What can we expect to see with a telescope with a 70mm aperture and a 10mm eyepiece?
We purchased my young daughter a beginner telescope for Christmas and she's super excited to look at the large planets. Our telescope has a 70mm aperture and two eye pieces (10mm and 20mm) How much, if any, detail can we expect to see on Jupiter and Saturn? I don't want her going in expecting to see Saturn's rings and come out disappointed! We are very new to this and I want her to have the best experience possible with the equipment we have. Thanks!
The magnification would be the ratio of the telescope's *focal length* to the eyepiece focal length. The 70 mm aperture is helpful to know that it has a good light-gathering ability, but without the focal length, it's hard to know now small the field of view will be. Can you edit the question add the focal length of the telescope, or perhaps there is an f/no? for example you might see "f/15" which means 70mm = f/15 and therefore the focal length f would be 1050mm, making the magnification about 80x and 40x for those eyepieces.
There are many good telescope-related questions and answers here, try to browse around. Also this answer might be helpful as well.
I'd suggest you carefully read What Can You See With Different Telescopes ? which is a useful article for beginners.
Wonderful will be Jupiter with the major bands and its moons as well as Saturn like a small jewelry. Not much colour with my bottle glass telescope . Moon will be a nice surprise too.
What you can see will depend on how much light pollution in your area as well. BTW you almost certainly (in decent dark conditions) can see Mars' moons too.
@CarlWitthoft. I think the moons of Mars would be very difficult (if not impossible) with a 70 mm telescope. They are a challenge for most observers with larger scopes due to their faintness and close proximity to a bright Mars. I used an occulting bar with an 11 inch (279 mm) refractor during the 2003 opposition and was able to see them for a short period. I would not recommend that an inexperienced user try it!
I agree with uhoh, we need some more info. See this webpage on choosing a telescope to familiarize yourself with some terminology: http://www.astro-baby.com/articles/beginners%20guide%20to%20buying%20a%20telescope/so%20you%20want%20to%20buy%20a%20telescope.htm --- Visit http://astronomy.tools/calculators/field_of_view/ with your numbers and choose what you want to look at, you'll see a simulation of how large it would appear and can determine what to alter to obtain a better view.
I would buy a good 2x barrow lens to go with that. She might see Saturn's rings as a haze. Good for looking at the moon. Maybe Mars. A good tripod is a must. I would suggest a camera mount. A light weight camera. Secure the front of the telescope with 3 rubber bands to the tripod. To reduce vibration. 2 seconds pause on the camera. For vibration to end. A telescope that size is a fair place to start on Photos. A 3 second exposure. For stars planets & such. She can get some good photo's. Also other photo's. 70mm is a good daytime telescope size. Make sure she never looks towards the sun with it. For night work you need a 90mm or above. Not into astronomy. But use a 90mm Vexin for photo work. Ships in the bay. Objects up in the mountains that can not be got close to in Asia. A camera makes it so much more fun. You can build a camera mount not hard to do.
As of right now, Saturn is not visible yet, it's too close to the Sun. You'll have to wait a few months until it becomes visible.
Jupiter is currently rising around 3 am, so it's only visible early in the morning before sunrise. Again, you'll have to wait until later this year for it to rise at a convenient hour in the evening.
Until then you can definitely observe the Moon. Your scope is powerful enough to show craters and mountains on the lunar surface. This is best done not when the Moon is full, but when there's some (or even a lot) of shadow on the disk. The terrain is much more easily visible near the edge between light and darkness on the lunar disk. When the Moon is completely full, the image is flat and lacks the contrast that makes the mountains visible "in 3D". Any amount of shadow, from 1% to 99% makes that stuff much more visible near the transition line.
That being said, let me try and answer your question.
The aperture per se is more than enough to see some detail on Jupiter and Saturn. The question is the overall quality of the instrument, and the precision of its collimation.
50 mm of aperture is enough to see the rings of Saturn. I see them in my 50 mm finderscope, when paired with a strong eyepiece. The overall figure is very tiny, but you can definitely see the shape of the disk crossed diagonally by what looks like a small sharp line - the rings. I assume in your scope it will look bigger (I don't know what's the focal length of the primary lens).
Titan, Saturn's biggest satellite, should also be visible not too far from the planet once in a while, but it's easily confused with a star.
Jupiter is definitely seen as a disk. Whether or not you can see the equatorial belts depends on a number of factors - but again it should be doable in that aperture assuming everything else is shipshape.
Jupiter's moons should be visible almost no matter what. You'll see them as anywhere between 1 and 4 little "stars" that are hanging around not too far from the planet, all in the same plane more or less. The configuration visibly changes within hours, and is very clearly different on successive nights.
You (or your child) could do drawings of what's visible in the eyepiece on two successive nights and this way show how Jupiter's moons are quickly revolving around the planet. It could be a fun activity for kids if done right.
Make sure the scope is stable. Handheld operation is impossible in the field of astronomy, the image would simply bounce around too much. The scope must be installed on some kind of mount or tripod. Even then some tripods are a little shaky, so be careful with it.
If your scope doesn't have a mount or a tripod, you can improvise something from as simple materials as a couple cardboard boxes.
Anything is better than handheld operation.
If your scope has instructions for how to perform collimation, do it. If it's a refractor, it's unlikely it will require collimation, so then please disregard this.
Make sure the scope is focused well. Point it at a medium-bright star and tweak the eyepiece position until the star looks as small as possible. Or point it at the Moon and make the image look as sharp as possible. People with less than perfect vision may require a somewhat different ideal focus (unless they are wearing their glasses, in which case they are the same as 20/20 vision folks).