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M42 Test - 17 Dec

jgs001

By jgs001
in Imaging - Deep Sky

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jgs001

jgs001

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A quick and very short session in between the clouds to check and adjust the scope balance on the NexStar and check operation...

9 Frames (total 186s), flats, flat darks and darks, stacked in DSS with a Log(Sqrt) stretch and a minor tweak in GIMP. It needs more work on the processing.

450d @ISO1600 on NexStar C80ED SLT

m42adj.jpg

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jgs001

jgs001

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Thanks gents. Billy, there doesn't appear to be a wedge available, and the way the mount fits to the tripod, it's not going to be an easy construction task, and quite possibly beyond my meager DIY skills. The mount head has the option for EQ tracking however.

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jgs001

jgs001

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Cheers Sam. Chris, I put the 450d in liveview mode, zoom it to 10x on the display, then adjust the focuser as normal, until the star is the smallest size I can get it on the display, then fire a test shot and zoom in on the preview all the way. I know this isn't the suggested way, the ideal being to touch the kit as little as possible but hey, it's what I got.

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ChrisEdu

ChrisEdu

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Thanks for that. It's good to know how people take their pictures. I think I'll be investing in a T-mount kit before too much longer. Another thought that went through my mind earlier was, what happens if you just point the camera with a long lens to the heavens and take multiple exposures? Is it possible to capture something like the Orion nebula like this?

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jgs001

jgs001

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I've caught both M42 and M31 (not the same image mind you) by mounting the 450d on a tripod with the kit lens at 18mm and firing off a bunch of 30 second exposures, then stacking. In fact in one of mine, I was told I caught the NAN (not that I could see it mind you). I did have a go at M45 with the Z2 at the equiv of 380mm, but the sub lengths of 3 seconds mean you ain't gonna get much. I know I've seen it posted a couple of times on here, I think it was something Ron (Barkis had) a chart showing the exposure lengths of a camera on a static tripod at different focal lengths before trailing would appear.

Hmm, now there's a thought, how many Deep Sky objects can you get in a single image using a camera mounted on a static tripod...

If you can mount the camera on a tracking mount, then you can get all sorts. Kevin, BeyondVision and others do just that with their Astrotrac widefield shots.

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jgs001

jgs001

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It's good practice. I've found that going beyond about 10 frames and you will start to lose the top right and bottom left corners in what looks like smearing after stacking. I can only think this is due to field rotation effects that go beyond what DSS can align. Take some darks too.

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Psychobilly

Psychobilly

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Here's an example of what happens using a fixed tripod Chris...

This is the result from"stacking" 11x30s exposures at 28mm you can see the rotation already...

11083_normal.jpeg

(click to enlarge)

remember at longer focal lengths on a static tripod you'll need shorter exposures to avoid star trailing... with a tracking Alt/Az you still get field rotation but reduced trailing if the alignment is pretty good..

Also any terrestrial objects in the frame will "trail" when the stars get stacked...

Billy...

Sorry John for the drift...but thought it easier to answer Chris's questions in thread...

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