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M101, a SW120 dusted off

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Hi all,

Not much to show here - compared to some recent remarkable images - but it's always fun to tinker around.

My SW120 has been unused for a long time, but I thought it could be nice to let it have a go for a change. I pimped it up with a JMI motorised focuser, and the SW reducer to see what I could do with it.

Looking at the setup it screams differential flexure - being guided by the ED80 - due to how I need to mount it all, but nothing too dramatic actually shows for the 4 min sub length I went for.

Flats proved tricky. On the RC I used very low light setting for the EL panel and went for 6-8 seconds. With the SW I was on lowest setting, and yet at 1 second the CCD got saturated with a familiar and dreaded streaky pattern. A couple of t-shirts sorted it out.

The final image suffers from concentric rings of unknown origin. I have yet to establish if the flats are to blame.

The Moon is close to full, and high winds shook the trees so I'm glad I have a tank of a mount.

2h 44m, 41 subs.

Thanks for looking and any hints for the rings, or whatever catches your trained eye is as always appreciated :smiley: .



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I can see the concentric circles you speak of...hmmmm. Did you use any background flattening or gradient removal in your processing? Sometimes those two processes give you this exact problem.

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Hi, yes I threw one dose of GradEx on it. In terms of flattening I tried a method to duplicate the image, copy into new layer that I made black and white, tweaked contrast a bit on this layer and then added back as 'luminance' at something like 50%.

It's the first go at the SW from my city location, and the first go at using the flattener/reducer. I think the rings may be reflection CCD/Flattener due to the bad LP. The whole sky is alight basically, and I'm lucky if I see 20 stars.

It would be nice to come up with a weapon against these anomalies... Thanks so much for looking and helping! :smiley:


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  • 2 weeks later...

Another attack...

The rings are still there...

This is the best 88 subs from three nights, so total 5 hours 52 min at f6.4.

Not great still, but I must say I like the golden Skywatcher - my first telescope still going strong.



Full resolution crop of the galaxy itself:


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