Star eater issues on Sony's

Started Jan 13, 2018 | Discussions thread
Ferguson
Ferguson Senior Member • Posts: 1,828
Re: Star eater issues on Sony's

Trollmannx wrote:

Ferguson wrote:

Trollmannx wrote:

Just for the record:

Sony full frame cameras without in camera image stabilization do NOT have the star eater issue when using any settings EXEPT bulb.

So I have an A7Riv and have been happily using it for the last month with both a long sony lens, and (not so well yet) a C11.

The C11 has a very long fokal lenght so unless the seeing is exeptional the stars will be blurred by turbulente. Blurred stars are bloated and usually not affected by the spatial filtering (which is designed to remove single pixel hot pixels). So in this case the star eater issue sound have litte effect.

Well, the main reason I keep using the Sony instead of getting a dedicated AP camera (probably mono) is the 400/2.8 lens. It's a terrific moderately wide field scope and the fast aperture certainly beneficial. There my imaging scale is more like 2 arc seconds per pixel, and tracking much better (because of the F2.8 and shorter exposures), so I assume there I might see this?

There are several things in this thread that confuse me with regard to when it occurs.

You say "without in camera image stabilization"-- but do you mean it is not capable, or is turned off?

Also, you say it is good up to 30s but not bulb. So if I use bulb but expose for 25 seconds (which it is aware of and labels in the exif) is it affected?

Plus Jim Kasson in his oft quoted review of the subject says "at 3.2 seconds all hell breaks loose", setting the bar a lot lower.

I guess next time out (which at present is forecast to be "later this year" here in SW Florida, continual clouds) I can do some experiments and try to see, but if they have already been done, it would narrow what I need to try.

I guess I also am a little unclear on the effect of dithering and integration on this; I guess to "see" it more clearly I need to look at individual frames. Here's an example.

That's a single, uncalibrated, debayered, stretched version of M33. The detail in there is almost below what you can see at all thanks to Florida community preference for daylight-bright streetlights. Here's what you get with 200 or so stacked, at about the same scale.

I guess what I'm trying to understand is all this very faint, very small detail -- did I lose a lot using the Sony camera? So might 50 subs have done this? Or, you can see massive amounts of color noise in the faint edges, is that partially coming from Sony munging the different channels differently?

AP is hard enough if the camera is a handicap. It already is from spectral insensitivity. But I love that lens, and I can't put a real astro camera on it (too short of flange depth).

So am trying to understand if it's hurting in particular operational modes, and if there are workarounds. E.g. if I manually set the shutter to < 30s does the impact go away? (Though there's Kasson's 3.2 seconds still hanging out there).

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 Ferguson's gear list:Ferguson's gear list
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