Tuesday, December 11, 2012

Raspberry Pi, Canon EOS 1100D and Gphoto

I finally have it! RS Components delivered it last week. Now all my free time has gone tweaking RasPi. :)

Because I plan to use RasPi as a media center, I chose Raspbmc as the operating system. It's based on Raspbian, which is basically Debian on ARM with some Raspberry specific packages. I'm sure I can get anything on this.

Then came the problems. Gphoto can control DSLRs and after initial problems, I got it working with my EOS 1100D. On RasPi, however, there are some more problems. First run works properly, but after the first I get only:

*** Error ***
PTP I/O error

*** Error ***
An error occurred in the io-library ('Unspecified error'): No error description available

After googling a bit and asking on #gphoto at Freenode, I found out the problem is not with Gphoto, but with Raspberry Pi. Hardware or software, no one seems to know.

There is a workaround!

After taking a photo with 

gphoto2 --wait-event=2s --set-config eosremoterelease=Immediate --wait-event=180s --set-config eosremoterelease=Off --wait-event-and-download=5s

the usb connection has to be reset. I found a piece of code to do just that: http://marc.info/?l=linux-usb&m=121459435621262&w=2. I copypasted that into usbreset.c, compiled it with gcc usbreset.c -o usbreset, and now taking photos seems to work. I'm running a loop of taking a photo, resetting usb and deleting the photos. While I'm writing this, it has successfully taken over 50 photos in a row.

Next I'm going to write a script to take photos, renaming them and sending them directly to my NAS.

Friday, November 16, 2012

Now I really found Ceres

It's a good thing I emphasized the word 'might' on my previous post. Turns out I did not find Ceres just yet. It's in the picture, but I looked at a wrong star.

There was a clear sky for a while the next evening after my initial photos. I was able to take another set of photos on 12th and 13th November about 24 hours apart. Now the movement of the dwarf planet is clearly visible.

I've marked the dot on both pictures. The right one is from November 12th and the left from 13th. Time is about 20:30 (18:30 GMT).

This doesn't change my opinion on Stellarium. Now I know for sure it shows the position of Ceres wrong for about 10'. I compared it for the position of Uranus (which I was able to photograph yesterday Nov 15th) and that is as correct as I can see on the photo.

Original photos:

November 12th
November 13th

Tuesday, November 13, 2012

I might have found Ceres

Emphasis on the word 'might'. (UPDATE: Didn't find yet. Details here.)

For more than a month it has been either cloudy, foggy, rainy or all at the same time. Stargazing or astrophotography haven't been possible. I even had two weeks paternity leave and I thought there must be at least one clear night during that but no...

But yesterday November 12th it was! I got my set out immediately after dark and started shooting. Ceres was my goal but it was still below the horizon. I started with Pleiades and continued on Messier objects near Ursa Major since they seemed easy to find on the camera. I still haven't checked the photos if I caught any.

About 20.30 (looks like my camera has it's time set wrong) Ceres has finally risen enough and I forgot everything else. According to Stellarium it was in Gemini near ŋ Gem. So that's where I aimed.

I stacked the image hastily, rotated it to match Stellariums alignment and started comparing stars. Much of my dissapointment I found nothing from the place Stellarium showed Ceres. Strange though. Its magnitude is supposed to be 7.13 and I could see stars with magnitude more than 11. It should easily visible.

Couple stars off, there was an extra one. Not where Stellarium says. And according to Stellarium, Ceres should never be where I think I see it. Nevertheless, an extra star on a place where should be nothing. Quite convincing. I still have to take another photo myself whenever the next clear night is and compare with it. Or try some astrometrics software to recognize everything in the picture, except for Ceres.

Here's the first stack I made. I really have to make a better one and try the astrometrics for it.

Sunday, October 7, 2012

Still waiting for my Raspberry Pi

I ordered a Raspberry Pi from RS Components in July 17th. That's the date in the order confirmation they sent me. Estimated time of dispatch was 11 weeks. That was last Tuesday and I still haven't heard from it. Looks like RS Components has had problems getting the devices. Had I ordered mine from Farnell I'd already have it. Even a Finnish electronics store is selling RasPi with delivery times less than one week... At least mine costs only about 30€. Otherwise I'd have already cancelled my order.

This page says I'll be getting my RasPi in late November. Also it should be Rev 2, but I have no idea how that is different from older boards.

My plan to use RasPi to control camera on EQ3-2 and shoot some stars will probably fail. Not because the camera or RasPi but because the tracking mount isn't accurate enough (with my skills at least) to track stars for more than 15 seconds with my equipment. We'll see... Maybe it's worth it just to make the camera shoot 50 photos continuously instead of ten it can shoot now.

I also had other plans for RasPi. A media center with XMBC. I just got an even better plan but that might be outside my skills. I have an old Luxor 3079 amplifier that looks like this:
Luxor 3079. Image borrowed from http://new-hifi-classic.de/forum/index.php?topic=2577.0
It's not working properly. There's a lot of static over everything I play unless the volume knob is exactly in the right position. Luckily that's a good level for volume too. Still it would be better if the thing worked without glitches like that. If I'm able to fix it, I could embed RasPi in it. Why? Why not?

Thursday, September 27, 2012

My first photos on Messier objects!

The first two nights I got enough time and good enough weather I went out and just took a lot of photos on different objects. I really should plan these things ahead. Now I just take a look at a star chart, point the camera somewhere I might get something interesting on screen and shoot. I like to think this as practicing the finding of objects, but it's really not that. It's just me trying to do everything at once...

I took photos of several Messier objects. At least 20 photos on each object but some photos were off focus or off target.

M57 - The Ring Nebula

I started collecting photons on 9th September and continued on 15th. First I didn't think I could actually get anything and my intention was just to shoot some stars and practice stacking on Deepskystacker. I was surprised to see this:

The Ring Nebula is quite easy to find. It's in Lyra, between Lyra γ and Lyra β. Total exposure of this photo is about 8 minutes.

I also have an entry on this in Astrobin.

M13 - Hercules Globular Cluster

This one was easy to find. I took one test photo and already the cluster was on finder. 30 more photos and on to finding the next object. With exposure time of 15 seconds the whole stack comes to 7 min 30 s.

You can definitely see it's a globular cluster. That's about it. No Mercedes-sign, not many pixels, but still a beautiful globular cluster. Quite nice for my first, I think.

M51 - Whirlpool Galaxy

Well... I got it on camera. Kind of. You really can't recognize it if you didn't know it's M51. I took a lot of photos on this but got the galaxy only on a few. So there's light from about 30 seconds here.

In case you don't believe there's something in the upper photo, I dug it out more with Darktable:

Yeah... I got it on camera...

M31 - Andromeda Galaxy

...and of course M32 and M110.

After M51 I tried M29. It looked quite easy to find on a star chart, but I really can't see anything on my photos. The rest of the evening I had my camera pointed on Andromeda. I took perhaps 30minutes of photos but what I didn't notice was that I had dew on the lens. 20 minutes of photos spoiled. Also the first 10 minutes aren't that great except the very first ones. Next time I'll take a blow dryer with me so I can dry the dew...

Since 15th of September it has been cloudy and rainy. Soon I'll have two weeks of paternity leave and perhaps there will be couple of good nights. I'll probably start with Andromeda since my failure last time bugs me quite a lot.

Wednesday, September 19, 2012

Deep sky objects and stacking

I've seen lots of awesome photos of deep sky objects. I always thought they are so small that you can't see them with your naked eye... But no. They're huge. Sky is full of galaxies and nebulae and many of them are bigger than the Moon. The problem is, they're too dim to see.

A telescope collects light from a bigger area than your eye, so it helps to see some objects. An other way to collect more light is long exposure photos. Ok... no news to people who knows about astrophotography, but I don't know who I'm writing this for. Problem with long exposures is the rotation of Earth, or the apparent movement of the sky. You can compensate it with a tracking mount, but better mounts cost more...

I'm still doing this with budget equipment. My kit:
  • Canon EOS 1100D - 300e
  • 75-300mm lens - 100e
  • EQ 3-2 with one motor - I bought it used for 200e
  • Stuff to put this all together - ~50e
Camera and lens are something one might already have and use for other stuff as well. So if you think of the total price, it would be here about 250e.

Now to the point: stacking pictures. With this budget kit, I can take 15 second exposures. Longer than that and the stars would trail. With better alignment for the mount I could probably go as high as 1 minute, but for now I settle for 15 s. A deep sky object might require several minutes exposure to be seen and perhaps hours to look good. I take a lot of photos with short exposures and then stack them together with specialized software. I've been using Deepskystacker but there are others as well.

To demonstrate the difference between a single 15 second exposure and 15 minutes of them stacked together, I'll show my first "masterpiece": Andromeda galaxy:

A single 15 second exposure

15 minute stack of 15 second exposures
Is there a difference? You can definitely see more of the galaxy. I am going to shoot the galaxy some more the next time it's possible and post an updated version. Perhaps this time I don't fail and adjust the focus in the middle of session so that the rest 30 minutes of exposures are out of focus...

Thursday, September 13, 2012

Testing the tracking mount

Finally there was a bright enough night to test EQ3-2. I needed to learn how to adjust it for this latitude and how to align it to Polaris. I have a polarscope but using that turned out to be more difficult than I thought. I got started with crude aligning to north without a compass. The idea was to take some photos with long exposures so I could see how long exposures I'm able to take.

First a test image without tracking:

The photo is taken with 300mm lens and 30s exposure and it looks like the lens was out of focus and the mount wasn't stationary all the time. However it gives an idea how much the stars trail with 30s exposures.

Another one with the tracking on:

Its about the same direction with 300mm lens (now with better focus!) and 30s exposure. Stars still trail a bit too much. Maybe 10s exposure is short enough?

Couple nights later I was able to photograph some more. And succeeded to align the mount better. This time I looked from a map where north is. :) 30s exposure looks like this:

Otherwise everything might be worse than the picture before, but I see no trailing at all. I wish I'd learn to align the mount like this every time.

Saturday, September 8, 2012

Camera and EQ3-2 tracking mount

I bought an used EQ3-2 tracking mount mainly for camera. Then I also had to buy a DSLR since I only had a pocket camera (Canon PowerShot SX200 IS). Internet said it would be fairly easy to mount a camera to EQ3-2, but I failed to notice there are several types of EQ3-2 connection plates. The one I bought wasn't the type for cameras...

It looked like this

and it's supposed to look like this

I bought a dovetail adapter for EQ3-2 and dovetail plate for camera

The final set up looks like this:

Next I'll have to learn how to align the mount properly. I have a polar scope so it should be easy but then I saw this: http://www.nightskyimages.co.uk/polar_alignment.htm. Maybe I'll prepare for a bigger operation...

Sunday, August 19, 2012

Controlling Canon EOS 1100D with Linux

I bought a DSLR camera mainly for astrophotography. Of course I use it for other photography as well (like 20GiB of photos of our 2 months old son) but reason for buying it was astrophotography. I decided to go as cheap as possible and found a Canon EOS 1100D for 300€. Not bad.

I can set the exposure time for 1100D to max 30s. While this is a long time, it's not enough for photographing nebulae or other dim objects. I got a tracking mount EQ3-2 which is supposed to make possible exposure times of couple of minutes. Still I have to take several exposures of the same object to get total exposures of maybe 20 minutes. I still haven't had a chance to test my equipment because of the summer here in Finland. Too much light even on midnight.

To take exposures longer than 30s I have to use camera's bulb setting. I use mainly Linux at home so I can't use Canon's EOS utility. Luckily there is Gphoto. It doesn't support all the cameras and for a while looked like 1100D wasn't on the supported list. I could take photos and change settings but couldn't get bulb to work. Developers on #gphoto in Freenode were kind to help me out and the correct commands for changing settings and using bulb are:

# gphoto2 --set-config iso=400
# gphoto2 --set-config shutterspeed=bulb
gphoto2 --wait-event=2s --set-config eosremoterelease=Immediate --wait-event=180s --set-config eosremoterelease=Off --wait-event-and-download=5s

The red --wait-event tells camera the exposure time in seconds.

I'll probably get the adapters required to mount camera on EQ3-2 next week and be able to test everything. Later I'm supposed to get a Raspberry Pi (might take two more months) and my plan is to use that to remote control the camera. I'll install Debian on the RasPi and use ssh to control it. If everything works as planned I'll get to sit inside while taking the photos of night sky.

If I blog here about instructions for something I usually write about it to a website as well. Blog doesn't work too well with information that might change and the reason for me to blog is to help others that might be doing the same thing. So you might want to check this page for Gphoto instructions.

Sunday, August 12, 2012

Planning to find Ceres

Last day of my summer vacation... Yesterday I was out rollerblading at 22-23 and it really started to get dark. Closer to midsummer that was the best time since it wasn't so hot anymore, but now, note to self, better go a bit earlier.

Anyways the darkess made me start planning future observations. Some time ago, might have been while watching Venus transition (btw I think I should blog about that as well even though it was months ago) I started thinking if it were possible to see dwarf planet Ceres with my telescope. Checking Wikipedia about Ceres tells me that its magnitude ranges from 6.7 to 9.3. Being still such a beginner at this, I really don't know if that's something I can see from my backyard.

I had taken photos of Orion's sword and Pleiades with Canon SX 200 IS, which is a compact camera with 60mm (or 12x) zoom. The photos were taken with exposure time of 1 and 2 seconds (on a tripod without tracking), 40 shots and then combined with DeepSkyStacker. I compared the photos with star charts (Stellarium) to see how faint magnitudes can be seen where I observe. Here's an example of Pleiades:

Pleiades with a few apparent magnitudes of visible stars.
So... The brightest star on Pleiades is 2.85. There are several stars of approximately magnitude 7. I could even see stars with magnitudes of 10 and 11.25 (according to Stellarium). I'm a little sceptical about that 11.25, but 10 seems reasonable.

For now it looks like it is possible to see Ceres. Nowadays I have better optics (Canon EOS 1100D and max 300mm zoom) and a tracking mount (EQ3-2). And of course I'd like to have a visual observation rather than a photo. First I'm going to find the dwarf planet on camera, then try to see it through a telescope.

Hello World!

For a while now I've been writing a blog about my hobby as a stargazer: Mikon tähtiharrastusblogi (Finnish only). The idea of the blog was to write down notes about everything I learn while looking through my telescope. Another motivation was to learn some web programming. I wrote the whole blog from nothing with PHP.

While this was (and still is) an entertaining project, I found out quickly that also wanted to share more static infromation than my blog makes possible. This blog is an attempt to do just that. Another framework I thought was Google Sites and perhaps that would have been a better choice for the static information... But I also wanted a blog.

My english is far from perfect. I hope I still get understood, and that I don't accidently say anything weird.

Most texts I write here are probably originally from my Finnish blog. The content there is more dynamic and I might do updates several times a day on some topic. I'll try to keep my posts here better planned.

Wednesday, June 6, 2012

Transit of Venus 2012

I started my amateur astronomy (or "stargazing" as the word seems to be) in march 2012. That's when I got my first telescope: Skyliner dobson 8''. The rest of the spring went by learning the capabilities of the telescope, my place for observations (backyard) and of course, myself. I really hadn't gotten into planning my observations or looking ahead. The transit came by surprise.

And by surprise I mean two weeks of warning. I had just enough time to go buy Baader AstroSolar safety film and build a casing to attach it to my telescope. I had already made plans for the June 6th when the transit happened but instead of cancelling that, I just took the dobson with me. This was a very good decision because it was too cloudy to see anything where I live, but a quite good weather where I was.

Sun rose about 4 am and I did the same an hour earlier. I drove to the tallest hill I could think of in the area. I'm glad I scouted the area the day before so I knew where to take my car and where to carry my dobson. It's not too heavy to carry outside and back in when I'm at home but couple hundred meters uphill the 25 kg starts to feel a bit.

Got the telescope ready, got my camera ready (after panicking a while about cameras battery which wasn't in the camera... Found it in the backpack after all), sun had already risen but there were clouds blocking the view. Couple of minutes of aiming the telescope. I hadn't thought of this. While watching the Sun, I really can't use the finderscope for aiming.

When I finally got the Sun on ocular I immediately saw a black dot over Suns disc. There were still some clouds blocking the view but they disappeared quickly. I switched ocular for camera and took this:

My first thoughts were that "Now I've seen it and even got a photo." Of course I wanted to see the rest 4 hours as well but it wouldn't matter too much if I didn't. Before 8 am (Finnish time, when the transit ended) it got cloudy several times but I stayed and waited for the sky to clear. It always did and I was able to take more photos and follow the end of the transit.

Here's the place:

And here are some more pictures:

Some of the pictures are on Google+ but some only on low bandwidth server. I'm not sure about Google's terms and conditions... I really would like to use Google+ images more, but I also hate to give anyone rights to use my pictures.

I wrote this on August 19th, but labeled it June 6th.