Surprised

[Demonperformer]

For the first time last night I finally got around to a serious dso imaging attempt. 102SLT on the 6SE [alt-az] mount using the mintron camera. As this stacks 256 1/50sec frames on the fly, I guess you would call each of the frames on the avi a 2.56sec sub.

OK my first surprise was the area of sky it covered. I was expecting something like half a degree, but it seems to be way more than that. Even though there are focussing and guiding issues with the result, I know the splodge in the middle of the nebulosity is the trapezium, because it was clearly visible through the eyepiece. I guess that would make the next brightest star (the righthand one of the group of three above) iota Ori, which is about half a degree away, which would make the entire field about 5deg by 4

Because my laptop saves the result as an avi rather than a vob, I had to manually select the frames for processing, selecting frames 128, 256, 384, 512, ... This resulted in a total of 23 frames being stacked in registax.

My second surprise was quite how much difference a dark frame makes. The first image shows the data without a dark frame. The second image shows the data with a dark frame taken with the lens cap over the telescope. There was a thread on here a while back about making dark frames by moving the telescope to an area of sky nearby without any bright stars and defocussing. The third image is the data processed with a dark frame taken like that. In each case, the settings I used in registax were identical. I would have thought that, as this final option takes into account the 'skyglow' as well as any problems with the chip, this would have produced a better result. But to my surprise, there is much less nebulosity in this picture compared with the 'standard' dark frame . Oh well, shows what I know!

I am, however, encouraged to go out again tonight (clouds permitting) and have another go at this, only this time running the image for something like 20 minutes instead of 2 and see if I get a better result.

One quick question about dark frames - am I right that I only need to take a short sequence of dark frame images on an avi as long as the sensitivity setting is the same as the data avi (ie each frame is equivalent to 2.56sec of capture) so I could still use a 2min darkframe avi (23 lots of 2.56sec) with a 20min data avi (~230/240 lots of 2.56sec)?

Oh and one final apology . I know that everyone will be bored silly with photos of M42 by this stage of the winter, and compared to most of the images that have appeared on the forum of it in the last few months these are nothing to write home about, but it really was the most convenient object to try this out on. I guess there's a reason this is one of the favourite 'first dso photo' objects.

Thanks for looking.

[Demonperformer]

OK, clearly talking rubbish.

Went to image moon this morning with same set up and it just about filled the frame, so clearly fov is about half a degree. Which leaves me completely at a loss as to what I have actually imaged above. Clearly some bit of nebulosity and it is in the Orion area. Other than that, your guess is as good as mine.

Will try to do better in future.

[Psychobilly]

Its definitely the trap region of M42....

[Helen]

You might want to see if you can set the avi frame rate to 0.4 fps if you can ( it use to work for me when I used a framegrabber and the watec video camera)

Helen