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ISS, Saturn, APOD, 1-22-2016

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#76 WarmWeatherGuy

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Posted 30 January 2016 - 11:01 AM

Why do you think the exposure is only 2.5 ms? Does the image only "look" like a 2.5 ms exposure?? 25 ms gives you 40fps already so that seems correct. If that's not the case, then it seems pointless to have an exposure setting showing incorrect and closure times!

 

Thanks for the question.

 

Ciao,

Mel

In this image there are two time periods marked A and B. I imagine that the shutter was open for time B and the data were being transferred to memory during the much longer time A - B.

 

If time B is 25msec then it is taking maybe 250msec to copy the data. If time A is 25msec then the shutter would be open all that time and the image of the ISS would be smeared over a length denoted by A.

 

 

ISS.jpg


Edited by WarmWeatherGuy, 30 January 2016 - 11:35 AM.


#77 ToxMan

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Posted 30 January 2016 - 11:08 AM

Hi Szabolcs,

 

Nice work documenting your effort. Your results were what I would expect...Until the fake showed up, it never occurred to me anyone was trying to get such images. And, did some searches, too. Because you have demonstrated it is possible, perhaps we will see more of these images. There are definite technical challenges, and with skill and refinement of techniques, better cameras, who knows?

 

Ironically, the few "near miss" images I found  on the internet are more appealing to me. If I was going to do a "pretty picture" or composite, I would be doing what Steve suggested the faker may have done to get his composite (2 scopes, 2 cameras)...except I would have a 3rd scope/lens for the background stars. Purely art. Saturn, ISS, star background...or one of the other planets.

 

Steve,

 

Piotr will know...others too, I'm sure.



#78 WarmWeatherGuy

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Posted 30 January 2016 - 11:37 AM


 

Steve,

 

Piotr will know...others too, I'm sure.

Yes, Cloudy Nights is awesome. I can't imagine a world without it.



#79 HxPI

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Posted 30 January 2016 - 12:25 PM

I think marker B is probably a little less than 25ms exposure and the next 25ms exposure shows ISS moved by the distance A, giving you a 40fps view. 80fps would give you double the number of ISS images in the same distance, albeit at a dimmer view. I don't think there is any appreciable time needed to save the image, unlike other CCDs, and it would be a constant value regardless of exposure setting. The image does seem to suggest that there is at least 100ms of time between the ISS images, if the ISS portion of the exposure is actually 25ms. That does seem strange to me and wouldn't add up to 40fps. Perhaps the exposure setting is the time interval between exposure operations and the actual exposure is something less. Why such a gap between ISS images is a mystery to me. Well hopefully someone in the know can elucidate.

 

Thanks for the clarification.

 

Ciao,

Mel

 

 

Why do you think the exposure is only 2.5 ms? Does the image only "look" like a 2.5 ms exposure?? 25 ms gives you 40fps already so that seems correct. If that's not the case, then it seems pointless to have an exposure setting showing incorrect and closure times!

 

Thanks for the question.

 

Ciao,

Mel

In this image there are two time periods marked A and B. I imagine that the shutter was open for time B and the data were being transferred to memory during the much longer time A - B.

 

If time B is 25msec then it is taking maybe 250msec to copy the data. If time A is 25msec then the shutter would be open all that time and the image of the ISS would be smeared over a length denoted by A.

 

 

attachicon.gifISS.jpg

 

 


Edited by HxPI, 30 January 2016 - 01:04 PM.


#80 metrolinaszabi

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Posted 30 January 2016 - 05:07 PM

Thanks for everyone for the interest 

 

As FireCapture saves all the settings, I know that my exposure time was set at 10.98 ms and the gain was set on 93. 

There isn't a working method or exact settings on this I think, good settings depends on a zillion different factors. 

What I really learned from imaging with dslr is to make a good estimate. This time I kept an eye on how Saturn looks on the laptop screen, knew that I sort of need high frame rate to get a decent result. Also I was aware that ISS will get dimmer by the time it reaches Saturn, from -3.5 to a much dimmer value which helped me a whole lot. 

I'm not that technical than some of you guys, instead what works for me is judging by looking. Of course at some occasions, like imaging planets it is good to have a value you can stick with, but this was a completely different story of course...

Well I might need to get used to the fact, that my photo is probably among the first few photos on which ISS is actually covering Saturn :)
 


Edited by metrolinaszabi, 30 January 2016 - 06:18 PM.


#81 wargrafix

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Posted 30 January 2016 - 06:17 PM

An epic post to be sure!!


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