Following the posting of some stunning Asto photographs I fancied giving it a go.
As there is no thread running with info that might be useful I thought I would get one going.
I have absolutely no idea of the techniques required or this, but faced with a forecast of cloudy skies for the next week I had one window of oportunity on Monday night.
A bit of research suggested I needed to cobble together a means of tracking the stars over a series of exposures. From Alex's comments and a quick read through Stevies astronomy magazines it seems that ' stacking ' a series of exposures is the way to go. So comming up with a means of tracking the night sky reasonably accurately over a long period was an important consideration.
Tracking over a long period seems to require the orientation to be set reasonably with regard to global altitude. A quick net search for images of telescope mounts confirmed this. By logging into
http://www.heavens-above.com/ and entering my location I was given this info. Observer's Location: Swaffham ( 52.6520°N, 0.6840°E).
Until I had some idea if I was going to be able to get reasonable pics then it was a
NO SPEND situation. I have several tripod heads. So by attatching a ball head first, platform angled at approx 50 deg and attaching a 501 fluid head reversed to that I had roughly the means. The 501 will not give vertical unless used in reverse. A rifle scope with cross hairs was the metod I chose as a tracking scope. To allow the camera to clear the rifle scope I used a 701 head locked up as a spacer. No time to make anything as the clock was ticking on the only clear night for 1 week plus.
As condensation was likely to be a problem, a dew shield from a bit of plastic drain pipe was made for the tracking scope and a larger lens hood attached with electrical tape to the metal hood af the 28mm lens.
At dusk the tracking system was checked against a bright star and found to be accurate over 15 mins, the time taken for the star to move from the centre along a crosshair to the edge. The riflescope is 4x so it showed how far stars move in quite a short time.
All geared up and ready then the skies clouded over. Skies started to clear around 11:00pm so kit set up. I only allowed about 20 mins for the rods in the eyes to kick in before starting to take pics for fear of more cloud comming in. That did allow the camera to cool down. About 3 deg C at this point.
I have yet to process the images to see the results. With the 28mm f2.8 lens wide open I took 19 frames at ISO 400, 30 sec exposure, and 33 frames with 12-24 f4 at 17mm with 30 sec at ISO 400 wide open. The D2X is not a high ISO camera hence limiting ISO but hopefully taking lots of images instead will compensate.
Total time taken was 1 1/2 hours. At the end of that the camera was soaking wet from the heavy dew. A well sealed camera needed in these conditions if used without protection.
I need to look again at the guidance method, as I found the crosshairs difficult to see even after an hour with my eyes recieving no exposure to white light. I hope any missalignment can be sorted by an image stacking program. I also need to make a plastic/polythene dew cover for the camera before another attempt.
I attach a couple of pics of the set up for info, pending processing of the images.
Don