Owner of Meade LX90 8-Inch f/10 ($1,299) Reviews 16-Day Forecast, Detects 47-Minute Clear Window at 3 AM Tuesday

PORTLAND, OR—With his Meade LX90 8-inch Schmidt-Cassegrain f/10 ($1,299) stored in a Pelican 1780 transport case beside a dew heater controller he has never connected, and a sixteen-day forecast spreadsheet open across eleven tabs showing a projected SQM reading of 19.8 mag/arcsec² over his Bortle 5 backyard during a 47-minute photometric window beginning at 3:14 AM next Tuesday, Portland resident Derek Voss has concluded that conditions are probably marginal anyway.

Voss purchased the LX90 fourteen months ago. The telescope has since been collimated four times—the third collimation notably cleaner than the second—and transported to the driveway on six occasions. Total tracked exposure time stands at eleven minutes, of which nine capture the roofline of the adjacent property following a miscalibration of the AutoStar controller that Voss describes as "a known issue with the v43 firmware I've since patched."

The go/no-go workbook cross-references Clear Outside, Astrospheric, and the NWS hourly ensemble model, weighting scores across five variables: seeing, transparency, humidity gradient, dew point spread, and what Voss labels "personal readiness coefficient," currently set to 0.4 following an incident last month in which he fell asleep before astronomical twilight ended. Tuesday's window scores 6.8 out of 10. Voss's self-imposed go threshold is 7.0.

"Technically it's a no-go," he said. "But Clear Outside's seeing confidence interval is ±0.3 arcseconds at that forecast range, so you can construct a scenario where it clears 7.0. I'm leaving it as a conditional pending Thursday's model run."

The conditional has been in that state for five weeks.

The LX90's 2032mm focal length is, Voss notes, the fundamental constraint. A consequence of the f/10 optical design, it demands seeing below 2.0 arcseconds before planetary image scale justifies any of this—a conclusion he reached in a separate nine-page document comparing the f/10 SCT against an f/6 Newtonian he does not own. That document established that Antoniadi I conditions occur approximately four times per year over Portland, and that on three of the four qualifying nights in the past fourteen months, Voss was traveling for work. The fourth night he was home but had set the go threshold at 7.2 following a run of poor forecasts he was attempting to filter out.

The folklore holds that weather is the variable, and patience is the strategy. The folklore has not reviewed Voss's data.

What the data shows: 22 candidate sessions identified, 9 with equipment prepared, 2 with observation attempted, 0 rated acceptable for archiving. On both attempted sessions, the LX90's periodic error—±12 arcseconds as measured by PHD2 over a 10-minute calibration run last September—introduced trailing that disqualified every frame at pixel level. Voss has since sourced a Celestron CGEM II mount he is researching as a replacement, its published PE spec of ±10 arcseconds representing what he characterizes as a meaningful improvement, pending independent verification from CloudyNights.

"There's a 2-hour, 11-minute window the following Thursday at 7.3," he said. "But that's contingent on a system sitting off the coast. 16-day confidence drops off a cliff past day 9. I'd rather wait until I have a reliable 5-day picture."

The LX90 itself is in excellent condition. Voss confirmed this during a tour of the storage shed where it winters, opening the Pelican case to display a primary mirror last cleaned in December with distilled water and lens-grade tissue. The star diagonal was recently replaced with a Baader Zeiss Mark III ($199) following a CloudyNights thread attributing contrast loss to the stock diagonal's dielectric coating. The improvement has not yet been observationally confirmed but is generally accepted in the literature.

At press time, Voss had adjusted the personal readiness coefficient to 0.55 in anticipation of an early night Monday, and had opened a twelfth tab in the workbook for mount comparison.