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[August 21st, 2017]
Orion XT8, Celestron 102mm f/10, 62mm Mayflower
10x50, and 16x32 binos
10" OO VX, 6" iOptron Mak-Cass, Orion 100ED
Quote:Mitch, the only thing I can think of off hand right now is dew. Since I have owned my Dob I can recal 2 times this has happened to me.
1. I was out viewing for about a hour and 45mins "Dob was out for a good hour before viewing" fan on the whole time. I viewed Saturn "good and sharp" then I went off viewing some DSO's. I was using filters at this time and started to notice my viewing wasn't that great "after 1 hour and 45mins" so I took my filter off and went back to Saturn. I get Saturn back in view and I was like "what?" Saturn was glowing/halo like fuzzy white. So I looked down fan was unplugged, lol. it's so dead quite around here I can hear the fan, but I had my ear phones on and didn't even notice it was unplugged. So I took my EP out and with a light looked at the secondary "Dew" looked down the tube "Dew" so I called it a night.
2. I will not go in detail with this one. but samething started to happen when I was out viewing. I looked down "fan was plugged in" I looked down the tube, primary was fine.. took the EP out to check the secondary "DEW" I was like "really??" so I packed it up for the night. I did check the bat's and they were very low.
All in all I never had any problems but those 2 times. But from what you are saying sounds close to my experience that I had. If it happens again check for dew on both.
Quote:yeah, the only thing worse than dew is frost! yep i've had a frosted over scope before. here is an awesome picture of one of my dob's i traded to a friend that was out too long in the cold at our dark site this past january. http://sanjoseastronomy.blogspot.com/2013/01/dedicated-astronomers.html
First and foremost observing love: naked eye.
Last but not least, telescopes.
And I sometimes dabble with cameras.
Quote:It's entertaining to hear you Californians chat about frost as though it's something exotic. To me, the only "awesome" thing about that photo is that the telescope is, for all practical purposes, frost-free. Its a rare winter night for me when the tube has that little frost at the time I decide to knock off for the night.
Quote: The worst problem is that sometimes at altitude, a low cloud forms, probably radiation fog. There will be a wind so it can be perfectly clear one minute, three minutes later, it's fogged over and everything is dripping wet, 4 minutes after than it's clear again but by the time the scope is dry enough to use, it closed out and dripping again...
Who you jivin' with that Cosmic Debris? "all science is either physics or stamp collecting" -- Lord Rutherford
Money can't buy happiness, but it sure makes living with misery a lot easier!
Quote: I've found my truss shroud soaking or frosted on nights where it was way above dew (or frost) point. Please elaborate more on "radiation fog"
Rob Astronomy compels the soul to look upwards and leads us from this world to another..... Plato
Quote:Yeah Mitch, it has to be dew. I had the same thing in June when the club had the outreach. Called it a night real quick.
I only had my dob out during the winter to get just a light frost on it. That was enough for me and I packed things up and called it a night. It was down to the 20's.
Quote: Quote: I've found my truss shroud soaking or frosted on nights where it was way above dew (or frost) point. Please elaborate more on "radiation fog" My elementary understanding is that Radiaton fog is fog that forms in a low lying place and forms because the ground cools from radiation. Radiation Fog Jon
Quote:The description of 'white chromatic aberration' is very suggestive of spherical aberration. A prominent 'fuzz' extending less than a planet diameter does not seem like fogging; dewing up has more of the effect of overall dimming the image.How does the scope perform at other times? Or is this a new scope?If the indoors and outdoors temperature are rather similar, there should be no need to run a fan.
-- Matt -observing since fall 2012 16" F/4.5 truss DOB / EON 120mm ED / 10" F/5 strut DOB Paracorr (T1 tunable),telrad, RACI finders, AltAz Tripod mount ES 82° 4.7,6.7,8.8,30mm AT Paradigm 60° 25,18,12mm Pentax XW 70° 20,14mm , Baader zoom observing list/notes.. beginning dslr astrophotos (moon/widefields)
Quote:The description of 'white chromatic aberration' is very suggestive of spherical aberration. A prominent 'fuzz' extending less than a planet diameter does not seem like fogging; dewing up has more of the effect of overall dimming the image.
I ache, therefore I am
Happy owner of-- A Mag 1, 12.5 inch Porta Ball A Dual Axis Equatorial Platform A PST Double Stack
Quote:It sounds like dewing of the secondary mirror, or both the primary and secondary mirror.
Quote:The backyard was pretty dark for once, so I figured it was a good time to take the Dob out to see what was causing my problems. As soon as I brought it outside, I watched the primary turn to dew instantly.
Quote:it happened because your air conditioner is turned lower than the outside dew point. Keep the air conditioner set higher or store the scope in a place that isn't air conditioned.
Quote:Quote:it happened because your air conditioner is turned lower than the outside dew point. Keep the air conditioner set higher or store the scope in a place that isn't air conditioned. I was told if the inside temperature is close to the outside temperature, there would be virtually no need for cooldown and use of the fan. Since my house remains at 77 F and outside temperatures at night are roughly 79 F I didn't think the difference would be so dramatic. I'm probably going to store my Dob on the lanai from now on, to avoid this.
Orion XT8 Pentax
It's a long night and tell me what else were you gonna do...
Quote:Was your scope right near a vent? Air coming out of register is much colder than rest of the house.
Quote:Temperature is only one parameter to dew, the other is humidity. The RH in an air conditioned room normally is around 50-60%. There is a big difference in RH (aka driving force) if you bring it outside at 80-90%RH even at the same ambient temperature. shien