Finderscope rings

Last weekend we made some rings for mounting a finderscope on the main telescope. Today I got the holes drilled and tapped so the rings are ready to use. The gallery below shows the adaptive pocketing paths that were used to cut both the part and the jig that allowed drilling the holes at +/- 120 degrees.

There is a video of the roughing operation at 2000 mm/min that will be online soon.


Barlow test

The big picture shows a normal photo through an f=1000mm F/9.8 telescope with a Canon 20D. The field of view should be around 1° 17‘ 20" according to this FOV calculator. The small frame is taken with an additional 2x Barlow lens between prime focus and the camera sensor. It ends up magnifying the image around 2.7- to 2.9-fold. I guess this could be tuned a little each way by inserting the Barlow differently in the focuser or with a T-ring standoff between the camera and the Barlow.

Something to try on the moon or bright planets once the skies are clear again...


Had hoped to shoot the Pleiades with some longer exposures today, but clouds rolling in prevented that. So some snapshots at ISO100 and 1/4s of Saturn instead. These are 100% crops, so maybe I need to get an adapter for eyepiece-photography for shooting planets at higher magnification?

The clouds caused this round halo-effect around the moon. By 23:00 it was impossible to shoot stars.

Moon photo

Pooling our hardware resources together in the lab, we now have a 102 mm F/9.8 (f=1000 mm) refractor on an EQ6 equatorial mount and either a Canon 20D or a Canon 400D to shoot with. When one camera is coupled to the scope the other one can simultaneously take a wide-field photo. Did not bother with polar-aligning the mount today, so just looked visually at the moon, mars (it happened to be close to the moon), and M42. The moon is so bright no tracking is really needed.

Here is the moon through a 102mm F/9.8 (f=1000mm) refractor with a Canon 400D at prime focus, set to ISO400 and 1/160s. Around 21:40 local time on Friday 15 Feb 2008.

Astrophotography in Finland is a cold hobby, I was somewhat unprepared for the weather so around 60 min in -7 C was enough for me...

Astrophoto test

I've made a first attempt at pointing my camera towards the night sky. Achieving good results is not an easy task - some people spend considerable amounts of time and money on the hobby of astrophotography ! (and the results are breathtaking)

Just a fun thing to do for me - for now... (they call it 'aperture fever' when you get hooked!)

Having read a little bit about wide-field astrophotography I experimented quite freely with different iso settings, exposure times, focusing etc. Out of about 70 pics, these are the better ones.
All of these are with my Canon 20D, shot from a stationary tripod with a cable release.

The moon shot at 200mm with a 70-200/F4L, stopped down to F22, shutter 1/160s and iso800. A ca 180% crop. I had the camera on program-mode, but it would probably have made sense not to stop down as much. The light-meter in the camera really does a bad job of metering in this kind of a shot. The only way to get the exposure right is to take lots of pictures with different shutter times. I really need to get that EF-mount adapter for the 500mm mirror tele-objective to get some nicer moon shots !

Ursa Major, partly hiding behind the trees. With 17-40/F4L at around 17mm, 10s exposure at F4 and iso1600. Click on the image for a full-screen version.

in the middle. 17mm/F4, 30s exposure at iso800. Click image for a full-screen pic.

Next I suppose I will have to learn about dark-frame substraction, "barn-door" tracking mounts, stacking multiple exposures, etc. Anyone interested should check out Canon_DSLR_Digital_Astro and digital_astro, but beware of the message volume, up to 1000 per month !
The only problem with this hobby in Finland is that it's only dark enough during the winter - and on clear winter nights it tends to be really cold. (think remote-controlled "go-to" mount and laptop-operated camera from the livingroom sofa...)