Wednesday, October 06, 2010

first light for Firstscope (Toronto)

Noticed a break in the clouds. During new Moon! Incredible. The swirling grey vortex over Toronto has abated. For now.

Took the Celestron Firstscope, and 2 eyepieces, out to the picnic table to cool. I wondered how thick the mirror was in this thing...

Scouted an observing location. The best was really in the middle of Diane and Mark's driveway but then I'd need a table and chair. Both of which were buried at the back of my garage. Whose access was impeded by battery power tanks, bicycles, empties, oil, and other bits. I stood, key in lock for moment, debating internally whether to fetch them. But conceded that this was, in part, to test the rapid speed of impulsive observing, with a grab-and-go telescope. So, no tables, chairs, power cords, batteries, computers, polar alignment, etc. Firstscope on picnic table. C'est tout.

About 30 minutes later, I propped it up on the BBQ (don't worry, cold, just to use as the stand), out of the glare of the streetlight, and took a look at Jupiter. Popped in the lower power, 20mm, eyepiece.

Immediately, I noticed colour on the planet. Fringing blue and red on the bright disk. Like a damned cheapo, department store refractor with plastic oculars! Then I tried to focus and I couldn't get good, precise focus. The damn thing needs collimation! Sheesh. That said, I could see clearly the 4 Galilean moons, 2 abreast. Well, at least in that respect, it works.

Put in the high power, 4mm, eyepiece. There was non-uniform fogging on the planet, again, illustrating the collimation problem. But then, I could see cloud bands on the surface of the gas giant. That surprised me a little.

After I loosened the big knob, I found both the altitude and azimuth motions smooth. The focuser was a tiny bit stiff. I did not detect any significant image shift when transitioning from in to out focus.

I checked the secondary mirror. There are 3 screws. Perhaps they can be adjusted. The secondary itself is held in place by a single bar. It looks like too can be adjusted, for elevation and tilt (just like an old Edmund Scientific!). The primary mirror might be adjustable—there are 3 screws, outside, near the back of the main tube. The centre of the mirror is not marked, however...

Considered Mizar and Alcor but quickly realised they were low, behind the neighbours to the north.

Considered Albireo. It was well-placed. I moved the feather-weight 'scope to the table top. It was too high, if I was going to sit on the bench. Could not spin it, like the Questar does within its fork mount. I moved the tiny reflector to the bench itself. This would work.

Without a finder scope, it proved challenging to find targets. Jupiter was easy. I just eyeballed it and did a bit of scanning. That I was now over top the OTA, not behind it, I had a harder time. In the end, I could not find the colourful double star. I turned to Vega with the intention of checking the Double Double. Again, it took a bit of effort but I finally found the bright blue white lucida star. At low power, I just needed to shift the field (100.0 minutes of arc) only slightly to spot the wide (faint) pair. They were nicely separated at the low magnification (15x).

Tried the highest power (75x, 26.4'), to see if I could resolve all four stars. No joy. Probably the collimation was interfering again. And the stooped angle I was viewing at. The terrible short eye relief of the 4mm is a problem too. Out of habit, I had taken off my eyeglasses; I put them on again to test the view. I could not see the field stop with my goggles on.

Considered trying "real" eyepieces in the little 'scope but I couldn't remember exactly where they were. I didn't want to fiddle. Again, this was partly of test of speed. Certainly the Firstscope is tough to beat in terms of setup (and tear down) time—you just need to consider cooling. I was surprised by the poor optical performance. But then, it is a golden rule, n'est pas, of reflectors, that before every session you collimate?!

I'll try tuning this thing, before round 2. Maybe pop on my old 6x30 finder scope. Or make a simple pinhole alignment jig. And I must try my regular oculars...

Maybe this one is a lemon...

No comments: