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False light on 10" RC Truss

Reflectors Troubleshooting
Ritchey Chretien telescopes GSO Family •6 replies•669 views
Jose Carballada avatar
Jose Carballada avatar
Just I checked my truss and I saw some false light to the sensor.

Any of you did you observe something like this on your tube?
Probably I will try solve this problem enlarging the baffle tube on the front end using a strip of self-adhesive black velvet.
What do you think, is it better to applied this solution on the baffle tube of the primary or the other one at the secondary one?

The problem is like it is described on http://interferometer-tests.blogspot.com.es/2013/06/2542000-10-ritchey-chretien-gso.html

and looks like this

   
Frank Breslawski avatar
Frank Breslawski avatar
Hi Jose,

this seems to be a known problem of the bigger RC scopes. Here is an interesting (German) link where this is described and also a solution by the vendors was published (http://forum.astronomie.de/phpapps/ubbthreads/ubbthreads.php/topics/1271364/Re:_Serienfehler_bei_GSO_RC_14). A new blend ring is necessary to solve that.

Best
Frank
Concise
Jose Carballada avatar
Jose Carballada avatar
Frank Breslawski:
Hi Jose,this seems to be a known problem of the bigger RC scopes. Here is an interesting (German) link where this is described and also a solution by the vendors was published (http://forum.astronomie.de/phpapps/ubbthreads/ubbthreads.php/topics/1271364/Re:_Serienfehler_bei_GSO_RC_14). A new blend ring is necessary to solve that.

Best
Frank

Thank you Frank, very good info from there.

They are discussing about the bigger versions of this tube but I am sure it's applicable on my 10" too.

I will try to reduce the size of the baffle tube like them. First I need some measures of the current baffle and I will take the decision of how much reduction I want to do.
I doubt the vendor has a solution for 10", I will contact them.

These pictures are so interesting.


8)
Jose Carballada avatar
Jose Carballada avatar
Ok, I started the tests with one temporal reduction to the tube.

On my 10" the baffle is 77mm outside, 73 mm inside and need to reduce 10mm in each side to not see the reducer inside de focuser.

I used foam to prepare the reduction and some tape to fix for test purposes.
Today is windy, 30 km/h with peaks of 80 km/h......  I will test it other day with real stars, maybe later I will take some flats.

 
  
 
Jose Carballada avatar
Jose Carballada avatar
Some great news after to take flats!!!!
Now I understand a lot of things....

These are the flats after pass the script FlatContourPlot in PI  (with the luminescent panel close to the front of the telescope):

before to correct the baffle


and after the correction


An additional info: now for obtain the same 13.000 ADU I need multiply by 2 the exposure time...

I think is not necessary to add any additional info here. 

Maybe only one conclusion? is it  not possible to use this tube with bigger sensor? what happen if I need to increase the new baffle aperture from the current 53mm to the original 73mm to avoid vignetting? is it impossible to avoid the reflections with the reducer??? this is something to consider.

also I added here the link to the flat stretched with PI

before correction


after baffle correction
Jose Carballada avatar
Jose Carballada avatar
Last test with real data.

without the corrector ring (look the reflection ring from TYC1472-613 on top of the image)


now the reflection ring is less important
Frank Breslawski avatar
Frank Breslawski avatar
A clear difference! Good work from you. But to be honest, I would expect from the vendors to deliver a spare part for free. In the end it’s a construction failure…

Frank