Monday, December 29, 2003

More On the Photon Instruments Refractor

I had mentioned a few days ago that the diagonal that came with the scope seemed a bit loose. I pulled out the micrometer and measured the inside diameter of the focuser, and the outside diameter of the diagonal. My best estimate for these is 1.994" and 1.992", respectively. A discrepancy of 2/1000th of an inch isn't enough to cause a problem. So why does it rock back and forth?

The focuser is actually a fairly large tube with a "collar" threaded into it. The collar is the 2" diameter component--but the collar's bearing surface is only a fraction of an inch deep. Once the diagonal has slipped into the collar, it is unsupported beyond the collar. I believe that this is what causes the diagonal to rock back and forth. It would take a fairly minor design change to correct this--make the collar perhaps 1.5" deep, and the diagonal would be fully supported. Fortunately, the collar is threaded, so it would be an easy change to make. Had I an engine lathe, I would just whip one out.

Thursday, December 25, 2003

Clear Skies! Finally!

I dragged my Photon Instruments 127mm refractor out this evening--stars, finally! The first look at Saturn was a bit disappointing--then I remembered that this is a big piece of glass, and it has to cool.

After about 30 minutes of excruciating cold weather (I am from California, remember), I was no longer seeing dramatic changes in image. With a 9mm eyepiece (127x), Cassini's Division was visible, although not spectacularly dark. For fractions of second, I could see a dark gray line all the way around the rings, at the ansae, and in front and behind the planet. At least at times, I could see a dark brown stripe in the planet's clouds. Turbulence seemed to be the limiting factor, not the optics. Going to a 6mm eyepiece (190x) did not improve the image in any obvious way. Trying to go above 190x was a waste of time because I am still struggling a little with balance issues on the mount.

Relative to the Ranger, I'm not sure that I am seeing any more detail (in spite of dramatically more aperture), although the image is quite impressively brighter (as well it should be--the Photon has more than three times the light gathering area).

Chromatic aberration? Yes. There is a definite purple fringe to Saturn's rings--something that I don't see in my reflector (of course--the virtue of reflectors), and somewhat more noticeable than in the Televue Ranger--but I haven't done a side-by-side comparison yet, so I can't give you anything more precise than "more." I will say that while I can see the purple fringing, I am not sure yet that I would call it objectionable. It is certainly time to try a Minus-Violet filter, and perhaps a Chromacor, to try either masking or correcting the aberration.

I looked at the Orion Nebula (M42) as well. I can't say that I saw a lot more through the Photon Instruments refractor than I can see with my Ranger, but then again, I was looking through the Ranger in the backyard, which is considerably darker than the front yard, where I had the Photon set up for observation.

One note about the mount: because I have it mounted on a Cave Optical equatorial mount intended for a reflector, the eyepiece on the Photon is down very low--and my neck feels it. The Photon needs an equatorial mount with enough tripod height adjustment to get the Photon up a couple of feet higher into the air.

I would say that the Cave Optical mount is certainly adequately steady for the Photon (unlike the 8" reflector that I usually have on it). No surprise; the 8" reflector weighs 31 pounds, and the Photon weighs 14 pounds.

I knew that I would need to replace the Cave Optical mount at some point, but perhaps sooner rather than later. I need to polish up the Cave Optical mount, and find someone who is restoring a Cave telescope who is willing to pay for a collector's item like this. Its value to a collector far exceeds its value to someone who needs a working equatorial mount.

One aspect of the Photon that was a little disappointing is the 2" diagonal that came with it. I'm not sure if perhaps I need to do some adjusting, but it did seem as though the diagonal was a bit loose in the focuser. This meant that even a little pressure on the diagonal caused significant image shift. I would really like to try using the Photon without the diagonal, but that would require me to lie supine to look through the eyepiece! Don't take this as a slam on the Photon Instruments scope; it isn't built like a Televue or an Astro-Physics, nor is it priced like them, either.

I will try to do a side-by-side comparison of the Photon and the Ranger tomorrow night (weather permitting). At least my initial impression is that the Photon, in spite of its clear advantage in aperture, doesn't do an obviously better job of revealing detail on Saturn than the Ranger. (Of course, I haven't had the chance to find out what really good seeing conditions might do for the Photon.)

The Ranger is cute and compact, and if it were not for the problem of an equatorial mount, the Ranger would be far more portable. Instead, the Ranger is only somewhat more portable. Still, the Photon will fit into my Malibu, and once I get a more modern mount, I should be able to move the whole collection of stuff to a dark sky site without any real struggle.

Tuesday, December 23, 2003

The Photon Instrument 5" Refractor Arrived Today: Snow Should Start Falling Shortly

All you skiiers in the Boise area should thank me. We had clear skies a couple of nights back, but since the new telescope has arrived, the clouds are solid, and it looks and feels like snow will fall this evening.

In terms of bang for the buck--especially impressive bang for the buck--it's hard to beat. It looks good, and what little chance I have had to try the optics so far, seems decent. There's an American flag flying a few hundred yards from us in one of the common areas of our subdivision. I can't count the stitches on the seams, but I am not far from that. A detailed test report is going to have to wait for clear skies.

Unfortunately, I have no 2" eyepieces to really try out the wide field capabilities of this scope, but I suppose that I will remedy that situation shortly.

Mounting it on the Cave Optical equatorial mount did not turn out to be too difficult. The tube rings use 6mm thumb screws, but they were too short to go through the Cave Optical saddle, so I had to run out and buy some 6mm hex head screws, and I borrowed a couple of washers from the neighbors next door. It is certainly quite sufficiently steady for visual or photographic use.

Saturday, December 20, 2003

My Reflector Isn't As Overweight As I Thought

I mentioned a few days ago that my 8" f/7 reflector needed to go on a diet, so that I could get it light enough to fit on a Losmandy GM-8 equatorial mount--and get fully into the 21st century.

I went out and bought a bathroom scale today--and I discovered that it wasn't as overweight as I had thought. The entire OTA (optical tube assembly), including the rotating ring assembly, is only 31 pounds. Going to a carbon fiber composite tube might well get me down to 20-22 pounds--light enough for the GM-8! This is encouraging.

I'm still trying to figure out whether to tackle a more dramatic change. Right now, I have an ancient 1.25" focuser, and a 1.83" elliptical diagonal. It is tempting to switch to a 2" focuser, so that I can use wide field eyepieces. If I go to a low profile focuser, I can reduce the diagonal to 1.3", reducing lost light and diffraction damage to the image.

The downside is that just about all the low profile focusers have very limited range. My current rack and pinion focuser has 3.75" of travel--enough that I can very comfortably use a camera as well, and still have the focal point inside the camera. Low profile focusers generally make you trade off focuser travel for overpenetration into the tube, possibly adding a new set of diffraction problems.

Anyway, there's no urgent need to make a decision right now. I just have to figure out what to do before replacing the current tube. If I am going to drill a bunch of new holes, I would rather do it in the current fiberglass tube, which bears the scars of an unfortunate incident involving my daughter, our Mitsubishi, and the garage.

Oh yeah, feel free to throw money in the tip jar for that Losmandy GM- 8.

Thursday, December 18, 2003

A Crisp, Clear Night in Boise

This is the first such night that we have had here in Boise in some weeks. I was able to drag out my 8" f/7 reflector for the first time since I obtained an easier to use laser collimator. Unfortunately, the atmosphere was still pretty turbulent (or perhaps those were tube currents inside my telescope).

The temperature contrast was strong enough that I could see the focus of the mirror changing. Over a period of about 30 seconds, the telescope went from perfectly focused to a bit fuzzy, because the temperature was changing the shape of the mirror. Saturn is an especially good target for this sort of change, because you have crisp lines (such as Cassini's Division) that you can see blur.

At 157x (9mm orthoscopic), Saturn was crisp, although somewhat small. The Cassini Division was more gray than black at the ansae (the extreme left and right sides of the rings), and only occasionally popped into view in front and back of the planet. I could see at least one cloud band on the planet itself--a medium brown against a very, very pale yellow body.

At 236x (6mm orthoscopic), everything started to fuzz up, with even the ansae portions of the Cassini Division only appearing briefly as the turbulence calmed down. At 283x (5mm ortho) and 353x (4mm ortho), the image wasn't any worse, just larger.

I used some of the money from the PayPal tip jar (thanks!) to pay for a slightly used Photon Instruments 127mm f/9 achromatic refractor this morning. With a little luck, it should be here next week, when I have a whole week off work.

Monday, December 15, 2003

Speaking Truth to Power

This Reuters news story leaves me uncertain whether to call this tactless and rude, or what the Quakers used to call "speaking truth to power":
VATICAN CITY (Reuters) - U.S. Hip Hop singer Lauryn Hill, from a stage used by the Pope, has shocked Catholic officials at a concert by telling them to "repent" and alluding to sexual abuse of children by U.S. priests.

The broadside came during the recording on Saturday night of a Christmas concert attended by top Vatican cardinals, bishops and many elite of Italian society, witnesses said.

Hill made her comments when taking the microphone to sing at the concert, held in the same huge hall and stage Pope John Paul uses for his weekly general audiences and other events. The Pope was not present.

"I did not come here to celebrate the birth of Christ with you but to ask you why you are not in mourning for his death inside this place," she said according to a transcript of her statement run by the Rome newspaper La Repubblica.


"God has been a witness to the corruption of his leadership, of the exploitation and abuses ... by the clergy," she said.

This was an apparent reference to the scandal in the United States last year over the sexual abuse of children by priests.
Alas, not just in the United States. Yes, it was just a few Catholic priests engaged in these crimes against innocence--but too many of these crimes were covered over by archbishops. The Catholic Church needs to do some serious penance for ignoring these crimes.

The hierarchy also needs to ask why they were prepared to ignore and tolerate homosexual actions within the priesthood for so long, when the Church's public pronouncements clearly recognized that homosexual action is contrary to the Bible.