Free Optical Testing for Telescope Mirrors
What started as an experiment became a fixture. We test Newtonian parabolic mirrors up to 18 inches free of charge, and email you the peak-to-valley error and Strehl ratio.
Free testing is paused. We are not accepting mirrors while the shop moves to Fresno. We intend to resume during 2027; the date is not set yet. Optical coatings return first, in January 2027.
What you get
Your mirror is measured on our computerized test system. You get an email report giving the peak-to-valley wavefront error and the Strehl ratio. We then repack the mirror and ship it back.
Strehl is the fraction of light the optic puts into the theoretical diffraction pattern. 0.80 is the threshold usually quoted as diffraction limited.
What it costs
The test is free. You pay return shipping at the carrier’s rate, plus $10 for packing materials and handling. Your return address must be able to receive UPS or FedEx — no PO boxes.
How to send a mirror in
These are the steps as they will work when testing restarts. Requests go through the customer portal instead of email and a printed form.
- Request a test in the portal, giving the mirror’s diameter and focal ratio.
- Wait for us to confirm. We control how many optics are in the building at once. Ship within a couple of days of that confirmation.
- Print the box sheet and put it in the carton. It carries your job number as text and as a scannable code.
- Enter your tracking number in the portal when the box goes.
- We contact you when the mirror arrives and again when it ships back. Expect one to two weeks in-house.
Please read how we want optics packed before you box anything.
Questions
Is the free test running at the moment?
No. It is paused while the shop moves to Fresno. We intend to resume during 2027; the date is not set yet.
Is the test really free?
Yes. You pay return shipping and the $10 handling charge, nothing else, and there is no obligation to buy anything.
What if my mirror tests badly?
We send you the numbers either way. Plenty of mirrors measure worse than their owner expected and still do everything that owner needs.
How long does it take?
About one to two weeks in-house, plus transit each way. We email you when your mirror arrives and again when it ships back.
Why do you do this for free?
It started as an experiment and became a fixture. Most amateurs have no way of measuring what their optic actually does.