Mars!

[catloaf]

Hi,

I looked at Mars on Sunday night through my 70mm refractor. Once the focus was perfect I could see a disk instead of a point of light which was fun. I was a bit disappointed that I couldn't make out hazy polar caps or even a darker mark which could be one of its many areological features. I live at the Jersey Shore, it's relatively dark since if I squint I can make out Orion's head. Is this the best I could get in my neck of the woods or would a 150mm dramatically change what I see?

[glappkaeft]

We could make out both polar caps and dark albedo features using just 70x magnification with my old "toy" 60 mm refractor (took it with me to the 36 cm refractor at the Uppsala Old Observatory for laughs - had it since I was 11) in downtown Uppsala, Sweden so unless there is something wrong with your scope it should be able to do better. Of course both I and the other guys present are all rather experienced observers and that makes a surprisingly large difference.

Which magnification did you use, how high up in the sky was Mars and what was the weather like (any haze etc)? Mars is also a planet where direct light into the optics or the eye can make the low contrast surface details hard to spot. It could also be bunch of other things and as is the custom with all equipment and observing questions I'm going to suggest that you contact the local amateur astronomer club. They can much better than I tell you what works locally, look at your equipment and teach you how to get the most out of it.

[RickJ]

I'm bothered by your mention that once focused Mars was a disk not a point. A planet such as Mars should never focus to a point. If you enlarged a point to a disk then you were defocusing a star.

A 70 mm refractor should give a fairly good image of Mars at 100x. If low in the sky little will be seen due to seeing distortions from looking through too much atmosphere. Planets are best seen when on the meridian (north south line bisecting the sky). It would be quite low in the early evening so little will be seen unless the night is extraordinary. By midnight it should be well up and detail seen.

As mentioned, except for the polar cap which is shrinking rapidly, the details are very low contrast. It takes some observing time to train the eye/brain to see such low contrast detail. An orange or red filter will help greatly to increase contrast of surface features. A blue filter will bring out the clouds, if any are present. Usually seen at the sunrise terminator or over the major volcanoes.

This is about the worst opposition for seeing Mars. It is only about half as big as it was 9 years ago. Yes, a larger aperture will help, up to a point. 150mm will have a bit more than twice the resolving power of a 70mm scope assuming similar optical quality and optical design. Comparing a 70mm refractor to a 150mm reflector however is a bit more complicated since the reflector has a central obstruction that scatters light and lowers contrast. But a 150mm refractor would be far more expensive. Still the 150mm reflector should show more detail than the 70 mm refractor but not quite twice as much. Ability to resolve small detail increases directly with aperture when in the vacuum of space. On earth the atmosphere will limit the gains to some extent but up to about 300 to 500mm the gain will be quite linear on very good nights. This depends on your local seeing however. Where I used to live 200mm would show about the maximum detail to be seen on a typical night but a few times of the year larger aperture would be used to great advantage. Just didn't happen all that often. Here 250 to 300mm seems the typical night limit. Only rarely does my 355 scope do significantly better than my 250mm but it does happen.

Again, as glappkaeft said, a local club will know your conditions and what works best. I don't know enough geography of New Jersey to help you find an astronomy club near you but google the term New Jersey astronomy clubs and you should get a lot to choose from. They can give you lots of pointers about how to get the most out of that 70mm refractor and be able to tell you if it is worth the money to get a larger one. You will be able to use their scopes as well to better see what each type of scope has to offer. Something nearly impossible to understand from advertising.

Dark skies are not needed to view planets. Steady air is what is important rather than dark skies. That usually happens when the object is as high in the sky as it can get, certainly not wen rising or setting.

Rick

[kilgoretrout]

As mentioned, except for the polar cap which is shrinking rapidly, the details are very low contrast. It takes some observing time to train the eye/brain to see such low contrast detail. An orange or red filter will help greatly to increase contrast of surface features. A blue filter will bring out the clouds, if any are present.

This is going to get me outside tonight; I didn't see any detail on Mars at 100x, but I never try using the filters. Or patience. Thanks Rick!

[redshifter]

This is going to get me outside tonight; I didn't see any detail on Mars at 100x, but I never try using the filters. Or patience. Thanks Rick!

If you aren't using patience, you may be in the wrong hobby...