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A Wide Field "Project" - Need Advise

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#1 mic1970

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Posted 10 October 2019 - 08:13 AM

https://www.cloudyni...a-to-andromeda/

 

In the post above, I was trying out a new star tracker mount and was going for the most forgiving shot I could think of.  However, I really loved the outcome.  

 

I have, for months, wanted to do my first "project" where you gather 10/12 hours of data.  I have seen many of them here, and they are inspiring.  If I made this wide field a project and collected 10 hours of data, would it work.  Would the pic collect so much star data there would be no definition, just a blob of white.  I'm hoping that if I can control star bloat I would see natural colors and cells of bright nebulousity.  

 

Anyway experts, what do you think would happen?


Edited by mic1970, 10 October 2019 - 08:18 AM.


#2 MikeMiller

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Posted 10 October 2019 - 09:52 AM

The star bloat is related to exposure length, so as long as you keep that under control you should be fine.  Your linked picture is pretty good, at fl 18mm you could probably take a much longer exposure and gather even more nebulosity.

 

Since it really depends on the camera, I would take some time to take exposures at a few different lengths to see which ones you like the best. The good thing about widefield is that basically any camera tracker will do great on getting good shaped stars.

 

It is late enough in the year that Orion is back in the sky. Your technique here would capture that amazingly.



#3 DubbelDerp

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Posted 10 October 2019 - 09:53 AM

I’m certainly no expert, but I think you’d be fine and surprised at the amount of detail you can extract with a longer widefield integration. Here’s 8 hours of the region between Cepheus and Cygnus at 50mm, over-stretched and over-saturated, for reference. It’s not quite as long of an integration as you are planning, but pretty close. A wider lens would just capture a wider field, in my limited experience. 
 

 

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#4 mic1970

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Posted 10 October 2019 - 10:10 AM

I don't know if this is the best approach.  I see how long I can expose the pic and keep round stars.  I then play with the f-stop and ISO until I get a 1/4 of the way on a histogram.  This seems the best way for me to lower the bat wings along the outside and keep my sky glow at bay. 

 

 

The star bloat is related to exposure length, so as long as you keep that under control you should be fine.  Your linked picture is pretty good, at fl 18mm you could probably take a much longer exposure and gather even more nebulosity.

 

Since it really depends on the camera, I would take some time to take exposures at a few different lengths to see which ones you like the best. The good thing about widefield is that basically any camera tracker will do great on getting good shaped stars.

 

It is late enough in the year that Orion is back in the sky. Your technique here would capture that amazingly.



#5 mic1970

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Posted 10 October 2019 - 10:12 AM

Very cool pic.  That gives me confidence.  In your eight hours, did you use any narrow band filters?

 

 

I’m certainly no expert, but I think you’d be fine and surprised at the amount of detail you can extract with a longer widefield integration. Here’s 8 hours of the region between Cepheus and Cygnus at 50mm, over-stretched and over-saturated, for reference. It’s not quite as long of an integration as you are planning, but pretty close. A wider lens would just capture a wider field, in my limited experience. 
 



#6 DubbelDerp

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Posted 10 October 2019 - 10:26 AM

No filters, just pointed the camera upwards and let ‘er rip. I think the lens was stopped down to f/4.0 with 5 minute sub length. The histogram was well over the 25% point, but I didn’t see any clipping so let it ride. The sky gradient cleaned up nicely in APP. 



#7 MikeMiller

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Posted 10 October 2019 - 04:25 PM

I don't know if this is the best approach.  I see how long I can expose the pic and keep round stars.  I then play with the f-stop and ISO until I get a 1/4 of the way on a histogram.  This seems the best way for me to lower the bat wings along the outside and keep my sky glow at bay. 

Yeah, this is a good point. Depending on where you are, sky glow might be a bigger problem than finding long exposures. Its best to just give it a try and see what you get.



#8 Jcwillis4

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Posted 10 October 2019 - 09:30 PM

Bat wings are typically an artifact of the Fstop being too open.  Step it down a couple stops and experiment until you get a good balance of exposure time needed to hit the right level on the histogram, and your lowest fstop that gives round stars.

 

After that, get your subexposures to hit the right level on the histogram, make sure things don't seems totally blown out on the back of the camera, and then just get as many subexposures as you can tolerate.  10 hours will get you quite a bit, but you might also be just as happy with 3-5 hours, depending on what you are shooting and at what Fstop.  You can always come back to the same target and get more exposures in the future.




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