced it with the lens reversed. Try using the scope terrestrially.
Not through a window! Does it offer a nice sharp, false-colour free
image up to about 60x or even more? If so, the objective lens probably
hasn't been messed with.

So, does your image problem move from eyepiece to eyepiece? (Assuming
you have more than one)

Chris.B

Hi Chris,
I'll do another star test on a clear night and get back to
you. It may be my interpretation of the test, I'm not that knowledgeable.
Keep an eye out for a new post. It may be a week or two
depending on the weather and when I get chance to do it.


Regards Richard




"Chris.B" wrote in message
om...
"Ricardo" wrote in message
news:BTVic.172$1f2.131@newsfe1-win...
Hi Chris,
Many thanks for the offer. I'm not snubbing you but I
might
give it few days just to see if someone a little bit closer gets in
touch.
The scope is a Vixen Custom 80mm that I bought a few
years
ago secondhand, through the Astronomy Now readers ads. I think I'm
probably
the 3rd owner. Although I've not dropped it I think it could have been
in
the past.

The Vixen Custom models are high quality, Japanese made, small
achromatic refractors. My Custom 90 offers nice sharp images in the
right seeing conditions.

If your telescope had been dropped the chances are that the objective
would be broken or badly chipped. So don't lay it flat on anything
where it can roll off, will you? I keep my refractors vertically
resting on their dewshields and always keep an eyepiece in place to
keep dust off the back of the lens.

As the Vixen has a fixed screw-on objective cell the chances of
objective misalignment are tiny. I wouldn't even try to bump it with
the locking ring loosened. The lens should be a good fit in the cell
so there's really nowhere for it to go in this size!

Shake the telescope gently to see if the objective lens rattles
slightly. To make sure the lens ring isn't actually loose allowing the
lens to flop backwards and forwards. Or too tight to allow a tiny
amount of freedom.

It may be that a complete idiot has dismantled the objective and then
replaced it with the lens reversed. Try using the scope terrestrially.
Not through a window! Does it offer a nice sharp, false-colour free
image up to about 60x or even more? If so, the objective lens probably
hasn't been messed with.

So, does your image problem move from eyepiece to eyepiece? (Assuming
you have more than one)

Chris.B