Astrophot : Eye Projection better than Prime Focus?

Hi,
I tried a spot at astrophotos on my ETX105EC using a Nikon digital camera
but was amazed to see that the pics taken using manual handheld eyepiece
projection is better than prime focus using a Scopetronics Dgi-T
combination. I get higher magnification using the former. Any idea why this
is so?
I'm guessing it has something to do with focussing.
Here are the comparison:

Eyepiece projection :
http://photos.groups.yahoo.com/group...da/My+Astro+Pi
cs&.src=gr&.dnm=Jupiter.jpg&.view=t&.done=http%3a//photos.groups.yahoo.com/g
roup/singastro/lst%3f%26.dir=/Jornada/My%2bAstro%2bPics%26.src=gr%26.view=t

Prime Focus:
http://photos.groups.yahoo.com/group...da/My+Astro+Pi
cs&.src=gr&.dnm=Jupiter+3+-+24+May+2003.jpg&.view=t&.done=http%3a//photos.gr
oups.yahoo.com/group/singastro/lst%3f%26.dir=/Jornada/My%2bAstro%2bPics%26.s
rc=gr%26.view=t

(You may have to cut and paste if the link above gets truncated)

Thanks

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Thanks

On Mon, 21 Jul 2003 01:48:58 +0800, "Jornada"
wrote:

Hi,
I tried a spot at astrophotos on my ETX105EC using a Nikon digital camera
but was amazed to see that the pics taken using manual handheld eyepiece
projection is better than prime focus using a Scopetronics Dgi-T
combination. I get higher magnification using the former. Any idea why this
is so?
I'm guessing it has something to do with focussing.

I can't compare the photos since I'm not going to join that particular Yahoo
group just to look at them.

What camera are you using, and what were the comparison images made with? There
are very few digital cameras that can even be used at prime focus, or with
eyepiece projection. For either of those, you need a camera with a removable
lens. Otherwise, the usual method with digital cameras is afocal projection,
meaning that you take a picture through the eyepiece using the lens built into
the camera. That can be done by holding the camera or by using an adapter like
those sold by Scopetronix.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Prime focus requires removing the eyepiece from the telescope and the lens
from the camera. The purpose is to get the image plane of the camera's
detector into the focal plane of the telescope.

(Of course you have to be able to get the focal plane of the telescope to
come far enough out of the focuser draw tube to hit the film plane of the
camera.)

Eyepiece projection is using an eyepiece in the telescope and no lens on the
camera.

Afocal is using an eyepiece in the telescope and a lens on the camera. Which
is what I believe you are doing in each case, only with different methods to
hold the camera in place.

On Mon, 21 Jul 2003 02:12:18 +0800, "Jornada"
wrote:

Hi,
Thanks for the reply. I am using a Nikon Coolpix 4300 camera.
For eyepiece projection, I merely focussed the scope, then place the camera
len on my eyepiece and take the pic directly.
For prime focus, I attach my camera to my eyepiece using a Scopetronics
digi-T and attempt to adjust the image on my lcd screen. It looks clear but
I can never be sure since the screen is so small....

The two methods you are using are optically identical, and are called afocal
imaging. Any difference you are seeing in results is purely a function of the
zoom and focus settings of the camera.

Eyepiece projection and prime focus imaging both require a camera without a
lens.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com