Telescope Reviews: Another new Lunt: First Light report

With the clear skies Sunday morning (10/25) I was finally able to try out my new Lunt LS60THaDS scope. It arrived on October 16th after a 17-month wait (I ordered it from OPT). It comes in two nice aluminum cases: a large one for the scope and a small one for the second etalon. Both have firm foam die-cut inserts. I bolted a dovetail onto the scope (it's got 1/4x20 holes in just the right place on its clamshell mount) and got a Sol-Searcher to use as a finder. After the requisite cloudy period due to the New Scope Curse, Sunday dawned crystal clear and so about 10:30 am I went over to a local park for an unobstructed view of the sun (too many trees around my house, too many soccer-playing kids at the local school). I used my Giro-2 with Tech2000 driver, which is a "track-and-train" drive. It sits on a Tech2000 Quick-Draw pier, lightweight, stable and easy to setup.

The scope itself (as you all must know) is a 60mm singlet with a focal length of 500mm, with an internal etalon giving about 0.8A bandpass. With a 25mm Coronado CEMAX eyepiece (20x), the view was stunning. There was a bright active region (AR1029) near the center of the disc and several small prominences around 8-9 o'clock. Tuning the etalon gave the expected modulations to the image.

Soon after I started looking, a satellite crossed the face of the sun. I took this to be a good omen, recalling the auspicious overflights of eagles at various important Roman events, as frequently recounted in Suetonius' "Twelve Caesars".

After tuning the scope's etalon to what I took the be the optimum position, I screwed the 50 mm etalon (which gives about 0.55A bandpass) onto the front of the scope and refocused. This etalon has its own tuning wheel, and after a couple of turns the image jumped out of the scope with astonishing contrast. The surface of the sun was covered with fine spiculations, the active region was even more impressive and as the tuning was varied the prominences became even more distinct. There were a couple of filaments in the lower left quadrant. The image was only a little dimmer and slightly redder, but the contrast enhancement was so substantial that those differences were unimportant.

Then I switched to my Denk II binoviewer with dual 25 mm CEMAXes. I had gotten Denk's Lunt bino adaptor from Russ at NEAF last April. It's essentially a low-power Barlow that replaces the tube at the front of the diagonal blocking filter. With the lowest and mid-range PowerSwitch settings (giving 28x and 48x respectively) it had no problem coming into focus and gave an excellent image, perhaps not exactly as sharp as with a single eyepiece but much easier and relaxing to view. I also tried a pair of 18mm CEMAXes (39x with the lowest PowerSwitch setting) and these also gave smashing views. I didn't try the PowerSwitch at it's highest magnification; I generally find the resolution at that setting to be not as good as switching to shorter focal length eyepeices. I've got pairs of CEMAX 12's and TMB 9's but didn't use them this time out.

After using the bino, I switched back to single-eyepiece mode with the 18 mm and was able to find some new limb prominences at 4-5 o'clock.

I find it really helps to use a black view camera shroud to improve the contrast by eliminating stray light and to keep your pupils as dilated as possible.

One thing about H-alpha viewing: As you move the image around in the field of view and play with the tuning, different parts of it change subtly in contrast and resolution. This seems especially true of the double-stack scenario, because the physics of the filters depend mightily on the geometry. The various tilts, focus, field curvature and magnification all have effects on the contrast and resolution. In particular, the settings that optimize the surface view are generally not quite the same as the settings that optimize the limb prominences, but at times I seemed to be able to lock in both at one time. But the primary image is so good that these variations are merely interesting rather than problematic.

Worth the wait (especially when the wait took place at the nadir of the solar cycle).

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C5 Orange Tube SCT, CPC 800 XLT SCT
Orion 127 Mak, StellarVue Nighthawk
Coronado Maxscope 40, Lunt 60mm H-alpha double-stack
5 1/4" f/5.2 home-built Newtonian
Denk II Binos
Giro 2/Tech2000 Giro Driver/Tech2000 QuickDraw Pier
Mallincam Color Hyper Plus
A zillion eyepieces and some more mounts
Mason & Hamlin BB 2140 mm (grand piano)
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