Daytime Viewing with the Mountain Instruments MI-250
When Larry Meyers of Mountain Instruments informed me that he’d been testing his new goto mounts during the daytime for object acquisition and goto precision, I was a bit incredulous to say the least. Daytime observing of objects other than the Sun, is not unheard of, just unusual. What reading and experimentation I’ve done with this would be like trying to locate Venus using local landmarks and a watch to line yourself up to know where to look the next day and exercises of that nature. I’ve owned an LX-200 for several years and many users have had good luck with this telescope during daylight when time and patience allowed for this pursuit. Carefully adjusted setting circles, manual or digital, will work also and many observers are adept and experienced enough to be proficient in finding objects in daylight. I for one clearly do not fit this last category.
Well, things have changed and like Larry, I’m now a believer in daytime observing. One reason I never gave this much thought was that in order to be aligned for daytime viewing escapades other than the Sun, your instrument has to be set up and calibrated somewhere that allows you to leave it out, a luxury I do not have at my home location. Since our Observatory building doesn’t have the instrument piers installed, a few weeks ago I set up the MI-250 Goto and my Astro-Physics 130mm EDT refractor in the spot where our club Maksutov will soon reside. It was aligned with a polar scope and eventually I drift aligned hoping to have an opportunity to shoot a few photographs with the coming New Moon period.
Like most of us, I work during the day and have little time to dedicate for the purpose of daylight observing. However, I’ve been at the site three or four times during the day in recent history meeting with site contractors and soliciting proposals to complete the interior road system. I’d been spending every clear night (and some not so clear nights hoping for improvement) working with the mount. It was aligned, modeled and prepared for a “warm restart”, which is the vehicle the Gemini system uses to power up in an aligned state, using the computer’s real time clock to compensate for time passage since last being energized. So, while waiting for my associates to arrive, I disengaged the turnbuckles, rolled the roof back a bit and after powering up the mount, installed a diagonal and 16mm Nagler eyepiece in preparation of slewing the mount to Venus. Before continuing, I wish to point out that I have the exact same Gemini electronics on my Losmandy G11 equatorial mount, which was installed as a retrofit kit. Initial use of this system was a frustrating series of hard learned lessons requiring many hours of trying to manipulate the servo motors to work properly with the worm and gear adjustments, along with a plethora of other aggravating factors to get the mount to slew without stalling.
I took a deep breath, entered the information with the hand controller and initiated a slew. Lo and behold, the pleasing sight of Venus in crescent was nearly centered in the eyepiece. Yikes, I like this mount! Okay, Venus is pretty neat in the daylight, but at nearly minus five magnitude, many observers have shared this experience. This is really bright, could have been a fluke…. Back to the object database, lets try Capella at just above zero magnitude; a new entry, slew and after a hard look to pick it out of the deep blue sky, there it is, again nearly centered. I think I could learn to like this.
I tried this again several days later with the same result; now I’m really starting to get intrigued about the range and possibilities of observable daytime objects. On Sunday, May 20th, a group of us were at the Observatory site painting, working on the grounds, doing odds and ends, etc., in preparation of our opening. I rode down on my motorcycle but made certain to bring a diagonal and a couple of eyepieces to take a look skyward as time permitted. I’d checked The Sky program to ascertain what was up and was surprised to learn that Mercury was 22 degrees away from the Sun, enough distance to safely take a look (all those warnings you’ve read about never observing the Sun without a proper filter are the real deal, always exercise care, never take a chance). Over the course of the several hours we were at the site we observed Mercury, Venus, Jupiter (don’t recall searching for Saturn, don’t know why), Capella and several other bright stars, the Moon (try finding this at 7.04% phase on a sunshiny day) and of course, the Sun. I viewed Mercury more that Sunday then I have in the last several years at night due to the planet’s elusive nature and it’s proximity to the Sun. In a wide field eyepiece (35mm Panoptic) you really had to search to find the .34 magnitude pinprick at 40% illumination against the blue field. Boosting the magnification indicated the planet to be a smaller version of Venus, almost in the same crescent phase. It was outstanding and an experience I plan to revisit whenever the opportunity beckons.
Thanks to the MI-250 mount, I’m no longer a closet daytime observer; I’m now an advocate of daytime observing and equipment use. Give it a try yourself, I'm sure you'll like it as well.
Kiro - May 2001