Cant focus DSLR

[Struders]

Today I received my t mount through the post and was just itching to use it!!

I could'nt wait till the sun went down so I screwed the mount onto the focuser then mount the camera to the scope. I focused it on a nearby wall no problems.

Come to focus on a star and I just can focus on it at all... the nearest I can get is when I focus all the way in and hits the stop, but its still way out.

What am I missing? some sort of additional lens/barlow?

scope is a skywatcher 130p and camera is Sony alpha 290

[Cornelius Varley]

This is a common problem with reflectors, there is usually insufficient inwards focus travel to allow a camera to come into focus. The easiest solution is to use a barlow lens which will move the point of focus further away from the primary mirror and allow the camera to reach focus.

Peter

[barkis]

It seems you don't have enough in focus travel to allow an image at infinity to focus on the sensor of the camera, a common problem with Newts. You could move your mirror an inch or so further up the tube. Re collimation will be needed. Another remedy could be to fit a lower profile focuser, or you could try Afocal imaging, which requires adaptors to fit your camera plus lens, to close proximity to an eyepiece. The least desirable route I think.

Ron.

[Viv]

I had exactly the same problem & completely agree with Peter - use a barlow

[x6gas]

Or I believe on your scope you can unscrew the EP holder from the drawtube to reveal a thread that allows you to screw your t-ring directly on to the drawtube. This not only gives enough back focus it also provides a rock solid imaging platform with no troublesome lenses in your optical path.

[Vega]

I did the above too with my 250px. Unscrew the eyepeice holder and et voila! You have a low profile Adaptor that will screw to your t-ring

Matt

[valleyman]

The two threads above are correct. I phoned FLO about this problem and the solution is very simple

First Unscrew the 1.25 EP holder from the OTA Focuser. when it is off you will see a small thread. You then screw the T ring for the Camera onto that thread. Once that is done you attach the camera to the T RING in the normal way. By doing this you have moved the Camera much closer to the secondary mirror. the problem with this though is you can not use any filters for astro.

2nd solutuion is to buy a 2" nose adaptor frm FLO £19. this will allow 2" filters to be used. you then screw the T ring to this and attach the Camera.

Then remove the EP adaptor from the focuser and slip the 2" nose into the hole that is left and use the 2 screws to hold all in place. You do not need to have the 2" EP adaptor fitted.....It all goes straight into the Focuser

[RikM]

I use the 2" adaptor and an LPR filter. This made a dramatic improvement in my images compared to when I used the T-thread on the focuser tube. The filter allowed me to take longer subs and the 2" size reduced vignetting on the images.

[Shibby]

When I had a 130P, I still couldn't achieve focus (Nikon) even when screwing the T Ring straight onto the focuser. For me, only a barlow enabled me to focus. Be aware that a barlow doubles your focal length & magnification though; this means you need twice as much exposure to achieve the same brightness.