First and foremost, you need to consider the diameter of the telescope or its mirror which is actually one of the important number that can describe the telescope. If you have larger diameter lenses then it would definitely offer high amount of resolution and it can help gather those lights from that of the astronomical objects. But they can actually cost your more. The good size for that of the first telescope is actually roughly around four inches. The bigger one tends to be more expensive and it can be inconvenient too. If you consider the bigger one it tends to be expensive and the bigger works better of course, though not to the shocking level.
The second one is the magnification which is unimportant and is sometimes hyped in the advertising claims for those of the inexpensive telescopes. When talking about astronomy, the very purpose of the telescope is to be able to collect those light that is from those faint objects and simply not to magnify it. Most visual observing is done through 50 and 200 powers.
There will be useless blur that can occur when there is too much magnification that is provided. The excellent rule of thumb to be able to determine the maximum usable magnification is to be able to multiply the diameter of the objective in millimeters by 2.5. On the nights that there is high atmospheric stability that is unusual, you can use the high power but make sure that you are not going to just count into it just to simply have the good result.
It will be better also that the eyepiece can be comfortable which means it can be close to the eyes so that it will clearly see the object. If the eye relief can be very small then you will need to bring the eye closer to that of the eyepiece, and it will be but impossible for you to be able to observe for a span of more the few seconds each time.
Last but not the least, you need to also look for the steady mounting or that of the shaky one that can ruin the observing experience and to prevent you from adjusting that of your mount just to make it steady which can often be tasking already into your part. Thus, the more that the mount is massive in its looks, then the better is its performance. Once you will be in doubt, try to make sure that you spend more time on scrutinizing the mount and make sure that it will be strong enough to not to move easily that can disrupt the view.