When you look up at the night sky, what do you see? Stars of different brightness and color, the Moon and some planets, constellations, and maybe the subtle glow of the Milky Way?
As amazing as our eyes are, they aren't all that sensitive to dim light. The night sky is actually loaded with objects we can't see. However, the invisible sky is easily seen with long camera exposures. A special type of light, Hydrogen-Alpha (Ha), is a deep red color and emitted by stars and nebula when their hydrogen gas is energized. This picture was taken with a Ha filter to more prominently show these nebulous regions.
Imaged almost from horizon to horizon, this mosaic of the Milky Way during our winter season is huge. But so are the nebula in it. For example, the bright round nebula just left of top center is the Rosette Nebula and it's more than twice the diameter of a full moon! Many are way larger than it. So the invisible sky isn't seen because it's small, it's because it's too dim for our eyes to see.
Several months ago I had made a mosaic of the Summer Milky Way taken in Hydrogen-Alpha light. Last night it was time to take the images to construct this picture, the Winter Milky Way, also in Ha light.
The mosaic is 11 frames taken with a 24mm lens on the SBig STF-8300M camera. Each frame covered 41 x 31 degrees and they are centered on 15 degree increments along Galactic Longitude 120 to 270. Every frame is actually a stack of (3) 180-second subs through the Ha filter. Stacking dramatically reduces noise in the image resulting in a smoother overall appearance.
I used AstroArt 7 to control the capture process. A script I wrote positioned my little iOptron ZEQ-25 mount toward the desired aim point in the sky, took the three images used for each frame, then moved to the next point. The whole capture process took about 2.5 hours.
A "big picture" like this helps to visualize how the various sky objects are positioned relative to each other. It also helps me to pick out future targets for close-up photos.
On Monday, December 21, 2020 the planets Jupiter and Saturn passed each other in the sky. They appeared closer together during this conjunction than others in hundreds of years.
The planets do move about in the sky, but their motion is slow enough that it's difficult to visualize it. So while leading up to the conjunction I started taking nightly pictures of the planets on December 6th. The individual images were then combined to show their relative motion in about 24 hour intervals. Unfortunately, two nights of bad weather prevented me from getting photos on those nights.
The sequence images were taken with a TeleVue NP101is telescope with a Canon 60Da camera. I also took a close-up photo of the planets using an AstroTech 10" RC telescope with ZWO ASI2600MC Pro camera. The close-up was then superimposed onto the sequence photos for the final composite.
If you'd like to see my more traditional picture of the conjunction jump over to the Astrophotography Solar System page to see how it looked from the back yard at sunset.
Comet Hale-Bopp was the last "great" comet prior to Comet NEOWISE that we saw back in July. That was over 23 years ago! Of course, photography was still in the film age back then. This picture was taken with my then-shiny Pentax ME Super 35mm SLR film camera and 200mm telephoto lens.
When I was looking through a box of old photos I came across an envelope with these in it. I wondered if scanning the negatives would yield a superior image compared to the original prints? On the night of April 4 1997, I had taken three photos at 60 second exposures. I scanned in those negatives and using today's techniques of stacking and stretching, the result was the image above. I'm happy to say that the newly processed image has much more detail in it than the original print. I think that the result is reasonably comparable to astronomy photos taken today. I'm glad I stuffed those photos in that box so many years ago!
In the mountains of New Mexico the temperatures vary quite a bit during the year. Summer overnight lows are typically in the mid-60s, while winter lows are usually in the mid-teens. Telescopes expand and shrink with these temperature changes. It turns out that the telescope mount also changes a little. The result is that the mount’s drive gear mesh needs to be adjusted to optimize performance for summer or winter operation.
In the case of my Titan mount, there’s a sweet spot in the gear mesh tension for best performance. If the mesh is too loose then excessive backlash degrades guiding performance. If the mesh is too tight then the motors have to work harder and may even stall or overheat. Adjusting for the right mesh tension has been a try it and see how it does game.
Enter my latest project: the Telescope Mount Power Monitor. This device displays the voltage and amount of current the mount is using. Knowing how much current the mount’s motors are using can indicate how hard they are working. So when adjusting the mount’s gear mesh watching for the point that the current starts to increase indicates “that’s tight enough”!
The monitor consists of three modules: a Feather M0 Express microcontroller, an OLED FeatherWing display and the INA260 Power Sensor. All the modules come from Adafruit. The software is written in “C” using the Arduino environment and is based on the example code that Adafruit provides. The total cost of the project was about $60.00, plus my labor of course.
The Monitor is placed in series with the mount’s power source and gets its own power from any USB power supply. The display provides real-time readouts of the current the mount is drawing and the supply voltage level. Hopefully, this tool will ease the gear mesh adjustment process this coming winter.
When doing deep sky imaging of objects like nebula and galaxies the Moon's presence is generally considered to make it a "no-go". Moonlight washes out all the object's faint details. And, the brighter the Moon the worse its effect. But avoiding moonlight severely restricts imaging time.
A relatively new type of filter, called a dual-band filter, can be used to regain some imaging time... even in moonlight! Most narrowband filter pass light in a single region of the light spectrum. The dual-band filter has two passbands, one centered on Hydrogen-Alpha (Ha) emissions and another centered on Oxygen III (OIII). While allowing those bands to get into the camera, the filter blocks all the other interfering moonlight. The dual-band approach is thought to work better for color cameras that the single band filters.
This time of year in New Mexico is monsoon season and cloudy nights are common. So when last night promised to be clear I thought I'd give a dual-band filter a try, since a very bright 99% illuminated Moon was in the sky. This image of the Eagle Nebula (M16) was taken using a TeleVue NP101is refractor and ZWO ASI2600MC Pro color camera. I took similar images without using a filter and with using a ZWO Duo-Band filter.
The comparison is pretty dramatic. The Eagle Nebula is mostly a Ha emission object and a perfect candidate for the filter. The reddish nebulosity is significantly more visible with the filter than without. So when a clear night comes along, the Moon won't stop me anymore!
Ever wonder how astronomical objects got their name? Dottie convinced our cat Mars to demonstrate how the Cat's Paw Nebula got its name. Of course, now Mars wants me to rename the nebula the "Mars Paw Nebula"!
The Cat's Paw nebula (NGC 6334) is located in the lower part of Scorpio, near the "stinger", and is actually pretty big... larger than a full moon. This area of gas and dust is an active star forming region. The nebula is too dim to see with the eye but a long camera exposure easily reveals it.
While Comet NEOWISE (C/2020 F3) continues to be a wonderful sight in the evening sky, I'm reminded of how weather dependent astronomy is. Here in New Mexico we're in the monsoon season. And true to its form, our night sky has been totally clouded out for the past several nights. Finally, on Tuesday the forecast for that night had improved to "mostly cloudy".
It was five days ago that I took a picture of the comet so I planned to set up my photo rig in hopes of getting a new image tonight. About sunset I started setting up the equipment: finding a good spot in the yard to see low to the northwest horizon, setting up and leveling the iOptron ZEQ-25 telescope mount, attaching the camera and connecting it to the laptop computer. By the time my neighbor Joe came over to watch the comet it was dark enough that I could polar align and synchronize the mount to the sky.
As it got darker, we waited... and waited. Every now and then a portion of the comet would appear among the clouds. Each time I'd start a sequence of image exposures in hopes of getting something useful. A few times it cleared enough that we could see the comet and its dust tail with the naked eye. Joe finally got to see why Neowise was special.
Even though the sky wasn't cloud-free, this image of Neowise nicely shows the comet's yellowish dust tail and bluish ion tail. And, in a way, the clouds add an interesting dimension to the picture.
Comet NEOWISE (C/2020 F3) has blossomed into a fine sight right now in the early evening sky. Dottie and I watched it last night and it was obvious low on the northwest horizon. Here in our dark skies I estimated that the tail was about six degrees long to the unaided eye.
Since the comet is very low in the sky I set up a photo rig on the driveway where I could see down to the horizon. I can't actually image that low from the observatory. This picture was taken at 9:18, about an hour after sunset, so it wasn't totally dark yet. Even though some clouds are in the way, a good amount of its dust tail is visible.
Thirty minutes later the sky was almost totally dark and the dim parts of the comet popped out. Now both the yellowish dust tail and the bluish ion tail really stand out and are very long. Jump over to the Solar System astrophoto page to see this image. Urban light pollution will mask the fainter parts of the comet too. So if possible, go to a darker location to view this wonderful comet. You'll see a whole lot more of it!
Astronomy and music go together... right? Well, I think so anyway. So I regularly have music playing in the observatory when I'm out there taking pictures. Dottie and my favorite pianist/composer is Robin Spielberg and I thought her song Spellbound would be a perfect match for an astronomy slideshow. So I put together a music video using some of my astronomy photos set to Spellbound.
Dottie and I met Robin about a year ago and shortly into a conversation I learned she loves astronomy pictures. Since then Robin has been enjoying my astronomy photos that I've shared with her. When I sent Robin my Spellbound Nights video she posted it on her YouTube Channel as the "Spellbound - Official Video". How cool is that!
Here's a link to the Spellbound music video. Take a look!