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First light Canon 200 2.8 - I'm impressed!

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#1 RJF-Astro

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Posted 12 August 2020 - 02:47 AM

Hi all, so recently I ventured into using camera lenses with my ASI1600. My main goal was to use my 3nm narrowband filters to do some more widefield narrowband imaging. As a regular photographer I only use manual focus primes, so I already had various options to try. These included the Zeiss 100 f/2, Zeiss 85 f/1.4, Nikon 105 f/4 macro, Nikon 200 f/4. I had a Samyang 135 f/2 and Nikon 180 f2.8 in the past although I have not used those for narrowband, only RGB. Recently I added a Mitakon-Zhongyi 135 f/2.8 and a used Canon 200mm f/2.8.

 

Why the long intro? Well because the Canon really blew me away. It was the first time when I looked at the stacked image afterwards, and corner performance did not dissapoint.

 

The image below is a HOO combination. When doing Ha I had an issue with recalibration after the automatic meridian flip (was temporarily using ST-4), so I only got 5x480 seconds. In the morning I decided not to take flats because I did not think it would be worth processing.

 

However 40 minutes was enough for a nice image. Without flat correction the field looked completely flat. I used a 72->52mm step down ring so the effective aperture was f/3.84. Really nice to see that the 1.25" mounted filters are easily handling this aperture.

 

For €350 this is one of my better astro purchases, highly recommended!

 

5x480s Ha and 25x480s O3:

 

20200808 NGC6888 200mm HOO.jpg

 

Full res on AstroBin


Edited by RJF-Astro, 12 August 2020 - 03:01 AM.

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#2 BackyardSpaceDude

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Posted 12 August 2020 - 02:58 AM

Awesome! Amazing results for not a huge investment.


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#3 RJF-Astro

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Posted 12 August 2020 - 05:05 AM

Thanks Jamie!

 

I will admit, I am a sucker for looks too. And I think it really looks nice on the rig. And that means a lot from me saying it, because this is my first Canon lens and I have never found Canon design really appealing.

 

XT017375.jpg



#4 Sandy Swede

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Posted 12 August 2020 - 05:22 AM

x2 on the manual focus primes.  Here is my Rokinon 135mm f/2.  I also have the Canon 200mm f/2.8 and am in the process of figuring out a better method for mounting the camera & lens combo.  I will now be able to go to school on your rig.  Thanks!

 

Attached Thumbnails

  • SW+Rokinon5.jpg

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#5 RJF-Astro

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Posted 12 August 2020 - 05:42 AM

That does look sturdy though, not bad! I use these guide scope rings on this dovetail. For the guidescope I had to drill two holes in the ring and mount the shoe with nuts and bolts. Pretty stable though, enough for a 200mm lens.

 

Tube rings would be less prone to flex, but harder to mount properly. The guide scope rings offer flexibility and I have not noticed any flexing with these 'widefield' lenses anyway.



#6 freestar8n

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Posted 12 August 2020 - 05:58 AM

Hi-

 

That's a very nice result - and when I saw it I was going to ask if you had some kind of lens support - and indeed you do.  I have a Canon 135 f/2 lens that is very sharp and I have posted some pictures with it on an ASI1600 - but I decided recently that it really needed a lens support because there is some sag in its attachment.  I have attached it several ways but the one I intend to use is the astromechanics one that can focus the lens remotely.  I don't think I see it in your image so I assume you focus manually.

 

Stopping it down a bit should help both with the field and with the 3nm filters.

 

When you set it up did you just tighten the ring mount for the lens by feel - or did you watch the field and make adjustments until the overall field was sharp?  I'm hoping to use my 135 wide open and expect to be doing some tweaking of the ring mount.  I hope to have it all set up in a week or so.

 

The ASI1600 and a good dslr lens is a great combo - especially with only needing 1.25" filters.

 

Frank



#7 Sandy Swede

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Posted 12 August 2020 - 06:18 AM

That does look sturdy though, not bad! I use these guide scope rings on this dovetail. For the guidescope I had to drill two holes in the ring and mount the shoe with nuts and bolts. Pretty stable though, enough for a 200mm lens.

 

Tube rings would be less prone to flex, but harder to mount properly. The guide scope rings offer flexibility and I have not noticed any flexing with these 'widefield' lenses anyway.

Thanks, it is very sturdy.  I purchased the lens bracket from:

Philippe LECA

46 Avenue Clémenceau-F1

77100 MEAUX

France

www.astrokraken.fr

 

Not cheap, but neither is the 3D printed construction.  Highly recommended.  The Canon 200mm f/2.8 is not used extensively for AP so it probably is not economically feasible for Philippe to design and print one for this lens.  Using your design would be more fun for me.  I love a challenge!


Edited by Sandy Swede, 12 August 2020 - 06:18 AM.


#8 RJF-Astro

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Posted 12 August 2020 - 09:56 AM

Hi-

 

That's a very nice result - and when I saw it I was going to ask if you had some kind of lens support - and indeed you do.  I have a Canon 135 f/2 lens that is very sharp and I have posted some pictures with it on an ASI1600 - but I decided recently that it really needed a lens support because there is some sag in its attachment.  I have attached it several ways but the one I intend to use is the astromechanics one that can focus the lens remotely.  I don't think I see it in your image so I assume you focus manually.

 

Stopping it down a bit should help both with the field and with the 3nm filters.

 

When you set it up did you just tighten the ring mount for the lens by feel - or did you watch the field and make adjustments until the overall field was sharp?  I'm hoping to use my 135 wide open and expect to be doing some tweaking of the ring mount.  I hope to have it all set up in a week or so.

 

The ASI1600 and a good dslr lens is a great combo - especially with only needing 1.25" filters.

 

Frank

Thanks Frank! No I tightened it by feel. I do not feel any sagging. The abberations I see suggest it is not completely centered (one side has some coma while the other has astigmatism or a combination of those two), but my guess it is the lens itself rather than the mechanical connection to the camera.

 

I do focus manually. It takes some time to get it right, but not undoable (unlike some macro lenses with their short focus throw near infinity). That adapter by Astromechanics looks really tempting though.



#9 mikefulb

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Posted 12 August 2020 - 10:07 AM

Very nice - certainly preferable to the pocket book than going to a full frame sensor + large filters + $$$$$.  :)



#10 Peregrinatum

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Posted 12 August 2020 - 10:12 AM

Thanks Jamie!

 

I will admit, I am a sucker for looks too. And I think it really looks nice on the rig. And that means a lot from me saying it, because this is my first Canon lens and I have never found Canon design really appealing.

 

attachicon.gifXT017375.jpg

Hey @RJF-Astro, looks great!  I think using SLR lenses with the CMOS camera adds a great dimension to AP...

 

Where did you get your adapter to connect the lens to the filter wheel?
 



#11 RJF-Astro

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Posted 12 August 2020 - 11:00 AM

Hey @RJF-Astro, looks great!  I think using SLR lenses with the CMOS camera adds a great dimension to AP...

 

Where did you get your adapter to connect the lens to the filter wheel?
 

Thank you! It is this one. It looks like Teleskop-Express is one of the few shops that has it in stock, although I have checked only a few US sellers.


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