Focusing

[Strugz]

I have a DSLR, t ring, t adaptor set it all up. So the t adaptor was put into the telescope's focuser. Had to have the focuser right out to get anywhere near a decent image, but still can't get focus. Would I need an extension tube or something?

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Skywatcher 130. 9mm 12mm 15mm 20mm 32mm revelation eps. Meade 10 x 50 bins.

[Luke]

I've not used a 130 myself but I've heard that they do not have enough inward travel of the focuser, so in that case an extension tube would not help. An extension tube would only help if you needed more outward travel, it solves the opposite problem.

If you do a search you should find more posts but I hope this helps:

http://stargazerslounge.com/beginners-help-advice/95620-what-do-i-need-take-pictures-my-skywatcher-130-a.html

[angusb1]

Unless you move the primary mirror up the tube you will not be able to get your DSLR near enough to the secondary to achieve focus without using a barlow. Putting a barlow between camera and focuser will move the focal plane farther out from the focuser so you can focus using the DSLR but will increase your focal ratio so a 2x barlow will make your scope F10.2 instead of F5.1. This means your exposure times will need to be longer so it will be fine for planetary and lunar imaging (bright targets) but you might struggle with DSOs.

[Strugz]

Thanks for that, will try the barlow next time out.

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Skywatcher 130. 9mm 12mm 15mm 20mm 32mm revelation eps. Meade 10 x 50 bins.

[Stephen]

As above, just verify it's outwards movement you are having problems with as it's normally the reverse (inwards.)

Other solutions to inwards focus problems include low profile focuser and if the scope supports it a direct t-thread attachment (though I suspect yours does not as you are using a t-adaptor.)

[Strugz]

It did seem that outward travel was the issue, but that contradicts everything else Ive read so far. So

next clear night I'm going to take a series of shots across the range to confirm. I'm going to make a Bhatinov as well.

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Skywatcher 130. 9mm 12mm 15mm 20mm 32mm revelation eps. Meade 10 x 50 bins.

[Starlight 1]

I had a SW130 and its got a direct thread on the focuser.

[Strugz]

I've also looked into upgrading the focuser, and to be honest I d be better off buying a new scope on a better mount, and using the 130 to take on holiday in the car!

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Skywatcher 130. 9mm 12mm 15mm 20mm 32mm revelation eps. Meade 10 x 50 bins.

[Strugz]

I had a SW130 and its got a direct thread on the focuser.

Aha! I shall check that right away

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Skywatcher 130. 9mm 12mm 15mm 20mm 32mm revelation eps. Meade 10 x 50 bins.

[Stephen]

Aha! I shall check that right away

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Skywatcher 130. 9mm 12mm 15mm 20mm 32mm revelation eps. Meade 10 x 50 bins.

If it has got one, it is "underneath" the 1.25" barrel - it should just unscrew

[Starlight 1]

If it has got one, it is "underneath" the 1.25" barrel - it should just unscrew

That right then I use a nikon 1.25 on the end and put the canon one over the top.

[Strugz]

Another thought..is there any value in trying to focus on something in daylight to see if I can get anywhere close to half decent focusing? At least so I can try out different setups to see if Im in the right ball park?

[ollypenrice]

Another thought..is there any value in trying to focus on something in daylight to see if I can get anywhere close to half decent focusing? At least so I can try out different setups to see if Im in the right ball park?

Certainly there is. If you can get something a couple of miles away there will be little to adjust when you get to the stars. Since I live in the mountains it's easy for me to focus at a distance of 15 miles or so but even using something a Km or two off will give you and idea.

Olly

[Starlight 1]

Day or night is the same thing try it .

[Strugz]

Perfect...Theres a church tower I can use about 1.5 miles away

[Strugz]

Yup the barlow seems to work. Thanks for that. There is a direct thread as well 'under' the end piece of the focuser, but I don't have anything else to fit that.

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Skywatcher 130. 9mm 12mm 15mm 20mm 32mm revelation eps. Meade 10 x 50 bins.

[Luke]

I would be surprised if it was lack of outward travel. Lack of inward travel is a common problem with Newtonians.

With refractors it's more likely to be lack of enough outward travel that stops you getting focus when imaging, where you can easily just add an extension tube to compensate for having shortened things up by removing the diagonal.

It did seem that outward travel was the issue, but that contradicts everything else Ive read so far.

[Stephen]

Yup the barlow seems to work. Thanks for that. There is a direct thread as well 'under' the end piece of the focuser, but I don't have anything else to fit that.

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Skywatcher 130. 9mm 12mm 15mm 20mm 32mm revelation eps. Meade 10 x 50 bins.

If the Barlow works, then it's definitely inward focus that's the problem.

When you say under the end piece, do you mean just under the barrel where the 1.25" goes in, or have you removed the wide threaded plate under that as well?

If it is a direct SLR one, you can unscrew the barrel only (not the plate) revealing the t-thread. Post a pic and we can confirm

Your camera t-adaptor then connects directly to that. This may enable you to focus without the Barlow.

[Strugz]

Yeah I can attach the t ring directly to the focuser without using the nosepiece .

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Skywatcher 130. 9mm 12mm 15mm 20mm 32mm revelation eps. Meade 10 x 50 bins.

[Stephen]

Yeah I can attach the t ring directly to the focuser without using the nosepiece .

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Skywatcher 130. 9mm 12mm 15mm 20mm 32mm revelation eps. Meade 10 x 50 bins.

Excellent so it's now camera-t ring-focuser meaning the sensors a good 30mm closer to the focal point than with the nosepiece. Question now is can you focus with it? (Try the church again.)

[Hightower]

Did you manage to focus like this?