Telescopes are a lot like fine, performance automobiles. Both can deliver a lot of enjoyment and thrills, but it helps if the machine is well tuned and if the driver has the skill and knowledge needed to get the most out of it.
Correct Collimation
A critical factor for discerning fine planetary detail is ensuring that the telescope is collimated correctly (owners of refractors generally need not worry about collimation). Subtle details can go undetected if collimation is slightly off. Checking collimation before observing should become a nightly ritual and with practice will only take a few minutes.
Cooling Down
A telescope needs to be at thermal equilibrium with the outside temperature in order to perform at its best since heat waves escaping from a telescope tube will cause distorted images. An hour or more may be required to ensure the telescope has sufficiently cooled down after moving it outdoors on a cold night. A star test that shows a rapidly moving or boiling image often means that the telescope requires more time to acclimate to the outdoors.
Seeing Conditions
An unstable atmosphere usually means that planetary observing will be less than ideal. Although not a hard and fast rule, rapidly twinkling stars often indicates poor seeing. Seeing conditions can quickly change with temperature fluctuations and viewing through the telescope is often the only way to determine the stability of the atmosphere. Avoid observing planets when they are low on the horizon. When planets are 40° or higher from the horizon, viewing is less affected by turbulent air since we are observing through less atmosphere. Telescopic viewing of deep sky objects is generally not affected by poor seeing.
Planetary Filters
Some coloured filters may enhance planetary details. Light blue (80A), very light blue (82A) and light green (56) often accentuate surface features of Jupiter. Remember that detail will not magically appear with the use of a coloured filter and that using one which is too dark for your telescope can reduce the amount of visible detail.
Owners of achromatic refractors may benefit from the use of a minus-violet filter which can greatly reduce the amount of chromatic aberration and therefore increase contrast and detail.
Know Your Limits
The level of magnification that can be used will depend on the quality and size of the telescope along with the seeing conditions for that night. 25x to 35x per inch of aperture is normally adequate for planetary observing. If images become fuzzy or soft, reduce the magnification until the image can be sharply focused. Observations of nebulas, galaxies and star clusters are often done at low to medium powers (50-100x).
Your Observing Location
Avoid observing overtop of houses or other sources of heat that can possibly distort views. Do not observe through windows or patio doors. Observing from a paved driveway may also cause heat-induced distortions.
Learning to See
The old adage “the more you look; the more you see” is apropos for planetary observers. After a few nights of observing, you will soon begin to discern fine details that were once overlooked. Practice makes perfect. Sketching, no matter what your artistic skill level, can also improve the ability to see subtle details.
