Captured Nov 15th, 2012_Part of Life

Yesterday, I spent a great afternoon of quality time with my grandson, Marek. We arrived back home at around 10:30 PM. The skies were clear and bright. I immediately made a pot of coffee and opened the observatory in preparation for a two hour run on a target that has eluded me. While waiting for the run to complete, i entertained myself by searching for meteors from the Leonid Meteor Shower and thinking up catchy phrases to print on t-shirts. Using a common theme, i came up with a phrase that seemed appropriate at the time. But for some reason, i don't believe that "Astronomers do it when it's so cold it will take your breath away" is going to be a big seller. 

I thought i had everything right. The alignment went well, the tracking was dead on, batteries were at full charge and i had a good lock with the autoguider. But after the run, i reentered the observatory and did a quick scan of the photos i had acquired. They were junk. Of the sixty photos i had taken, only a small handful were usable. Upon closer examination, i discovered that one of the cables had gotten tangled and had been pulling against the scope for the entire run. I hadn't checked the cables. Oh well, the forecast is for clear skies tonight...

I like to start each post with a photo. The image i used today was taken from a few shots that were gathered Thursday night before the clouds moved in. Because this is not the first time i have forgotten to check the cables and ruined a set of photos, I thought the Thursday night image was appropriate. The Dumbell Nebula is about 1300 light years distant. Sixteen shots at two minutes each. ISO 1600. 

clear skies...

Captured Sept 15th, 2012_The Milky Way_Numbers

About two hundred years before the birth of Christ, Eratosthenes, the curator of the Great Library of Alexandria, decided he was going to measure the circumference of the Earth. He knew that at noon on a given day, in Syene, a city to the south, a stick planted perpendicular to the ground cast no shadow. So he did the same thing in Alexandria and on the given day, at noon, dutifully measured the angle of the shadow. He divided that angle into 360 and multiplied the result by the distance between the two cities. He then announced to the world the circumference of the Earth. Seems so simple, but he was right. He measured it to within two percent of the the number we have today. With two sticks. While he was at it, he correctly measured the distance to the Sun and Moon. But the powers that ruled the world at that time decided that the Alexandrians were just too smart for their own good. The library and almost all the knowledge contained within it were destroyed. Fifteen hundred years later, Columbus had a hard time convincing a crew to sail with him. They all thought they were going to fall off the edge of a flat world. 

Now for the numbers i want to talk about. If the earth didn't rotate at all, it would be the end of the world as we know it. But the astrophotography opportunities would be incredible! Not having to worry about rotation would allow me to collect HOURS of data without a hitch. At the Equator, the surface of the earth spins around the axis at just over 1000 miles per hour. Since where i live is so much closer to the axis, the speed is more like 700 miles per hour. Eight inches from the North or South Pole, the Earth is spinning at a robust 2.1 inches per hour. And that is about the speed my telescope mount rotates in the opposite direction. If i can get the axis of the scope to line up exactly parallel to the axis of the Earth, i can offset the rotation of the Earth and shoot pictures as if the Earth was not rotating at all. Not an easy task, and i spend an incredible amount of time on acquiring that alignment. But there are other ways....

The magic number is 600. That is the number i commit to memory. I don't even remember where i got it. I would assume i made some sort of google search on how to avoid star trails in photographs. In the next few lines i'm going to explain how to use it. 

The camera i use is a canon t2i. i bought it in a package deal containing two lenses. One lens is a 18mm to 55mm zoom, and the other is a 55mm to 250mm zoom. Nothing special, but not a bad package. The trick to photographing the stars off a fixed tripod is to limit each exposure to a time period that does not show discernible star movement. You can take as many photos as you like, they just have to be very short exposures. How short? Thats where the number 600 comes into play. If i wanted the greatest magnification possible from the lenses listed, i would take the larger lens and set the zoom at 250mm. If i divide 250 into 600 the result is 2.4. That is the maximum exposure i can use at 250mm. I can take as many pictures as i like to gather more light, but each shot can be no longer that 2.4 seconds. There will be no star trails. Just nice crisp stars. Several galaxies and nebula can be captured at these settings. If i were to set the zoom at 100mm, i could acquire shots at 6 seconds each. Once i have all the photos i want, i dump them into the freely available DeepSkyStacker. It does all the work of combining all the light data and aligning the stars in all the shots into one nice photo. 

The photo at the top of this post was taken at the Black Forest Star Party. I was using just the camera on a tripod. the lens was set to 18mm to allow 30 second exposures. (actually,  600/18=33.333 but 30 seconds is the highest autoexposure setting on my camera) The ISO would have been set at 1600 and the fstop as open as i could get it. I don't remember how many photos i collected, probably more than 20. It's a view looking toward the center of our home galaxy, the Milky Way. I used nothing more than the camera, tripod and a wired remote button.

(i know my daughter is going to read halfway thru this post and start mumbling "blah, blah, blah, tech, blah, tech, blah...". But that's ok, i'll explain it to my granddaughter in person.)

clear skies...

Captured Oct 25th 2012_Orion Nebula_Getting the Ingredients Right

A friend of mine had mentioned that she would like to start a baking blog. I think that's a great idea. I wish her the best of luck and look forward to checking out the blog. Here is my version of a baking blog.

Like most men, i barbecue (insert manly grunt here). I can make a decent plate of pasta and a potato soup that is excellent. I've even been known to bake a loaf or two of bread. But i have never actually baked a cake. I have WATCHED someone bake a cake, and that probably qualifies me enough for this post.

If you were going to bake a cake, you would make a trip to the market. It's important to know what ingredients are needed and you would only want the best. "Good enough" would not be a part of your vocabulary. After gathering all the ingredients, you would mix them in the appropriate portions and order. Then you would preheat the oven and start the baking process. Now, you wait. Eventually, hopefully, you will pull an excellent cake from the oven, let it cool and decorate it. But many a sitcom has included in it's plot the hapless baker that removes the unidentifiable lump from the oven, walks to the trash bin, and unceremoniously dumps it. All the icing in the world will not make a bad cake good. It's all about the process.

Now for the photo. After making major modifications to my scope setup, I had been out for two nights gathering data. Only to find that after "baking" the data, i didn't have a photo good enough to work with. I could not understand what was wrong. There are many things involved. Alignment, sky condition, focus, temperature, exposure, the list goes on. Something was wrong, and i had no idea what it was. But on the third day, the Clear Sky Chart called for excellent viewing. That night, i made a conscious effort not to accept "good enough". That night, i would get the ingredients just right.

I opened my "DogHouse" observatory early. Nothing changes much. The tripod is bolted to the floor to reduce error. The camera is mounted on the back of the telescope and is rarely removed. While it was still light, i shot 5 flats at the exposure and ISO that i was planning to use that night. My target for the night was the Orion Nebula. An easy target that is bright enough not to require a lot of exposure time. I did a star alignment to get the sky map situated correctly, followed by a mechanical polar alignment to get the axis of the mount just right. I followed this with another star alignment just in case something got bumped during the polar align. After that, i concentrated on focus, focus, focus. When it was finally dark enough for good photos, i shot 20 exposures of 2 minutes each at ISO 1600, followed by 5 Darks and 5 Bias. After i was done for the night, and the observatory was closed, i manually went through the photos i had gathered. I rejected 6 on sight, and started the rest of them cooking. In the morning, i pulled the cake from the oven, and it barely needed icing. I'm still not sure what i was doing wrong on the previous two nights, but i suspect that when setting up, i was settling for "good enough". The best thing i can do is to remove that phrase from my vocabulary.

My next post? ummmm.... How few ingredients are actually needed to bake a great cake.

clear skies...

Captured Nov 10th 2012_Flame and Horsehead Nebula

Sometimes, less is more. My setup includes an SCT with an 8 inch mirror. Riding piggyback on the SCT is a small guidescope for tracking purposes. But last night, after setting up the alignment, i capped off the main scope and mounted the DSLR camera on the little guidescope. The guidescope has less than 1/3 the magnification of the main scope, but last night, i was going for field of view. 

I love the constellation Orion. This time of year, around midnight, it dominates the sky. And it is just full of interesting targets. The main star in this photo is Alnitak. It is the leftmost star in Orion's belt. Alnitak is about 730 Light years from earth. Just below and to the left of Alnitak is the Flame Nebula (NGC2024). It is about 900 to 1,500 light years away. Also below Alnitak and to the right is the Horsehead Nebula (IC434),1500 light years distant. I've been wanting to include all three components into one photo for some time. Last night was the night.

This image consists of 60 photos at 60 seconds each. ISO1600. I took five darks and five bias. i used no flats. Everything was stacked in DeepSkyStacker and then processed in Photoshop. I really didn't do much processing. Just a generic histogram stretch and a bit of gradient work. That was it. I like this photo, but i think that on the next clear night i get, i will concentrate on the horsehead nebula with the main scope. 

clear skies...