Thin T-adapter

[zelonisv_bob]

My Rebel t1i cannot reach focus for prime imaging.  Without using a tele-extender and an extension tube, my focuser at maximum inward travel appears to fall just shy of being able to focus an image on the camera's sensor.  I currently use a Celestron T-adapter which is 11mm. thick.  I probably need an adapter of 5mm or less.  Do any of you know of such a thin adapter.  By the way, I've found a source for the Baader Ultra Thin (2mm) that costs in the vicinity of $89, more than I'd like to spend.  Also, I'm confused about the metric thread and pitch options.  Suggestions would be appreciated.  

[astroman133]

As I suggested when you posted to the other thread, you should investigate moving the primary mirror upward, closer to the secondary mirror, in the optical tube. That should allow you to focus the camera without needing a different T-adapter.

 

The typical T-ring is screw mount using a male 42×0.75 (42 mm diameter, 0.75 mm thread pitch) metric thread.

[s3igell]

Before spending that money, you really want to Confirm that you will be able to Reach Focus if only you could shave off those additional 9mm (Celestron T-Adapter minus Baader Ultra-Thin 2mm).

 

The easiest way to do this is to use a Sheet of Paper to identify the Focal Point for your Newt:

1) Aim your Newt at the Moon using an Eyepiece or the Finderscope.  And make sure that your Mount is Tracking.

2) Remove the Eyepiece.

3) Hold a Sheet of Paper over the Focuser Drawtube, and move In-Out until the Projected Moon is in Sharpest Focus.

4) Measure the Distance between the Paper and the Top of the Focuser Drawtube.

 

Hopefully that is toward the higher-end of your 11mm range, so that with the Baader Ultra-Thin you will still have a bit of Focuser Travel in order to Perfect your Focus.

[s3igell]

As I suggested when you posted to the other thread, you should investigate moving the primary mirror upward, closer to the secondary mirror, in the optical tube. That should allow you to focus the camera without needing a different T-adapter.

 

The typical T-ring is screw mount using a male 42×0.75 (42 mm diameter, 0.75 mm thread pitch) metric thread.

This Option should be investigated, but...

 

Most News have a Solid Tube with a Solid Mirror Frame that provides ONLY a few MM of Travel on the Collimation Screws.

Anything else requires Disassembly and PRECISION CUTTING of the Scope Tube and Accurate Drilling of New Mounting Holes.

Quite the Undertaking to simply Save the existing T-Adapter.

[astroman133]

I was not suggesting that he modify the mirror mount/optical tube in any way. Simply to move the mirror as high as possible while maintaining collimation.

[zelonisv_bob]

Thank you all for your advice.  I realize that moving the primary mirror forward would work, but after rebuilding my Newtonian scope, I spent many, it seemed, frustrating hours collimating it.  Until the memory of that process fades away, I'll continue using the 2X tele-extender and extension tube.  Next chance I get, I'll do that projection of the Moon on paper to see exactly where the focal plane is for my 10" f/4.5 mirror. 

[jimwc6491]

Check out this website they have a lot of camera, "T" adapters etc. you might find something in your price range.

this link takes you to there extension section, but they have lots of other adapters that might work.

I have used some of there adapters and they are of high quality.

 

https://www.telescopeadapters.com/26-extension-tubes