ASTRO: Pictures of the GSO 6" RC

Thanks for the comments on my "first light" picture.
Some wanted to see images of the scope itself, here they come.

The picture "GSORCfront.jpg" shows the inside of the tube with the baffles.

"GSORC.jpg" shows the setup used for imaging M33 (ED80 as guidescope on a
parallel bar). Focus for the RC is quite far behind the scope, so I had to
use a long imaging train to come to focus, which is probably one of the
reasons for unsharp stars on one side of the image (other reason could be
the adjustment of the focuser; there are no problems with collimation of the
mirrors, the scope arrived in perfect collimation).
Another problem with this setup was, that the focuser (which is different
from the ones sold in the US by AstroTech) is not screwed to the back of the
scope directly but secured by a screw-on ring (silver colour) that has a
longer thread than the back of the scope, so it does not press the focuser
very firmly against the back of the scope.

"GSORC2.jpg" shows the scope after receiving a 5cm extension that fits
between the back of the scope and the focuser, thus allowing for a shorter
imaging train. The extension also has a longer thread, so the focuser can be
firmly attached to it. I hope that this will give me sharp stars over the
whole field, if not I'll have to adjust the focuser (which is not difficult,
but will cost me precious clear-sky-time).

Stefan

Stefan Lilge wrote:
Thanks for the comments on my "first light" picture.
Some wanted to see images of the scope itself, here they come.

The picture "GSORCfront.jpg" shows the inside of the tube with the baffles.

"GSORC.jpg" shows the setup used for imaging M33 (ED80 as guidescope on a
parallel bar). Focus for the RC is quite far behind the scope, so I had to
use a long imaging train to come to focus, which is probably one of the
reasons for unsharp stars on one side of the image (other reason could be
the adjustment of the focuser; there are no problems with collimation of the
mirrors, the scope arrived in perfect collimation).
Another problem with this setup was, that the focuser (which is different
from the ones sold in the US by AstroTech) is not screwed to the back of the
scope directly but secured by a screw-on ring (silver colour) that has a
longer thread than the back of the scope, so it does not press the focuser
very firmly against the back of the scope.

"GSORC2.jpg" shows the scope after receiving a 5cm extension that fits
between the back of the scope and the focuser, thus allowing for a shorter
imaging train. The extension also has a longer thread, so the focuser can be
firmly attached to it. I hope that this will give me sharp stars over the
whole field, if not I'll have to adjust the focuser (which is not difficult,
but will cost me precious clear-sky-time).

Stefan

I see they saved a lot of money by going to an external focuser. Most
high priced RC's focus by using a stepper motor to move the secondary.
I've always wondered if that had an effect on correction. Moving the
main mirror does in a SCT or Mak. They also use carbon fiber rather
than aluminum for more stable focus during dropping temperatures. How
does it compare to your Meade in this respect? Sag from a focuser that
isn't rigid could explain your tilt. Shim ring might help.

Good baffling is comparatively cheap but few do it for some reason.
Rather broad spider surprises me. Makes for nice spikes.

Rick

Rick,

I think that altering the distance between the two mirrors will affect the
optical design, so I am OK with an external focuser as long as it rigid
enough. The supplied focuser is quite far from "high end", but these scopes
certainly have a different focuser in the US as the one I have is branded by
a german dealer, so he obviously got the tube from GSO and supplied his own
accessories.
Now that I have shortened the backfocus by adding the spacers in front of
the focuser I am quite confident that the focuser will be able to hold my
cameras without sagging. I don't think it could hold a heavy SBIG camera.

In the two nights I have been able to image with this scope I have not
noticed any focus shift, but there was not a large drop in temperatures. I
would guess that the scope is small enough not to require a carbon tube.

Stefan

I see they saved a lot of money by going to an external focuser. Most
high priced RC's focus by using a stepper motor to move the secondary.
I've always wondered if that had an effect on correction. Moving the main
mirror does in a SCT or Mak. They also use carbon fiber rather than
aluminum for more stable focus during dropping temperatures. How does it
compare to your Meade in this respect? Sag from a focuser that isn't
rigid could explain your tilt. Shim ring might help.

good looking scope Stefan

that focuser looks pretty solid too


"Stefan Lilge" wrote in message
...
Thanks for the comments on my "first light" picture.
Some wanted to see images of the scope itself, here they come.

The picture "GSORCfront.jpg" shows the inside of the tube with the
baffles.

"GSORC.jpg" shows the setup used for imaging M33 (ED80 as guidescope on a
parallel bar). Focus for the RC is quite far behind the scope, so I had to
use a long imaging train to come to focus, which is probably one of the
reasons for unsharp stars on one side of the image (other reason could be
the adjustment of the focuser; there are no problems with collimation of
the mirrors, the scope arrived in perfect collimation).
Another problem with this setup was, that the focuser (which is different
from the ones sold in the US by AstroTech) is not screwed to the back of
the scope directly but secured by a screw-on ring (silver colour) that has
a longer thread than the back of the scope, so it does not press the
focuser very firmly against the back of the scope.

"GSORC2.jpg" shows the scope after receiving a 5cm extension that fits
between the back of the scope and the focuser, thus allowing for a shorter
imaging train. The extension also has a longer thread, so the focuser can
be firmly attached to it. I hope that this will give me sharp stars over
the whole field, if not I'll have to adjust the focuser (which is not
difficult, but will cost me precious clear-sky-time).

Stefan