Focusing Prime Focus

[balloonboy (Greg)]

Hi all

This is my first post here - no doubt this has been discussed previously - I have a Nikon D5000 D-SLR with T-ring and a Skywatcher 130mm (1000mm Focal length) reflector.
I want to try out prime focus photography however after screwing the camera directly to the eyepiece holder, I found that it will not focus on distant objects. I have read that the focal point is closer to the scope (?). Anyway, is there a method of fixing this problem without cutting bits of my tube?

thanks in anticipation.

Greg

[[1ponders] (Paul)]

You could try a lower profile focuser along with using a Prime Focus Adapter rather than screwing the camera to the eyepiece holder. Even then you may not get close enough

[[1ponders] (Paul)]

btw is your focuser 2" or only 1.25"?

[balloonboy (Greg)]

Thanks for the fast response Paul - my focuser is 1.25"

[Screwdriverone (Chris)]

Hi Greg,

I have the same SW135 and you will find that the DSLR wont be able to achieve focus. You may have to use eyepiece projection to get an image onto a DSLR chip.

I have the same problem with my 12" dob, can't get the focuser in enough to achieve any sort of focus. I used a Bintel camera adaptor and dropped in my 10 and 20mm Skywatcher Eyepieces to take pictures of the moon. Not as nice as prime focus obviously, but it worked quite well.

Cheers

Chris

[balloonboy (Greg)]

Thanks Chris

Sad news indeed . I was looking forward to prime focus photos. I've done a little afocal with my compact digital camera and the moon shots turned out beautifully.
http://photos-c.ak.fbcdn.net/hphotos..._1261691_n.jpg

Oh well - have to concentrate on something else....

thanks
Greg

[mswhin63 (Malcolm)]

I am not sure of your prime focus set-up but my DOB had the same problem.

I was able to fix this but not sure if your reflector will have the same adaptor.

Here is the guff, I can't take a photo of my camera setup because the camera used for the set-up nice to have a second camera.

My SW can unscrew the 1.25in adpator to leave a T-thread. I then purchaced only the EOS to T thread adaptor - https://www.bintelshop.com.au/Product.aspx?ID=5551 and was able to screw it directly into the 1.25in adaptor.

It give me an extra 1" available for prime focus adjustment.

I can't say this would work for you but never know.

[Screwdriverone (Chris)]

Thanks for the tip Malcolm,

This will work on my 12" dob, but alas, the SW135 only has a 1.25" rack and pinion fixed tube focuser, so this wont work on Greg's or my smaller reflector.

I'll try it on the dob though, I already have the bits you mention and never thought of it.

Thanks

Chris