Getting back to the area of obstruction versus a diameter by diameter comparisons:

The Orion 170mm Mak has an obstruction 41mm in diameter

The ratio of areas is 5.82%....whereas the ratios of diameters is 24.1%. **This is a significant difference **

**What does this do to the Airy disc energy distribution patterns? How does the aluminum deposited coatings further destroy image contrast?**

**Lastly you have the number of surfaces with say 88% reflectivity versus the multicoated lens surfaces of *****98% transmission each....What is the final result? 88.6% for the triplet, 68.6% for the Maksutov.**

**88.6% of 140mm is 124.04mm**

**68.6% of 170mm is 116.62mm**

**Should I further substract 5.82% from the Maksutov but none from the Phantom? In that case 109.83mm for the Maksutov.**

**Light Gathering power will be 18.70x human eye for the Mak, 23.84x eye for the Phantom triplet. Final figure of 7.11" diameter for the 9.25" Celestron without the diagonal 50.64x LGP of human eye.**

***I don't know the actual values**

**Dan Kahraman**

***Calculation for Celestron 9.25"**

**Celestron 9.25 obstruction by area 13.12%**

**Transmission corrector plate 0.98*0.98=.9604**

Primary mirror and secondary mirror 0.96*0.96=.9216

**0.8851% of 9.25=8.19"**

**subtract 13.12%...7.11" without diagonal**

**Edited by LMcKeen, 07 December 2021 - 09:41 AM.**