Thursday, November 16, 2017

Carnival of Space #535

Hi all and welcome to another issue of Carnival of Space. Before going into the articles here are two nice picture I took in the last weeks. You might need to enlarge them to see properly:
The moon and Aldebaran
The moon and Aldebaran

Venus and Jupiter
Venus and Jupiter


And to this week articles:

UniverseToday
CosmoQuest
NextBigFuture
  • Xcor was making a suborbital reusable launch vehicle (a suborbital spaceplane). XCOR filed for Chapter 7 bankruptcy Wednesday in the Eastern District of California.
  • NASA is providing an update on the first integrated launch of the Space Launch System (SLS) rocket and Orion spacecraft after completing a comprehensive review of the launch schedule. The new launch date for an unmanned first flight of the Space Launch System is Dec, 2019. This is NASA’s stretch goal target rather than June 2020 which is what the review expects will happen
  • An explosion occurred on Saturday, Nov 4, 2017 during a test of a “Block 5” Merlin engine, which will be used in a future generation of the company’s Falcon 9 rockets.
    It was a engine qualification test and no one was injured.
    The block 5 Falcon 9 will have higher thrust on all of the engines and improvements on landing legs compared to the block 4 Falcon 9 Full Thrust. There are also a number of small changes to streamline recovery and re-usability of first-stage boosters. Alterations to the launch vehicle are primarily focused on increasing the speed of production and efficiency of re-usability. SpaceX aims to fly each Block 5 first stage ten times with only inspections in between, and up to 100 times with refurbishment.







Sunday, June 4, 2017

Carnival of space #512

Hi all and welcome to CoS #512 with many great articles from the astronomy fandom!
And in this issue, we will go from the first black holes to new features on the moon. From Triton to Jupiter, to new rockets technique and to some space history and talks about the future. Spare yourself a hour and enjoy!
Carnival of Space #512
Carnival of Space #512

With no further delays, let us start.

From "The evolving planet"
From "Universe Today"

From "Chandra"
From "Blasting News"
From "Business Insider"
From "Thought co"
From "Planetaria"
  • A stormy, turbulent world: New science results from Juno reveal ‘whole new Jupiter
From "Next Big Future"
  • "Rocket Lab" broke new ground today when its Electron rocket reached space at 16:23 NZST. "Rocket Lab" has said they will charge $5 million for each rocket. The SpaceX Falcon 9 has a launch cost of $57 million. "Rocket Lab" will launch up to 225 kilograms. The Falcon 9 can launch 22800 kilograms to low Earth orbit. "Rocket Lab" 3D prints almost all of parts. They use carbon composite materials for many parts which are lighter. "Rocket Lab" uses advanced batteries to enable electric turbopumps.



Wednesday, March 1, 2017

Use your camera as a telescope

A camera can be a small telescope. It collects lights, it has a larger aperture than your eye. A lens is a 
lens.

As I wrote in a previous article: How to photograph stars and constellations, you can use any camera to photograph the sky. You should be realistic and understand that you are photographing mostly wide-filed photos. Entire constellations or large objects with a telephoto lens. The photos will help you see more stars, observe their different colors, and even to find deep sky objects such as clusters, nebulas and even galaxies.

A DSLR is recommended and the better your lens the better the results but even with a compact camera it is possible to get nice results.

Photos can be taken from anywhere but to avoid light pollution it is best to go to darkest as possible places. No need to mention that a sturdy tripod is a must.

The major problem of photographing stars is that the earth rotate and the stars are smudged from dot to lines. You can use this rotation to produce great star trails photos but our aim in this specific article is to better see the stars and faint objects.

The rule of thumb is that the longest exposure should not be more than 500/focal-length. For example, if you use a 28mm lens you can expose for 18 seconds without noticing much smudging. These number is correct for Full-Frame cameras. If you are using an APS camera, you should adjust by the crop factor (mostly 1.5) so 18 seconds becomes just 12. If you are using a telephoto lens you will have shorter exposures time.

So what to do? Use higher ISO, 400 800 or even 1600 depends on your specific model and open the aperture as possible.

Focusing is another important matter. Manual focusing is a must. Try to find a bright star and use LiveView to better focus. If you are not sure, check your photo after a single exposure, zoom into it and adjust the focus as needed.

A release cable/remote is also necessary to prevent the shake caused by pressing the shutter. If you do not have a remote/release cable use the self-photo feature to add 2 seconds delay before each photograph.

To save time I take the first photo with a very high ISO (3200 or 1600), short exposure and without noise reduction. After I set the composition as I like I use a lower ISO and the longest possible exposure. Usually, I use the built-in "log exposure noise reduction" but it can be done later in a software if you take one or two photos of the same exposure time with the lens cap on. 

To take your photos to the next level you will need a tracker device. The tracker is pointed to the polar star (or to the relevant area in the southern hemisphere) and rotates in the opposite direction to the earth, thus eliminating the smudging and enables longer exposures.  I am using the Ioptron tracker, if you are handy you can build your own device (look for instructions to build a "barn door tracker").

If you go for a tracker notice that there are models with additional small finderscope which will give you much better results and you should buy that model. also notice that some models have a 3/8" mount while most tripods have a 1/4" mount, so a small adapter might be required (It is very cheap adapter). 

Using the tracker is simple you put it on a tripod, points it to the north star, use the finderscope for exact alignment (I use a small app for my smartphone to do this - Polar scope finder, there are also free apps for this purpose). Put the ball-head on the tracker (carefully, not to move the tracker) and point the camera to the area you want to photograph. From time to time check that the tracker still points to the correct place.

Here are some examples, all photos are 30second exposure. the Pleiades cluster - M45 - is a nice object for 300mm lens.
M45-Pleiades
M45-Pleiades
 Here is the same photo without tracking, the difference is clear.
M45-Pleiades
M45-Pleiades
 The double cluster in Perseus.
 The double cluster at Perseus
הוסף כיתוב
 The beehive cluster (M44) at Cancer.
 The beehive cluster (M44) at Cancer.
 The beehive cluster (M44) at Cancer.
 The great dog with Sirius, the brightest star.
The great dog - Canis Major
The great dog - Canis Major
 Here is the same photo of Canis Major without tracking. Since the focal length is wider there isn't much smudging but there is still a considerable amount.
The great dog - Canis Major
The great dog - Canis Major
Orion constellation. With blue Rigel (bottom right) and orange Betelgeuse (Top left), Orion belt in the middle and even a hint of Orion Nebula (m42) 
Orion constellation
Orion constellation


Tuesday, November 15, 2016

Supermoon


From time to time, you hear news about a big and bright moon that has not been seen in the last ten, twenty, or even a hundred years. Such moons have the nickname, "supermoon". Here are some facts and information about supermoons. All numbers and times relate to the supermoon of November 14,2016.

What is a supermoon?
A supermoon is a term for a full moon that is near perigee. The perigee is the point in the moon's orbit that is closest to earth. The moon is full once a month and also at perigee once a month. From time to time, the moon is both full and near perigee around the same time and the result is a somewhat larger and brighter moon, a.k.a. "supermoon".

What will be the distance to the current supermoon?
The closest distance to the moon varies each month and averages around 357,000 kilometers. The earth's distance from the current supermoon  will be 356,511 kilometers (227,118 miles). This distance is the distance between the earth's and moon's centers. The exact times (UTC) are:
  • Moon at Perigee 13:24 
  • Full Moon 15:54 
  • The moonrise varies for different locations.
Is the change of the moon's size significant?
The difference between a distant moon ( >400,000 km) and a close moon is indeed significant and can reach 40,000 km which are 14% of the distance. This difference has an impact on the apparent size of the moon and 14% is is the number you will probably see in the news; however, I think they should calculate the difference based on the average distance of the moon, which is just half of that.  
The best (and only) way to see that difference is to take two photos and compare them. See the image below for example:




The smallest distance since 1948
Headlines such as "Nearest moon since 1948" are factually correct but are meaningless. As mentioned above the distance is between the earth's and moon's centers. The distance of the moon to a specific observer on earth is different and changes throughout the night as the earth revolves. 
Since 1948, there have been many others supermoons, some of them only 100 km farther than this supermoon. But if an observer on earth sees the moon before or after the exact perigee, this 100 km is negligible to the change due to earth's rotation (which is 6300 km about the same as earth's radii, in just a few hours). Such small changes of 0.1% have no effect on the moon's apparent size. It might be that for a given observer in a given location, there was a nearer moon after 1948.


Why is the moon orange or particularly large when it rises?
The red rising moon is due to the atmosphere and the big rising moon is an illusion. Read more about the large red moon here. Both phenomena are not related to the moon being a supermoon.

Will I see any difference in the size of the moon?
Probably not. If you go out and look at the full moon you, will see that it is very bright. Maybe you'll notice it is brighter than the previous evening's moon, but that is true for every full moon. To see a change in the moon's size, you will have to compare the moon to something. To what? It is more or less the same as the day before and certainly one can't recall how a very far away moon looked several months ago. If you want to compare the difference in the size of the apparent moon, you need patience. Take some pictures, wait patiently for seven months (When then the full moon will be distant) and then take more photos.

What about the brightness of the moon?
The brightness of the moon is a whole new ball game. The moon's apparent size depends only on its distance, but the brightness depends on other factors as well. So if the news reports about the distance are at least credible to some extent, the reports on the brightness are almost always completely wrong.

Explanation:
The two most obvious factors that affect the brightness of the moon are the moon's distance from the earth and also the earth's distance from the sun. As the two of them are the smallest possible, the brightness increases. The earth is close to the sun at the beginning of January, which is part of the reasons why this November's supermoon arrived the news.

Are there more important factors to the brightness of the moon?
Yes, there are more, and the most important of is the phase angle, which relates to the distance of the moon (in degrees) from the ecliptic. The farther the moon, the less bright it will be. For the current supermoon, the moon is more than 5 degrees from the ecliptic so it will not be so bright after all.

When will the moon be the brightest?
Suppose we have a full moon at perigee (closest to earth), we assume that the earth is at perihelion (closest to the sun), and we assume that it is also just on the ecliptic. In this situation, the moon would be at its brightest. But under these conditions, we would be in the middle of a very deep lunar eclipse, which is a great event to observe, but the moon is not seen at all. For this reason, the moon has a theoretical maximum brightness limit, but that limit can never be observed.

When will be the brightest moon that can be observed?
Think again about the conditions in the previous section. The only compromise that can be done is that the moon will not be full, but just a little before or after (a difference of few hours) which means that the moon is as close as possible to earth, the earth is as close as possible to the sun, and the moon is almost full. This is just before or after a full lunar eclipse.

When is the next lunar eclipse with these conditions?
The last supermoon eclipse was January 9,2001, and the next time will be an eclipse on December 12, 2114. The brightest supermoon between 1800-2200 will be on January 3, 2151, when the earth is almost at perihelion. These dates are from the book, "More Astronomical Morsels" by Jean Meeus.

So what is all the fuss about?
As usual, much ado about nothing. But if such news will make people go out and observe the moon, so be it. The full moon and especially the rising of the moon are always an experience. Take a look for yourself in the video attached!

What other things you recommend we observe?
The moon is always interesting to observe. Even a small pair of binoculars will show many details on its surface, which change daily depending on the phase of the moon. Eclipses are always interesting, and conjunctions of the moon and planets or bright stars are interesting. Actually, one day after this supermoon, on November 15, 20161, the moon will cover the star Aldebaran in Taurus. This occultation will be visible to observers in Southeast Asia.

More questions?
Write them in the comments and I'll be happy to answer!