Newbie question

I just got a small Celestron Nextar 114 GT from my wife for Christmas. I
haven't played with a scope since I was a kid so my interest is now struck
once again. I did a fair amount of reading here and elsewhere and went out
tonight for my first viewing. After letting the scope stabilize for about 2
hours outside, all my images came out looking as if there was a veil coming
from each point of light.

I have crudely constructed what sorta looks like what I was seeing. You can
see it at http://www.windvisions.com/C114/saturn_veil.jpg and
http://www.windvisions.com/C114/star_veil.jpg for Saturn and a typical
star/point of light.

What would be causing this? Is this coma? Is this correctable with this scope?
It did the same with both of the eyepieces that I had, 10mm and 25mm, so I
suspect it is something with the primary mirror. The seeing was about as bad
as it could have been, with neighborhood lights all around.

Also, what would be the typical eyepiece limit of this setup?

If this keeps my interest enough I may consider upgrading to something better
or building one eventually.

Glenn

In article Y0rHb.47971$hf1.15500@lakeread06, says...

What would be causing this? Is this coma?

From http://www.opticalmechanics.com/about_coma.htm it sounds like it is coma
EXCEPT that it does not seem vary across the field. When looking at
The Pleiades for example, all of the stars in the system have this same veil.

Glenn again

According to http://astronomy.trilobytes.com.au/s....htm#alignment it
looks like everything is way off. I'll try the method he suggests.

Glenn

In article hXrHb.47973$hf1.20652@lakeread06, says...

In article Y0rHb.47971$hf1.15500@lakeread06, says...

What would be causing this? Is this coma?

From http://www.opticalmechanics.com/about_coma.htm it sounds like it is coma
EXCEPT that it does not seem vary across the field. When looking at
The Pleiades for example, all of the stars in the system have this same veil.

Glenn again

Definitely looks like a collimation issue. Due to its built in Barlow lens,
collimating the 114 GT can be bit trickier than most Newtonian though.

http://www.grcooperjr.com/_disc2/00000029.htm




"Glenn Woodell" wrote in message
news:rfCHb.48330$hf1.32970@lakeread06...
According to http://astronomy.trilobytes.com.au/s....htm#alignment
it
looks like everything is way off. I'll try the method he suggests.

Glenn

In article hXrHb.47973$hf1.20652@lakeread06, says...

In article Y0rHb.47971$hf1.15500@lakeread06, says...

What would be causing this? Is this coma?

From http://www.opticalmechanics.com/about_coma.htm it sounds like it is
coma
EXCEPT that it does not seem vary across the field. When looking at
The Pleiades for example, all of the stars in the system have this same
veil.

Glenn again

In article et,
says...

Definitely looks like a collimation issue. Due to its built in Barlow lens,
collimating the 114 GT can be bit trickier than most Newtonian though.

http://www.grcooperjr.com/_disc2/00000029.htm

Thanks. That link was no good but I'll do some searching.

Glenn

On Sun, 28 Dec 2003 02:15:20 GMT, (Glenn Woodell)
wrote:

I just got a small Celestron Nextar 114 GT from my wife for Christmas. I
haven't played with a scope since I was a kid so my interest is now struck
once again. I did a fair amount of reading here and elsewhere and went out
tonight for my first viewing. After letting the scope stabilize for about 2
hours outside, all my images came out looking as if there was a veil coming
from each point of light.

I have crudely constructed what sorta looks like what I was seeing. You can
see it at http://www.windvisions.com/C114/saturn_veil.jpg and
http://www.windvisions.com/C114/star_veil.jpg for Saturn and a typical
star/point of light.

What would be causing this? Is this coma? Is this correctable with this scope?
It did the same with both of the eyepieces that I had, 10mm and 25mm, so I
suspect it is something with the primary mirror. The seeing was about as bad
as it could have been, with neighborhood lights all around.

Also, what would be the typical eyepiece limit of this setup?

If this keeps my interest enough I may consider upgrading to something better
or building one eventually.

You've already seen a number of good responses, but the drawing
reminds me of something else.

Try to find another scope to do some viewing.
Although the drawing does look like a mechanical issue, it is also
something that show up when the observers eyes water and he/she gets
into the wrong position. There other reasons, including (if you'll
pardon the expression), eye boogers floating around. Every one has
them to some extent and the eyes watering is a way of cleaning them
off the lens. Of course they then tend to float around until the
observer wipes their eyes.

But...be that as it may, try another scope and have someone else look
through yours.

Although my eyes test well (No astigmatism, or cataracts, I do wear
bifocals and take them off for viewing) I often get the same effect.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair?)
www.rogerhalstead.com

Glenn

(Glenn Woodell) wrote in
news:jEEHb.48797$hf1.4723@lakeread06:

In article et,
says...

Definitely looks like a collimation issue. Due to its built in Barlow
lens, collimating the 114 GT can be bit trickier than most Newtonian
though.

http://www.grcooperjr.com/_disc2/00000029.htm

Thanks. That link was no good but I'll do some searching.

Glenn



Another thing to check. The problem you describe could also be caused by
dew settling on the secondary (or even primary if really bad).

L.

In article ,
says...

Another thing to check. The problem you describe could also be caused by
dew settling on the secondary (or even primary if really bad).

Things were MUCH better tonight. After doing a rough collimation the coma was
almost gone completely. So at least I know where the problem is. I'm goign to
do some mods to my scope/tripod/power etc. to make things a little more
convenient. I'm also finding more resources now. I think it's going to be a
good first scope.

Glenn