| |
 |
|
|
Science Forum Index » Astro - Amateur Forum » Need help: We cannot see any stars in our new telescope, but
Page 1 of 1
|
| Author |
Message |
| Guest |
 Posted: Thu Feb 22, 2007 8:16 am |
|
|
|
|
My girlfriend and I bought a new reflecting telescope for christmas,
and so far have been unable to use it to view any stars.
We have looked at the surface of the moon, and we have looked into a
neighbours front window, and both have been seen with perfect clarity.
But whenever we try to view *stars*, the most either of us can ever
see is a dull, greyish disc (and when i say dull, i mean, very dull -
like the lowest brightness of light you can see before pitch-
darkness). We move the focus up and down, we try each different lens
that is available - still nothing. We jiggle the eyepeices around in
case things aren't lined up properly, still nothing.
Our options are a 2X Barlow lens and an Erector lens, and a 20mm, 12mm
or 4mm eyepeice. We have tried all 6 combinations of lenses.
*We know there is nothing blocking any of the lenses, each one is
transparent when you take the telescope apart.
*We know the telescope itself is fine - as i said, we can clearly see
the moon (and a neighbour's living room...) without any issues at
all.
*When we place a light in front of the telescope, we can see a bright
circle, so everything seems to be lined up fine.
*We have calibrated the finderscope, and repeatedly made sure that
bright, recognisable stars (tonight we have been using Betelgeuse) are
in the centre, and that they are clear of clouds. Still nothing.
Why can we never see any stars?
It seems impossible to believe that nobody has ever had this problem
before, seeing as we seem to have a perfectly functional astronomical
telescope, that we have been using for months without success. But no
trouble-shooting guides (or instruction booklets) that we have located
so far have mentioned our problem. Usually somebody will say to make
sure your eyes are lined up with it ("the eye is a part of the whole
optical system"), but we move and jiggle things around, and anyway -
we can see the moon fine, and when a light is placed in front of the
telescope, we can see a bright circle, so that can't be it.
Does anyone have any suggestions?
There must be someone out there - there must be many someones! - who
have started out on a telescope and had the exact same problem. If
you're out there, please help! |
|
|
| Back to top |
|
| Ed |
| Posted: Thu Feb 22, 2007 9:24 am |
|
|
|
Guest
|
Why don't you tell us a little more about the telescope? What brand is
it? What model number is it? Where did you buy it? Do you still have
the receipt? |
|
|
| Back to top |
|
| Bob Schmall |
| Posted: Thu Feb 22, 2007 10:10 am |
|
|
|
Guest
|
david.alexanderus@gmail.com wrote:
Quote: My girlfriend and I bought a new reflecting telescope for christmas,
and so far have been unable to use it to view any stars.
We have looked at the surface of the moon, and we have looked into a
neighbours front window, and both have been seen with perfect clarity.
But whenever we try to view *stars*, the most either of us can ever
see is a dull, greyish disc (and when i say dull, i mean, very dull -
like the lowest brightness of light you can see before pitch-
darkness). We move the focus up and down, we try each different lens
that is available - still nothing. We jiggle the eyepeices around in
case things aren't lined up properly, still nothing.
What you describe sounds very much like out of focus stars. Before they
come into focus stars show discs that are brighter or dimmer depending
on how far they are out of focus. Using a low power eyepiece, try
racking the focuser all the way in (toward the tube) while looking at a
bright star. If the disc appears to brighten and grow smaller but
doesn't focus into a sharp point, then your focuser is too far from the
main mirror or lens. It doesn't have enough "in travel" to reach focus.
Next rack it all the way out. If the same brightening and size reduction
happens but you can't reach focus, then the focuser is too close to the
primary mirror or lens.
If the latter situation shows up, then try this: very carefully slide
the eyepiece out of the focuser while keeping the object in its field of
view. If you move it completely out of the focuser and it focuses, then
you have a couple of options:
1. Buy an extension tube to move the eyepiece farther from the
mirror/lens. Contact one of the many retailers or manufacturers that
advertise in one of the astronomy magazines.
2. Take the scope back--it is flawed.
3. Practice until you become very proficient at holding the eyepiece in
your hand outside the focuser.
Option 2 is recommended.
Bob |
|
|
| Back to top |
|
| Guest |
| Posted: Thu Feb 22, 2007 10:17 am |
|
|
|
|
Boy, that sure is strange. I know you said, "Our options are a 2X
Barlow lens and an Erector lens, and a 20mm, 12mm
or 4mm eyepeice. We have tried all 6 combinations of lenses.". So,
why don't we decompose this problem by removing all eyepieces - just
on the off chance their is something in the way of an alignment
issue. Anyhow, point the scope at, say, Sirius - since it is so nice
and bright. You should be able to view from some point behind the
scope and see the star. If you can, then introduce an eyepiece - just
the 20mm. Remember, the moon, and presumably the neighbor's living
room are relatively bright objects.
Just a thought. I'm sure someone will come up with additional tests
you can perform to diagnose this condition.
Bill |
|
|
| Back to top |
|
| Carsten A. Arnholm |
| Posted: Thu Feb 22, 2007 11:04 am |
|
|
|
Guest
|
WJShaheen@aol.com wrote:
Quote: Boy, that sure is strange. I know you said, "Our options are a 2X
Barlow lens and an Erector lens, and a 20mm, 12mm
or 4mm eyepeice. We have tried all 6 combinations of lenses.". So,
why don't we decompose this problem by removing all eyepieces - just
on the off chance their is something in the way of an alignment
issue. Anyhow, point the scope at, say, Sirius - since it is so nice
and bright. You should be able to view from some point behind the
scope and see the star. If you can, then introduce an eyepiece - just
the 20mm. Remember, the moon, and presumably the neighbor's living
room are relatively bright objects.
Just a thought. I'm sure someone will come up with additional tests
you can perform to diagnose this condition.
Bill
If he can see the moon alright, then he is in focus and should be able to
see stars without any problems. Star focus = moon focus. My guess is the use
of barlow etc. makes a narrow field. It can be hard to find stars for
behinners.
Advice: When the moon is up, remove the barlow and use the longest focal
length eyepiece (smallest magnification). Focus the telescope on the moon.
Then try to find stars (don't refocus). It should work.
Clear skies
Carsten A. Arnholm
http://arnholm.org/
N59.776 E10.457 |
|
|
| Back to top |
|
| Ol' Duffer |
| Posted: Thu Feb 22, 2007 11:16 am |
|
|
|
Guest
|
In article <1172146583.124127.313110@h3g2000cwc.googlegroups.com>,
david.alexanderus@gmail.com says...
Quote: My girlfriend and I bought a new reflecting telescope for christmas,
and so far have been unable to use it to view any stars.
We have looked at the surface of the moon, and we have looked into a
neighbours front window, and both have been seen with perfect clarity.
But whenever we try to view *stars*, the most either of us can ever
see is a dull, greyish disc (and when i say dull, i mean, very dull -
like the lowest brightness of light you can see before pitch-
darkness). We move the focus up and down, we try each different lens
that is available - still nothing. We jiggle the eyepeices around in
case things aren't lined up properly, still nothing.
This may be too obvious, but no one else mentioned it yet so...
Are you outdoors? Trying to view through a window will blur and
distort, making unusable for anything but the brightest objects
at low magnification. |
|
|
| Back to top |
|
| Greg Crinklaw |
| Posted: Thu Feb 22, 2007 11:24 am |
|
|
|
Guest
|
For stars forget the Barlow and use your 20mm eyepiece only. If the
moon is up focus on it first. Are the craters sharp? Make sure you
have your finding device aligned properly so you can reliably point the
scope. Then point it at the brightest star you can see. When in focus
a star will appear as a tiny point of light, much like it does to your
unaided eye. The best focus is when it is smallest. If after doing
these things the problem persists then you do indeed have a problem and
you should check back here.
Greg
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)
SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html
To reply take out your eye |
|
|
| Back to top |
|
| W. H. Greer |
| Posted: Thu Feb 22, 2007 11:37 am |
|
|
|
Guest
|
On 22 Feb 2007 04:16:23 -0800, david.alexanderus@gmail.com wrote:
Quote: My girlfriend and I bought a new reflecting telescope for christmas,
and so far have been unable to use it to view any stars.
You may find the following website useful:
http://home.earthlink.net/~8-h-haggis/observing/beginners.htm
Quote: We have looked at the surface of the moon, and we have looked into a
neighbours front window, and both have been seen with perfect clarity.
But whenever we try to view *stars*, the most either of us can ever
see is a dull, greyish disc
Does the dull, grayish disc appear to move when you move the
telescope? If you point the telescope away from that disc does the
disc disappear from view?
Did you see a darker disc inside the dull, grayish disc?
Did the diameter of the disc appear to change when you adjusted the
focus?
Quote: Our options are a 2X Barlow lens and an Erector lens, and a 20mm, 12mm
or 4mm eyepeice. We have tried all 6 combinations of lenses.
Use only the 20mm eyepiece without the Barlow and without the Erector
lens when you attempt to see stars in the future. You can switch to a
different eyepiece *after* you've succeeded in seeing stars with the
20mm eyepiece.
Quote: Why can we never see any stars?
Insufficient information to tell . . . If you can see a star with the
naked eye, you should be able to see the same star with the telescope.
The telescope will make the star appear brighter; but not necessarily
larger. Stars are too small and too distant for your telescope to
show as anything more than tiny points of light.
My best guess at this point, with the limited information available
is:
Your finder is not lined up precisely enough with the main telescope;
and you're observing from a location where few stars are visible. When
you (attempt to) point the telescope at a bright star, the star is not
near enough to the center of the field to notice. Since there's no
bright star to be seen, you have nothing to focus on. Attempts to
focus the telescope now result in a *less* focused telescope. The
combined effects of a bright sky with few naked eye stars and an
unfocused telescope that's not pointed at a bright star leaves you
with nothing but unfocussed, gray sky to see!
Quote: Usually somebody will say to make
sure your eyes are lined up with it ("the eye is a part of the whole
optical system"), but we move and jiggle things around, and anyway -
we can see the moon fine,
It *can* be more difficult to line your eye up properly when the
telescope is pointed at a star. The reason: A star appears as a tiny
point of light. The Moon appears *much* larger and is *much*
brighter.
Quote: Does anyone have any suggestions?
Focus the telescope on the Moon using the 20mm eyepiece. Once the
telescope is focused on the Moon, it will also be focused for the
stars.
Point the focused telescope at a bright, naked eye star. If you don't
see the star right away, try moving the telescope around a *little*
(It may not be pointed exactly at the star); but don't attempt to
change the focus from where you set it when observing the Moon -- at
least not until you see one or more stars when you look through the
eyepiece.
Look *through* the eyepiece; not *at* the eyepiece -- just like when
you're looking at the moon through the telescope.
If unsuccessful, check the eye lens of the eyepiece for dew or frost
with the aid of a dim light. Also verify that the finder is properly
adjusted -- This latter point is *very* important!!
If there are bright lights nearby, try to set the telescope up in a
location where the lights don't shine; or at least choose a location
where the brightest lights don't shine.
Keep us informed concerning the results of future efforts and we
should eventually be able to properly diagnose and solve the
difficulty.
--
Bill
Celestial Journeys
http://cejour.blogspot.com |
|
|
| Back to top |
|
| Rich |
| Posted: Thu Feb 22, 2007 8:25 pm |
|
|
|
Guest
|
On Feb 22, 7:16 am, david.alexande...@gmail.com wrote:
Quote: My girlfriend and I bought a new reflecting telescope for christmas,
and so far have been unable to use it to view any stars.
We have looked at the surface of the moon, and we have looked into a
neighbours front window, and both have been seen with perfect clarity.
But whenever we try to view *stars*, the most either of us can ever
see is a dull, greyish disc (and when i say dull, i mean, very dull -
like the lowest brightness of light you can see before pitch-
darkness). We move the focus up and down, we try each different lens
that is available - still nothing. We jiggle the eyepeices around in
case things aren't lined up properly, still nothing.
Our options are a 2X Barlow lens and an Erector lens, and a 20mm, 12mm
or 4mm eyepeice. We have tried all 6 combinations of lenses.
*We know there is nothing blocking any of the lenses, each one is
transparent when you take the telescope apart.
*We know the telescope itself is fine - as i said, we can clearly see
the moon (and a neighbour's living room...) without any issues at
all.
*When we place a light in front of the telescope, we can see a bright
circle, so everything seems to be lined up fine.
*We have calibrated the finderscope, and repeatedly made sure that
bright, recognisable stars (tonight we have been using Betelgeuse) are
in the centre, and that they are clear of clouds. Still nothing.
Why can we never see any stars?
It seems impossible to believe that nobody has ever had this problem
before, seeing as we seem to have a perfectly functional astronomical
telescope, that we have been using for months without success. But no
trouble-shooting guides (or instruction booklets) that we have located
so far have mentioned our problem. Usually somebody will say to make
sure your eyes are lined up with it ("the eye is a part of the whole
optical system"), but we move and jiggle things around, and anyway -
we can see the moon fine, and when a light is placed in front of the
telescope, we can see a bright circle, so that can't be it.
Does anyone have any suggestions?
Yes. Buy the book, "Nightwatch," READ IT and come back in a few
months. |
|
|
| Back to top |
|
| Llanzlan Klazmon the 15th |
| Posted: Thu Feb 22, 2007 9:38 pm |
|
|
|
Guest
|
david.alexanderus@gmail.com wrote in news:1172146583.124127.313110
@h3g2000cwc.googlegroups.com:
Quote: My girlfriend and I bought a new reflecting telescope for christmas,
and so far have been unable to use it to view any stars.
We have looked at the surface of the moon, and we have looked into a
neighbours front window, and both have been seen with perfect clarity.
But whenever we try to view *stars*, the most either of us can ever
see is a dull, greyish disc (and when i say dull, i mean, very dull -
like the lowest brightness of light you can see before pitch-
darkness). We move the focus up and down, we try each different lens
that is available - still nothing. We jiggle the eyepeices around in
case things aren't lined up properly, still nothing.
Our options are a 2X Barlow lens and an Erector lens, and a 20mm, 12mm
or 4mm eyepeice. We have tried all 6 combinations of lenses.
*We know there is nothing blocking any of the lenses, each one is
transparent when you take the telescope apart.
*We know the telescope itself is fine - as i said, we can clearly see
the moon (and a neighbour's living room...) without any issues at
all.
*When we place a light in front of the telescope, we can see a bright
circle, so everything seems to be lined up fine.
*We have calibrated the finderscope, and repeatedly made sure that
bright, recognisable stars (tonight we have been using Betelgeuse) are
in the centre, and that they are clear of clouds. Still nothing.
Why can we never see any stars?
It seems impossible to believe that nobody has ever had this problem
before, seeing as we seem to have a perfectly functional astronomical
telescope, that we have been using for months without success. But no
trouble-shooting guides (or instruction booklets) that we have located
so far have mentioned our problem. Usually somebody will say to make
sure your eyes are lined up with it ("the eye is a part of the whole
optical system"), but we move and jiggle things around, and anyway -
we can see the moon fine, and when a light is placed in front of the
telescope, we can see a bright circle, so that can't be it.
Does anyone have any suggestions?
There must be someone out there - there must be many someones! - who
have started out on a telescope and had the exact same problem. If
you're out there, please help!
One more bit of advice. Try and find out if there is an astronomical
society or club in your area. You will have a source of invaluable support.
Klazmon
|
|
|
| Back to top |
|
| Starlord |
| Posted: Thu Feb 22, 2007 9:46 pm |
|
|
|
Guest
|
Along with all the replys you got, here is something else that is a must
read:
Telescope Buyers FAQ
http://home.inreach.com/starlord
--
There are those who believe that life here, began out there, far across the
universe, with tribes of humans, who may have been the forefathers of the
Egyptians, or the Toltecs, or the Mayans. Some believe that they may yet be
brothers of man, who even now fight to survive, somewhere beyond the
heavens.
The Lone Sidewalk Astronomer of Rosamond
Telescope Buyers FAQ
http://home.inreach.com/starlord
Sidewalk Astronomy
www.sidewalkastronomy.info
The Church of Eternity
http://home.inreach.com/starlord/church/Eternity.html
<david.alexanderus@gmail.com> wrote in message
news:1172146583.124127.313110@h3g2000cwc.googlegroups.com...
Quote: My girlfriend and I bought a new reflecting telescope for christmas,
and so far have been unable to use it to view any stars.
|
|
|
| Back to top |
|
| dogman |
| Posted: Thu Feb 22, 2007 9:59 pm |
|
|
|
Guest
|
On Feb 22, 8:38 pm, Llanzlan Klazmon the 15th
<Klaz...@llurdiaxorb.govt> wrote:
Quote: david.alexande...@gmail.com wrote in news:1172146583.124127.313110
@h3g2000cwc.googlegroups.com:
My girlfriend and I bought a new reflecting telescope for christmas,
and so far have been unable to use it to view any stars.
We have looked at the surface of the moon, and we have looked into a
neighbours front window, and both have been seen with perfect clarity.
But whenever we try to view *stars*, the most either of us can ever
see is a dull, greyish disc (and when i say dull, i mean, very dull -
like the lowest brightness of light you can see before pitch-
darkness). We move the focus up and down, we try each different lens
that is available - still nothing. We jiggle the eyepeices around in
case things aren't lined up properly, still nothing.
Our options are a 2X Barlow lens and an Erector lens, and a 20mm, 12mm
or 4mm eyepeice. We have tried all 6 combinations of lenses.
*We know there is nothing blocking any of the lenses, each one is
transparent when you take the telescope apart.
*We know the telescope itself is fine - as i said, we can clearly see
the moon (and a neighbour's living room...) without any issues at
all.
*When we place a light in front of the telescope, we can see a bright
circle, so everything seems to be lined up fine.
*We have calibrated the finderscope, and repeatedly made sure that
bright, recognisable stars (tonight we have been using Betelgeuse) are
in the centre, and that they are clear of clouds. Still nothing.
Why can we never see any stars?
It seems impossible to believe that nobody has ever had this problem
before, seeing as we seem to have a perfectly functional astronomical
telescope, that we have been using for months without success. But no
trouble-shooting guides (or instruction booklets) that we have located
so far have mentioned our problem. Usually somebody will say to make
sure your eyes are lined up with it ("the eye is a part of the whole
optical system"), but we move and jiggle things around, and anyway -
we can see the moon fine, and when a light is placed in front of the
telescope, we can see a bright circle, so that can't be it.
Does anyone have any suggestions?
There must be someone out there - there must be many someones! - who
have started out on a telescope and had the exact same problem. If
you're out there, please help!
One more bit of advice. Try and find out if there is an astronomical
society or club in your area. You will have a source of invaluable support.
Klazmon
- Hide quoted text -
- Show quoted text -- Hide quoted text -
- Show quoted text -
You also need to keep your eyeball back from the eye piece several
millameters 1/4 1/2/ inch. |
|
|
| Back to top |
|
| |
|
Page 1 of 1
All times are GMT - 5 Hours
The time now is Fri Dec 05, 2008 1:59 am
|
|