Author: Allan Hall

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Observing the moon in daylight

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Moon in daylight? You have seen it, I have seen it, it is broad daylight and there in the sky is the moon. If you stop and think about it you realize that the moon is up in the daytime just as much as it is at night, we just don’t tend to notice it. In my opinion this is a direct result of the fact that the moon has a much higher contrast at night since it is the only rock we see directly illuminated by the sun.

moon in daylight when imaged

The picture above was taken during the day on March 31st 2012. It is a stack of images run through registack to improve detail and sharpness. Yeah, it might be a little too sharp, but that’s OK with me.

One question I always get asked is if I shot that picture in the daylight, why is the sky black? Remember that the moon is very bright, even the moon in daylight is a light gray rock being lit by the sun. The atmosphere is lit by scattered light. In order to darken the moon so that it is not just a white blur you have to reduce the amount of light hitting your camera sensor. This reduction not only darkens the surface of the moon but the sky around it as well. If you look close you will see that the sky around the moon in the above image is not really completely black although it is very dark.

What the moon in daylight to our eyes

In this picture you can see the blue sky, but the moon is way too bright. This is why when you take an image and want to be able to see the surface details you need to darken the image.

What does this mean if you just want to observe the moon in daylight and not take pictures? Remember that moon filter or polarizing filter you use at night? Yup, use that in the day too. The amount of sunlight bouncing off the moon is the same whether it is also shining on you (daytime) or not (nighttime).

If you don’t have one or you want a really nice one there are a few options. First you can purchase neutral density filters which simply reduce the amount of light by a specific amount. The trick is that these reduce all colors of light equally making your view darker, but still correct. You can get both a Baader Planetarium Neutral Density 2″ ND 3.0and a Baader Planetarium Neutral Density Filter 1.25″ ND 3.0 which covers either 2″ or 1.25″ needs. Note the ND 3.0 specification as there are ND 0.9 and ND 0.6 versions as well. The 3.0 is the darkest of them and if you are going to bother I would get the darkest to start with.

You could also go with a variable polarizer which can provide a similar experience. It works by removing stray light that comes in a different angle and only allowing direct rays of light. These can make for sharper images by reducing glare and stray light but often do not cut light as much as the neutral density filters listed above. They also come in both sizes as well such as the Orion 5562 2-Inch Variable Polarizing Eyepiece Filter and the Orion 5560 1.25-Inch Variable Polarizing Filter.

I enjoy viewing the moon in daylight in winter as it is much warmer. Just remember that the seeing conditions are typically worse in the day than at night. This is minimized in the winter when you have the cold crisp air but the light scattering off of particles in the air still present an inferior image in daylight as compared to night.

moon in daylight over some trees

This still is a great way to do some outreach without having to have a group of kids and their parents tripping all over your equipment in the dark in the library parking lot. It is also a lot of fun to observe while waiting for it to get dark so you can observe or image other targets.

When you are ready to do some exploring you can use Sky & Telescope’s Field Map Of The Moon or the Sky & Telescope’s Mirror-Image Field Map of the Moon. I never go out without one of these in my astrophotography kit. These little laminated maps are fantastic for identifying features without getting so detailed as to be overwhelming.

Where do you look? Before the full moon, look in the afternoon. After the full moon, look in the morning. Regardless go outside and look up into the sky!


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Carl Sagan’s Birthday!

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One of my childhood hero’s, Carl Sagan was instrumental in getting me and keeping me interested in science and astronomy in particular. I still remember my father and I watching the TV show Cosmos in the late 1970s. It, like any TV program back in those days, was a big family event which sometimes included popcorn or actual TV Dinners on a TV tray (this did not happen very often). Carl Sagan On November 9th, 1934 in Brooklyn, New York, astronomer, astrophysicist and cosmologist Carl Edward Sagan was born to Russian immigrant Samuel Sagan and New York housewife Rachel Molly Gruber. Sagan’s interest in science was ignited at the 1939 New York World’s Fair at the age of four. That fire was continued with his exploration of the public library at the age of five. He was looking for a book about stars. He also took trips to the American Museum of Natural History with his friends at the age of six or seven, again looking for books. His education included a bachelor’s degree in 1954, bachelor’s degree in physics in 1955, Master of Science in physics in 1956, and a PhD in both astronomy and astrophysics in 1960. His popularization of science kicked into high gear with the writing of Cosmos. The book was made into a very popular television documentary named Cosmos: A Personal Journey.

Cosmos The show consisted of thirteen episodes and originally aired in 1980. Cosmos has won an Emmy, a Peabody Award, and been seen in more than sixty countries by over half a billion people. This was so popular that it has been rereleased multiple times worldwide with the latest being the digitally restored and remastered 2009 five-disc DVD set in the UK. His show even sparked a spinoff Cosmos: A Spacetime Odyssey [Blu-ray] hosted by Neil deGrasse Tyson who was an acquaintance of his. Sagan’s widow, Ann Druyan who was a coproducer of the original series is an executive producer on the new series.

He wrote several other science related books including A Pale Blue Dot in 1994 as a sequel to Cosmos. His book The Dragons of Eden: Speculations on the Evolution of Human Intelligence even won a Pulitzer Prize. Sagan was also a science fiction author writing such books as Contact, which was made into the movie Contact [Blu-ray] or Contact (DVD) starring Jodie Foster and Matthew McConaughey. This movie won the 1998 Hugo Award for best dramatic presentation. 

Carl Sagan was the designer of the gold plaques containing the universal message from Earth on two Pioneer spacecraft as well as the gold record on the Voyager spacecraft. Many of his theories and ideas have been proven over the years including the surface conditions of Saturn’s moons Titan and Europa and his ideas on global warming.

One of Sagan’s greatest passions was the search for extraterrestrial life. He served on the SETI Institute Board of Trustees. He was one of the founders of The Planetary Society with Bruce Murray, and Louis Friedman in 1980. The society promotes and participates in astronomy and planetary sciences. It is quite possible that no other person in the history of astronomy has been as successful at popularizing astronomy and science in general as Sagan. Carl Sagan passed away on December 20th, 1996 at the age of 62.

carl sagan Happy birthday Carl Sagan, we miss you!


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Burnham’s Celestial Handbook

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Burnham’s Celestial Handbook is an astronomy book that has been something I have heard about over and over again ever since I have really been into astronomy. I was always dubious as to their value to my astronomy as they were old (1978), not available new that I could tell (if they were really good, wouldn’t they still be in print?) and pretty large (2138 pages total).

Burnham's Celestial Handbook covers After getting a set in good shape from a used book store, for more than the original new price I might add, I have spent some time looking through them and actually using them. What I have found is that they can indeed be very useful.

Burnham's Celestial Handbook spines If nothing else, Burnham’s Celestial Handbook will make you learn. To use them you need to read the first 101 pages which tell you how to use the books. These pages alone are worth the price of admission as they discuss topics such as sidereal time, celestial coordinates, the classification of stars and galaxies, the H-R diagram of stellar luminosities, spectral classes, and of course, the nomenclature used throughout the book. Even if you are familiar with most of this the review is quite nice. After getting antiquated with the basics he starts systematically and alphabetically going through all the constellations detailing all the objects within each one. The pages are filled with pictures, charts, diagrams and his “descriptive notes”.

Burnham's Celestial Handbook star chart A great example is his notes for Alpha in Canes Venatici: “ALPHA (12 Canum) Mag 2.89 (slightly variable); Spectrum A0p or B9.5p. Position 12537n3835. Name- COR CAROLI, “the heart of Charles”. The popular story is that the star was so named by Halley in honor of King Charles II of England. According to R.H.Allen, “This was done at the suggestion of the court physician Sir Charles Scarborough, who said that it had shone with special brilliance on the eve of the King’s retun to London, May 29, 1660.” Of course the text goes on quite a bit just about this star but this excerpt should give you the general idea of the wealth of not just scientific information but the story behind some of it as well.

Burnham's Celestial Handbook sample pages One could spend their lifetime simply following in the footsteps of Burnham as laid out in Burnham’s Celestial Handbook. How he completed such a fantastic work is beyond me. That may be why such a project is a rarity. If you have not read at least some of this set I urge you to do so. If you have a copy and no longer ready it, I would ask you to share it with others. Make sure that your astronomy club’s library has a copy.

You can often find copies of this wonderful astronomy book on Amazon.


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DIY light cylinder for taking flats; small, light, battery powered

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My most popular DIY project which I think is now in at least two of my books is this one. Since so many people enjoy it I thought I would post it on the blog for everyone to use. Remember that this is primarily for inspiration and not really meant to be a recipe for one that will work with your scope.

Well since I have started really working on my post processing I have noticed the need to start shooting flats. The problem is, you must shoot flats without moving the camera, scope, focus, anything. This means they have to be shot on site, right before or right after shooting your lights.

There are a couple of problems with that. All the designs I have seen are large boxes, I don’t want to carry around a large box to the dark site and besides, something that large might disturb the dust bunnies and mess up the whole idea of flats. Next problem is if anyone else is there, flicking on a light could get me shot (this is Texas here, heh). So what do I do?

First thing I do is come up with a list of what it needs to be able to do, so here goes:

1) It must be easily portable, small and light. Anything heavy can mess up the scope’s setup.
2) It must be reasonably accurate. The light must be uniform in illumination.
3) It must be reasonably inexpensive, the EL panels I have been looking at run about $100, lets keep it under that.
4) It must be usable when other images are right next to me, no light leaks.
5) It must be servicable, meaning I can repair it, replace things, etc.

Off to Home Depot I go! I know they thought I was some terrorist getting bomb supplies, I walked up and down every isle grabbing weird items, putting others back, fitting things together that were completely unreleated. Boy did I get some weird looks! After about an hour I left with this:

diy01

This was two 4″ PVC sewer pipe connectors, a 6″ flashing connector for I think a stove exhaust vent, a can of PVC glue, two translucent lids, a 6″ plastic floor drain grill, and a bag of bolts.

Next stop, Radio Shack!

diy02

Here I found 4 white 3v LEDs, 4 LED mounts, a rocker switch, a 4 AA battery holder, and a project box. Next stop, Wal-Mart!

diy03

Left to right we have a box of male and female electrical connectors, some styrofoam plates, glue and some velcro.

Now its time to start working on stuff. The first thing I needed was a Proof Of Concept. For this I put things together and mounted it on the scope with just some clear tape and used one of those battery powered lights you press down on the top to turn on. That gave me my first flat:

diy04

This clearly shows I need flats. This image has been stretched and desaturated, it was brown (used an incandescent bulb). Next was to test out the batteries and LEDs:

diy05

Good! Now I know I can get them all lit up. Lets mount the battery pack to the top of the project box with hot glue:

diy06

Now we drill holes in the project box, four large ones for the LED mounts and two (well, four now cause I goobered!) smaller ones to bolt the project box to the drain grill:

diy07

Now we bolt the box on the grate and install the LEDs:

diy08

Now I open the package of velcro and take the fuzzy strip and run it around the inside of the 6″ metal connector, on the opposite end of where it will mount to the drain grill as this will protect the paint on the outside of the dew shield. Next we glue the two 4″ sewer pipe couplers together and mount them inside the 6″ metal connector:

diy09

Here is the outside view:

diy10

After a little wiring, we cut the paper plates into two circles for difusers, here is the first one installed:

diy11

So I turn on the lights and there is a problem, the light is nowhere near even enough to take a flat:

diy12

But I am not as stupid as I look! (or feel sometimes), I had actually planned on this and so I install the second difuser in it’s place four or so inches in front of the first diffuser and I get this:

perfect light for taking flats

HA! Nice even illumination! Lets put it on the scope:

Set up to take flats

And take a flat to see how it works:

A nice looking flat

So a little information:

Size = 7.5″ diameter x 10″ tall/long
Weight = 2lbs 4oz with batteries
Cost = $60 buying everything except a little wire and solder
Time to construct = About 3 hours
Exposure for about 40% sat on histogram = ISO800 1/60th sec

Now since the light goes down the inside of the sewer pipe couplers, to leak out it would have to come back up the outside of the couplers, curve around the end of the scope, and go down the metal coupler on the outside. I don’t see much light doing that. After dark tonight I will give it another test and let you all know how it goes.

Hope you enjoyed!

Allan

 


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Dark site etiquette

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Dark site etiquette is an important part of astronomy to ensure that everyone enjoys their evening under the stars.

Dark site etiquette

When you are going out to an astronomy club dark site there are some guidelines you should follow to make it an enjoyable experience for everyone. Some of them probably seem like commons sense, and they are, to someone who understands what is going on. Unfortunately a lot of newcomers have no idea and this can cause friction. Help avoid the friction and stares by following a few simple astronomy etiquette guidelines.

Dark Site Etiquette Guidelines

  1. If you park anywhere near where people are observing make sure you arrive before dark and park your vehicle so that the headlights are pointed away from the observing field. This makes sure that when you leave before the serious observers or astrophotographers (and you will leave before them unless the sun has already risen) your headlights will do as little damage as possible.
  2. Get everything out of your vehicle as soon as you arrive. Stack it next to the vehicle if needed but whatever you do avoid opening the doors and causing the lights to come on repeatedly after dark. It is amazing how bright your interior lights are once everyone’s eyes have adapted to the dark. Many astronomers and astrophotographers go one step further with this dark site etiquette by removing or disabling their interior vehicle lights completely.
  3. Speaking of amazingly bright lights, do not use that super bright LED flashlight or the light on your phone to shine on the walkway so you can see where you are walking. Wait by your car until your eyes adjust to the darkness or bring a dim red astronomy light (available on Amazon or telescopes.com) to light your way. Even if your light is red, never shine it at anyone’s eyes or towards their equipment unless you ask first. Astrophotography is about photographing dim lights in the night sky, many of them red, so your red flashlight will ruin an hour long exposure and tend not not make you any friends. If you want a red flashlight used one specifically for astronomy as they are not stupid bright, one such as the Celestron 93588 Astro Night Vision Flashlight is an excellent choice and very affordable. Getting a dedicated red light for this will show everyone you really care about dark site etiquette.
  4. Never touch someone’s telescope without their express permission. They could be imaging and you are fumbling for an eyepiece to look through, destroying their image they have been exposing for the past hour. Or maybe they are in the process of aligning their telescope and your touching could move it off center messing up the computer’s calculations. Or they could be one of “those” people and they could get pretty hostile that you got handsy with their $1200 eyepiece on their $10,000 telescope (why did you bring it out here then goofus?).
  5. Watch where you step. Remember that many of these telescopes run off power cords, and those power cords run across the ground to outlets. Also watch for the legs of tripods. Tripping over either one can completely destroy an astrophotographer’s entire evening and cause a visual observer to waste thirty minutes or more setting everything back up.
  6. Use the restroom before you come out, some dark sites have no facilities. The bushes may be fine for you but you will be in mixed company and quite possibly have other people’s children running around.
  7. Laser pointers should only be used by experienced astronomers who frequent this dark site. Not only is it dangerous to point a pointer towards a person, it is more than bright enough to ruin someones image should the beam enter the area where they are shooting. In addition, it is not only bad astronomy behavior, but it is also a federal crime in the US and many other countries to point at an aircraft. Do you know where the local flight patterns are around this dark site? I know exactly where they are around mine because I constantly see planes there.
  8. If you borrow something, take it back immediately when you are finished. This is not only respectful but makes sure that the item is available should someone else want to borrow it.
  9. Lastly, if you take your children, please make sure they understand the expected astronomy behavior and keep a close eye on them. While most astronomy events welcome children and indeed are geared towards them in many cases, everyone wants both the child and the very expensive telescopes to survive the night undamaged.

When in doubt about astronomy behavior, ask around. Most astronomy gatherings have more experienced people who will be happy to lead you around and show you the appropriate dark site etiquette. Don’t let these guidelines scare you, we all make mistakes. As long as they see you are making an effort you will probably be excused for any little faux pas you may inadvertently commit.

I hope you enjoyed my article on dark site etiquette!


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Getting Started: Visual Astronomy released

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Getting Started: Visual Astronomy is quite a departure for me as most of you know I am primarily an astrophotographer and spend comparably very little time visually observing. When you are imaging for up to ten hours at a stretch however that still leaves a lot of time for visual observing, so compared to many others around me I do a lot of visual observing. It is all relative. There are a lot of fantastic books on general astronomy and observational astronomy. The one thing that I could never find however is a book that got right to the point on how to visually observe that was easily portable. This led me to do the research and write my own.

Getting Started: Visual Astronomy Getting Started: Visual Astronomy is a standard sized book just like my others that gets right to the heart of the matter. It is designed to get you up and observing quickly. It answers all the basic questions and some of the more advanced ones as well making sure you know how to use the equipment you have, and what equipment you may be interested in purchasing. From naked eye observations, through binoculars and all the way to the different types of large telescopes, you will find all the information you need to get out under the stars and begin your journey. It even includes a few biographies of important people such as the father of modern observational astronomy, Galileo Galilei, so that you get a feel for the history of observational astronomy.

You can get more information, read the table of contents and introduction and more at the book’s home page here:

https://www.allans-stuff.com/va/

Look for Getting Started: Visual Astronomy in both print and Kindle editions from Amazon. The first person to review the book on Amazon had this to say: “This book will help you get started in Astronomy and answers every question you have plus plenty more you didn’t know you had. From buying your first telescope to how to read star maps this book offers a step by step guide on everything. Written in a well structured format that makes the information easy to digest. Well worth the sticker price for the amount of information contained. I highly recommend.”

I hope you enjoy Getting Started: Visual Astronomy!


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Difference between DSLR and CCD astrophotography

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The difference between DSLR and CCD astrophotography cameras is pretty immense. Most people when searching for astrophotography equipment for beginners choose DSLR astrophotography because they either already have one or they are far cheaper to start with. When you go from DSLR astrophotography to a monochrome CCD you lose live view, but gain chip cooling. You lose color but gain sensitivity. You can lose pixels but gain resolution. Wait a minute! How can you gain resolution if you lose pixels? Easy, you no longer have the Bayer matrix turning every four pixels into one so your monochrome CCD in effect has four times the stated resolution. Yeah, I know it isn’t that cut and dried, but seeing the images from both it sure starts to ring true. Here is a DSLR astrophotography image of M8 taken with a 16.7MP Nikon D7000, 36 300sec lights and 25 darks:

M8 by DSLR I always thought this was a pretty good image for unmodified DSLR astrophotography, and it is.

Once I decided to switch to CCD astrophotography I started looking for a camera trying to find the best CCD camera for astrophotography. Out of all the choices out there for astrophotography CCD cameras I picked an Atik 383L monochrome as it fit my needs and budget the best. Now here is the same target, same telescope, same mount, same capture software, same processing software, but with only an 8MP monochrome CCD shooting through a 6nm Hydrogen Alpha filter. That’s right, HALF the resolution:

M8 showing Difference between DSLR and CCD astrophotography Something else I forgot to mention, this is only 4 480sec exposures and 4 darks. Yep, one fifth of the total exposure time and about one sixth the number of darks. I don’t even know what to think except CCD astrophotography rocks. Why exactly was it I waited so long to go monochrome? I have no idea.

So now the thing that people always bring up when looking at monochrome CCD astrophotography is to shoot narrowband or RGB with filters on monochrome takes three times as long because you have to shoot through three different filters. True enough, but when I can get results like these with one fifth of the total exposure time, even if I have to shoot through three filters it still works out to less time exposing to get better images. I am still working on combining the Ha, OIII and S2 together to make a single color image and unfortunately the night I took this image I did not get enough usable OIII or S2.

Sure there are lots of things still to work out when switching from DSLR astrophotography to shooting CCD astrophotography but with a start like this it sure looks promising.

Stay tuned for the results of the first color combination coming soon!

I hope you enjoyed seeing the Difference between DSLR and CCD astrophotography!


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