Telescope Maintenance

Viewing Conditions

Viewing conditions affect what you can see through your telescope during an observing session. Conditions include transparency, sky illumination, and seeing. Understanding viewing conditions and the effect they have on observing will help you get the most out of your telescope.

Transparency

Transparency is the clarity of the atmosphere which is affected by clouds, moisture, and other airborne particles. Thick cumu- lus clouds are completely opaque while cirrus can be thin, allowing the light from the brightest stars through. Hazy skies absorb more light than clear skies making fainter objects hard- er to see and reducing contrast on brighter objects. Aerosols ejected into the upper atmosphere from volcanic eruptions also affect transparency. Ideal conditions are when the night sky is inky black.

Sky Illumination

General sky brightening caused by the Moon, aurorae, nat- ural airglow, and light pollution greatly affect transparency. While not a problem for the brighter stars and planets, bright skies reduce the contrast of extended nebulae making them difficult, if not impossible, to see. To maximize your observing, limit deep sky viewing to moonless nights far from the light polluted skies found around major urban areas. LPR filters enhance deep sky viewing from light polluted areas by block- ing unwanted light while transmitting light from certain deep sky objects. You can, on the other hand, observe planets and stars from light polluted areas or when the Moon is out.

Seeing

Seeing conditions refers to the stability of the atmosphere and directly affects the amount of fine detail seen in extend- ed objects. The air in our atmosphere acts as a lens which bends and distorts incoming light rays. The amount of bend- ing depends on air density. Varying temperature layers have different densities and, therefore, bend light differently. Light rays from the same object arrive slightly displaced creating an imperfect or smeared image. These atmospheric distur- bances vary from time-to-time and place-to-place. The size of the air parcels compared to your aperture determines the “seeing” quality. Under good seeing conditions, fine detail is visible on the brighter planets like Jupiter and Mars, and stars are pinpoint images. Under poor seeing conditions, images are blurred and stars appear as blobs.

The conditions described here apply to both visual and photo- graphic observations.

Figure 5-1.Seeing conditions directly affect quality. These drawings represent a point source (i.e., star) under bad seeing conditions (right). Most often, seeing conditions produce images that lie some where between these two extremes.

While your StarSeeker telescope requires little maintenance, there are a few things to remember that will ensure your tele- scope performs at its best.

Care and Cleaning of the Optics

Occasionally, dust and/or moisture may build up on the lenses of your telescope. Special care should be taken when clean- ing any instrument so as not to damage the optics.

If dust has built up on a lens surface, remove the dust with a brush (made of camel’s hair) or a can of pressurized air. Spray at an angle to the lens for approximately two to four seconds. Then, use an optical cleaning solution and optical cleaning tissue to remove any remaining debris. Apply the solution to the tissue and then apply the tissue paper to the lens. Low pressure strokes should go from the center of the lens to the outer portion. Do NOT rub in circles!

You can use a commercially made lens cleaner or mix your own. A good cleaning solution is isopropyl alcohol mixed with distilled water. The solution should be 60% isopropyl alcohol and 40% distilled water. Or, liquid dish soap diluted with water (a couple of drops per one quart of water) can be used.

To minimize the need to clean your telescope, replace all lens covers once you have finished using it. This will prevent con- taminants from entering the optical tube.

Collimation

(For StarSeeker 114mm and 130mm)

The optical performance of your StarSeeker telescope is directly related to its collimation, which is the alignment of its optical system. Your StarSeeker was collimated at the factory after it was completely assembled. However, if the telescope is dropped or jarred severely during transport, it may have to be collimated. The StarSeeker 70mm and 80mm are refrac- tor-type telescopes that have fixed optical systems that should not come out of collimation. The StarSeeker 114mm and 130mm, however, have collimation screws that can be used to adjust the alignment of the primary mirror.

To check if your telescope is in collimation refer to figure 6-1. If you look into the eyepiece adapter (without an eyepiece) at the top of the focuser, this is what you should see. If the reflec- tion of your eye is off center, then collimating is necessary.

The StarSeeker 114mm and 130mm reflectors come with a collimating cap. This is a simple cap that fits on the focuser drawtube like a dust cap, but has a hole in the center and a silver bottom. This helps center your eye so that collimating is easy to perform.

In addition to the collimating cap, you’ll notice a small ring label on the exact center of the primary mirror. This “center mark” allows you to achieve a very precise alignment of the primary mirror; you don’t have to guess where the center of the mirror is. You simply adjust the primary mirror position (described below) until the reflection of the hole in the col- limating cap (the “dot”) is centered inside the ring.