object not in centre

[Petehog72]

Morning all, had the best night observing in a very long time last night, some real gems of the night sky seen, my issue is getting the object into the centre of the screen on our laptop, we have a celestron 8se and the camera is a neximage 5, I centred the object which happened to be Saturn last night in the centre of the eye piece, switched over to the camera but couldn't get it centred, very frustrating and ended up just observing instead which was awesome, but we really want to get some image data, I would appreciate any advise,

 

clear skies    Pete

[ollypenrice]

It's a common problem due to the very small field of view when you combine a small chip with a long focal length. It's made worse by the moving mirror focuser which introduces considerable image shift. Obviously your focus in the eyepiece will almost certainly be miles away from focus in the camera, so changing the focus will move the image right off the chip.

There are two possible solutions. 1) fit the scope with a conventional focuser at the rear so that you can refous between EP and camera without image shift or 2) install a flip mirror system which has an EP holder at right angles to a camera holder. With a bit of messing about you can get the camera focused and then move the EP up and down so it, too, is in focus. You then have the mirror feeding light to the EP, centre the target, then flip the mirror to send light to the camera.

I've never used a flip mirror but do have a conventional rear external focuser on my SCT. It makes life much easier.

Olly

[Petehog72]

Many thanks for the reply mate, ill have a look into an external focuser, i havent heard of them before so will do some research, its very frustrating messing about to try and get the image and loosing out on time trying to find 

[ollypenrice]

2 hours ago, Petehog72 said:

Many thanks for the reply mate, ill have a look into an external focuser, i havent heard of them before so will do some research, its very frustrating messing about to try and get the image and loosing out on time trying to find 

'Very frustrating' might be the understatement of the year!

You'll find a range of focusers here. https://www.firstlightoptics.com/focusers.html

Because webcams are light you don't need to go for anything too fancy but, if you win the lottery, go for the Feathertouch...

Olly

[SonnyE]

Getting everything par-focal is most frustrating.

I used a flip mirror box for a while when I began. It worked well. Once I got the eyepiece adjusted to be par-focal to my camera at the time.

But as I progressed into computerized imaging, the box found a home in my accessories case, and I use my guide scope camera, and my main imaging camera, on screen (computer display).

But it takes time, and careful adjusting. I would never expect to remove and replace something and find everything fine. So I chose one over the other.

And I chose a computer display because more eyes can see it.