Allan
16-01-2014, 01:19 PM
I have had my XT12g for almost a year now. In that time I have never achieved a good star test with it. The diffraction rings were always blurry, uneven, rough and were not round. I have a Ronchi eyepiece and the image in that was a bit ragged as well, the only error I could see was an over corrected mirror.
I was getting poor planetary views out of the scope as well. Eventually I got so frustrated with it that I put in an order with Carl Zambuto for a new mirror. Now, I don't have the mirror yet, but I thought I should at least spend some money on the secondary mirror to compliment my new primary. So I ordered a 1/30 wave secondary from Antares.
The original secondary was attached by double sided tape, which is not ideal. I installed the new mirror in the accepted way, with 3 drops of silicon, and used wooden skewers to keep an air gap between the mirror and the stalk while the silicon cured.
So last night I used the new secondary for the first time and the improvement it has made to the telescope is like night and day.
The star test looked totally different. The diffraction rings are now sharp and round. The lines in the Ronchi eyepiece are now razor sharp. The pattern was very easy to read and clearly showed a turned down edge.
But importantly, I turned the scope to Jupiter and it showed a world of detail like I always thought I should see in a 12" but haven't until now.
Obviously something was not right with either the original secondary, or the way it was attached to the stalk. The cost of the new secondary now seems like a small price to pay for the huge improvement it has made. I am still going to fit the Zambuto when it is ready. I'm sure it will show a nice improvement over the original primary, considering as well that I can see it has a turned down edge and is slightly over corrected.
I pass this on out of interest and also for those who have similiar scopes that may be experiencing the same problems that I have had.
I was getting poor planetary views out of the scope as well. Eventually I got so frustrated with it that I put in an order with Carl Zambuto for a new mirror. Now, I don't have the mirror yet, but I thought I should at least spend some money on the secondary mirror to compliment my new primary. So I ordered a 1/30 wave secondary from Antares.
The original secondary was attached by double sided tape, which is not ideal. I installed the new mirror in the accepted way, with 3 drops of silicon, and used wooden skewers to keep an air gap between the mirror and the stalk while the silicon cured.
So last night I used the new secondary for the first time and the improvement it has made to the telescope is like night and day.
The star test looked totally different. The diffraction rings are now sharp and round. The lines in the Ronchi eyepiece are now razor sharp. The pattern was very easy to read and clearly showed a turned down edge.
But importantly, I turned the scope to Jupiter and it showed a world of detail like I always thought I should see in a 12" but haven't until now.
Obviously something was not right with either the original secondary, or the way it was attached to the stalk. The cost of the new secondary now seems like a small price to pay for the huge improvement it has made. I am still going to fit the Zambuto when it is ready. I'm sure it will show a nice improvement over the original primary, considering as well that I can see it has a turned down edge and is slightly over corrected.
I pass this on out of interest and also for those who have similiar scopes that may be experiencing the same problems that I have had.