From: "Jack Schmidling" 
To: 
Reply-To: "Jack Schmidling" 



----- Original Message -----
From: "Jerry B. Hillman" 

> I already have one. Because Polaris isn't very bright when viewed through
an
> uncoated mirror I couldn't really see the edges of my eyepiece Ronchi
lines.
> Not enough contrast.....

Forgot about that problem but now that you mention it, I had the same
problem testing my 16".

However, it's worth the effort to do it on a bright star just for the sake
of having another "opinion".

I would not think that your description of the image would be caused by
just a bad edge.  Make sure that you are working with only 2 or 3 lines or
the test is useless.

For what it's worth, my best view of Mars up to that point was about the
last time I had my 16" out before coating.   I could walk back and
forth
between it and my 10" and the difference was striking.  I don't think
the seeing has been that good here since then but such is life.

> For collimation, I have a laser collimator.....

Whatever works.  I happen to like my ET2 Autocollimator but anything should
get you close enough for the Ronchi test.

> Finally, an out of focus star image will show the secondary shadow. If it
> isn't centered, then something is wrong....

Not sure I follow.  If it's not centered, it's not collimated but let's get
bact to your star test....

You said the oof images were not round and this is what caught my
attention. Could you again describe your test.  Forget the infocus image
for now, it is too seeing dependent to be of any value if you can't get
past the oof test.

I just jumped into this and don't want to talk down to you so just a quick
review so I know where you are at.

> BTW - Those Easy Tester devices are pretty neat. I am intigued by the Easy
> Tester II.  I may buy one. It might make collimation easier....

Again, I do not wish to commercialize and will be happy to tell you how to
make one if interested but I can not live without it anymore.

Having said that, like all collimation devises, this only gets you close.
The final tweek must be done on a star.

js

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