My pleasure, I'm honored someone would be using my small App 
It's been a while but I don't think I went back and "fixed" a startup issue where the Dew point is 50 until the first actual reading is made.
To report Dew Point I created a Virtual Dew Point device. No inputs are needed it is only used to display the results.
/*
Dew Point App V003
2020-07-05
Think we don't need to store the lastTEMP and lastHUMID. We can just read them when we need to make a calc.
2020-07-20 (open) added Virtual DewPoint Calc device to display the below results.
*/
definition(
name: "DEW Point Calculator",
namespace: "hubitat",
author: "JohnRob",
description: "DEW Point Calculator",
category: "Convenience",
iconUrl: "",
iconX2Url: "")
preferences {
page(name: "mainPage")
}
def mainPage() {
dynamicPage(name: "mainPage", title: " ", install: true, uninstall: true) {
section {
//log.debug (" 25 beginning of section")
input "thisName", "text", title: "Name this DEW Point Calculator", submitOnChange: true
if(thisName) app.updateLabel("$thisName")
input "tempSensor", "capability.temperatureMeasurement", title: "Select Temperature Sensor", submitOnChange: true, required: true, multiple: false
input "humidSensor", "capability.relativeHumidityMeasurement", title: "Select Humidity Sensor", submitOnChange: true, required: true, multiple: false
//log.debug (" 30 end of section")
} // section
} // dymanicPage
} // mainPage
def installed() {
initialize()
}
def updated() {
unsubscribe()
initialize()
}
def initialize() {
//log.debug (" 45 begin initialize")
def dewpointDev = getChildDevice("DEWPoint_${app.id}")
if(!dewpointDev) dewpointDev = addChildDevice("hubitat", "Virtual DewPoint", "DEWPoint_${app.id}", null, [label: thisName, name: thisName])
dewpointDev.setDewPoint(0)
subscribe(tempSensor, "temperature", handlerTEMP)
subscribe(humidSensor, "humidity", handlerHUMID)
state.lastHUMID = 50 // these are in the app and will not display in the child
state.lastTEMP = 50 // 50/50 DEWPoint = 32
}
def calcDEW() {
def dewpointDev = getChildDevice("DEWPoint_${app.id}")
//log.debug " 56 state.lastTEMP ${state.lastTEMP}"
//log.debug " 57 state.lastHUMID ${state.lastHUMID}"
operandHUMID = state.lastHUMID.toDouble()
operandTEMP = state.lastTEMP.toDouble()
def dewPoint = (operandTEMP - (9 / 25) * (100 - operandHUMID))
//log.debug " 62 dewPoint = ${dewPoint}"
dewpointDev.setDewPoint(dewPoint.toInteger())
//return
}
def handlerHUMID(evt) {
state.lastHUMID = evt.value
//log.debug " 65 last Humidity = ${evt.value}"
calcDEW()
}
def handlerTEMP(evt) {
state.lastTEMP = evt.value
//log.debug " 71 last Temperature = ${evt.value}"
calcDEW()
}
// --- eof ---
//tempSensor.currentTemperature
//humidSensor.currentHumidity
