Polar alignment and Messier 81

That’s M81, first time I found it in this light polluted town. Also the first time I polar aligned my Celestron NexStar 5SE. I highly recommend polar aligning your scope, especially when you’re gonna do astrophotography. Why? Because a polar aligned telescope only turns on one motor (i.e. more precision) and the photos don’t rotate from one frame to the other. But because the alignment procedure is quite involved and not well documented in the manual (or on the internet for that matter), here’s what to do if you too live on the Northern hemisphere. PS: This is the absolute minimum. We’ll cover an additional wedge align in another post.

1) The NexStar 5SE has a wedge. This wedge must be lifted such that it’s adjusted for your latitude. In my case, I live at latitude 52º, so I align the base plate to the 52º mark. You can do this during day time:

2) Setup your telescope outside to let it adjust to the temperature and power on the NexStar computer and the GPS. Set it up in this initial position, pointing to Polaris. You can move the tripod around such that Polaris is more or less centered. It is important that you point your telescope to Polaris as good as you can.

3) Wait until the GPS is linked:

4) When the GPS is linked, choose EQ North Align:

5) The first thing the NexStar asks you to do is “Set Alt to Index”. You need some light (e.g. from a red lantern) for this, and it means that you use the up/down controls of your NexStar hand control to align the two arrows:

When you have done this, the telescope is pointing towards the ground! This is exactly as it should be!

6) The NexStar now asks you to “Find the Meridian”. This is the tricky bit:

You now have to slew the telescope with the hand control’s right arrow button so that it points towards the sky AND is aligned to the meridian. In the sky, the meridian is the imaginary great circle on the celestial sphere. It passes through the north point on the horizon, through the celestial pole, up to the zenith, through the south point on the horizon, and through the nadir, and is perpendicular to the local horizon. This means you have to swing the telescope clockwise for a half turn until it points to the sky again, away from Polaris. It helps me to put my iPhone with a compass app on top of the telescope until it is aligned North to South:

Your telescope now points to the sky, away from Polaris!

7) Now choose “EQ Auto Align” and align the telescope as you normally would do to two of the suggested stars:

8) Voila! Your NexStar is now polar aligned. For more accuracy, you can still use “Precise GOTO“. In fact, that’s how I found the above Messier 81. My first trial with the regular Messier menu found nothing. But “Precise GOTO” yielded a much better result; M81, dead center!

Of course I would like to improve on this result. I think I can aim a little higher on the following, considering the equipment stays the same:

• Find a place with less light pollution.
• Take more pictures.
• Also do a wedge align and generally make sure M81 stays better centered on the ccd.
• Spend more time focusing.
• Experiment with exposure settings. At 10″, M81 seems to “blow out” at the center. So less may be more here.

Stay tuned for another photo of M81.

Comet C/2009 P1 Garrad

Just like comet Hartley 2, I found this very faint (magnitude 8.3) comet C/2009 P1 Garrad using PRECISE GOTO on my Celestron NexStar 5SE with the exact coordinates of C/2009 P1 Garrad at that time, according to Carinasoft Voyager 4.5 software.

You can see the UTC date and time in this picture. I took a few dozen frames using my Meade DSI II pro ccd camera attached to my Celestron NexStar 5SE telescope. I was standing in front of our house in Zeist, the Netherlands, which is terribly light polluted. Finding a comet of magnitude 8.3 is pushing the limits of what can be seen in this area, so I was glad I could find it quite easily with my NexStar auto two star aligned to Vega and Altair. It was a beautiful night and the moon wasn’t up yet.

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Moon Zoo: Crater Survey from The Zooniverse on Vimeo.

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To compare….

You decide; the above picture of M3 was taken with Teide 2 at slooh.com, under excellent weather conditions in the Canary Islands in Spain, virtually free from light pollution. I reserved a slot on Sunday, April 10, 2011 to get this image of M3 and compare it with my own. The specs of the telescope are:

Dome 2
Primary Instrument: 0.35 meter f/11 Schmidt-Cassegrain
Field of View: 13.1 × 8.8 arc-minutes
Camera Resolution: 2,184 × 1,472 pixels

Compare this to my picture with a modest NexStar 5SE in my light polluted backyard.

Limits… or not

This is my latest picture of Messier 3. I took a few hundred images of 6 seconds each using Nebulosity with my Macbook Pro in the garden. On top of my Celestron NexStar 5SE telescope was a dew cap, which does make a lot of difference it turns out. The Lumicon deep sky filter was also in place (just before the zenith prism). All images were taken with the Meade DSI II pro ccd camera. From time to time I hand adjusted the NexStar to center the globular cluster M3 in the ccd. I don’t autoguide (yet). The NexStar 5SE isn’t equipped to use an autoguider, though I’m sure it would be possible to hack together some sort of autoguiding system. In fact, I wouldn’t be surprised if the electronics are identical to the NexStar 6SE which does have an autoguider port. But enough about that.

Inside, I handpicked the best pictures, which left me with 266 frames to stack in Nebulosity. I subtracted with a bad pixel map and aligned all the pictures using Translation + Rotation + Scale while saving each file instead of a stack. I love this technique, because I can then preview all the aligned pictures and toss out the ones that are slightly mis-aligned, or blurry. I find it easier to decide when I see all the pictures aligned. I then stacked the remaining frames using None (fixed) and did some post processing with curves and levels. I sharpened the image using Sharpen. I find Sharpen and Laplacian sharpen filter nicer for globular clusters than Tighten star edges.

Of course it took me at least 6 hours in total (imaging and post processing) to create the above picture. Which brings me to the limits of image quality. I created a similar photo of M3 months ago, and that photo was of much less quality. There is of course a sharp limit in terms of image resolution, based on the diameter of the main mirror of the NexStar 5SE, which is five inches. Maybe the above picture is hitting that limit. But the light pollution and the camera quality – which could easily be blamed for lesser quality pictures by a novice – certainly aren’t the true limits of taking beautiful pictures. By taking enough pictures and taking the time to read the manual of Nebulosity (and trying out several techniques), it seems to me that the picture quality to a certain degree is a function of the amount of time spent. Or should we say, the lack of boredom

Imaging the Sun

Imaging the Sun is very dangerous without the proper filter. In this case I used AstroSolar (from Stichting De Koepel in Utrecht, the Netherlands) in front of my NexStar 5SE. In order to Solar System Align with the Sun, you will have to allow it in the menu of the NexStar. You will find this in the Utilities menu under Sun Menu. Once enabled, Solar System Align will let you align with the Sun. I held a bit of AstroSolar filter in front of the viewfinder to center on the Sun. Then I took a whole bunch of photos with Nebuolisty and stacked the best ones to this image. With the enormous amounts of light from the Sun, a short exposure time (like 0.002 seconds) will be enough, so it was easy to get a lot of pictures in a short amount of time. But the fuzziness of the Sun spots makes it hard to align them.

Knowledge is power – M42 the Orion nebula

I would never have dreamed that I would’ve been able to capture the above image when I just got the Meade DSI II pro ccd camera. This is actually my first ever color image with the monochrome camera, and also the first time I’ve imaged M42. Still in my backyard in light polluted Zeist. So what’s the difference? Well, I read the entire manual of the amazing astronomy software called Nebulosity! I also created flat frames and bias frames, bought a dew cap for my Celestron NexStar 5SE and really took the time to capture 100 red, 100 blue, 100 green, 100 luminance and 100 dark frames. And the results could be better the next time! Because I have yet to start with EQ mounting and wedge aligning my telescope. It’s like with just about everything else in life: if you put in the extra hours, eventually it will pay off.

CHDK

For those of you with a Canon point and shoot camera and who love to take pictures of constellations and such, there’s a really cool firmware hack called CHDK. This particular (non permanent) adjustment to your Canon camera will let it shoot in raw and – more importantly – use much longer exposure times, up to something like 30 minutes! Yes that’s true, 30 minutes!! All you need to do is download the right CHDK for your camera and copy it to a bootable SD card. Then make sure the card is locked (don’t worry, you can still take pictures with it with the lock enabled) and it will boot up with CHDK options. My little Canon Powershot SX 200 IS now has the above menu (and a lot more). Tons of fun, but you gotta be somewhat adventurous to get it all working.

Comet Hartley 2 and metadata

I took this photo on the night of October 9, 2010, in my garden in Zeist, the Netherlands. I had been trying to see this not-so-bright comet for a while now, but finally succeeded. How? Of course! I used precise goto on my Celestron NexStar 5SE. I first found its exact coordinates using Voyager, my favorite OSX planetarium by Carinasoft. A comet moves pretty fast, so you may want to get the coordinates of the exact minute you are trying to hunt it down. At that moment, comet Hartley 2 was at R.A. 02h 44m 37.18s and Dec +56° 12′ 37.9″. My NexStar was of course already linked to GPS satellites and auto two star aligned to Polaris and Albireo. The NexStar computer suggested Mirfak (α Persei), which I centered in the eyepiece. It then instantly slewed to Hartley 2 which was dead center in the eyepiece. I had to use averted vision at first to see it, but quickly got used enough to the dark to see it. I did use the light pollution filter, but it just shows it is possible to find such a faint object in terrible light polluted surroundings with a magnificent instrument like the Celestron NexStar computer.

A few notes about astronomy metadata:

- I have my photo of Comet Hartley 2 in my FlickR photostream. Simply by posting it in the astronomy.net flickr group will add notes and tags to it with the exact coordinates, some of the bright stars, etc. It is also called the “Blind astronomy solver” and it’s a wonderful free service for your FlickR astronomy photos.

- Adding FlickR tags will make your photos easier to find at any rate.

- But if you are really serious about your astronomy metadata: there’s a standard for it called AVM. I won’t even begin to explain it, because there’s a cool site with everything you could dream for, including white papers and a plugin for Adobe products. It works fine with Adobe Bridge on my Macbook Pro running OSX. It’s the future of information. Learn about it now. Metadata is uber cool. A good place to start is XMP panels in Adobe Bridge.