Tonight a bright half Moon will be just under 4° from the Pleiades star cluster. The Moon will be 43% illuminated, bright, but the cluster is bright enough to be seen even against a bright Moon. As the Pleiades move to the west over coming months there will be a few more lunar conjunctions, with increasingly smaller crescents.
The Old is New Again
Bear with me. Still moving much of the old Darker View material to the new platform. Thus you will see posts from the old site appearing here as new posts. The easiest way for me to transfer the old stuff is to cut, paste, edit for freshness, and re-post. It will be a long process.
Deep Violet, an 18″ f/4.5 Dobsonian
In April 2001 I realized a dream that had been many years in the dreaming and a year in the making, a large aperture dobsonian.
- The scope had to have sufficient aperture to take advantage of the dark skies available near Tucson. I wanted to see spiral arms in galaxies.
- The design was to be visual only. No drives, but provisions for an equatorial platform at a later date.
- The mount would be a no compromise rigid structure, capable of allowing good optics to perform at their best.
- The scope had to fit through a standard doorway.
- The scope had to fit in the cargo compartment of a Ford Explorer Sport without dropping the seat for safety during transport.
- The eyepiece must not be an excessive distance above the ground, allowing use while standing on the ground much of the time. (But then, I’m 6’2″ tall)
Over a decade of engineering experience has taught me that a well defined set of specifications can make all the difference at the end of a project. With these design goals in mind the plan then progressed rapidly.
The Moon and Jupiter
As the Moon slides along the line of planets in the evening sky, it becomes Jupiter’s turn to make a pair. The Moon and Jupiter will be under 4° apart tonight. A brilliant pair with the -2.2 magnitude Jupiter beside a 25% illuminated crescent Moon.
Finding Venus in the Daytime
It is possible to see planets in the daytime. Both Jupiter and Venus are bright enough to see fairly easily in full daylight if conditions are right. You need to know where and how to look, but once glimpsed they are fairly easily seen. It is the knowing how that makes it possible. Try these simple hints…
- Try when the planets are far from the glare of the Sun, in the first hours after dawn or last hours of the day are best.
- Clean air is necessary. If the air is hazy, dusty or smoggy it will hide the planets from view, particularly when near the Sun. There will just be too much solar glare to pick out the planet. For the same reason try when the planet is high in the sky and you are looking through much less air.
- The human eye will relax and defocus if there is nothing to focus on. This happens when looking at a plain expanse of blue sky. You could be looking right at the planet and not see it. A few puffy clouds around, or better yet, the Moon, will give the eye something to focus on, allowing the planet to be easily seen.
- Put the Sun out of sight to reduce glare. Simply position yourself in the shadow of a tree or building to get a better view.
- Pick a day when the Moon is near the object you are looking for, it will provide a simple signpost to the correct location.
It is this last hint that can be particularly useful today. Venus is about 4° degrees south of the Moon this afternoon. If you can find the Moon in the late afternoon check just below it and to the left for Venus. The planet will be about a eight lunar diameters away from the Moon, seen as a bright star-like object. Tomorrow it will be Jupiter’s turn, and you can try again to see a planet in the daytime.
Have a try.
Mars Opposition Reminder
One week from today, on March 3rd, the planet Mars will pass through opposition.
Mars orbits the Sun every 1.88 years, with Earth only taking one year for each orbit. Like two runners on a track the two planets race each other around the Sun. But we have the inside lane, lapping the red planet every two years. These events are called opposition, when Mars is closest to us and best positioned for viewing by earthbound telescopes.
Closest approach of the two planets is not necessarily on the same day as opposition, but can vary up to two weeks. This year closest approach will occur March 5th with the two planets approaching to 99,331,411 km (61,721,554 miles) at 07:01HST.1 At this distance the red planet will show a disk 13.89″ arc-seconds across in the eyepiece.2
Mars during the 2005 opposition
Do not worry about viewing on the 3rd or 5th, any time in the month leading up to and after opposition the viewing will be very good. With even a modest telescope it should be possible to see the bright polar caps and light and dark markings on the planet.
All month Mars will be visible throughout the night, high in the sky at midnight. This is the time to enjoy observing our closest neighboring planet while it is nearby and high in the night sky.
1) 2012 Mars Opposition at SEDS
2) The 2012 Aphelic Apparition of Mars
A Red LED Desk Lamp
Need a red lamp to provide soft red illumination around the telescope? Described here is an easy way to do this. Take a commonly available desklamp and convert it to LED’s. This is a single evening project, taking just a few hours to accomplish once the parts have been obtained.
I have found the resulting light extremely useful when observing. No more holding the flashlight in your mouth when reading charts or making observing notes.
Because the light can light up a whole area when turned fully on it can be used as a worklight when breaking down gear and packing it into the vehicle without bothering other observers at a dark observing site. Or you might build the 120V version for a personal observatory.
I have also found that these lights also make great gifts for fellow astronomers.
To accomplish this we will disassemble the lamp, remove the 12V bulb and replace it with an array of LED’s. To control the brightness we will install a variable regulator to allow dimming of the lamp from completely off to very bright. An option is to install another connector to allow DC power to be supplied from a battery for field use.
Before embarking on this project be sure to read this entire article. Having the entire task in mind will help you plan ahead. It is important to use safe electronic assembly techniques to avoid any risk of damage or injury when making the modifications or when using the lamp. We will make no modifications to the high voltage side of the transformer to insure the lamp remains safe to use.
One secret to the lamp is the LED’s. These wonderful devices convert a small trickle of electricity into a very bright red light. Be sure to get ‘Ultrabright’ or ‘Superbright’ types that put out at least 3000mCd (millicandela). I found some that put out 6000mCd that I use in my lights at All Electronics. Perfboard, regulators and many of the other parts can also be purchased there.
Continue reading “A Red LED Desk Lamp”The Moon and Venus
Yesterday saw the Moon near Venus, tonight will see the pair even closer. It will be hard to miss the bright pair only 5° apart. Venus will be shining brilliantly at about -4.2 magnitude next to a 17% illuminated Moon. Jupiter can be seen 16° above the pair. Mercury is visible just above the sunset.
Rebuilding a 12.5″ f/5 Truss Tube Dobsonian
Mechanically the scope had a few problems. The truss tubes were attached with separate hardware top and bottom, so that setup required over 20 minutes of sorting through screws and futzing with eight separate truss tubes waving around the whole time.
The elevation bearings had been set about 1/8th inch off from each other leading to a side to side twist when the scope was moved in elevation. This was not a major problem when using the scope visually but would make the use of digital setting circles impossible as DSC’s require orthogonal axis in the scope.
The ground board was a bit undersized, making the scope prone to tipping when used at low elevation.
The rebuilt scope is essentially finished with the usual tweaking and small adjustments remaining. Things are coming out very well and a few of the changes are worth passing along to the ATM community. In the sections below I will concentrate on practical details in hope of conveying some of the finer points in telescope making.
Continue reading “Rebuilding a 12.5″ f/5 Truss Tube Dobsonian”
The Moon and Venus
The nice evening planetary alignment continues tonight. This evening will feature a nice pairing of Venus and the Moon. It will be hard to miss the bright pair only 8° apart. Venus will be shining brilliantly at about -4.2 magnitude next to a 10% illuminated Moon. Jupiter can be seen 16° above the pair. Mercury is visible just above the sunset. The Moon and Venus will be even closer tomorrow night, only 5° apart.