Focusing problem Nikon D7000

[syoudM42]

Does anyone know why I cannot focus my Nikon d7000 DSLR on my telescope. The set up is a Skywatcher 150p explorer Newtonian 6" (older Blue coloured OTA) has the older style rack and pinion focuser. I have previously used  my older Nikon D5000 to image the Moon, Saturn and Jupiter with some success. It has been in focus with this for the lunar images mainly. However I have recently changed my set up. I changed the standard skywatcher eyepieces to Plossl eyepieces. I have fitted a skywatcher electric motor focuser. Its absolutely fantastic optically looking through the eyepieces especially since I upgraded to Plossl eyepieces, however the problems begin as soon as I introduce the DSLR to try and image what I have seen in the eyepiece.  

I have introduced a new camera a Nikon D7000. Since this time I have struggled to image and achieve focus.

I traditionally used a T mount with a lens correction holder to hold an eyepiece to focus through. I then tried doing it prime focus and still no joy. I removed the 1.25 adapter from the focuser tube on the telescope in an attempt to reduce the focal distance for the focal plain of the camera.  

Still no joy and I am getting rather annoyed. The focuser on the telescope is cranked right down to its lowest point and it is just still out of focus. I am presuming now its a focal plain problem with distance from the sensor of the camera and secondary mirror. I have tried using the D5000 again since and the focuser is right down close to the minimum of the focus tube on the mount of the telescope. I am aware skywatcher do a 150 PDS which has a shorter OTA thus shorter distance tube length between the primary and secondary mirrors. Is this the problem with mine, longer tube.

Could a low profile Crayford focuser solve this problem by bringing the DSLR closer to the secondary mirror. ???

I would be extremely interested if anyone else has had a similar problem and how they solved it as I am getting very frustrated.

[bogdog]

use a t-ring on dslr and get a barlow lens that screws into the t-ring,but remove lens from the barlow (using it as a xtension tube)

maybe this will bring you focus in prime

EDIT:

this barlow

http://www.firstlightoptics.com/celestron-eyepieces/celestron-2x-universal-125-barlow.html

can try with lens removed (black part at bottom unscrews) or leave on and try

[jambouk]

I'd have thought with a reflector, the problem is lack of inwards travel; use the barlow but leave the optics in it and that will bring the focal point outwards and make focusing on the sensor achievable.

James

[steppenwolf]

Could a low profile Crayford focuser solve this problem by bringing the DSLR closer to the secondary mirror. ???

The problem you have is a common one with this focuser but I am surprised that the D5000 works and the D7000 doesn't - I am sure that the mounting face to sensor is the same for both? However, a low profile Crayford focuser would allow you to reach focus (I use a Baader SteelTrack on my SW 250 for imaging). You could also consider using a Baader coma corrector as not only will this help you to achieve better images but it will also give you about 10mm of extra inwards travel - BUT you would have to have a custom adaptor made for it to fit your existing focuser (see below).

[Kropster]

Sounds like not enough inward travel..... the sensor can't get in to the focus point.

That is the thinking behind the 150 PDS....it has a shorter tube to allow the focus point to move out further, making DSLR photography possible.

[syoudM42]

Thanks everyone for replies. Thought it could be the focuser travel.