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Daily Moon Phase
- 6. Using Polarie for Timelapse with Panning effect – Vixen Polarie Star Tracker Tutorial Video
- 5. Using Polarie in Southern Hemisphere – Vixen Polarie Tutorial Video
- 4. Advance use of Polarie – Vixen Polarie Star Tracker Tutorial Video
- 3. Camera Set Up – Vixen Polarie Star Tracker Tutorial Video
- Basic Set Up – Vixen Polarie Star Tracker Tutorial Video
Text & Images by William Chin, Malaysia
On the 17th January 2013, a comet named C/2012 F6 (Lemmon) begun its journey southward through the constellation Crux (Southern Cross). I have taken the opportunity to do imaging of it before dawn. I am imaging the comet using the Vixen Polarie star tracker.
Doing astro-imaging in Malaysia, we always need to deal with the fast changing of the weather. The sky can be clear within a few minutes and also will be cloudy after 5 minutes later. The advantage of the Vixen Polarie is that it can be setup pretty fast within 5 – 10 minutes (depending on individual skills). Borg 50 mini scope with focal length of 250mm was used for the imaging. Since, this mini scope attached with a DSLR camera is not more than 1kg, the Vixen Polarie just good enough to handle this setup.
The Polarie was setup using the Vixen Polarie tripod that come with ball head. The mini scope and DSLR camera was attached on the Vixen Polarie by using another ball head. The polar alignment was roughly done by using the Polar Meter which is an optional accessory for the Polarie. I just spent about 10 minutes to complete the setup and ready for imaging!
The camera was set at ISO200. Exposure time is 20 seconds only. This is because my imaging site was very near to the Kuala Lumpur. Longer exposure will cause the whole picture become too bright and details will be washing out. A total of 57 frames were taken within a clear sky window of only about half an hour. During the imaging, I noticed that the star field drifted a little bit but the drift mainly due to the not accurate polar alignment. Although the tracking of the polarie at focal length of 250mm is not that accurate, but due the single exposure just 20 seconds, the Polarie handled this exposure very well without trailing the stars.
The Vixen Polarie star tracker handled my comet imaging session very well and it is very good for casual astro-imaging of any celestial objects. The clear sky window only last for about half an hour on that night. I can’t imagine if I setup a proper equatorial mount, how much time I will spent and end up with cloudy weather later on…The only thing I forgot to do is to take an image of the Polarie setup while I am shooting the comet. In fact, at that time, I don’t have extra camera to do so…my bad.
Jan 10, 2013
The Moon on Jan 10, 2013 at 5:46pm at its smallest distance of 360019 km to Earth.
Moon and Venus are in conjunction on Jan 10, 2013 at 8:54pm. At the moment of the conjunction the objects are not visible. In local, they are only be observable on Jan 11, 2013 at 6:34am when their separation is 8.0-deg ENE.
Jan 12, 2013
New Moon occurs on Jan 12, 2013 at 3:44am. On this day, the Moon is between the Sun and Earth.
Procyon is in opposition with the Sun on Jan 13, 2013 at 8:35am and therefore at its best visibility of the year. Procyon transits at local midnight. It’s bright and visible to the unaided eye.
Jan 15, 2013
Best visibility for earthshine on the Moon occurs around Jan 15 just after the end of dusk. Sunlight is reflected from the Earth to the night side of the Moon. Its night side appears to glow faintly and the entire orb of the Moon is dimly visible.
Jan 19, 2013
First quarter of the Moon occurs on Jan 19 at 7:46pm. On this day, the Moon is best visible right after sunset.
Jan 22, 2013
Moon and Jupiter are in conjunction on Jan 22 at 10:32am. Moon is 0.9-deg S of Jupiter. This is a very close conjunction of the two objects. At the moment of the conjunction the objects are not visible. You can observe them on Jan 22 at 3:02am when their separation is 4.9-deg W.
Moon is on Jan 22 at 6:20pm at its furthest distance of 405347 km to Earth.
Visible Planet – Jupiter
After sunset in the evening, Jupiter is visible high in the ENE in the constellation Taurus (Bull). It is very bright at magnitude -2.7 and a prominent object in the night and twilight sky. Best observing time is at 10:10 pm in the N at an altitude of 72-deg.
As a world renowned optics maker, Japan Vixen has come out an entry level model of refracting telescope – Space Eye 70M AZ. Due to the objective lens of 70mm, we believe it’s mostly for beginners and children who have curiosity when looking up to the nightsky. SE 70M is a achromatic refractor with a simple design alt-azimuth mount and aluminium tripod. When we receive the set, we are so anxious to find out how it performes.
There are two eyepieces, 20mm and 10mm respectively with 1.25″ barrel OD. The two eyepieces seemed fairly good for their coating and we believe they would work better than many other entry level model (as they are generally provided with 2-elements H-eyepiece). Other standard accessories are mirror diagonal and a 5x finder scope.
For a first time user, this alt-azimuth mount is very easy to access and operate. It comes with two-way controls, side-to-side and up-and-down with fine adjustment knobs. When we’ve got chance to first light the telescope, the sky was good enough to see the Moon and Jupiter.
We were so excited when we have close-up view on Jupiter. The cloud bands are fairly clear although the magnification is at 70x. The children were impressed to view through it as the first encounter. Due to the small aperture, we thought the magnification might be limited, however, we wish to try to push a little higher when we have opportunity to get a barlow lens or a high power eyepiece.
Then, the Moon was another “wow”! The craters were revealed and resolved clearly with only a 20mm eyepiece. We found a bit false color around the edge of the Moon when it’s magnified with 10mm eyepiece. This is the phenomenon we believe it’s called “achromatic aberration”. But, to us the aberration is not too bad and the image was appeared focused and sharp still. What we believe is the coating and design of the eyepiece may help in this case.
Overall, we think this unit is well suited for a family who probably need one for casual viewing for nightsky. Since the tripod is not heavy at all, it’s recommended that high position is not a good idea. And for children, they are very fast to adapt to the operation. Of course, we find it a while to align the finder scope and this should not be left to kids to handle.
Last but not the least, Space Eye 70M is a refractor which creates upright images that is applicable in the day viewing. Sun viewing must be observed and monitored by the adults anyway and a safety solar filter is very necessary . A certified solar safety filter will filter 100% of UV and IR and 99.999% of visible light. At this price and the optical performance, we are confident that this is definitely a true telescope, not the one from departmental stores or toy shops, and the one that for first time users.
Vixen Polarie review (2)
By William Chin
Landscape astrophotography is a type of photography which composes of nice landscapes (sceneries) on Earth with the night sky that full of stars. Usually we just mount a DSLR camera (with wide angle lens) on camera tripod and start exposure that shorter than 30 seconds. Such method of astrophotography also known as fixed / stationary astrophotography. The exposure of 30 seconds or shorter is to prevent stars become trailed in the photograph. Although we can increase the ISO value of the camera but this will reduce the dynamic range of an image and appeared too grainy from the perspective of some photographer’s standard. Hence, image quality dropped.
The Vixen Polarie provided an opportunity to increase the exposure time while the landscape still clearly been seen (figure 1). Now we can lower down the ISO speed and get a relatively better quality astrophoto. This is especially good for those cameras that with ISO not higher than ISO1600.
FIGURE 1. With longer exposure at 90 seconds, more stars visible in the photograph while the landscape still appeared clearly been seen. Taken using Vixen Polarie w/Canon EOS 40D (UV/IR cut filter replaced), ISO800, Canon EF 16-35mm lens set at 16mm, F/2.8, 90 sec. exposure.
Nothing to worry about the noise that accumulates associated with long exposure time. The increment of the noise is square root of the true signal. For example, if we expose at 30 seconds with ISO800. The signal is 25. Then the associated noise is 5. Now we expose at 120 seconds at ISO800. The signal now should be 100. The associated noise will be 10. From here you can see that when we increase the exposure time, the signal accumulated linearly but the noise was accumulated slower. In term of signal to noise ratio, you can see that it is increasing with longer exposure.
One thing should be aware that with longer exposure, the landscape might become blurring. Thus, we must determine an exposure time just nice for both stars and landscape. I shall do the test in the near future.