Samyang 135mm Cynus - with L-Extreme

[powerlord]

So folks were saying this wouldn't work as lens is too fast, but my results seem pretty decent ?

This is 6d with 135mm fully open, and a 2" L-extreme screwed on the end via some step down filter rings.

I know the framing isn't the best, but I didn't want to cut off the Crescent Nebula 😞

63 x 300 subs at 3200.

Me and Startools seems to have had a falling out, with whatever I try with it generating total mince, so just processed manually with affinity photo. and startnet++ for some star fiddling.

Edited August 15, 2021 by powerlord

[simmo39]

That looks brilliant!

[assouptro]

That’s proper moody! 
almost storm clouds! 
so much nebulosity  

what camera? 

thanks for sharing 

Bryan 

[powerlord]

3 hours ago, assouptro said:

That’s proper moody! 
almost storm clouds! 
so much nebulosity  

what camera? 

thanks for sharing 

Bryan 

Canon 6d

[Chefgage]

On 15/08/2021 at 08:08, powerlord said:

So folks were saying this wouldn't work as lens is too fast, but my results seem pretty decent ?

This is 6d with 135mm fully open, and a 2" L-extreme screwed on the end via some step down filter rings.

I know the framing isn't the best, but I didn't want to cut off the Crescent Nebula 😞

63 x 300 subs at 3200.

Me and Startools seems to have had a falling out, with whatever I try with it generating total mince, so just processed manually with affinity photo. and startnet++ for some star fiddling.

Very nice! Shows what a full frame sensor can produce compared to my smaller sensor using the canon 200d. I have shot the same image using the samyang 135mm and my field of view is smaller (but very happy with the result,).

[powerlord]

Just a note to say - Ivo Jager, the developer of Startools saw my post and offered to help with my issues - he spent a ridiculous amount of time putting some long details PMs with pictures together for me and going through various possible isses and settings. Amazing support.

In the end, it was my unwillingness to cut of the crescent nebula which was leaving in lots of stacking artefacts and the edges - this causes the wipe not to work as I'd want. Also I interpreted the docs wrong in regard to the bi-colour workflow.

I will process a startools version today and post that for comparison.

 

[happy-kat]

That's super help, I get the reluctance to crop as I'm often also over preserving dodgy edges.

[Victor Boesen]

Excellent image! Mind if I ask what the thread size on the lens is for step down rings?

[assouptro]

On 15/08/2021 at 13:50, powerlord said:

Canon 6d

I have one of those too that I modified 
although I don’t use it as much these days since 

I also teamed it up with my 135 to do a similar shot! 
I have a cropped version that’s cleaner but also cuts out the crescent nebula, there’s just so many stars!! 

 

Only filter was an Idas d2 

[powerlord]

yeh, that's why I used starnet++ - I think shots like this sometimes, to my eyes anyway, just look better with the stars really cut back.

here's the step downs

[happy-kat]

If you had had a 1.25 could you have used your nifty filter adaptor with your 6d

[happy-kat]

If you really want the Cresent could you do a stack on just that side of the lights range then process and stitch that panel to your other process with cropped artifacts.

[powerlord]

well, that is for aps-c really. It will be ideal for that. For 6d, I modified one to fit my 6f but 1.25 fitlers are not big enough to cover a FF sensor - so you will get a large amount of vignetting. Provided you are going to crop in quite a bit it would work though. Before I for the mono camera and all the gubbins, I shot north america in Ha like that with my 300mm F4 L lens as it was the only way I could shoot Ha - and it worked very nicely.

stu

[vlaiv]

On 15/08/2021 at 09:08, powerlord said:

So folks were saying this wouldn't work as lens is too fast, but my results seem pretty decent ?

This is 6d with 135mm fully open, and a 2" L-extreme screwed on the end via some step down filter rings.

Nice image.

I guess people were referring to converging beam configuration rather than putting the filter at the front. If you place filter between sensor and lens - then it sits in converging beam, and with F/2 beam - angles the light hits the filter can be very large - like >15°. This reduces efficiency of the narrowband filters as it shifts light away from the filter band. It acts as aperture stop for all the rays hitting sensor at larger angles.

In the configuration that you were using - you again did not use lens at F/2. 135mm F/2 lens has aperture of 67.5mm (135 / 67.5 = F/2). When you place 2" filter in front - you are effectively creating aperture mask. 2" filter has something like 46-47mm of clear aperture - let's go with 47mm. 135 / 47 = ~F/2.9. Your lens was effectively stopped down to F/2.9. Not sure if this is better or worse than having filter in converging beam though. It's probably better.

In any case, those are just technical details.

[astro mick]

That is really something.

Mick.

[powerlord]

2 hours ago, vlaiv said:

Nice image.

I guess people were referring to converging beam configuration rather than putting the filter at the front. If you place filter between sensor and lens - then it sits in converging beam, and with F/2 beam - angles the light hits the filter can be very large - like >15°. This reduces efficiency of the narrowband filters as it shifts light away from the filter band. It acts as aperture stop for all the rays hitting sensor at larger angles.

In the configuration that you were using - you again did not use lens at F/2. 135mm F/2 lens has aperture of 67.5mm (135 / 67.5 = F/2). When you place 2" filter in front - you are effectively creating aperture mask. 2" filter has something like 46-47mm of clear aperture - let's go with 47mm. 135 / 47 = ~F/2.9. Your lens was effectively stopped down to F/2.9. Not sure if this is better or worse than having filter in converging beam though. It's probably better.

In any case, those are just technical details.

I know that vlaiv - but its a 2" filter and a canon 6d and canon fit lens. there ain't anywhere do put a 2" filter between the lens and body. 🤔

However seeing as the lens is so fast, I figured I'd get away with the aperture reduction - which as you calculate - is still very fast. And i get sharper stars from the aperture reduction.

I didn't say it was F2 - just 'fully open' - since I am using the filter as the aperture mask basically. no need for using the petal aperture.

@happy-kat was referring to the 3d clip in filters I printed - which allow a filter to BE put between DSLR and lens - but only 1.25in ones, and really only APS-C cameras.

This was my 'thinking outside the box' solution to using an L-extreme wth my 6d without the expense of a FF clip in.

Within reason, I can now  use that 2" filter in a similar configuration with lots of my other lenses, or my 1200D AND when I want to use one of my OSC ZWO cameras then it can go between the camera  and lens, or telescope.

So allowing one filter to be a bit more flexibly used. 👍

Oh I will add, one issue with this config is that the filter is exposed. and that's not ideal, as they are not really made to be open the the elements - it's needed quite a bit of cleaning and I'm sure it will wear out long before it should.

But the worry voiced by others that it just wouldn't work. i.e. just wouldn't capture enough Ha what with it being such a fast lens, combined with the light angle issues you mention - just .. well don't seem to be issues. I'm getting really nice clear shots, lots and lots of Ha and Oiii, and it's doing an awesome job of cutting any light pollution. It seems to me, its a really good option for folk wanting to buy just one (lets face it..very expensive) filter and get the use of it with all the configurations of cameras, lenses and telescopes they have.

just my 2c anyhoo.

stu

Edited August 17, 2021 by powerlord

[vlaiv]

3 hours ago, powerlord said:

I know that vlaiv - but its a 2" filter and a canon 6d and canon fit lens. there ain't anywhere do put a 2" filter between the lens and body. 🤔

However seeing as the lens is so fast, I figured I'd get away with the aperture reduction - which as you calculate - is still very fast. And i get sharper stars from the aperture reduction.

I didn't say it was F2 - just 'fully open' - since I am using the filter as the aperture mask basically. no need for using the petal aperture.

I think that is better way to stop down the lens as you say - there is no diffraction from blades.

Either that or 3d printed aperture mask that screws in the filter thread.