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There are two circumstances under which you will see the secondary mirror
1. When the eyepiece focal length is longer than about 7x the f ratio.
2. When the eyepiece is not focussed.
1. When the eyepiece focal length is longer than about 7x the f ratio.
If you have the exact scope shown in the link, it is 76mm diameter and 700mm focal length. It's f ratio is 700/76=f9.2
Consequently the longest eyepiece you can use before seeing the secodary is around 60mm. It is very unlikely you'd have an eyepiece of this focal length. The longest eyepiece shown as supplied is only 20mm.
2. When the eyepiece is not focussed.
Is it possible you are using the high magnification 4mm eyepiece and the thing they call the magnifying lens to look at stars? If so, and the image is not reaching focus it is normal to see the silhouette of the secondary mirror spider against the out of focus image.
A very good quality 76mm scope will have a maximum usable magnification of about 150 power. This instrument is not likely to fall into the "very good" category so you probably don't want to use the 4mm eyepiece.
The eyepieces supplied give these magnifications
20mm........38x
12.5mm.....61x
4mm.........190x
The barlows or what they call magnifying lenses will push the magnification way too high and shift the focus. Perhaps that is why the image may be out of focus. Suggest you don't use the barlows at all with the 4mm. The 1.5x or 2x with the 12mm eyepiece will probably be the highest useful magnification.
This is all generic advice. If you can give more specific info about how you were using the scope, eyepieces etc when you saw the secondary we can possibly nail down the problem. The scope will magnify 525x but won't ever produce a clear image at any magnification over 150x possibly less.
The pictures shown were not taken with that telescope. You will be able to see the Moon in good detail, see the rings of Saturn, maybe a couple of belts on Jupiter. You won't see galaxies like that shown in the photo. Concentrate on bright nebulae, globular and open clusters rather than galaxies which are almost all quite faint.
Here are some bright targets to try first (on a moonless night)
Nebulae
Orion Nebula
Eta Carina
Tarantula Nebula
Globular Clusters
NGC 104 (aka 47 Tucana)
Omega Centauri (not in a good position for observing now - Autumn is better)
Open Clusters
Jewel Box
NGC 3532
Joe
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