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Trying again - Looking for best technique with my equipment

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#1 RoscoeD

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Posted 27 September 2023 - 01:51 AM

Got very little response last time (except off topic).  Try a different approach.

 

I use ASI Air for my imaging and a 533MC OSC camera.  I have a quality solar filter to place over my objective lens.  FWIW I also have a Nikon D750 and a T-mount but have never tried using either on my scope.

 

Hoping to try out whatever advice I get during Oct annular eclipse.

 

Given my OSC camera and AA+, what would be the best way to capture an eclipse? Not looking to document the whole thing, just get a sampling of cool pictures.  I imagine that even with a filter exposure is key here.  I had a crazy thought and wondered if I could use the "auto" routine for flats.  That calculates the exposure automatically to push the peak of the histogram to the ⅓-½ point which I suspect could work.  Never tried video with this camera since it's not a planetary.  

 

I do have the ASI290MM Mini but have only used that as a guide camera and not connected to the main scope.

 

I could try the Nikon but having never hooked that up before not even sure I have the right cables nor how to implement it.

 

(Please don't tell me to put the camera down and enjoy it.  I've seen my share of eclipses; I want to shoot this one)

 

Thanks in advance!



#2 foxwoodastronomy

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Posted 27 September 2023 - 05:48 AM

Roscoe, I am an expert eclipse photographer, the old-fashioned way, with a DSLR camera on the back of a telescope, and a wired remote shutter release.  In your post, I did not see that you listed the telescope you plan to use and what your field of view will be using the 533MC OSC (I have no experience with that camera). That is the first essential step in eclipse photography, your field of view.  Will you end up having a DSLR camera photography equivalent of around 600mm with your setup?



#3 RoscoeD

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Posted 27 September 2023 - 06:06 PM

Sorry...my equipment is listed in my signature.  That said, I have a 419mm FL (71mm aperture) but the tiny sensor works like a crop...no clue what the effective FL is with the sensor.  So I used Stellarium to simulate the FOV of the sun in my camera/scope (no flattener)

Sun FOV

 



#4 foxwoodastronomy

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Posted 27 September 2023 - 08:32 PM

Roscoe, yes, I missed the gear list, but would not have been sure that was exactly what you planned to use at the eclipse.  Thanks for doing the simulation, that is helpful.  So, the image is square, and it looks like you have about one solar diameter on all sides.  I have attached some ways to look at solar FOV and made a simulation of your image with solar diameters for comparison.  Just guessing, it looks like you are working at about 800mm effective focal length in the DSLR world (although with a square image in your case).  Some would say that is a little tight.  You will cut off some corona in your longer exposures.  But it will probably look great.  With most modern DSLR cameras most guys are working at 500 to 600mm FOV because the sensors are so sensitive and can image out to 5 or 6 solar diameters easily with guiding.  In recent eclipses, I worked at 900mm (2017 and 2019) but in 2024 I will work at 600mm.  Back in the slide film days (2001 and 2002) I worked at 1,000mm.

Attached Thumbnails

  • film example fov.jpg
  • solar diameter scale.jpg
  • roscoe FOV copy.jpg


#5 RoscoeD

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Posted 27 September 2023 - 09:23 PM

Thanks for that.  I can certainly leave the 0.8 flattener installed.  It will add 25% space around the frame.  I didn't consider corona, I thought getting close would be the best.

 

My D750 is full frame...I could try to use that.  Without the flattener that would be a true 420mm, but it would be a very high resolution 420mm.

 

Still looking for words of advice on how to best image with:

1) the ASI Air and 533 (if that the way I go), or...

2) D750 (either manually or with ASI Air).

 

In both cases, should I shoot video or stills?



#6 foxwoodastronomy

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Posted 27 September 2023 - 09:52 PM

Stills or video depends on what your resolution will be, what your range of bracketing can be, and if you are going to try to do HDR processing later.  No single exposure of totality can be the proper exposure because the dynamic range of the brightness is so great. So, whatever you choose to do, think ahead to get images that will allow you to do HDR processing later.

Attached Thumbnails

  • bracket corona.jpg


#7 RoscoeD

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Posted 27 September 2023 - 11:12 PM

What I'm seeking is the approach that will take the least effort...not because I'm lazy but the more clicking I need to do the more likely I'll screw something up.  

 

The D750 will do 5 frame brackets up to 2 EV apart or 9 frame brackets 1 EV apart (both give ±4EV from center exposure but either 1 or 2 EV stops).  Thoughts?

 

I've no idea how to use the AA+/533 camera.  Still hoping someone with that combination can help me out.  Soon...



#8 foxwoodastronomy

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Posted 28 September 2023 - 05:34 AM

Like I said, I am "old school."  I have never done eclipse photography working with EV bracketing.  In the previous image I posted the shutter speeds go from 1/2000 to 1 full second.  And you could actually image the corona longer; 2, 3, or even 4 seconds to get better Earth shine on the Moon for a final composite.  I have a D750 also, but never played with auto bracketing.  I don't know how to figure out a comparison between the range of 18 to 21 progressive shutter speeds to what that range would be in EV.



#9 SkipW

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Posted 03 October 2023 - 12:21 PM

Like I said, I am "old school."  I have never done eclipse photography working with EV bracketing.  In the previous image I posted the shutter speeds go from 1/2000 to 1 full second.  And you could actually image the corona longer; 2, 3, or even 4 seconds to get better Earth shine on the Moon for a final composite.  I have a D750 also, but never played with auto bracketing.  I don't know how to figure out a comparison between the range of 18 to 21 progressive shutter speeds to what that range would be in EV.

The difference between 1/2000 second and 1 second exposure times, all else equal (ISO sensitivity, f/ratio, filters), is +11 EV.

 

Each time you double the exposure by doubling exposure time, or doubling ISO setting, or decreasing f/number by √2 [square root of 2], the EV changes by +1. Halving the exposure changes the EV by -1.

 

A range of ±4EV from center exposure is a range of 8 EV from least to most. 1/250 second to 1 second is an exposure time difference of about 2⁸, so 8 EV. Similarly, 1/1000 to 1/4 sec, etc.



#10 foxwoodastronomy

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Posted 03 October 2023 - 07:58 PM

SkipW,  thanks for that comment!  That was great and just what Roscoe needed!

What you are saying is my manually bracketed EV range was +11.  The D750 built-in bracketing will only allow him to get +8 EV range (not enough)

Understand; that is why I do my entire bracketed sequence manually.  It doesn't take that long for me to do it.  The only other option is to script with a computer.  Thanks again for that additional information, it's very helpful.



#11 RoscoeD

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Posted 04 October 2023 - 01:59 AM

But are you shooting 1/2000 and 1s at the same time to blend (HDR) or are you shooting 1/2000 when it's bright and 1s during the dark moments?

 

When I shot the lunar eclipse a couple years ago (?) I would let the camera find the "optimal" setting and then bracket around that.  Seemed to work...but I understand a lunar eclipse has much less dynamic range than a solar eclipse.



#12 winbag4

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Posted 04 October 2023 - 11:47 AM

But are you shooting 1/2000 and 1s at the same time to blend (HDR) or are you shooting 1/2000 when it's bright and 1s during the dark moments?

 

When I shot the lunar eclipse a couple years ago (?) I would let the camera find the "optimal" setting and then bracket around that.  Seemed to work...but I understand a lunar eclipse has much less dynamic range than a solar eclipse.

You would shoot your range of bracketed exposures all during totality. You will get different details in the corona with each different exposure. Around 1/2000s, you will probably be getting chromosphere and very low corona (it depends on your exact equipment). At 1s, you will be getting outer corona, and the lower/inner corona will be washed out. In between these (1/1000, 1/500, 1/250, 1/125, etc.) you will progressively get more of the outer corona as your exposures get longer. For an HDR image, you then combine all of these images in processing afterwards.

 

So to answer your initial question, when it is bright (just before C2, for beads/diamond ring) you are limited to short exposures. When it is dark, shoot as big of a range as you can, because you will get something different with each exposure.

 

If you're interested in going in-depth, here is a link where you can get an idea for some rough exposure times with your setup: http://xjubier.free....seExposure.html


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