Top equipment, but hazy sky!

Last night I was in Tai Po. The main task was APO testing. The dealer imported a few APM/TMB APOs. It was a rare chance that one could have a side by side comparison of 100mm/F800mm, 130mm/F1200mm and 203mm/F1420mm APOs. The 203mm/F1420mm was owned by the dealer. The other two APOs were goods. However, it was ruined by the bad sky condition! The sky was very hazy. The seeing was very bad. The moon was covered by a yellowish Arabian mask. It would be nice if you are not stargazer. When I back home, I browsed around the Internet. It seemed that all local observation sites, like Pak Tam Chung, were disappointing. I got ready the equipment in my boot in the afternoon. It would be meaningful to know how good those APM APOs compared with Equinox. Finally I decided not to setup my equipment and just tried those APOs.
At a first glance, the tube material was robust lightweight polymer. Both 100mm/F800mm and 130mm/F1200mm can be mounted on EQ3Pro. I forgot to carry both APOs and got a feeling of how heavy they were, but they should not belong to heavy class. Everything was strongly and nicely built. The base and the bracket of the finder scope were quite unique. I would not say it is stylish, but the design concept was neither Japanese nor Chinese, but German. The Feather Touch focuser was solid. Well back to the main dish, optical performance. Both APOs delivered high contrast images. I tried another 12” Newtonian last night. The Newtonian deliver brighter images, but it contrast was far below than that of APOs at similar magnifications. We boosted the magnifications to 288X and ~500X for 100mm/F800mm and 130mm/F1200mm respectively. These mean we pushed the limit to 72X/inch (288X) and 96X/inch (500X) respectively. The 100mm/F800mm was able to handle 72X/inch. Although the Jupiter image was breakdown under 96X/inch for the 130mm/F1200mm, one could still see some color fringes of Jupiter. That was not a flat images disc of Jupiter.
Last night there were two points I especially want to mention, the chromatic aberration and the resolution of the surfaces the Jupiter’s satellites. When I used the APOs to observe the Jupiter, the north pole of the Jupiter was a bit bluish. The dealer said it was due to atmospheric chromatic aberration, not the chromatic aberration of the APO. Here comes the question! Is the dealer telling the truth? To me, this is a physics question. If the optics got no or low astigmatism, the chromatic aberration should be cylindrical symmetric. There should be false color around the star, not just appearance in certain direction. My conclusion is that the bluish color at the north pole of Jupiter was caused by atmospheric aberration. One can do some experiments to verify this. Use the same telescope to observe the same object and see if the position of the aberration changes with time. About the resolution of the surface of the Jupiter’s satellites, moon surface, we saw all four satellites, IO, Europa, Callisto and Ganymede. The dealer and I were not sure about the moon surfaces were revealed or they were just Airy discs. As the magnitude of those satellites were small, probably larger than 5. When I observed the satellites by the 100mm/F800mm APO, it seemed that I saw the 1st order diffraction ring, but I was not sure. But it was possible that it was Airy disc. When we used the 130mm/F1200mm APO, the image of the satellite improved a bit. The hazy sky kept on discourages us whole night. It seemed that the 130mm/F1200mm APO gave a more solid image. However, it was illusion or fact. We need to wait for the sky. But it is highly possible that these two APOs will be delivered to new owners. So what can I do! Ha! Ha! Use theory to justify it! As these two APOs were claimed to be diffraction limited, we can do some calculations and see if it is possible to see the moon surface.
The visual angles in arc second of the satellites are:
IO 1.2”
Europa 1”
Callisto 1.6”
Ganymede 1.7”
By using the Rayleigh Criteria, we can calculate the theoretical limit of the resolution of the telescope.
R = 1.2 L/D where R is the resolution, L is the wavelength and D is the diameter.
The resolution calculated is in radian, we can convert it back to degree easily. In order to get a feeling of how good is the optics, I assume the average wavelength of visible light to be 550nm. After some simple calculations, for diffraction limited optics, the resolution of different diameter in arc second is given below:
100mm 1.36”
130mm 1.05”
203mm 0.67”
It means that 100mm APO is not able to resolve the Jupiter’s moon surface. The image was just an Airy disc. The 130mm APO can barely resolve the Jupiter’s moon surface. The 203mm APO can resolve Jupiter’s moon surface. This is a simple discussion, meaning that if the optics is diffraction limited, it is possible to resolve it. On the other hands, the practical optic is not possible to go beyond the theoretical limit.

APM 100mm/F800mm

APM 130mm/F1200mm

Newtonian 305mm/F8.5

Equinox 120ED and DBK21

Last Friday,18th September 2009, I got a chance to use the Equinox 120ED and Imaging Source DBK21 and DMK41 in the field. The sky condition was exceptionally good. I went to Pak Tam Chung at about 10:00pm after monitoring my daughter’s homework. Since I got lot of outstanding tasks, time was limited for me. I planned to image the Jupiter and one to two deep sky objects, but I end up with the Jupiter only. The main reason was that I was inexperience in handling the Imaging Source camera. I’ve learnt the basic of how to image Jupiter from David, but lack practice. This was the first time I use the DBK to image Jupiter. I knew some crucial parameter in imaging the Jupiter. However mirror setting could ruin the photo! It takes time to learn and art cannot be rushed!

When I arrived PTC, I started the setting at once. I was kind of slow and inexperience in setting up the equipments. Since this telescope was a rare species in PTC, It attracted some stargazers. Finally when the setting was done, we viewed Jupiter. Everyone was amazed by the 120ED. Mirror God used his, prestigious telescope tester, Takahashi 3.6mm eyepiece, to test the Equinox 120ED. Here was his exact wording:

"Hmm... 幾好幾好！真係唔錯！雖然唔係一級的鏡，只是色差差少少！好少！只係輸比Astrophysics少少！想不到兩枚玉都有咁好performance！"

This was not the end of the story. When I finished the setup of DBK 21, the movie shocked everyone. It was because I was green in setting the DBK, everyone knew it when they saw my clumsy acts, but the movie was quite sharp already before stacking. It was good because the seeing & transparency were good. These unleashed the power of Equinox' optics and the power of DBK's electronics. My comment is that Equinox 120ED delivers high contrast, high color saturation and high resolution images in its own class. The color was a bit warm and yellowish in viewing Jupiter. The price is good. No complain for such performance price ratio, $13800 for a 120ED! If one wants to take serious photos, a Feather Touch focuser is needed, perhaps a high quality reducer. I am still very busy on school’s work and no time to learn how to stack the photos. The photo below is just a default click-click-click output of Registax 5.0. I will process it seriously later.

Jupiter, Equinox 120ED, TV 5X, DBK 21

The Delighting Jupiter and Moon 賞心「月木」

Starting from mid August, I was busy preparing the commencement of the academic year. Although I had a few stargazing activities, I didn’t have time to record what I have done. I did visual observation for the Jupiter opposition. I tried my friend’s Obsession 18” UC. I placed the telescope order for my school etc. I was lucky enough to have the full support from my principal that I can buy enough equipment to start astronomy in school. We bought a Sky-Watcher Equinox 120mm ED Refractor, a Sky-Watcher Dobsonian 12” Collapsible, Sky-Watcher EQ3Pro equatorial mount, Binoculars, The Imaging Source DBK 21 and DMK 41 etc. All the equipment enables me to start stargazing activities, promoting science education and enriching the NSS Physics teaching in Astronomy and Space Science.

Last night was the first stargazing activity this academic year. I made an elegant Chinese name for this activity, 賞心「月木」Delighting Jupiter and Moon. I used the Stellarium to find out the appropriate time to hold this activity. It was because my school was surrounded by a public housing estate and a hill. The field of view from the school roof is very narrow. Without careful planning, the observation would definitely be doomed! Originally I planned during the observation time, the Jupiter and the moon would appear between the gap of two buildings, finally I changed the observation site from the school’s roof to a nearby roundabout. I guessed students would be happier with an unobstructed view.

After a short introduction about the Jupiter and the Moon, we went to a nearby roundabout. The transportation was easy as we had about 20 students. However, the setting was quite exhausting! The temperature was high and I needed to setup three telescopes. Finally I gave up and ended up with two refractors. You know I need to control and discipline about 20 students in the street and at the same time I needed to setup the equipment, it was really something! A few of my students were good. They asked if they could help. But I did not have enough time to train them about the setting. I dare not to let them do it! I don’t want to risk the expensive equipment. Well! I will train them afterward. Anyway, I finished the setting in wet! When I finished setting up the first telescope, Equinox 80ED, everyone was amazed by the Moon. This was the first time they saw maria and craters. The second wave came after the setting up of second refractor. The target was Jupiter. Everyone was shocked by the Jupiter and its 4 moons, Io, Europe, Ganymede and Callisto! This was the first time in their life that they had such a close contact with Jupiter! I was the prime master of climax! I deliberately increased the magnifications gradually. Every time when I boosted up the magnification, changed to a shorter focal length eyepiece, everyone was so amazed and excited! The only defect of the activity was that students needed to wait for a long time! The queue was quite long! When it was about 9:30pm, a few students reported me that there were a few drops of rain! I was scared and packed all the telescopes at once. When we backed school, there was no rain at all! What a false alarm! Some students were not very happy because they didn’t have a chance to look at the Jupiter! I promised them to organize anther activity shortly and they will have the first priority to join!

After dismissing the students, I stated in the school and did some more observations with another Physics teacher in the school. We used the Sky-Watcher 12” Dobsonian and Equinox 120ED. Due to the light pollution, we only observed the Moon and Jupiter. Both seeing and transparency were modest. The magnification was about 200-300X. We were not able to explore the limit of these two telescopes. However, the primarily visual ability was good. A further test is needed.

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

Solar Eclipse Photos Processing

After taking a rest and having summer class, I can process the solar eclipse photos took yesterday. I want to make something special rather than post a lot of photos in my blog. Finally I made two photos. One is a close-up and the other one is a wide-angle. I used the photos taken by using C5, Thousand Oaks type 2+ filter, D90 and HEQ5Pro, to make the solar eclipse close-up photo. I used the photos taken by using 18-200mm VR, Baader solar film and D80, to make the solar eclipse wide-angle photo. I like the orange image produced by the Thousand Oaks type 2+ filter. It gives me a moody and warm feeling. On the other hand, the Baader solar film gives white images. It gives me cool and harsh feeling. Anyway, from the photos, one can see that some photos are interfered by clouds. The bloody clouds ruined the last few minutes of the eclipse! Life is like this! Never mind! Just enjoy the process and happily wait for the next solar eclipse.

I like this one the best. Sometimes clouds decorate the eclipse!

When I process the photos, I find I can do it better next time. First of all, I used the programmable shutter to shoot the photos. However, the time interval was two minutes and one minute when the eclipse was close to maximum. This strategy was not so flexible when I process the photos. At the end of the day, one needs to select constant time interval photos in order to give a dynamic feel of the eclipse. As you don’t want the photos to overlap each others, so the desired time interval would be three to four minutes. However if you do this, the noxious clouds or other unexpected event happened, say an airplane fly by, you are forced to miss one slap-shot! So if you set the time interval to one minute, then you can have better options to select from. In addition, if you have a chance to observe the total eclipse, it is better to use the full power of your camera. The corona is easily missing!