Photographing the Stars

[Don Hoey]

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

[Alex Paul]

Don: Your engineering mind is a joy... Excellent set up... I will be participating in the is thread as soon as I get some errands done.... I think we will cover a lot of sky in this thread.... Registax is an outstanding stacking program for astro work....I think your 30 second timed exposures stacked will produce excellent results provided you are getting away with little to no star trails... One of the key elements to a succesful stack... The more distortion you have the more pronounced it becomes when images are stacked.... Your scope idea with crosshairs for tracking alignment is brilliant...... I'll be back.....Alex

[Alex Paul]

Well I have some stuff to show for demonstration but of course I don't know how to add the shots in thumbnail form.... Some would say how do you get dressed in the morning..... To that I reply, I have no idea....So I guess I will forget it for now....Alex

[ollieholmes]

Im going to follow this thread with interest and maybe even give it a go.

[Saphire]

Alex to add the photo, go to advanced which is just below where I am typing now, move down to manage attachments and load your picture as normal. It creates a thumbnail in the thread.

[Don Hoey]

Alex,
I have now downloaded Registax V4 and the 48 page manual. A lot of reading here in order to understand something of what is going on. I have got a few days to get some handle on the program as the weather forecast for the next 7 days are not too encouraging for a repeat shoot.

Info for uploading an image into a post is in my post #4 in the ' Manual macro on the cheap ' thread.

Superb images in the gallery btw. Something not quite right with my pc settings. Unable to add a comment unless someone else has.

Unlike yours, my scope Nikon ED82A is a fieldscope, well corrected for Astro viewing at 1/10th wavelength, but not good for this sort of thing. See attached pic and laugh . With the camera adaptor on it is effectively f13. So at the moment I am limited to photographic lenses. 12mm - 300mm, so widefield is the better route.

Don

[yelvertoft]

Don, your ingenuity never ceases to amaze me. I'm assuming that you are using the cross hairs to align the target and tracking manually to ensure a consistently repeatable image to stack?

Duncan

[Don Hoey]

Originally Posted by yelvertoft

Don, your ingenuity never ceases to amaze me. I'm assuming that you are using the cross hairs to align the target and tracking manually to ensure a consistently repeatable image to stack?

Duncan

Got it in one Duncan. Now if I can find a cheap one with illuminating reticule I will have it made.

Got a tiny led torch yesterday to see if I can come up with a mod to save buying the proper job the guy tried to sell me.

It is great for anything as at 4x is wide field and when set up with just the scope on I can be on anything faster than most with an angled scope. Stevie uses it with the scope when cruising the skies at night.

Don

[Alex Paul]

Don: What a beauty of a fieldscope that is.......Your set up is anything but laughable.... You have an excellent engineering mind my friend... Widefield work is a fabulous option as well...Now that I have the info on posting thumbnails I will get involved with the thread in a show, tell, ask, and share kind of way... I will start tomorrow... I am going to take a quick look for conditions for some shooting tonight....Orion is in view at about 3:00am to the east of me and gets perfect for shooting at about 4:00 am right now..... I will help with the fast track to using Registax... It will do most things automatically including choosing the stackable images, aligning them, and stacking....It is actually a lot more straight forward than it appears in the beginning... I will also show how to set up and use a Webcam for imaging, using a laptop and a program called KCCD which allows you to do everything from the laptop once webcam is attached to scope and mount is aligned...Extremely high quality images with very little noise.... I spent some time playing with it and it is what I was playing with at the time I started wanting to get some sleep at night. I didn't go as far as I did with shooting the DSLR but I learned some basics and the results once you get a good handle on it are fantastic! Talk about best bang for the buck... Great imaging using a 49 dollar webcam ....Take care pal...Thanks for getting me fired up with this again.....Alex

[Alex Paul]

Thank you Christine... I knew it had be something simple I just can be dumb at times ....Thanks a lot.....Alex