Focus issues with a Newtonian/DSLR & Baader 1.25

[Galactic Wanderer]

HI all, 

Quick query about attaching a 1.25 inch Baader UHC filter to (f5) newtonian - camera does not achieve focus. It looks to be due to the lack of focus travel, particularly being f=5. Ideally do not want to use a barlow, but if this is the only way to get any sort of result then am happy to give it go. 

Currently using a 1.25 to 2 and t 1.25 adapter, greatly increasing the distance between the focuser and the camera. Any way of potentially reducing this? 

Best, 

GW 

[ONIKKINEN]

Just how long is your adapter train, can you grab a picture of the setup with the camera attached?

[Kon]

Unscrew the 1.25 to 2 adapter nosepiece and screw your camera with a T-ring to it. I can achieve focus with my DSLR and 200P this way.

[Galactic Wanderer]

On 23/02/2024 at 14:07, Kon said:

Unscrew the 1.25 to 2 adapter nosepiece and screw your camera with a T-ring to it. I can achieve focus with my DSLR and 200P this way.

This is how I normally attach but 1.25 UHC filter adds the complication 

[Galactic Wanderer]

On 23/02/2024 at 13:52, ONIKKINEN said:

Just how long is your adapter train, can you grab a picture of the setup with the camera attached?

T-ring to Celestron 1.25 adapter (which UHC filter screws into), then 1.25 back to 2 adapter. 

Edited March 27 by Galactic Wanderer

[carastro]

Bit late now that you have spent the money, but wouldn't a clip in filter have been better rather than this 1.25 to 2" arrangement which is extending the distance.  Assuming they do a clip in UHC filter.  I used to use a CLS clip in filter.  

Edited March 27 by carastro

[Carbon Brush]

Yes the camera is much too far away from the scope.

As a daylight test, point your scope at a distant object.
Get rid of all the 2" & 1.25" stuff.
Wave your camera (with live view) in mid air above the focusser.
When you see a focussed image, you have a measure of how much/little adapter train is permissible.
This will guide you on what components are allowed.

I have used this technique on various scopes (newt, Mak Newt & frac) to get a feel for the size of the problem.
In some cases it has meant rummaging in my bits box for the correct spacers/adapters. Hopefully this is the case for you.
In one case it justified the purchase of a lower profile focusser!

If you find you are only looking for a couple of millimetres, look at the main mirror fixings.
Moving the mirror up the tube a little will push focus out.
Depending on the scope, you have to go a long way to make the light spill over the secondary to any extent.

HTH, David.

 

[woldsman]

You can get a lower profile T-ring (the one you have adds the standard 11mm to the 44mm distance to sensor on the DSLR to yield 55mm back distance).

eg https://www.rothervalleyoptics.co.uk/baader-ultra-short-t-mount-canon-eos.html?gad_source=1&gclid=EAIaIQobChMI6_DftrWUhQMVHpFQBh2SbgZSEAQYASABEgKtYfD_BwE

You probably have alternatives to the Celestron adapter  (if the 1.25 filter is screwed in here) which is occupying a lot of space.

Finally, if you could share a picture of the scope itself there may be options there to reduce the focus distance as part of the focuser unit may unscrew. 

+1 to daylight testing - always a great place to start.. 

Edited March 27 by woldsman

[Galactic Wanderer]

5 hours ago, Carbon Brush said:

Yes the camera is much too far away from the scope.

As a daylight test, point your scope at a distant object.
Get rid of all the 2" & 1.25" stuff.
Wave your camera (with live view) in mid air above the focusser.
When you see a focussed image, you have a measure of how much/little adapter train is permissible.
This will guide you on what components are allowed.

I have used this technique on various scopes (newt, Mak Newt & frac) to get a feel for the size of the problem.
In some cases it has meant rummaging in my bits box for the correct spacers/adapters. Hopefully this is the case for you.
In one case it justified the purchase of a lower profile focusser!

If you find you are only looking for a couple of millimetres, look at the main mirror fixings.
Moving the mirror up the tube a little will push focus out.
Depending on the scope, you have to go a long way to make the light spill over the secondary to any extent.

HTH, David.

 

5 hours ago, woldsman said:

You can get a lower profile T-ring (the one you have adds the standard 11mm to the 44mm distance to sensor on the DSLR to yield 55mm back distance).

eg https://www.rothervalleyoptics.co.uk/baader-ultra-short-t-mount-canon-eos.html?gad_source=1&gclid=EAIaIQobChMI6_DftrWUhQMVHpFQBh2SbgZSEAQYASABEgKtYfD_BwE

You probably have alternatives to the Celestron adapter  (if the 1.25 filter is screwed in here) which is occupying a lot of space.

Finally, if you could share a picture of the scope itself there may be options there to reduce the focus distance as part of the focuser unit may unscrew. 

+1 to daylight testing - always a great place to start.. 

Thanks both, super helpful and definitely confirmed what I originally thought. I don't have that much to play with in terms of mm adjustment, I'm adding a good few cm from where it's usually focused. I'm a bit short on these sorts of adapter bits and pieces haha. I think to Woldsman's point, the Celestron adapter can be knocked off entirely. Something in this sort of vein (I think) slots straight into the 1.25 to 2, removing a good 3-4cm from the train. https://www.ebay.co.uk/itm/313079134159?chn=ps&_ul=GB&_trkparms=ispr%3D1&amdata=enc%3A1gusBRbbUSuyKRR5DawI74A53&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&mkscid=101&itemid=313079134159&targetid=1647205088280&device=c&mktype=pla&googleloc=9045888&poi=&campaignid=17206177401&mkgroupid=136851690655&rlsatarget=pla-1647205088280&abcId=9300866&merchantid=137597110&gad_source=1&gclid=CjwKCAjwh4-wBhB3EiwAeJsppHXkI0oCw1jhJVWragnd5W1E7_y0sXrbjXFAChpFbCwc3mnE7BsVExoC_P8QAvD_BwE

[bottletopburly]

On a stock 200p the 1.25 “ adapter unscrews from the base part , you can then screw into your T adapter and that’s all you need to achieve focus