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First Light Canon 300mm f2.8 on the Crescent Nebula

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#1 cuivienor

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Posted 18 June 2019 - 12:43 AM

It may be the rainy season here in my Tokyo Bortle NaN zone, but I managed to get 7.7 hours of data on the Crescent Nebula, with:

- 154 x 180s

- Canon 300mm f2.8 lens stopped down to f3.5 (first light)

- Astromechanics lens controller (first light)

- ASI071MC Pro (first light)

- OPT Triad Ultra filter

- EQ6R mount

- Almost full moon

 

All controlled by N.I.N.A.

 

After all the issues I had with the Triad Filter and the 294MC Pro, it is a huge relief to see it working so well from a very, very light polluted zone.

 

C&C Welcome! As usual, I'm never, ever satisfied with the colors I get.

 

Cheers,

 

Yannick

Attached Thumbnails

  • drizzle_integration_DBE_Stretched_Curves_Processed_Bright_Resampled_Desaturated_Small.jpg

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#2 james7ca

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Posted 18 June 2019 - 03:52 AM

Considering the moon and light pollution that looks very good.

 

The ASI071MC should be a very nice camera for astrophotography since it comes from the same family of sensors used by the Sony NEX-5 and Nikon D5100. In fact, my completely unmodified NEX-5N camera produced what is probably my favorite image of the North America Nebula (taken from a dark site). I need to revisit that data set since I think I still have about twice as many subs to process and I also extended the coverage over to the Pelican (a 1 x 2 montage).



#3 BABOafrica

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Posted 18 June 2019 - 08:48 AM

Very nice image. Mostly interested to see that you could be good resolution with the Canon 300mm lens.



#4 Mert

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Posted 18 June 2019 - 12:34 PM

IMHO that is a great image and specially taking into account

these conditions you have to fight.

The Triad filter is working as they state, for a OSC camera this

is tremendous!

I also have a Triad filter, not the ultra, and it does a fantastic

job fighting light polution!

The colors I believe are fine, you can always tweak things until

they are the way you are satisfied with it.

What does your sky look light, like your flat panel? ( in my

case it does many times )



#5 cuivienor

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Posted 18 June 2019 - 09:33 PM

Thanks for the feedback! Yes, for just 7 hours of data, with an OSC sensor, from Tokyo, I'm quite happy with the results! The 071MC sensor is outstanding. I used to have the very first NEX-5 version, and I loved it. Those sensors are truly something!

 

But I did noticed something interesting when decomposing into separate R, G, and B channels: the Green channel is in perfect focus, but the focus on R and B is a bit soft! I guess it could come from the optical system, the Bayer matrix, or others.

I also noticed that the lens has a filter holder integrated (!) and that it had a transparent (?) filter in there, that might have hurt the image. So I'm removing that going forward!

Cheers,

 

Yannick



#6 BABOafrica

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Posted 19 June 2019 - 09:17 AM

The lens ... has a transparent filter ???  You mean the Canon 300mm lens ???

 


.

I also noticed that the lens has a filter holder integrated (!) and that it had a transparent (?) filter in there, that might have hurt the image. So I'm removing that going forward!

Cheers,

 

Yannick



#7 Kevin Ross

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Posted 19 June 2019 - 02:35 PM

A lot of the big high end telephoto lenses have filter holders at the rear of the lens. This allows you to use smaller filters, so you don't have to have a huge monster filter at the front of the lens.


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#8 freestar8n

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Posted 20 June 2019 - 02:39 AM

Nice work.  Did you use NINA for autofocus - or was it manually focused?

 

I haven't used NINA and I don't know how it focuses.  So if you did use it can you explain how it worked?

 

It's especially good as first light both for the focusing system and camera.

 

Thanks,
Frank



#9 cuivienor

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Posted 20 June 2019 - 03:26 AM

@freestar8n: yes NINA for autofocus, with it running every 45 minutes.

 

I've been focusing a lot on autofocus (can't believe I hadn't intended that pun), and have contributed code that helps with star detection for all sensors, plus more improvements for OSC (including unlinked stretch, that does the same as the PI unlinked STF and enhances star contrast) - all of these are in the latest nightlies. I still have a couple of enhancements I coded that are awaiting approval from the devs to be merged into NINA.

 

So auto-focus is working very well indeed. The AF system moves a certain distance out, computes HFR, then moves gradually back in until it detects two trend lines. Or if there's only one trend line it will move further in or out as require until it has two trend lines. Its main weakness was star detection, but it's much better now.

 

Cheers,

 

Yannick



#10 freestar8n

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Posted 20 June 2019 - 04:01 AM

Thanks Yannick.  For my 135 f/2 the individual steps were pretty big in terms of focus change - so I felt it was more limited by the lens internal mechanics than anything else.

 

It's good to know it is all working with the 300.  Oh - and it was stopped down to 3.5 so that probably helps, too.

 

Thanks,
Frank



#11 cuivienor

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Posted 20 June 2019 - 04:34 AM

I'm not sure about the 135mm, but AF works fine with 10 step intervals for the 300mm (which I originally focused at F2.8), and 5 step intervals for the 200mm f2.8.

Yeah, it's not quite usable wide open at F2.8, there is some star distortion in the green and blue bands...


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