Why is Mars blury?

[Worthen911]

I am new to using forums to get answers, but thought I would give it a try. Last night I was using my 10 inch Dobsonian to view Mars with my family. I was disappointed that when I switched to a lens to increase the power, Mars appeared blury in spite of the surrounding stars being pin points of light. Can some one explain why this happened, and is there a way to fix it?

Thanks,
Greg

[RickJ]

No object disappoints newcomers more than Mars. It is a very difficult object needed the best of observing skills learned over years of experience. Your experience is typical.

Stars are high contrast objects and a point source. Mars is very small and very low contrast. It will never look all that sharp. There will be instants of good seeing where it will sharpen up. Depending on your local conditions these may be often or few and far between. If the jet stream is nearby you will never get it to look very good. Always view Mars when it is as high as possible, thus near the meridian. This means late at night. Early evening it will be too low for any scope to show it clearly. At my 47N location I'd not even try before midnight. It would be just too low to see anything through the atmosphere.

Be sure your collimation is dead on. Low contrast objects like Mars suffer greatly with even the slightest error in collimation.

Thus it is about the most difficult of the naked eye planets to see much detail. This opposition is a poor one as well, next in two years slightly worse then things will get better. Unfortunately, for northern viewers the close oppositions happen when Mars is low in the sky where seeing is poor to begin with.

Rick

[Worthen911]

Thanks, Rick. Our viewing was earlier in the evening, and Mars was lower in the sky. Your explanation of Mar's low contrast challenges for viewing also make sense. I will have to try later at night without the kids and recheck my scope's collimation.

Greg