Saturday, June 26, 2021

Indoor Observatory

Inventing the Indoor Observatory
Above: observing indoors with a focus on the Moon - the sky portal size, area of visibility and which objects are visible at any given date and time, are calculated with an astronomy app. The Celestron CGX/L goto mount with the short OTA 14-inch EdgeHD catadioptric is ideal for indoor observing through an opened window or window glass. Adjacent to the telescope are indoor electrical receptacles, camera imaging computers and accessory racks - the epitome of indoor observatory convenience.

Indoor Observatory
The indoor observatory includes telescopes kept in a room inside a home, and are used for observing through window glass or an open window, in a comfortable regulated environment. This achieves the greatest convenience.

Left: small Dobsonian tabletop telescopes, like the upgraded "grab and go" collector's
signature edition Celestron FirstScope, are extremely convenient when observing indoors

Chromatism
Instruments, such as optical atmospheric chromatic dispersion correctors (ADC), may be used to compensate window glass to improve the overall image quality and to reduce and mitigate optical defects. 

Plane Dimension
Telescope optical orientation to the plane of window glass is corrected through software.

Observing Through Window Glass
Obtaining good astro imaging through window glass necessitates image processing to correct double images, image softening, planar deviation, contrast reduction, color skewing and other factors.

Left: the Moon through the indoor Celestron 14" Edge HD

Experiments were performed with large and small telescopes and the result compared for the notion of an indoor observatory. Telescopes reside indoors, completely isolated from the outdoor elements, such as bugs and mosquitoes, extreme heat and humidity, and bitter cold and wind.

Remote Controls
Extra remote observatory control elements are not needed and power is readily available, often with several computers. Visual observing and imaging are possible with astro imaging using computer image processing to improve the images. 

Telescope Aperture
Telescope size makes a difference in the quality of the observation. Observing through window glass is a lot like observing through the atmosphere - small telescopes perform better across the smaller wavefront than larger scopes because they look through a smaller diameter of window glass which will have less deviations.

Window Glass Quality
Other defects up for compensation and correction include off axis planar orientation, nonhomogeneous glass, and chromatism. The quality of the float window glass can also widely vary.

Room Reflections
Eliminate and minimize internal nuisance ghost reflections from the glass window by turning off indoor lighting.

Left: the Moon image taken with the indoor 2.99-inch Celestron FirstScope Dobsonian is processed to subtract window glass. Imaging through window glass can change the focus, reduce contrast and soften the image.

Double Image
The double image anomaly can result from two sided reflections off the window glass, front and back surfaces. Design image processing to subtract (more complex) or suppress (more simple) the weaker of the two images, which is normally the backside image coming back through the first surface.

Glass Thermal Insulation
Be sure to avoid thermally insulated glass of the double pane type. This would create additional unwanted reflective images and aberrations. Window glass can also cause thermal convection if the indoor and outdoor temperatures vary too much. In this case there are two corrective options. Make the temperature indoors the same as outdoors, or use lucky imaging techniques.

Polar Align Indoors
The indoor telescopes are set up, calibrated to north as needed using a compass, and positioned for maximum viewing. 

Window Size
It helps to observe through a large deck glass door to see more of the sky. Of course a small telescope and a small bedroom window sill may be ideal.

Glass Avoidance
As a simple option, put on bug repellant, slide the window open, equalize the temperature differential, and bypass the glass.

Telescopes Indoors
Telescopes kept indoors under regulated temperature and humidity have an advantage and will not be as prone to dewing. In some cases, expensive large outdoor telescopes were known to dew over inside the sealed Schmidt-Cassegrain tubes, ruining the telescope or causing a very complicated repair disassembly.

Sky Area of Visibility
A portal of sky visibility is determined and a planetarium app calculates which objects will be visible in the window on any given date and time. It can also determine how long the object will be visible.

Blast from the Past: Old school telescopes often had the front end capped with a flat of conventional 1:1 plate glass. These telescopes were primarily visual and the user dealt with any problems caused by the telescope's glass window. Essentially these old telescopes were looking through a window, not much different than a house window.

Left: Celestron's cell phone mobile sky app, free SkyPortal, can determine the window of opportunity for available objects at a given date and time when observing from indoors

Indoor Observatory

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