SL Crons for astrophoto

[helged]

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Hi folks! Anyone with SL 35mm or SL 50mm that have checked - or can test - how stars are represented towards the corners of the image at f2? Are the stars points, as they should be, or are there optical aberrations, coma,...? To test this, one needs tripod, focus on the stars, aperture of f2, max 15 sec shutter speed, high-ish ISO (1600 or 3200). And a clear sky... 

[darylgo]

I would do this, we have a clear night, a waxing crescent moon, however I don't have the lenses requested.  I have thought that a testing simulation would be an interesting endeavor and giving it some thought perhaps an led with many pinpoint lights could work.  So I tried this with a 50 Summicron M and there was no coma, slight chromatic aberrations but very minimal.  I haven't used this lens for stars and can't be quite sure the simulation is valid.  Then I attempted this with a lens sadly plagued with coma, the 21mm Summilux and the coma appeared making the simulation appear valid, maybe.   The Milky Way should be appearing soon so it's time to go out and shoot.

 

 

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[helged]

6 hours ago, darylgo said:

I would do this, we have a clear night, a waxing crescent moon, however I don't have the lenses requested.  I have thought that a testing simulation would be an interesting endeavor and giving it some thought perhaps an led with many pinpoint lights could work.  So I tried this with a 50 Summicron M and there was no coma, slight chromatic aberrations but very minimal.  I haven't used this lens for stars and can't be quite sure the simulation is valid.  Then I attempted this with a lens sadly plagued with coma, the 21mm Summilux and the coma appeared making the simulation appear valid, maybe.   The Milky Way should be appearing soon so it's time to go out and shoot.

Thanks! 28Lux-M does kind of work, but the aberrations were too large/visible for my taste... I have the 50APO-Cron-M, I will run a test with this lens. 

[Simone_DF]

You may want to check one of the Laowas, they come in L mount now. Maybe the 15mm F2:

https://www.lonelyspeck.com/laowa-15mm-f-2-fe-zero-d-lens-astrophotography-review/

[darylgo]

The 50 Lux Asph M is a great performer wide open,  I’m guessing the Apo would be also.  

[tommydom]

@helged I used the SL35mm on my SL2 for some tripod shots in my light polluted skies here in Fairfax VA. There is some CA in the shot but not as bad as a non-APO lens. I have been attempting to do wide field images and and use PixInsight for processing, but have really fallen short of my goals here. I do suspect that I have some technique issues, but have a lot to learn if I want to keep using this camera system for astrophotography.

Attached are 2 crops from one shot at the end of a 15 shot interval run, SOC with only White (+100) and Black (-100) adjustments in C1, SL2, Sl35mm f/2, ISO800, 4sec, 807px square.

The grey-ish crop is near center and when pixel peeping, there is some elongation, and some hot pixels. And the CA is not very evident.

The darker crop is at one corner, and there is some CA. The hot pixels show up "perfectly".

I will state that I have been working on technique when not shooting terrestrial shots now and again, and my technique is not what it could be.

 

Tommy.

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[helged]

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7 minutes ago, tommydom said:

@helged I used the SL35mm on my SL2 for some tripod shots in my light polluted skies here in Fairfax VA. There is some CA in the shot but not as bad as a non-APO lens. I have been attempting to do wide field images and and use PixInsight for processing, but have really fallen short of my goals here. I do suspect that I have some technique issues, but have a lot to learn if I want to keep using this camera system for astrophotography.

Attached are 2 crops from one shot at the end of a 15 shot interval run, SOC with only White (+100) and Black (-100) adjustments in C1, SL2, Sl35mm f/2, ISO800, 4sec, 807px square.

The grey-ish crop is near center and when pixel peeping, there is some elongation, and some hot pixels. And the CA is not very evident.

The darker crop is at one corner, and there is some CA. The hot pixels show up "perfectly".

I will state that I have been working on technique when not shooting terrestrial shots now and again, and my technique is not what it could be.

 

Tommy.

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Thanks, much appreciated! This looks good.

The SL16-35 is not a good option for stars. The SL24-90 is excellent - and actually among the lenses with least optical (+in-body correction) artefacts I have tested - for focal lengths between 24 and 50mm (and shoot wide open). Another fine lens is the Sigma 14mm f1.8 ART (although there are variations between copies; I tested three lenses before a found an excellent one...).

[tommydom]

I agree about the SL16-35 as I tried that one out before I purchased the 35mm. 

Here is a link to a wide field shot (cropped, essentially the center of the frame) using the SL2 and the SL35mm, f/2, 15 shot interval, ISO3200, 4sec in much darker skies - Buxton NC - using a tracker mount. The shot was processed in PixInsight (lights, darks, flats) and in C1.

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[helged]

44 minutes ago, tommydom said:

I agree about the SL16-35 as I tried that one out before I purchased the 35mm. 

Here is a link to a wide field shot (cropped, essentially the center of the frame) using the SL2 and the SL35mm, f/2, 15 shot interval, ISO3200, 4sec in much darker skies - Buxton NC - using a tracker mount. The shot was processed in PixInsight (lights, darks, flats) and in C1.

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Great - the Orion Nebula shines beautifully! 

[Eclectic Man]

I have used the 50mm Apo from Reading, UK.  The first is the middle fo the frame, the second is top left corner. Same frame at f/2, 1 second at iso 800.

 

 

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Edited February 16, 2021 by Eclectic Man

[helged]

On 2/16/2021 at 4:59 PM, Eclectic Man said:

I have used the 50mm Apo from Reading, UK.  The first is the middle fo the frame, the second is top left corner. Same frame at f/2, 1 second at iso 800.

 

 

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Just to avoid misunderstandings: This is SL 50-Cron? (the othe alternative being the 50-APO-Cron-M).

[Eclectic Man]

It was the SL 50mm f/2 Apo AF lens, not the manual focus M lens.  I was testing the quality of the images and how well I could focus the lens.  Click on the image to see that stars and compare.  The full image is:

 

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Edited February 18, 2021 by Eclectic Man

[baoluo.ma233]

In case you would like to check how well it performed for milky way shots, here's mine from last summer. 

Now I’m looking for the 28 F2 and its astro ability 

Cheers 

Edited February 18, 2021 by baoluo.ma233

[helged]

1 hour ago, baoluo.ma233 said:

In case you would like to check how well it performed for milky way shots, here's mine from last summer. 

Now I’m looking for the 28 F2 and its astro ability 

Cheers 

Thanks, I agree that the SL2 is an interesting Candidate. The photo is not included in your post, however..