Tŷ Du Observatory

I can’t believe it’s been 4 months since I was last on here! I have done some imaging since the last post but not much, and nothing this year due to the weather conditions. In fact the last time I imaged it snowed and I had to dry my mirror with a hair-dryer. The mirror now has clumps of dust where the snowflakes melted.  I’ll give it a wash before too long.

Anyway, the reason why I thought I’d write something today is to let everyone know that I’m about to build my own roll-off-roof observatory.  I’ve purchased a metal shed which is approx 10′x10′ (3m x 3m) and after searching everywhere for a round section column form to cast the pier I’ve decided to make my own mould from ply which will give a square section, but I have the ply so I can make it at no cost.  I’ve booked 2 weeks off work in March to do the build so I’m currently in the planning stage.

My wife managed to topple the mount this week which luckily didn’t hit anybody or anything on the way down and the only damage appears to be a broken locking lever from the weight shaft.  Its a black cast component that fits over a brass square topped bolt.  I’ll make a new lever when I get a minute. I won’t know if there’s any internal damage until my next viewing/imaging session – fingers crossed.

I’ll take photos and make comments throughout the build so keep watching for updates.

I used an unexpected day at home to make a Hartmann Mask to help me focus the Canon 300D DSLR.  Using the vanes on the secondary to focus has always been good enough with the Atik Camera and even the web cams before, but the the field of view with the Canon means the spikes on the stars are very small and hard to see if they are perfectly formed or not.  After looking at several designs I decided to build the 3 triangle model out of a printer box I had lying around.

Here’s the mask (it’s not really this colour):

The tabs on the side bend over to “hook” over the top of the scope, but in use I had to use some masking tape to hold it in place.

The resulting image when out of focus clearly shows 3 separate images for dimmer stars but shows six large spikes on bright stars like Arcturus here:

When in focus the the 3 images become 1 and the spikes on the bright star become very clear:

The secondary vanes still make spikes so I get an extra 4 to help focusing.

So after focusing the camera (and I think it could do with another tweak), I took a few images before the battery ran out.

M3 Globular Cluster

M13 Globular Cluster

M27 The Dumbbell Nebula

NGC6946 Spiral Galaxy

I’m disappointed that even with 3 minute exposures NGC6946 is still very faint.  With the Atik 16ic this galaxy was brighter using 1 minute exposures – but that’s the difference between a CCD and a CMOS camera I guess.

Next time out I’ll see if I can get the focus even sharper.  I’m also trying to work out how to get the 2″ LPR filter I bought into the light-path given that the camera adapter doesn’t have filter threads.  I’m so glad I haven’t bought a coma corrector yet as this would screw into the same non-existent threads!

I took a couple of 5 minute frames across the “mexico” of the North American Nebula (NGC7000) but they won’t stack so I can only view the frames individually. I’m sure I have caught some nebulosity and comparing my image with others I can make out some structure, but I think I’d need to take lots of these, on a clear night with good seeing and better focus to make anything worth showing here. Maybe next time.

Another clear weekday night, so I can’t image for too long.  I’ve taken a few frames of M51 and M81 and also taken some dark frames before moving the scope back to the Veil.  With time being limited I decided to try 30×120secs initially and I’ll see how they turn out.  I’ve taken a dark frame at the same exposure and iso setting (iso1600) before and I’ll take another after. As I’m imaging remotely it’s not practical to run out between each shot and wait in the cold for 2 minutes while the camera takes a black photo, so I’ll make do with just 2 dark frames.  I haven’t worked out what to do about bias and flats yet.

Here’s a quick and dirty draft image using 14×120 second frames and 1 dark.  I’ve streched and tweaked the image to try and bring out the detail in the nebula, but its still very faint on the left of the image.

The Veil Nebula (NGC6960)

Hopefully I’ll be posting a better image here after I’ve got all the data in.

Another quick effort before wor. I managed to get another 10 shots but DSS only stacked 35 of them.  There’s more detail in there I just need to tease it out using photoshop.

The Veil Nebula (NGC6960) 35x120 seconds

I have another dark frame to add to the stack but I don’t have time at the moment.  Maybe later

Update: Saturday 26th September

I was able to create flats and bias frames as I leave the camera connected to the scope so the light path hasn’t changed since these images were taken the other night.  Reprocessing has annoyingly made things worse not better as there seems to be some structured noise that is accentuated by the new processing.

Example of noise

I’m guessing the noise is a result of imaging at iso1600 rather than adding flats and bias frames but only time will tell as I take more images. Unless someone knows the answer and would like to make a comment

I’m currently trying the same flat frames with the Veil image from the 12th as I’m sure the flats will remove the bright area on the image.  I opened the combined flat in Photo shop and stretched it to find an exact match for my bright area which I may have blamed on coma in a previous post. The iso value of the flats doesn’t match the iso value of the lights so I’m not sure I’m going to get anything, but I’ll keep trying.

—–End Update —–

Session details:

Imaging: Canon 300d (unmodified) – Skywatcher 250 Newtonian scope on EQ6Pro mount

Guiding: PHD -Atik 16ic on 60mm refractor

Processing etc: EQMod, Starry Night, Canon Remote Capture, PHD DSLR Shutter, Deepsky Stacker and PhotoShop CS2

Another clear night!! All summer without so much as a break in the clouds and now 4 clear nights in a row.

Clearer than last night, there doesn’t appear to be as much high cloud. I’ve been shooting for the last 2 hours but I’m not happy with the focus so have just returned from making a few adjustments. Fingers crossed, it’s a bit hit and miss trying to focus on stars through the view finder on the camera, but I think I’ve improved things.

Here’s M81 (before changing the focus).  It’s too close to the meridian now to start taking more shots so I don’t have anything to compare with it.

M81 (Bode's Galaxy)

I’ve moved on to the Spindle Galaxy (M102) which is very small in the Canon’s field of view so I don’t know if I’ll get anything worth showing.  On the Atik16ic the spindle didn’t quite fit in the frame, I used to try and get it across the diagnal, but now it’s a tiny blur in the middle of the frame.

Hmm, not too happy with the M102 results so far. I wonder if I can fine tune the focus on something like M13. The globular clusters have enough stars to allow me to find a round star (given the amount of coma I have) somewhere that I can focus with.

Scrap all the images I’ve taken over the last 90 minutes or so.  The trouble with changing the focus is that its not an exact science, especially when you have the standard skywatcher focuser  It looks like I was a fraction out, but more so than I was before.  I finally managed to get it closer by changing to 10 second subs on M2 using the small JPG option.  This allowed me to quickly (20 minutes) change the focus, take a shot, change the focus … you get the idea.  I’m now taking a short series of M2’s in the hope I can prove to myself that the focus is indeed better than before.  The wind has picked up now though so I have even more variables to contend with.

M2 Globular Cluster

After M2 I turned back to M27.  I was pleased with my previous efforts, but I think the new shots are much better.

M27 (Full Frame)	M27 (close up)
After changing the focus and reducing the exposure time I have much better star shapes across the whole frame.	The nebula cropped from the previous image.

Here’s another NGC6960 – The Veil Nebula (West). I tried shorter exposures but more of them. This is 26×60 seconds from a set of 35.

The Veil Nebula (West)

NGC6946 is a galaxy that I often come back to. Last year my images were used by Belfast University as I’d managed to capture a super nova event before the big boys turned their scopes in that direction. The Atik does a better job of bringing the detail out, but it’s another view of an old favourite.

NGC6946

M52 The Scorpion Cluster is one that I caught with the Atik some time ago. I’m not a huge fan of open clusters (because they didn’t fit in my FOV!) but this one fits nicely onto the Canon sensor.

M52 The Scorpion Cluster

M31 The Andromeda Galaxy has just made it past the meridian, but the battery has run out in the camera. I only managed 3 frames but it’s now 03:02 and I don’t think I’ll change the battery – I need some sleep.

M31 The Andromeda Galaxy

I even got the bonus galaxies M32 and M110, that wasn’t planned

I’ve just been reading some articles on DSLR Astro work and I think I need to start looking at BIAS, Darks and Flats.  I’ve used Dark Frames previously with webcams but didn’t need them with the Atik. On my next clear night I’ll try and do things properly.

Another clear night, or so I thought.  It wasn’t until after midnight that I realized I’d been imaging through the clouds. That’s always the danger when you choose to sit in a nice warm room while the scope is remotely controlled in the cold night air. At least it didn’t rain.

I took some more shots of the Veil, but when viewed through cloud it’s not easy to make out even with 10 minute subs! M3 was a starting point, with M101 next. M101 was very faint and I should have realized then that something was not right. It’s usually bright on short exposures but 17×90 second frames wasn’t enough to show any of the detail on this spiral galaxy.

M3 Globular Cluster	M101 Galaxy 17x90 secs	The Veil Nebula (West)
		I’ve really stretched this to bring out the wispy strands of the nebula, and in so doing have accentuated the bright area that appears in all my Canon images. I think this is something to do with the collimation of the scope and/or the camera being slightly off the central axis of the light path. Maybe when I get a coma corrector it’ll go away