Star test help...

I've only had my new FS102 out three times since I received it and I've been
pretty happy with the views. Nice dark backgrounds and pinpoint stars. My
concern is that I have not been able to produce an airy disc pattern. Keep
in mind this is my first quality refractor and I've only seen an airy disc
one other time in a friends scope so I'm a novice evaluating and star
testing.

Last night I had my 7mm UO HD abbe ortho in the scope and I had Vega
centered in the fov when it was nearly at zenith. All the fainter stars
around Vega focused to nice pindots but I was never able to get a nice sharp
focus or an airy disc on Vega. I didn't think to look at the diffraction
rings inside and outside of focus but I will next time out.

What are you thoughts? Am I doing something wrong? Is Vega not a good star
to use?

Thanks
Brian A

"Brian A" wrote in message
news:ZsyUa.151791$ye4.103957@sccrnsc01...
I've only had my new FS102 out three times since I received it and I've
been
pretty happy with the views. Nice dark backgrounds and pinpoint stars. My
concern is that I have not been able to produce an airy disc pattern. Keep
in mind this is my first quality refractor and I've only seen an airy disc
one other time in a friends scope so I'm a novice evaluating and star
testing.

Last night I had my 7mm UO HD abbe ortho in the scope and I had Vega
centered in the fov when it was nearly at zenith. All the fainter stars
around Vega focused to nice pindots but I was never able to get a nice
sharp
focus or an airy disc on Vega. I didn't think to look at the diffraction
rings inside and outside of focus but I will next time out.

What are you thoughts? Am I doing something wrong? Is Vega not a good star
to use?

Thanks
Brian A

7mm is too low of a magnification. Try at least 200x. You also need steady
seeing;
otherwise, the airy disc will move around and won't show you a nice textbook
round
circle.

Ron B[ee]

On Sat, 26 Jul 2003 17:00:41 GMT, "Brian A"
wrote:

Last night I had my 7mm UO HD abbe ortho in the scope and I had Vega
centered in the fov when it was nearly at zenith. All the fainter stars
around Vega focused to nice pindots but I was never able to get a nice sharp
focus or an airy disc on Vega. I didn't think to look at the diffraction
rings inside and outside of focus but I will next time out.

Vega is so bright that the glare can obscure the edge of the
diffraction disk. Try a neutral density filter (or if you don't have
one, put sunglasses on as you look through the eyepiece).
Also, the brightest stars suffer the worst bloating in unsteady
skies.

Dan Chaffee

Thanks for you input guys. Mother Nature doesn't look like she's going to
cooperate with me for a while but I'm breathing a little easier know I
wasn't doing it quite right.

Brian A

"Dan Chaffee" wrote in message
...
On Sat, 26 Jul 2003 17:00:41 GMT, "Brian A"
wrote:

Last night I had my 7mm UO HD abbe ortho in the scope and I had Vega
centered in the fov when it was nearly at zenith. All the fainter stars
around Vega focused to nice pindots but I was never able to get a nice
sharp
focus or an airy disc on Vega. I didn't think to look at the diffraction
rings inside and outside of focus but I will next time out.

Vega is so bright that the glare can obscure the edge of the
diffraction disk. Try a neutral density filter (or if you don't have
one, put sunglasses on as you look through the eyepiece).
Also, the brightest stars suffer the worst bloating in unsteady
skies.

Dan Chaffee