Imaging with the Samyang 135mm f2

[aleixandrus]

Hi. To not make this thread even longer I've just created a new thread about some issues I'm having with flats and the Samyang 135. I can update this post with the conclusions (for future references) but now I ran out of ideas. Any help is welcome.

 

[aleixandrus]

Happy new year to everyone!

This is a "quick" processing of the Question Mark Nebula. I've stacked a SHO master light with no flats to perform a 'quick and dirty' editing just to test if I can ignore them, but somehow I managed to do the processing to the final stage. There are some issues there (specially in the background and nebulosity colors) but... hey! I think I can get some nice pics although I didn't resolve my issues with the flats 😅

For those interested in the details: EQ6R + ASI183MM Pro + Samyang 135mm @ f2.8 300s each with S2 (~7h) + Ha (~5h) + O3 (~7h) Baader 6.5nm filters

[ollypenrice]

This is posted on the deep sky board but since it's a 42 panel Samyang 135 mosaic I'll pop it here as well. Love this lens!

Olly

 

[Laurin Dave]

32 minutes ago, ollypenrice said:

This is posted on the deep sky board but since it's a 42 panel Samyang 135 mosaic I'll pop it here as well. Love this lens!

Olly

Hi Olly...  I'm sure you know what's just off the image.... but just in case  ..   When can we expect this?  (no need to wait for Mars and a comet)

Dave

[ollypenrice]

20 minutes ago, Laurin Dave said:

Hi Olly...  I'm sure you know what's just off the image.... but just in case  ..   When can we expect this?  (no need to wait for Mars and a comet)

Dave

Oh no! We have a widefield Flaming Star and a huge California-to M45 already... Madness! But Paul is mulling over something an order of magnitde madder than that...

😁lly

[aleixandrus]

Holly molly! My 12 panel mosaic is just a nightmare, I can't imagine what something so big will be like 🫣

[tomato]

On 05/01/2024 at 16:11, ollypenrice said:

Oh no! We have a widefield Flaming Star and a huge California-to M45 already... Madness! But Paul is mulling over something an order of magnitde madder than that...

😁lly

"The Olly and Paul Deep Sky Photographic Atlas of the Northern Hemisphere", I'd buy a copy.👍

[Phillyo]

Afternoon folks,

I'm getting a little tired of the amount of cloud cover we have in the UK, and whilst I love my little Redcat51...at F4.9 compared to the sammy it's a bit slow. So, I'm considering selling the Redcat and just going back to the Samyang lens for a bit and operating it at either F2 or 2.4 etc. to make the most of what (if any) clear skies we do get.

I currently use the Antlia ALP-T filter but it's the none fast version and I'm wondering if people know if the fast version from Antlia is still technically the 'best' suited or if anything else is better these days (L-Ultimate, or one of the new quad band filters perhaps?)

I'm also considering a second sammy at some point to run a dual rig in the hope I can double the light gathering or run it side by side for a wider FOV.

Thanks,

Phil.

 

[Elp]

I still use my Lextreme for OSC, don't really have a problem with it.

Regarding dual lens, if you can do it it's definitely worth it as I decided a while ago it had to be done due to the minimal opportunities to image. I've managed to get mine rigged so I can do the same target with both, imaging mono is suddenly so much faster in fewer sessions.

[Phillyo]

16 minutes ago, Elp said:

I still use my Lextreme for OSC, don't really have a problem with it.

Regarding dual lens, if you can do it it's definitely worth it as I decided a while ago it had to be done due to the minimal opportunities to image. I've managed to get mine rigged so I can do the same target with both, imaging mono is suddenly so much faster in fewer sessions.

If it's ok with you, I might pick your brain (via DM) regarding your setup at some point in the future. I'll likely try and sort it over summer when I'm not imaging. I assume you've likely posted about it on this topic further back? If so I'll scroll back and see what I can find

[Elp]

I might make a specific thread at some point as I've been putting it together for a while in different forms, think I've reached a fixed finalised setup with it.

[Phillyo]

Awesome! I'll look forward to reading it if you ever get around to it.

Phil

[Simon Pepper]

Hopefully a quick one I have ordered myself the 135 again and curious what's the quickest way to test the corners to see what kind of copy I have. Should I use a DSLR or should I attached my dedicated camera and spacing etc? Thanks 

[Elp]

Probably use your largest sensor and take an image of a detailed grid pattern. BUT, a star test is more of a test for lenses as there can be potentially at least three or four different types of aberrations which come from point light sources which you won't necessarily see in daylight images. Also note it might not be a conclusive test, most of the issue with the lens is tilt, the lens itself might be fine, the way it mates to a mounted surface makes the difference, also due to the fact it's a heavy lens so will droop slightly if not supported from underneath.

You don't need to take a tracked shot of a starfield, any short exposure on a fixed tripod will do, but I guess it depends on your skies as to when you can do it.

Edited January 10 by Elp

[Simon Pepper]

2 minutes ago, Elp said:

Probably use your largest sensor and take an image of a detailed grid pattern. BUT, a star test is more of a test for lenses as there can be potentially at least three or four different types of aberrations which come from point light sources which you won't necessarily see in daylight images. Also note it might not be a conclusive test, most of the issue with the lens is tilt, the lens itself might be fine, the way it mates to a mounted surface makes the difference, also due to the fact it's a heavy lens so will droop slightly if not supported from underneath.

You don't need to take a tracked shot of a starfield, any short exposure on a fixed tripod will do, but I guess it depends on your skies as to when you can do it.

Thanks Elp good advice let’s prey for clear skies within the 30 day free returns lol! 

[Elp]

In the meantime just take a few images with it in general. It's a great lens, fantastically sharp, not really a carry around lens though due to the weight.

[Adreneline]

1 hour ago, Simon Pepper said:

curious what's the quickest way to test the corners to see what kind of copy I have.

I cannot take any credit for this as I was pointed in this direction by a fellow AB user.

Surprisingly you can get a very good idea of the performance of your lens and camera attachment using a lens star test sheet.

I use my Samyang 135mm with an ASI183MM and over the past four years of using the ASI183 with the Samyang, a RedCat 51 and a 6" RC I have convinced myself there is a slight problem with one corner of the sensor - the sensor has not been mounted orthogonal to the image train. I purchased a Gerd Neumann CTU to try to null this sensor misalignment but the weather has been terrible for months and not conducive to spending time outside by the scope using NINA Aberration Inspector to fully understand the problem and hopefully correct the misalignment.

I was advised to print five of these off and mount them in the corners and centre of a piece of card. I chose the aspect ratio to match my sensor- an ASI183MM.

You don't need to focus at infinity - I had my card about 7.5 metres from the lens - the most I could comfortably manage indoors:

I did spend some considerable time trying to ensure I had everything orthogonal and very, very aligned accurately.

This was the first image I took ....

... and I think you can see the dark areas in the middle of the corner patterns are (a) not the same and (b) not the same as the centre pattern.

I took dozens of images whilst carrying out incremental adjustments with a CTU - this is what an introduced 25 micron tilt of the CTU will do to the patterns:

... that is 25/1000th of a millimetre.

After much playing around with the CTU and note taking I ended up with this:

... which I think is marginally better than where I started.

I accept that there is no substitute for an actual star test and feeding the resulting image into ASTAp / Siril / PI and analysing the star quality across the image.

Since doing the above the great UK weather has not provided me with a single opportunity to check my lens with a real star test.

If nothing else the above method allows you to identify image train droop and tilt and maybe start to correct the problem(s) BUT a star test is always going to provide the acid test.

Hope this is of interest.

 

[Simon Pepper]

9 minutes ago, Adreneline said:

I cannot take any credit for this as I was pointed in this direction by a fellow AB user.

Surprisingly you can get a very good idea of the performance of your lens and camera attachment using a lens star test sheet.

I use my Samyang 135mm with an ASI183MM and over the past four years of using the ASI183 with the Samyang, a RedCat 51 and a 6" RC I have convinced myself there is a slight problem with one corner of the sensor - the sensor has not been mounted orthogonal to the image train. I purchased a Gerd Neumann CTU to try to null this sensor misalignment but the weather has been terrible for months and not conducive to spending time outside by the scope using NINA Aberration Inspector to fully understand the problem and hopefully correct the misalignment.

I was advised to print five of these off and mount them in the corners and centre of a piece of card. I chose the aspect ratio to match my sensor- an ASI183MM.

You don't need to focus at infinity - I had my card about 7.5 metres from the lens - the most I could comfortably manage indoors:

I did spend some considerable time trying to ensure I had everything orthogonal and very, very aligned accurately.

This was the first image I took ....

... and I think you can see the dark areas in the middle of the corner patterns are (a) not the same and (b) not the same as the centre pattern.

I took dozens of images whilst carrying out incremental adjustments with a CTU - this is what an introduced 25 micron tilt of the CTU will do to the patterns:

... that is 25/1000th of a millimetre.

After much playing around with the CTU and note taking I ended up with this:

... which I think is marginally better than where I started.

I accept that there is no substitute for an actual star test and feeding the resulting image into ASTAp / Siril / PI and analysing the star quality across the image.

Since doing the above the great UK weather has not provided me with a single opportunity to check my lens with a real star test.

If nothing else the above method allows you to identify image train droop and tilt and maybe start to correct the problem(s) BUT a star test is always going to provide the acid test.

Hope this is of interest.

 

Very interesting stuff definitely over my head with the CTU but I’ll give this a go to see if anything jumps out at me as a big issue! 

[Adreneline]

4 minutes ago, Simon Pepper said:

definitely over my head with the CTU

One of these:

https://www.firstlightoptics.com/adapters/gerd-neumann-camera-tilting-unit-ctu-xt.html

 

[tomato]

1 hour ago, Adreneline said:

I cannot take any credit for this as I was pointed in this direction by a fellow AB user.

Surprisingly you can get a very good idea of the performance of your lens and camera attachment using a lens star test sheet.

I use my Samyang 135mm with an ASI183MM and over the past four years of using the ASI183 with the Samyang, a RedCat 51 and a 6" RC I have convinced myself there is a slight problem with one corner of the sensor - the sensor has not been mounted orthogonal to the image train. I purchased a Gerd Neumann CTU to try to null this sensor misalignment but the weather has been terrible for months and not conducive to spending time outside by the scope using NINA Aberration Inspector to fully understand the problem and hopefully correct the misalignment.

I was advised to print five of these off and mount them in the corners and centre of a piece of card. I chose the aspect ratio to match my sensor- an ASI183MM.

You don't need to focus at infinity - I had my card about 7.5 metres from the lens - the most I could comfortably manage indoors:

I did spend some considerable time trying to ensure I had everything orthogonal and very, very aligned accurately.

This was the first image I took ....

... and I think you can see the dark areas in the middle of the corner patterns are (a) not the same and (b) not the same as the centre pattern.

I took dozens of images whilst carrying out incremental adjustments with a CTU - this is what an introduced 25 micron tilt of the CTU will do to the patterns:

... that is 25/1000th of a millimetre.

After much playing around with the CTU and note taking I ended up with this:

... which I think is marginally better than where I started.

I accept that there is no substitute for an actual star test and feeding the resulting image into ASTAp / Siril / PI and analysing the star quality across the image.

Since doing the above the great UK weather has not provided me with a single opportunity to check my lens with a real star test.

If nothing else the above method allows you to identify image train droop and tilt and maybe start to correct the problem(s) BUT a star test is always going to provide the acid test.

Hope this is of interest.

 

Very impressive, I reckon the UK leads the world in "stuff to do to improve your astro imaging while it's cloudy"

[Simon Pepper]

I have another question if I may it’s probably been answered already but this is now a mega thread and a bit of a needle in a haystack! Lens has arrived and I have ordered the Samyang adapter from FLO as well as mounting rings etc etc, however my understanding is I need circa 44mm backspacing but I plan to shoot unfiltered the camera is 2600 and I am unfamiliar with it as in the past I have had the 6.5mm to the sensor this is 17.5 and is female on camera side so I believe I am missing an adapter? Does anyone have some insights on what else I need to order here and how to get to 44mm? Thanks 🙏 

Edited January 28 by Simon Pepper

[Elp]

A camera like a 183/585/533 has a 6.5mm front of camera to sensor distance. They use an 11mm m42 female to female connector to get the 17.5mm distance. As your camera already is 17.5mm front of camera to sensor with a female m42 thread in the front it should just screw into the ZWO Eos filter drawer directly, have you tried it?

See here:

https://www.firstlightoptics.com/zwo-accessories/zwo-filter-drawer-for-canon-eos-lenses.html

[Elp]

This adaptor does the same thing too, I've got both:

https://www.firstlightoptics.com/zwo-accessories/zwo-adjustable-eos-lens-to-t2-adapter-for-all-asi-cameras.html

[Simon Pepper]

@Elp I was planning on no filter I am bortle 4 and 2600 already has IR cut so that’s why I aas confused. 

[Elp]

What adaptors have you got currently? The above just make it easier to mount as you don't need to mess around with backspacing much with or without filters. I setup and breakdown every time and have never had issues other than the typical tilt.

 

Edited January 28 by Elp