Welcome to the Curdridge Observatory Astronomy, Telescope and Astrophotography Blog

The DSLR experiment continues. This time with a mosaic. Each panel of this two-framer of part of the M31 region is made up of about 12 x 300s exposures at ISO800.

The Canon 350D DSLR is mounted at prime focus on my 8 inch 1000mm focal length Newtonian telescope. The camera is modified with a higher band-pass IR filter, but no light pollution filters have been used.

As you can see I've made a poor job of joining the two sections together. Getting the background colour flat across the whole image is proving troublesome.

Because of this I've pushed the background rather too dark, so more processing practice needed!

Click here for a larger sized version.

The ongoing experiment with DSLR astrophotography is coming along fairly well. Here is a fairly large integration (about 4 hours exposure) on part of the IC1805 Hear NEbula complex (also known as the Rolling Stones Nebula).

After spending so much time hiding behind a hydrogen alpha filter, I've almost forgotten about star colours. The DSLR gives a nice quick route to a full colour image. Of course, they have their drawbacks with noise and so forth, but this this has been a lot of fun.

Processing colour DSLR astro photos in photoshop is yet another learning curve I'm struggling with.

IC1805 Heart Nebula with 8 inch F5 Newtonian and the homemade mount. No filters. Click through for the larger version.

Slowly getting the hang of this DSLR astro imaging lark.

Lesson from last night: Remember to charge the batteries for the camera!! I'm using 6 x AA rechargeable batteries to run the camera, but I think i forgot to charge them because they ran flat around 12:30 this morning. I didn't change them because I was asleep in bed at the time!!

Anyhow, here is what you can do with a Canon 350d and an 8 inch Newtonian telescope in about 10 mins...A part of the M31 Galaxy...

We're trying something new for the Curdridge Observatory: Colour imaging with a Canon DSLR camera! For many years my astrophotography has been dominated by monochrome hydrogen alpha imaging with the odd tri-colour narrowband image thrown in for good measure. I've never seriously used my Canon 350d DSLR on the telescope. Previous explorations of traditional RGB imaging have never come to much: Normally due to the difficulty of flattening 4 different images taken through filters with a mono CCD camera.

Some recent weekends spent down at the New Forest Observatory playing with Greg's 10 mega-pixel colour CCD cameras have inspired me to see what can be done with my 8 mega-pixel Canon 350d DSLR. Some years ago this digital camera had its internal infra-red filter swapped for the Baader replacement with a view to doing some astrophotography. The occasional dabble aside, I've never really attempted any serious work with it.

The goal here isn't to produce any jaw-dropping images. There countless Canon DSLR cameras strapped onto the business end of 8 inch Newtonians out there. It isn't anything new. Think of it more as an exercise in preventing stagnation. Variety to regenerate the soul a bit.. Hopefully I might end up with something to stick on the wall which prints out in a format larger than a postage stamp.

Truth be told, I like a new bunch of problems to solve.

So how does one do this DSLR Astrophotography business?

Step 1: Get your DSLR modified with a replacement internal IR filter that lets light through at common astronomy wavelengths (i.e. Hydrogen Alpha and Sulphur). I'd already done this years ago.

Step 2: Attach your DSLR to the telescope. This required a serious bit of hunting around my house to find the Canon-M42-T adapters. Alas, when attached the Baader MPCC the spacing was all wrong. A bit of lathe work soon had the camera attached to the coma corrector with the correct spacing. This then fits the 2 inch focuser on the scope.

Step 3: Make the DSLR camera talk to Maxim. Easy enough – The maxim EOS II driver works splendidly and soon I was operating the DSLR camera just like real ccd camera.

Step 4: Make your shutter release cable. Cheap serial USB converter and an opto-isolator and that problem was solved. Maxim can now make the camera do long exposures over 30s.

Step 5: Figure out the calibration process. Turns out you need nice high value flats and you MUST have bias calibration of the flats. Other than that I found dark frames useful to knock out the amp glow. Dithered guiding via maxim removes most of the hot pixels without a darkframe.

Step 6: Power the camera. This was fun. Using the built in rechargeable battery for a night of astrophotography is a bad idea, so first I see a very cheap Canon mains adapter on Amazon. Turns out it has the wrong shaped plug on it. A bit of Cathartic negative feedback results in a replacement that fits and powers the camera. However, this seems to have created a monster earth loop somewhere – turn the DSLR camera on and the telescope mount starts doing random slews - I joke not!!! Resigning myself to using batteries of some sort I buy 6 decent rechargeable AA batteries and a 6 batter holder instead.

Step 7: Filter out the light pollution. No money this month due to car tax. No money next month either due to new mirror. Put either a Hutech LPS or a Astronomik CLS filter on the note to Santa. Donations welcome. 2 inch or DSLR clip please :)

Step 8: Focus it. FocusMax and Maxim all work together with my ASCOM electric focuser and the DSLR to get a good focus. Slow, but it works. Getting decent focus was one of the horrors that put off DSLR imaging for a long time.

Step 9: Find out the collimation is terrible with the larger sensor and phaff about with optical alignment for a few nights.

Step 10: Run off 20 x 180s frames and see what you get!

Here is the Bubble Nebula and M52 region. Click for full sized version. Still need to tweak the collimation a bit. M42 here I come! :)

After spending a lot of time and energy getting the mini-WASP telescope array up and running at the New Forest Observatory, it was a pleasant change to do some imaging back at the Curdridge Observatory.

Last night a brief clear spell gave me time to dust off the homemade GEM telescope mount. Happily everything seemed to be behaving after few weeks of neglect. I was a bit worried the telescope was had got the hump with me running over to play at the NFO.

With the clouds starting to come in, I only had time to take 4 x 900s exposures of the very bright Bubble Nebula region with the Hydrogen Alpha filter in place.

For a change I decided to let Maxim handle the guiding the DIY mount instead of PHD guiding. Surprisingly it seems to work better than PHD guiding, which was unexpected. Using Maxim to do the guiding opens up the ability to dither the sub exposures a bit to handle the hot pixels and noise. The standard webcam settings in Maxim didn't seem to work for long exposure, but a bit of informed tweaking on my part got it working.

Maxim also supports plate solving: Quite nice to point the mouse at any star in the image and have it tell you the RA/DEC coordinates and the catalogue number automatically. Opens the door to a bit of asteroid spotting if I feel so inclined :)

Anyhow, here is the image: Pretty noisy because it is only 1 hour of data, but much better than nothing!

Recently Greg remarked that setting up a new astrophotography imaging system puts you right back at the beginning of the learning curve: How right he is! One problem after another needs solving, and you need a lot of discipline to focus on the problems and not fret about wasting good imaging conditions. Last Sunday we certainly did more than our fair share of problem solving in the twin domes of the New Forest Observatory. Multiple telescopes breed multiple problems!

However, I did my fair share of fretting about the wasted imaging time. This was the first time I'd actually been at the New Forest Observatory during a decent dark, clear moonless night. I was extremely impressed about the lack of light pollution: Much better than the skies at the Curdridge Observatory. The Milky Way was clearly visible overhead.

Once I'd got everything working, I was itching to try and image something. Lots of setup work remains (such as collimating the CCD cameras) but I was in a position to try some sort of imaging by about 11pm. The goal here was to prove we could synchronise and image with the two computers and two cameras at the same time, whilst using a dithering autoguider, calibrate the images (flat fields etc) and stack the data from both cameras together into a finished image.

The result was never going to be beautiful - both cameras are out of collimation, and the focusing wasn't great, but I was able to gather some frames from the IC1805 heart nebula region with both M26C cameras on the two Sky 90 telescopes with just the light pollution filter in place. The two telescopes weren't particularly well aligned either, but the image below consists of about 2 x 5 x 600s frames - i.e. five frames of ten minutes exposure contributed from each camera. This is where I was reminded of the shocking power of the mini-WASP parallel telescope array: 100 minutes of data in 50 minutes of imaging. Seductive stuff.

I also did a few frames in the M33 region which you can see underneath. This demonstrates the huge field of view of just one camera on the mini-WASP array.





Images reproduced by kind permission of The New Forest Observatory

Another busy couple of days at the New Forest Observatory over the bank holiday weekend working on the mini-WASP astrophotography array.

First job was upgrading the automatic computer-controlled dome rotator on the Pulsar 2.2m telescope observatory. Our first prototype used two 0.5Nm torque stepper motors. Whilst this proved that the idea worked, they didn't quite have the speed or torque required. Greg purchased some 2.2Nm Nema 23 hybrid stepper motors designed for CNC use, and looked very beefy and up to the job.

I wired up the new motors to the Stepperbee controller board and proved that the motors worked in the study. We then did all the metal-work required to mount the new motors in place of the old motors.

After some problems with earth-loops and truculent computers we got the new motors working properly with the observatory computers. My software runs on the the observatory computer and communicates with TheSKY to fetch the telescope position and sends the required signals to the motor controllers. A solid state compass provides closed loop positional feedback.

The motors easily slewed the dome at 3 or 4 degrees per second. We were able to run it even faster, but it is a bit terrifying at high speed - we don't want to lob the dome into the next garden! Here is a video of the system in action. I was very pleased with the speed!



This activity managed to use up most of Sunday afternoon. The skies looked very promising, so we set out to try some imaging. Whilst Greg concentrated on setup work in the old South Dome, I ran the mini-WASP array in the North dome, working my way through various problems, but was able to grab a few dozen frames of some nice targets with both cameras operating in parallel. Bed about 3am.

After a late start on Monday we tidied up a few problems and set to work with some stolen sheets and shirts to try and get a decent flat field. The best arrangement consisted of a couple of layers of white shirt attached to the Sky 90s with elastic bands pointing at the open telescope dome slit. A large thick white sheet was draped over the entire dome slit - providing a double diffused light source which provided a decent flat. Calibration with these flats and some bias frames removed all of the vignetting on the images from the previous night.

Next job is to look at the gigabyte or so of FITs files and see if there is a decent image lurking in them!

I've had an epic weekend of work and partying to celebrate the launch of the New Forest Observatory mini-WASP telescope facility: Probably the most advanced amateur wide-angle astrophotography facility in the country.

The mini-WASP system is named after its big brother, the Super-WASP system. Mini-WASP consists of two wide field refractors with two 10MP Starlight-Xpress CCD cameras and filter wheels. Eventually the system will boast 4 such cameras and scopes. Under this array of imaging equipment is a Paramount ME equatorial telescope mount on a custom aluminium pier. The rig is housed in a 2.2m Pulsar Optical observatory dome.

I turned up at Greg's around 11am on Saturday. After trying out some software I'd written to synchronise the 4 cameras and 4 computers, we erected Greg's new 6m by 4m marquee. This was kind of fun with only two chaps and no clue how it went together. Much of the remaining afternoon was spent tuning the automatic dome rotator system and generally making preparations for the following day's party.

During the evening we has a lucky bonus of some clear skies. I set to work in the observatory about 9pm to polar align the Paramount using a rather humble webcam and a copy of K3CCDTools: Despite the simple tools, I got the job done. Beneath deteriorating skies we were able to grab a few long exposure frames to validate the polar alignment. This test culminated with both cameras running automatically in parallel for the first time.

Sunday was party day. We got up fairly early (some earlier than others) and I collected Little Pete from the train station at the god-forsaken time of 9.15am. The morning was spent cooking and preparing for the guests who started to arrive around 11am. The rest of the afternoon vanished in a blur of activity: Cooking, eating, talking etc. As chief astro-engineer geek, I made sure lots of would-be astronomers got their hands on the Paramount joystick control for a test drive.

We had to endure one of Greg's powerpoint lectures, but were rewarded with a lot of superb puddings, one of which was more densely packed than a neutron star with yummy things. Surely gravitation pudding collapse was only averted by "ice-cream degeneracy pressure"? After discussion with my old physics professor, Brian Rainford, the solution to the cosmological "Dark Matter" problem was found in Helga's chocolate fondue.

After people left we reversed the process by dismantling the tent, tidying lots of stuff up, driving home and collapsing in bed.

A very successful weekend, and very enjoyable. Hopefully it won't be long before Greg dazzles us with his first completed mini-WASP image.











Most of the photos by Pete because I forgot!

In an ideal world, we'd all have our telescope observatories at the top of mountains with totally uninterrupted views in any directions. For those of us who do not have a handy mountain in the back garden, we have to contend with trees and houses getting in the way. This creates a hard limit on the objects we can use for Astrophotography. It would be nice to have a perfect horizon, but most of us cope by patiently waiting for the required target to arrive in a region of clear sky. British astronomers have lots of patience!

Most of us modern astronomers use computerised star chart programs. Such software allows you to enter the horizon limits in each direction and create a local horizon line (yellow on the chart) above the zero degree horizon (grey on the chart).

With the installation of my new homemade telescope mount combined with the passage of time, my map of the local sky has changed. The annoying huge tree to the south east has grown, whilst pruning has created some gaps in other areas. As it was cloudy today, I decided to recreate my horizon map.

This is a simple yet time-consuming task. You have to slowly move the telescope around the sky, using the scope to locate the line between the sky and the trees/houses. The telescope mount tells us at which altitude the telescope is pointing. This information is recorded around various points of the sky - the job only takes a hour or two.

Then is is a case of entering this data into your planetarium software (Skymap wins an award here for dreadful such a dreadful interface) and use the resulting plot when planning your observations. When it is dark, it is very easy to suddenly find yourself shooting images through a tree and wondering why the stars like so odd. With a decent chart setup it is easy to avoid silly mistakes.

Here we can see my plots in each direction. As it happens, most of my astrophotography is done in the north east, as this does the darkest sky. Many interesting objects appear in the south as well, but I can usually only track these for a couple of hours, so it is harder to get a decent image.

Finally the skies cleared last night to allow a bit of astrophotography. Still learning the foibles of my own homemade GEM mount, but hopefully we are starting to get somewhere. This is 9 x 1200s exposures combined and stretched a bit. Art 285 camera with Astrodon 6nm Ha filter on a F5 8 inch newtonian. The full resolution version has an image scale of around 1.33 arc seconds per pixel.

NGC 7380 is the open cluster of stars discovered by Willian Herschel's little sister Caroline in 1787. Of course, they wouldn't have spotted much of the nebulosity in the region - the is is catalogued in the Sharpless catalgoue as sh-142.

The major problem with the data is the horrific star shapes. Although the scope is guiding ok in RA, the DEC guiding is still rubberbanding all over the place. More work required.

Click here for the full sized version