Focus problems

[Rocket Pooch]

Hi all,

Had a chance at last yesterday night to play with my SAC8.

On my Orion (UK) 8" Newt I could focus fine with no problems whatsoever.  

However, I connected the SAC8 to my Sky Watcher 80mm F5 Refractor and I could not achieve focus because the focuser would not slide in far enough into the scope.

It seems the SAC8's CCD is quite a way back in the case.

Has anyone else had this problem?  If so how did you resolve it?

Thanks


Chris

[Rick]

You could try using a barlow, as it will pull the focal point out. That may be enough for it to reach the CCD.

[Whitters]

Rick's suggestion is better than mine, which involves a hacksaw;-)

[Rocket Pooch]

thought about that but it would defeat the object of buying a short focal length telescope

[Mike]

Chris I had the exact same problem with my newt and a CCD camera.  I had to dismantle the cam in the end and put it into a home made box so that the CCD with the CCD further into the tube.

Without the aid of lenses there is not a lot you can do about it I am afraid short of finding a way to get the CCD closer and into the focal point.

[ This Message was edited by: Mike on 2004-03-17 11:51 ]

[Rick]

Indeed. Any idea how close to the focal plane you're managing to get the CCD?

[Whitters]

Chris how are you connecting the camera to the telescope?

[Rocket Pooch]

Well I will say now hacksaw's and drills are out

The thing just connects using a 1-1/4" tube as normal.  I did contact a Skywatcher 80F5 group on Yahoo yesterday and they all think I actually need extension tubes and the focus point is way back from where the camera was?  Little confusing this because I could see a bright circle getting closer as it focused in; but they all seem to have had the same problem and it should focus out?

Apparently the telescope is designed to use a diagonal and this effectively adds 2-3" onto the length of the tube, therefore I need to move the CCD back by that amount?

I'm going to give this a try, but as we all know the weather conditions are not going to be good at all over the next week, so whilst I will probably be able to focus on some cars up the road, M51 will elude me probably until mid April (on holiday soon)

One thing, I was looking through my test images and one of them has a fading streak from top left to right, look like either one of those things Miriam never sees or one of those CCD thingies Paul was talking about.

I'll let you know if my tube needs extending next time I get it out?

See ya


Oh and light pollution, my god with the SAC8 its really bad, as in very very very bad.  Must get more filters.


[ This Message was edited by: csuddell on 2004-03-18 08:25 ]

[Rick]

Streaks that are CCD artifacts tend to follow  the CCD read-out direction so end up paralell to the edges of the image. Streaks at other angles probably have an external cause. Aircraft, satellite, meteor, moth, snow....

[Mike]

.....cosmic ray.....

[Rocket Pooch]

Is that a hippy comment Mike