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Obviously doing something wrong here....

Kazzmaniandevil

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kens

kens

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Two possibilities: either the focusser wont go in far enough or it wont go out far enough

If it wont go out far enough you need an extension tube.

If it wont go in far enough you need to remove any extension tubes and hope it works

Many newtonians are not designed for astrophotography and even removing all extensions is not enough to get focus.

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Astrosurf

Astrosurf

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Have you tried connecting the camera to the scope's focusing tube with just a plain T adaptor? I'm wondering why you're using a Barlow. It'll increase the scope's focal length and therefore its speed so imaging will require longer exposures.

Alexxx

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D4N

D4N

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The 130SLT isn't designed with imaging in mind so focuser travel will be an issue, it is unlikely that you would be able to achieve prime focus without a Barlow. That you cannot focus with a Barlow is most unfortunate as the only thing you can do then is modify the telescope so that the main mirror is closer to the camera.

You can test if infocus is definitely the problem by trying in the day, if you can focus on near objects but not far ones then it is definitely infocus. If you can't focus on anything then you may need an extension tube but this would be unusual on a visual Newtonian.

/Dan

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Kazzmaniandevil

Kazzmaniandevil

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Tested the Barlow on the camera during daylight today and focused fine on an object 800ft away. Also aligned the finder scope a bit better. I'm guessing that if the Barlow focuses on an object at 800ft away fine I'd need to extend the tube to focus better on stars?

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D4N

D4N

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From the position you have the focuser at for focus 800' away you probably need to wind it in a centimetre or so to reach focus at infinity, do you have any focuser travel left?

/Dan

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kens

kens

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To focus on an object more than 800' away(e.g. a star) you will need to wind the focusser further IN. If there is no more adjustment (travel) left that is not possible.

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D4N

D4N

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It depends on how far from focus you are, I shaved quite a lot off the focuser on my 130P to make it more suitable for imaging.

This can gain you a couple of cm of focuser travel, if you need more then it involves moving the primary mirror. You may get a few mm by adjusting all the collimation screws but you would likely have to move the mirror up the tube to gain anything more than that.

This is the focuser off my 130P, not sure how similar it is to your scope but you should be able to see where it has been cut back.

The bolts were added to lock it and prevent sag.

a6d5b57e33f72aafa45ba8f0188b5464.jpg

/Dan

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happy-kat

happy-kat

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I see.

It is tracking but not equatorial so exposure times will need to be very short.

Your mount tracks by a series of up/down left/right movements which don't directly follow the earth's rotation even though the object is kept in the centre of the view. So star trailing when imaging will become apparent if the exposure time is too long.

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happy-kat

happy-kat

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The tripod with just your camera and a short lens will enable you to have a go at imaging and your exposures might be in seconds. Lots of images stacked can create a picture.

Have you tried search to see what others have managed?

It is free to experiment, point your telescope at m42 with camera (no barlow) focus then experiment how many seconds before you get star trailing... If you need the barlow to focus. Then just work with your camera and a camera lens on your mount.

You might need to get a mount adaptor to fit your camera to the mount (take the telescope off, contact an astro seller to understand what adaptor you might need).

You don't have an imaging setup so need to be creative in having experiments to learn what is and is not possible.

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Jokehoba

Jokehoba

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Just to echo what others have said and add my own experience...  

I have a Skywatcher 130P (so almost identical to the Celestron). At first I could only reach focus on my Canon 1100D in combination with a x2 barlow - after all, it is designed for visual observing. The SW eyepiece holder has an M42 external thread (similar to what can be seen in Dan's photo above) which can fit directly onto a T-adapter. This helped but still wasn't enough.

So I opted to move the primary mirror (i.e., shorten the tube) initially by about 20mm. This was fine until I later bought a coma corrector, and had to cut a further 15mm off the length! It's now pretty useless for visual... But great for AP.

Actually, shortening the tube isn't that difficult - just takes a bit of courage (or madness!) to make the first incision.

John 

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Kazzmaniandevil

Kazzmaniandevil

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Sorry my why post has been answered. Thanks to you all for your explanations. I'm certainly struggling to understand the terminology which has not been helped by my dyslexia. Many websites have a tendency to go complicated in their explanations so everybody's help has been really useful !

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