Tonight was the night I had been waiting weeks for. After so much rain and clouds, finally a clear sky with above average transparency and good seeing. Earlier in the day I double checked the collimation of my Apertura AD8 in preparation for a few late night hours of viewing.
A waxing gibbous moon was about to slip below the horizon so I started taking my gear outside just after 10:00PM to setup in the driveway. My primary objective for the evening was to put the AD8 through its paces and if all went well, see M101 in the process.
The trees in my yard provide me with narrow pockets of open sky so my choice of targets is limited. Tonight, Ursa Major was on center stage. With the scope fully temperature adjusted, I inserted my 30mm 2″ eyepiece, uncapped the finder scope and ran into my first minor problem.
The Orion XT8 I had briefly had a red dot finder (RDF). Although it was difficult for me to use, if aligned properly it was accurate in lining up the scope with a target star I could see in the sky. Put the red dot on the star. Nice and simple.
My Apertura AD8 however is equipped with a Right-Angle-Correct-Image (RADI) finder scope. It is basically a very low power scope bolted to the main scope with a set of crosshairs in the view. What you see in the scope is exactly what you see in the sky, just a very small section at a time (5-degrees). It sounds easy to simply point the finder scope at a star and go but I found it anything but. I ended up needing to use nearby trees as reference points to figure out which star I was looking at in my finder scope! It shouldn’t be that hard. I may have to add a Telrad or build a set of setting circles to overcome this problem.
Using the finder scope I located Mizar, a beautiful example of a Double Star in Ursa Major. It is the star at the bend of the handle of the asterism “Big Dipper”. From there it was easy to follow the line of bright stars (81, 83, 84, 86 UMa) toward M101. Just below 86 UMa is a “belt” of four stars about half the distance to M101. I used the second star from the left in that belt to point almost directly to M101 about a degree away. The reward was the very faint 7.9 magnitude Spiral Galaxy that had been eluding me.
M101 has a very dim surface brightness making it more difficult to see than a similarly rated 7.9 magnitude star. This is because the light from the galaxy is spread over a much larger area (arcseconds or arcminutes). Still, I was able to avert my vision and see it was a fairly large galaxy. I added a 2x Barlow to my 30mm to increase the magnification and I was even able to make out one or two bright stars in one of the spiral arms.