Not sure if its been mentioned in the pages of science homework here, but Stellarvue already did their homework on this.
As Jim says its not about a single scope, nor single manufacturer. But, we need to be accurate when describing this. My sense is that things were not as you say - "StellarVue already doing the homework". Rather, they scrambled to stop the bleeding when presented with deficiency in design of their "flagship" telescope. In other words, it was damage control.
From their website:
In the summer of 2023 based on customer requests we implemented a slight change in our process to move the final optical correction toward the middle of the visual spectrum. During the spring of 2023 we tested this process extensively to ensure that photographic performance would not be compromised due to this change. Both red and green figured, high-Strehl SVX objectives delivered the same excellent color correction free of the dreaded "blue bloat." Since most of our customers are imagers, it was important that we took the time to test the results before we implemented this change. Based on our findings, we modified our final spherical correction slightly to ensure that our objectives are now most accurate in green light.
This is totally marketing. The verbiage on the website has changed perhaps a dozen (or more) times on this very subject. At one point, it was a cornucopia of buzz words strung together that made little sense to anyone with even elementary knowledge of optics and light. Its unlikely they (StellarVue) performed "extensive testing" to insure that nulling in green would not cause any untoward issues. Some of the world's best refracting telescopes used as astrographs from Takahashi and Astro-Physics have been best corrected in the green and green-yellow for decades. Nulling in green is a well known tenet in optics that leads to best performance in both visual and photography. If StellarVue would have user-tested this scope visually on objects a large APO is meant to resolve - the planets - this would have been obvious even to the novice when comparing it to a scope more neutrally corrected.
From a personal perspective, Guys/Gals, we need to stop romanticizing this. It was not a natural evolution of the StellarVue design. It was a forced change the market demanded after amateur testing uncovered the issue. This might not sound good on a company website but that's precisely what happened. An evolution of design is a positive and iterative process of self-improvement using information gleaned from internal R/D where incremental changes make the product better. This is not what happened here. Rather, its somewhat analogous to the Ford Pinto and it was made worse by the manufacturer taking a tough stance toward the client and the test and attempting to discredit the tester. Then the usual StellarVue apologists piled on.
At the end of the day until we, collectively, stop glamorizing what was an operational screw-up, we'll continue to have these arguments and I'll politely continue to call out folks who try to impart their version of reality into the discussion - and this includes StellarVue. Often, the best thing to do is admit it, fix it, and move on. Not sugar-coat what was, largely, a self-inflicted issue with flowery gobbly-gook type of language.
EDIT: I also recall someone mentioning last time this came up that most places use red lasers simply because they are much cheaper than green in the quality level and power needed for the process.
That was me, HERE and HERE. And its a good point in which to re-visit.
Red lasers are less expensive overall and work better in interferometry as their light is coherent over longer distances and their wavelength fluctuation is less when compared to green lasers. Red is the standard in business and industry as the most surfaces being measured are reflective and the results can be scaled to any wavelength (color) using Algebraic expressions. When measuring lenses, there is no easy way to scale the results between different wavelengths. Red is also most common in the ZYGO brand of interferometers that have become the standard by which others are measured.
Edited by peleuba, 24 July 2024 - 01:45 PM.