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First Time with OSC

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#1 damarks913

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Posted 15 September 2021 - 12:20 PM

Last Night was my first time using any kind of OSC camera. I was simply excited to actually see sharp stars against a black background. I tried to take some test shots, but they seemed incredibly black with bright white stars. I will try to post a couple of the 90 second exposures I took, along with the 6 second live view captures.

 

I previously was using a Nikon D600, and regularly got decent 120s light frames on the Skyguider Pro.

 

I was using APT, QHY168C, WO Zenithstar 61 with 61R flattener/reducer, no filter, riding a Skyguider Pro. I was using the Unity Gain of 10, offset 50.

 

Sooooo many questions, but just a couple to start. What should my 6 second Live View frames look like? What would the accompanying 90 second frames look like by comparison?

 

Just want to know if I am on the right track. 



#2 ChiTownXring

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Posted 15 September 2021 - 12:40 PM

Your live view should only show bright stars and the 90 second views will depend on the brightness of the target you are shooting and what you will see on a single sub.. Assuming you have the right back focus and you are indeed in focus then you should see something in APT when it does a quick stretch of the sub.


Edited by ChiTownXring, 15 September 2021 - 12:44 PM.


#3 DRK73

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Posted 15 September 2021 - 12:45 PM

What program were you using to capture? In most cases (unless you're imaging a very bright nebula) stars are all you will see in an "unstretched" straight out of the camera exposure. Everything else you're imaging is going to be very dim compared to the point-sources of light in your pics (the stars) - they're still there but the signal is going to be buried in the noise. 

 

Most photo-editing programs have a program where you "stretch" the image using a histogram tool. 

 

Your capture program may have a function where it can apply a gentle stretch to the image, as well, to help you figure out if you're framing your subject the way you want it, or not.


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#4 matt_astro_tx

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Posted 15 September 2021 - 02:18 PM

Yep.  My capture tool does an autostretch to let you see what's in the data.

 

To the OP, what were you expecting vs. what you saw?



#5 damarks913

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Posted 15 September 2021 - 03:16 PM

Yep.  My capture tool does an autostretch to let you see what's in the data.

 

To the OP, what were you expecting vs. what you saw?

I guess just a lighter image, similar to what I would get with the DSLR, more light, but I also have to remember that I'm not taking DSLR images any more. :-)



#6 matt_astro_tx

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Posted 15 September 2021 - 03:50 PM

I suppose there are other factors at play.  Like, what ISO did you typically shoot at with your DSLR?  ISO is more or less equivalent to gain on an astro camera.  So if you were shooting with a high ISO you would definitely see more color on the preview screen.



#7 bobzeq25

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Posted 15 September 2021 - 04:49 PM

Last Night was my first time using any kind of OSC camera. I was simply excited to actually see sharp stars against a black background. I tried to take some test shots, but they seemed incredibly black with bright white stars. I will try to post a couple of the 90 second exposures I took, along with the 6 second live view captures.

 

I previously was using a Nikon D600, and regularly got decent 120s light frames on the Skyguider Pro.

 

I was using APT, QHY168C, WO Zenithstar 61 with 61R flattener/reducer, no filter, riding a Skyguider Pro. I was using the Unity Gain of 10, offset 50.

 

Sooooo many questions, but just a couple to start. What should my 6 second Live View frames look like? What would the accompanying 90 second frames look like by comparison?

 

Just want to know if I am on the right track. 

Forget all those minor details above.   6 seconds versus 90 doesn't matter.  Honest.  <smile>  This is the big deal.

 

Some programs you use for viewing will "stretch" the data (as will the LCD on the back of a DSLR), some will leave it unstretched.  "Linear".  That _completely_ changes what things look like.

 

You want to start out with linear data, some processing operations do _not_ work well with stretched data.  People looking at linear data for the first time think something is horribly wrong.  It isn't.  If you're not saying "where's my nebula?" you're doing something wrong.   Your eyes just don't see linear.

 

Below is an example.  A linear version of a stack of 32 180 second frames of the Rosette (including the essential bias, flats, darks.  Don't stop imaging without them.), and the final image.  Magic.

 

This is what you want.

 

Rosette(32l,f,b,d).jpg

 

Rosette Nebula_small.jpg


Edited by bobzeq25, 15 September 2021 - 04:54 PM.

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#8 cougarone

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Posted 15 September 2021 - 06:12 PM

I ran into the same issue using a OSC on M31 (using SV130) and all I saw was a tiny puff, first time taking pictures through a telescope.  I have  now been working in Pixinsight and said wow theirs the data !!  Just keep at it, the data is in the details


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#9 damarks913

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Posted 15 September 2021 - 07:20 PM

Thank you all so much.....I have definitely taken the Red Pill.....


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#10 cougarone

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Posted 15 September 2021 - 10:55 PM

Yes, welcome to the bank drainer club, but well worth it. Until I processed the data in PixInsight ( still watching vidoes) I thought I didn't capture the targets (even though i saw them through an SV80 mounted on top of my SV130 in which I had an eyepiece for visual to make sure I got the target (guide scope mounted on top of SV80) . My next step is to take more than 10 , 3 min exposures and learn how to do the lights, bias, flats, etc.  and work it into my processing.


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