Laser Hazard

As a physics teacher, I clearly understand the potential danger in using laser. The power of ordinary laser pointers is large enough to hurt eyes in a few seconds if direct laser beam is shone on the eyes. The damage is Irreversible! The green laser pointers used in stargazing are much more powerful than that of ordinary laser pointers. Usually the power of a green laser is larger than 10mW. The power of ordinary laser pointer is usually less than 1mW. One can imagine what will happen if green laser beam is directly shone on eyes! Even the scattered light may hurt your eyes. It is a good practice to turn on the green laser at a level higher than the eye level. In addition, I am used to standing behind the one who are using the laser. Last night I encountered a very dangerous situation. As usual I stand behind the one who are using the green laser. He was shining the laser beam to the eyepiece and the laser beam came out from the objective. Ah.. This was a new method to test the direction of the telescope. While I was watching at the back of him, the scatter laser beam shone on my eyes! Gosh! Since the field was very dark. I went to the toilet and see if any problem with my eyes! God bless! Yeah! There was no blind spot visually! I guess most eyepiece cases are black in color. This lowered the intensity of the scattered laser beam. If not, the result would be disastrous! Well! After this bad experience, I have concluded the followings precautions:
1. Make sure no people in the direction of fire.
2. Shorten the fire time when you fire the laser.
3. Don’t wear shiny watches or decorations on your hands when you operate lasers.
4. Don’t look at the area around the laser pointer, even it is not directed at you.
5. Stand sideway to the one who is operating the laser.

Equipment Review

Back to spring of this year, I started my interest in astronomy. I bought my very first binoculars from Grand Eye, read books and surfed the Internet. Astronomy has become my hobby. I don’t know how long I will stay with this hobby. Apart from my major, physics, in the past I got several hobbies, computer, music, philosophy, Chinese literature, English literature, aquarium, psychology etc. Once I get into the hobby, I will push myself to learn it. My character is that I will get myself to a certain level in a specific field. Now astronomy is my craze! After a while, perhaps several years, I will stop. However, I will pick up again after leaving it for some time. Different books can be found in my bookshelf. I bought several telescopes in the past few months, 10x50 binoculars, 10x42 binoculars, unbranded 5” refractor, NexStar 4SE, Equinox 80ED, C5, LS35THaDx. The NexStar 4SE OTA was sold because of the perchance of C5. I think C5 is the upper limit of a grab-and-go scope for me. Now the C5 become my most favorable scope because of the delayed arrival of Meade 8” ACF SCT. My recent interest is planetary imaging. Without a long focal length telescope, I cannot go too far. In term of optics, I like Equinox 80ED. It is high contrast, good color tone and good resolution. The dead knot of 80ED is that, its focal length is too short for planetary imaging. However, I am sure that it will become my favorable weapon in deep sky imaging. It takes time for me to be ready for deep sky objects which involve in skills and equipment. We have fewer numbers of solar planets than the number of deep sky objects. Deep sky objects are gorgeous, huge, mysterious and unreachable! After waiting for more than a week, finally a ridge of high pressure started to form. The sky condition last night was fair, but just could not wait for any longer. I went back after a wedding banquet! When I arrived at PTC, it was 11:30pm already. Due to limited time, I tried the newly bought Tele Vue 5X Powermate and did a visual test. I told Bingsze to bring his Meade 5X TeleXtender so that we can do a fair test on both barlows (Powermate is in fact exactly a bawlow optically). The local dealer of Meade did this test before, but it is not convincing. The test result and photos posted by him were unexpected. From his photos, Meade beat Tele Vue! As Tele Vue is the icon of top quality in the field, people suspected the result.

http://www.grandeye.com.hk/barlow_comparison.htm

However, there is no follow-up from different parties. My curiosity drove me to find out the answer. I did a preliminary visual test last night. The telescope used was an unbranded 110ED and the eyepiece was Sky-Watcher 5mm eyepiece. The target object was Jupiter. There were totally 4 stargazers involved in the test including myself. In terms of visual observation, we cannot reach the same conclusion. One of a well known stargazer, Mirror God, said that the two 5X barlows were very close. However Meade 5X TeleXtender got a bit more chromatic aberration. He added that it would be better to use Newtonian to perform the test, as it is chromatic aberration free. In terms of cost performance ratio, Meade wins. Bingsze said the performances were very close and Tele Vue got a bit better in chromatic abberation. Lewis said both barlows got very similar in revealing details, but Meade got a bit better chromatic aberration. My conclusion is that the performances were very close visually. Powermate reveals a bit more details and the contrast is a bit higher. Since the performances of the two barlows are very close, we need to perform another photographic test next time. However, we all think that as the differences were hard to tell and we did not come to the same conclusion. The Meade 5X TeleXtender should be the best buy because it just costs about 60% of Tele Vue 5X Powermate. However this test was not comprehensive. It is desirable to use a Newtonian to perform the visual and photographic test.

Tele Vue 2.5X and 5X Powermates

Last night I also tested the unbranded 127mm refractor which I bought from Boss Kwan. It has been sitting in the store room for a few months. Every time I got a chance to go stargazing, I used to test the more expensive equipments I owned. They are Equinox 80ED, C5 and NextSTar 4 SE. It is a prejudice! I found that this unbranded 5” refractor was good in the sense that the resolution is reasonably high and the image was bright. The weak point was obviously the chromatic aberration. The chromatic aberration of this 5” refractor is considerably better than my other achromatic refractor, ETX 70. Purple edge was shown when it was focused before the focus. Green edge was shown when it was focused beyond the focus. When it was in focus, there were a bit greenish edges. The view of Jupiter was bright, sharp and showed good details. After viewing this unbranded 5” refractor, I must say it is my excellent choice! It is simply unbeatable! No complaint for just $1680!

Unbranded 127mm F750m Refractor

Sidewalk Astronomy and Telescopes Watching

Last night neither transparency nor seeing was good. However, it was a year of International Astronomy’s monthly activity, sidewalk astronomy. The activity was held in Tin Shui Wai, which is far away from Tseung Kwan O. I was happy to join the activity because my wife decided to go with me. When we arrived virtually all the telescopes were pointing to the moon. This was the brightest object that could amaze the general public. The most interesting thing for me to join this activity was I can have a chance to try different telescopes. The biggest telescopes are always eye-catching, the TMB 8” APO and the Takahashi M-250. Just an impression, the TMB 8” APO gives better contrast. I couldn’t tell the different between sharpness because they were using different eyepieces and the magnifications were different. Anyway the Ethos eyepiece was impressive in terms of view angle. I just wonder my eye’s view of view is too small compared with Ethos FOV! It just gave you a feeling of cruising around the moon. One cannot describe the FOV of an airplane’s window! Well all these, 8” APO, 10” Takahashi and Ethos, are expensive. I deliberately look at some down to earth telescopes. Believe it or not, Sky-Watcher 5” Maksutov-Cassegrain was really good. The image of the moon was crispy and the contrast was high. I remembered once there was a used one in the forum a few months ago. The owner asked for $1700 if I remembered correctly. Hmm…. I missed a chance.

TMB 8" APO

Takahashi M-250

After I walked around for a while in Tin Shui Wai, I decided to go to have my own star gazing. I rang my friend Lewis and our destination was Lung Ha Wan. We arrived at Lung Ha Wan at about 10:30pm. But the favorable location was occupied by some midnight divers! Gee! We wanted to try a new location, but it was just being occupied by others! Anyway, Lewis and I looked around and see if it was a good location for star gazing. But sky was very hazy and we could only see the Vega, the Jupiter and the moon. As there were no favorable car parks, we decided to go to good old Pak Tam Chung.
When we arrived Pak Tam Chung, there were no star gazers! I was fooled by those posts in the forum. Maybe everyone went to Tin Shui Wai. Well! We two lonely twins stated to setup our scopes and practice. The sky condition became very bad. When we arrived we could see the blurred moon, the fading Vega, the dim Polaris and Perhaps the bright Jupiter. I tried to setup the HEQ5Pro as quickly as possible. At the point I wanted to do the polar alignment, the Polaris was gone! So I used the compass to solve it. Unexpectedly the alignment done was quite good. The tracking of Jupiter was good. We shot the Jupiter with different imaging device, D90, 450D, SPC900NC and LPI. Both D90 and 450D have life-view which was very useful in focusing. But all the photos taken by D90 were unsatisfactory! We don’t know clearly why D90 failed. Maybe it was because of the flip mirror of D90 in the life-view mode flips before the release of the shutter, while 450D not. The small vibrations of flipping the mirror caused the burred images. As a Nikon user, I need to figure it out! This needs another investigation. My second task was to align the NexStar 4SE mount. It just couldn’t track the sun probably during the recent solar eclipse. I believe that ex-owner didn’t get it alignment in 2-star alignment or 3-star alignment once. According to the manual, one needs to get NexStar alignment once with at least 2-star alignment once before it works properly. However the noxious clouds covered the sky. You know! Finally I gave up and went to have dessert in Sai Kung. Today I tried to process my photos. I still don’t know how to use Registax. The photos shown were just click-click-click product.

Jupiter: C5, TV 2.5X, ISO 1600, 1/25, 450D

Jupiter: C5, TV 2.5X, ISO 1600, 1/25, D90

Jupiter: C5, SPC900NC, 1200 frames, Registax

Jupiter: C5, TV 2.5X, SPC900NC, 1200 frames, Registax