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HD11 First light with reducer -- what am I looking at?

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#1 tbirdz12

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Posted 08 March 2021 - 01:15 PM

Happy Monday..

 

Ok so I have a new HD11.. Reducer was backordered for 2 months.. I did try the scope with out it and no problems.. stars looked fine.

 

I try to put the reducer on and it will only screw on 1 revolution.. not cross threaded.. its like diameters don't match... so it feels strong enough to support camera so I try it.

 

Slew over to Regulus... and this appears in view... Its so odd looking and sharp along the edges and center that I don't think its an out of focus star so I didn't run through the entire focus range (should have in hind sight)..

 

Could this actually be the star way out of focus?

 

Specs say 146mm back focus from reducer which I have but thats probably assuming the reducer screws on all the way?

 

Any input is appreciated..

 

Ive contacted vendor regarding the reducer not screwing on all the way.

 

Thanks

Tim

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#2 pyrasanth

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Posted 08 March 2021 - 01:20 PM

Congrats on fitting the reducer.

 

What you are seeing is the star considerably out of focus, The reducer considerably changes the focus position of your optical system- all you need to do is refocus with the focus knob and you will be back in business. There is nothing wrong and this is expected.

 

If using an Edge HD system your back focus has not been altered however the point of focus has so you will need to move your main mirror with the focuser knob.

 

Are you sure you have the right reducer?- there are models for the Edge HD and the standard C11- make sure your reducer is designed for your optical tube- it should screw on more than 1 thread- this is an issue you need to resolve with your dealer.


Edited by pyrasanth, 08 March 2021 - 01:23 PM.


#3 tbirdz12

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Posted 08 March 2021 - 02:16 PM

Congrats on fitting the reducer.

 

What you are seeing is the star considerably out of focus, The reducer considerably changes the focus position of your optical system- all you need to do is refocus with the focus knob and you will be back in business. There is nothing wrong and this is expected.

 

If using an Edge HD system your back focus has not been altered however the point of focus has so you will need to move your main mirror with the focuser knob.

 

Are you sure you have the right reducer?- there are models for the Edge HD and the standard C11- make sure your reducer is designed for your optical tube- it should screw on more than 1 thread- this is an issue you need to resolve with your dealer.

Ok Thanks... thats wild its so sharp out of focus that much...   The reducer says EdgeHD 11 on it so I hope thats correct.... lol.

I appreciate the quick response!!



#4 carolinaskies

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Posted 08 March 2021 - 02:27 PM

Happy Monday..

 

Ok so I have a new HD11.. Reducer was backordered for 2 months.. I did try the scope with out it and no problems.. stars looked fine.

 

I try to put the reducer on and it will only screw on 1 revolution.. not cross threaded.. its like diameters don't match... so it feels strong enough to support camera so I try it.

 

Slew over to Regulus... and this appears in view... Its so odd looking and sharp along the edges and center that I don't think its an out of focus star so I didn't run through the entire focus range (should have in hind sight)..

 

Could this actually be the star way out of focus?

 

Specs say 146mm back focus from reducer which I have but thats probably assuming the reducer screws on all the way?

 

Any input is appreciated..

 

Ive contacted vendor regarding the reducer not screwing on all the way.

 

Thanks

Tim

 

 

 

Sounds like you have the wrong reducer or the threads are defective as the threads should match up and thread at least 4 complete revolutions.  First inspect the threads on the back of the telescope to see that there are no burrs, then do likewise on the female threads of the reducer.  If no burrs then likely there is a defect.  Do try when putting the reducer on to rotate counter clockwise to feel when the threads are aligning then move slowly forward, but do not force the threading it should smoothly engage. 

The image you show is of course an out of focus star.  You can check the backfocus(5.75") by threading on the visual back to the reducer and then your diagonal. Try an eyepiece and see if the star focuses, and you can use a barlow tube(without the lens in it) as a spacer and see if the star gets smaller as you move the eyepice further up. If it does not then the primary is definitely in the wrong position and you need to turn it counter clockwise until you see the image start to decrease into a point.  Distance of backfocus alters the quality of the image more than the focus point if you are need the specification distance. 



#5 Umasscrew39

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Posted 10 March 2021 - 06:44 AM

Tim

 

You should post a picture of your optical train with the reducer on and mark where you calculated the 146mm backfocus.  It will make it much easier for us to help.  The reducer and scope baffle have many threads but sometimes it is hard to connect the reducer due to the metal on metal connection, especially when it is cold, or it may not be aligned correctly.  

 

Bruce




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