A though on star trial photography using P40/65+

[mAlKhamis]

Hmmm . . . . This is very interesting. I'll try 10 or 15 exposures with my h3d 39 next time I have a really clear night just to test the technique. If one of the issues is sensor heating shouldn't I have have the issue running back to back exposures?

hi Woody, i think you gonna do fine with hessy , if each frame had 4 min of exposure multiply that by 15 frame = 1 hour , should be perfect for the circular movement, blending 15 frame will be very easy compared to 80 or 120 frames

good luck and cheers!

 

[bdp]

Hi Mohammad,

I think I need to point towards Octans, being in the southern hemisphere

Can I ask you why a 5D wouldn't be any good? I have the MK I and I can turn off long exp NR which is responsible for the black frame.

I think my computer could handle it - it's the latest 2 x 2.93 tower chock full of RAM

Woody - You may be fine with the Hassy - each back has it's own method of determining when to do a black frame afaik. I think the Sinar calculates how long it has been since the last exposure and if it has been longer than say 5 or 10 minutes it decides it should take a black ref frame after the next exposure. So I don't know how it would go if I just did continuous 1 sec exposures back to back. It may pause after 10 minutes to do a new black ref file then keep going. On the eMotion backs you can force it to take a black ref after the next image is captured by pressing a button in the menu - I don't know what this is for. However I have discovered it will take a black reference image after every capture if the shutter speed is longer than 1 sec.

Maybe I'll get some sort of image wide open at 1 sec if the stars are bright and I could bump the ISO to 200. The NR in the Sinar software is very good, so might be able to clean up the noise without killing the stars. Also could play with the black clipping as Doug suggests although I haven't read his thesis.

Ben

Ben

 

[mAlKhamis]

Hi Mohammad,

I think I need to point towards Octans, being in the southern hemisphere

Can I ask you why a 5D wouldn't be any good? I have the MK I and I can turn off long exp NR which is responsible for the black frame.

I think my computer could handle it - it's the latest 2 x 2.93 tower chock full of RAM

Woody - You may be fine with the Hassy - each back has it's own method of determining when to do a black frame afaik. I think the Sinar calculates how long it has been since the last exposure and if it has been longer than say 5 or 10 minutes it decides it should take a black ref frame after the next exposure. So I don't know how it would go if I just did continuous 1 sec exposures back to back. It may pause after 10 minutes to do a new black ref file then keep going. On the eMotion backs you can force it to take a black ref after the next image is captured by pressing a button in the menu - I don't know what this is for. However I have discovered it will take a black reference image after every capture if the shutter speed is longer than 1 sec.

Maybe I'll get some sort of image wide open at 1 sec if the stars are bright and I could bump the ISO to 200. The NR in the Sinar software is very good, so might be able to clean up the noise without killing the stars. Also could play with the black clipping as Doug suggests although I haven't read his thesis.

Ben

Ben

Hi ben,

sorry I'm bad when it comes to star navigation :deadhorse: i think you are right

regarding the 5D mark ii cons for this method based on my little experience:

1. battery goes out very fast, so i advice you to have a grip or extra batteries.

2. you need to turn off the NR for this type of photography, however 5D's images with NR turned off are horrible, needs lots of post processing.

3. Jpeg and SRaw modes are also terrible in quality wise. however if you are planning to use the full 21MP raw files, maybe your computer can handle stacking 120 images, but mine don't thu i have 27 inch C7i with 16 ram, for some reason it crushes during that process.

4. it's much better to use higher ISO's in this type of photography, i've tried my friends D3s at ISO 1000 and the results were just amazing, very colorful star trials with NR turned off.

maybe there is something wrong with 5D's mark II, but for this type of photography, we failed to produce a high quality images with 4 5Ds cameras, what we have concluded is that when we turn the NR off, the true face of the 5D reveals itself, however that's not the case with 1ds mark III, turning off the NR doesn't affect the image quality at all.

cheers!

M

 

[bdp]

Hi Mohammad,

OK, thanks I'll take my AC adapter for my 5D then, and shoot raw to maximise quality.

Ben

 

[mAlKhamis]

good luck Ben and enjoy cheers!

 

[Analog6]

I have a book called the Photoshop Darkroom by Davis which he uses a Statistics script (available in CS3 & 4) to stack the images.
File/Scripts/Statistics and set stack mode to Maximum
The result he shows is very good, just needed some foreground lightening to make a point of interest.
I have not tired this myself yet.

 

[mAlKhamis]

I have a book called the Photoshop Darkroom by Davis which he uses a Statistics script (available in CS3 & 4) to stack the images.
File/Scripts/Statistics and set stack mode to Maximum
The result he shows is very good, just needed some foreground lightening to make a point of interest.
I have not tired this myself yet.

yap Odille, I'm aware of it, however this action, the one that can be downloaded above, is much easier to use and it produces pretty much the same results, and yes we need to use a light source for a foreground interest :thumbs: you got it thank you for your response and cheers! my friend :thumbs: