Dome Seeing In Your Observatory

[herbhighstone]

Hello to all the folks --

I highly recommend that you search Google for " dome seeing observatory " . You'll find some extremely practical information about how to improve your local seeing by building your observatory in the right way.

"Dome seeing" is a degradation of your telescope's image quality because of various problems near and inside your observatory. A lot of it is caused by items that store heat such as concrete floors, heavy metal telescope parts, and other structural components that are heated by the sun. As night falls and temperatures get lower, all this hot stuff radiates a lot of heat into the air around it. And so you have nasty thermal air currents that make your local seeing very wobbly.

Basically, you want to avoid heating up your telescope and everything around it during the day. So you build in a thermostatically controlled fan to reduce heat buildup inside your dome. You also paint the dome and building white to reduce heat absorption from the sun. You avoid heavy stone walls and paved parking areas right next to your dome. Think lawns! And you set up a vigorous air circulation at sundown to make the air temperature inside your dome the same as it is outside.

This may require the opening of several large, screened doors to rapidly purge all that heat from your observatory. You'll want screen on the doors to keep the skunks out. And I don't mean the neighbor's kids! Or maybe I do --- the dirty little rats!!

You'll also find that many amateur telescopes, and ALL modern professional telescopes, are mounted at least 3 meters above ground level.

Fifty years ago, even professional astronomers were clueless about dome seeing. This is why the older professional telescopes have squatty domes that are very close to the ground. Yes, even Palomar! And also these low-slung domes have tons of uninsulated metal and concrete, as well as motors and other equipment that pours heat into the air all night long. That's a total contrast to the big telescopes of today, where all heat sources are fanatically insulated to minimize dome seeing.

You've probably drooled over the magnificant planetary seeing that people in Florida are constantly bragging about. Perhaps one of the biggest factors here is the very small difference between daytime and nighttime temperatures in Florida. This helps greatly in reducing thermal effects in and near your telescope.

When you search Google for " dome seeing observatory " you'll find some great tips about improving your image quality by getting rid of stray heat. And additionally, there are lots of photos of amateur observatories to look through. Fun stuff! I was surprised to see that some people have very nice domes built into their houses. Why not? It only costs about $50,000. Spare change, correct?

So if these lucky and wealthy humanoids are awake at 3 AM in the morning, they can wander a few feet across the hall from their bedroom, push a couple of buttons, and use their telescope for half an hour or so. I feel such envy! SUCH ENVY! Is it a sin to covet thy neighbor's telescope? To heck with his wife! I want that dome!

Best wishes from Herbert Highstone

[Bob_riggs]

Hello Herb,

Thank you for making some very good points about thermal concerns in and around observatories, be they small or large.

I would make a point, though, about the downside of having an observatory attached to one's domicile. I know of one fellow who went to great expense and effort to just that end, and had to scrap the project due to the thermal eddies produced by the surrounding roof surfaces. He went on to build a very nice ob, but well distanced from his home.

Roofs and walls tend to produce a massive "heat-sink" which makes other than casual observing virtually impossible, early on in the evening/night at any rate. However, as you point out, at 3am the thermal currents may have abated to a tolerable degree.

IMHO, all things considered, it is far better, space permitting, to have an ob detached from any adjoinging structure for just this reason.

Cheers, and clear dark skies!

Bob