Test your optics.

I have often wondered how good the optics are on my budget scopes.
I have a number of scopes(4) all budget off the shelf Chinese made and the best
I could find is that they are sold as diffraction limited, which is ¼”wave, and
I accept this figure. But it has been niggling me to know if there is a way to test
this myself.

I stumbled across this software Winroddier see tech.groups.yahoo.com/group/roddier/files/
whilst browsing Cloudy Night forum sometime ago and decided to give it a try.

It took me a while to figure it out as I’m not great with new software but having
joined the Yahoo group and downloaded the cook book it’s quite straight forward.
I do things slightly different form the cook book, so if interested just ask, but
if you want to know any tech stuff join the group and ask the experts

Anyway here are the test results for my Celeston 100mm F9 ED refractor scope.
This is just a screen shot I can post individual photos if need be..

Just one other thing, I know some of the top telescope makers will give a certificate
of quality but most don’t and I find it strange that we have to search and search
and read reviews by others to help us decide, sure to God if you want to sell
your product and you could stand over the results why not post them. Rant over.




Tony

Prior to asking this, be gentle, I'm not an optics expert...

Isn't a Strehl ratio of 0.964 ptetty good, even for a mid range scope? If so, it would be pretty darned good for a budget 'scope.

Yes Dave, 0.964.in my reckoning is very good and I was very pleased with the out come,
I ran the test three times and got similar results, I got 0.97, 0.967 and 0.964 the only
thing I changed was the image size. The first test was actual size no crop and the other
two I reduced the image size in both cases, which I think had an effect on the out come, but
I’m not sure ??

Tony

thanks for that Tony, it will be interesting to run this on my scopes and see what it comes up with.