Imaging with the Samyang 135mm f2

[Adreneline]

@malftobe I should have clarified that it is the filter glass thickness that changes the focus point by an amount essentially equal to 1/3 of the glass thickness, so my Astronomik increases the nominal 44 mm by 0.33 mm - my Baader by 0.66 mm. Because I don’t compensate for the extra 0.33 the focus point on the lens is before the L with the Baader. Hope that makes sense. 🤞

Adrian

[geeklee]

11 hours ago, woldsman said:

Also histograms are not just for DSLRs & unless you clip data, there are pros and cons to a range of histogram points.

I realise this 😉 I've never exposed long enough to get my histogram peak anywhere near there in narrowband (1/3rd along). 

Here are three example single subs - using a 6nm Astronomik MaxFR Ha filter (@ ~F2.6)

300s:

180s:

120s:

I managed to find an old sub from just a UVIR cut filter on an OSC camera (533MC Pro) and the Samyang. Understandably the peak is further to the right as this was F2 and broadband.

 

Edited July 13, 2022 by geeklee

[wxsatuser]

14 hours ago, geeklee said:

I think you're making life unnecessarily complex for yourself doing this.  Not sure about the 1/3rd distance from the left - that might be a DSLR thing? 

You are correct as the 20>30% histogram thing is to gauge where the RAW histogram is just detached from the lefthand side with a dslr.

It is this value because one would normally view the histogram on the back of the camera where the image is a processed jpeg.

[woldsman]

11 hours ago, wxsatuser said:

You are correct as the 20>30% histogram thing is to gauge where the RAW histogram is just detached from the lefthand side with a dslr.

It is this value because one would normally view the histogram on the back of the camera where the image is a processed jpeg.

Thanks for this explanation! 

[malftobe]

Thanks for everyone's help on this great thread, it is a fantastic resource.  And an extra shout out to spacing expert @Adreneline!

After my third night of testing with the Samyang, I think I'm getting closer!  Last night with the new m42 adaptor, a 3mm extension and 2x 0.1mm spacers I got much nicer stars across the frame and focus is about 1mm before the end of the focus travel at L.  Should all add up to 44.7mm backfocus (I think).  This is with the lens stopped down using the aperture ring to f4.

 

 

 

The night before yielded this effect when I attempted to get to f2.8 using a 49mm step down ring on the front of the lens with the aperture ring set wide open at f2.  This with nearly the same spacing setup as most recent above, but with an additional 0.1mm spacer, so my focus was much better than the first night using the m48 adaptor.  I assumed the crescent star shapes at the left side of image was due to droop as it is a heavy camera, and the short extension only threads in to about 2.5mm of the 4.8mm thread on the camera, so I have ordered a zwo camera holder as many others on this thread use - hopefully this combination of holder and step down ring will get me right where I want to be. 

 

Hopefully further tests tonight!

 

[Adreneline]

57 minutes ago, malftobe said:

Should all add up to 44.7mm backfocus (I think).

Sounds good. Mine is currently 44.4 mm and focuses on the foot of the 'L' with the Asronomik Ha and SII filters and before the 'L' with the thicker Baader OIII (no doubt if I inserted ~0.3 mm spacer the OIII would focus on the 'L' but then the Ha and SII would be beyond the end stop of the focus ring - must buy that Astronomik OIII!!).

I decided to remove the EoS fitting and purchased the AstroJolo M42 adapter to allow easy attachment to my TS-Optics manual filter drawer. The screw M42 is really rigid and essentially overcame any droop. As a belt and braces approach I use the WO ring to support the lens and then the ZWO camera ring to support the camera itself; a bit of shimming is required to get it all lined up but it has made for a really solid, non-flexing image train.

The SY35 is a great lens and really rewarding to use and it is worth going the extra mile to get good stars across the f.o.v.

By the way I also use a 49 mm step-down-ring which gives me about f2.6 - I find it much better than stopping the lens down using the f-stop ring on the lens itself and avoids the diffraction spikes - which I prefer.

Good luck and happy imaging with the Samyang!

Adrian

[malftobe]

33 minutes ago, Adreneline said:

As a belt and braces approach I use the WO ring to support the lens and then the ZWO camera ring to support the camera itself; a bit of shimming is required to get it all lined up but it has made for a really solid, non-flexing image train.

 

Using the same rings - can't think where I got that idea!  Looking forward to getting the callipers out and rummaging around to find something suitably sized to pack the height difference out....

 

37 minutes ago, Adreneline said:

 

By the way I also use a 49 mm step-down-ring which gives me about f2.6 - I find it much better than stopping the lens down using the f-stop ring on the lens itself and avoids the diffraction spikes - which I prefer.

 

 Hoping to achieve similar, I already have the 49mm ring from my reading on here, may eventually end up with something around 43mm stepped down as I already suffer a bit of vignette as my filters are undersized for my camera!  So hoping to find a good compromise on that front.

 

Just a quick question - to work out your f ratio above, rather than the "advertised 135mm", do you use 129mm from the plate solving to calculate your f2.6?

[Adreneline]

30 minutes ago, malftobe said:

Just a quick question - to work out your f ratio above, rather than the "advertised 135mm", do you use 129mm from the plate solving to calculate your f2.6?

Yes. I assumed the plate solved focal length was the most accurate result - comes up on the ASIair and is confirmed by Astrometry.net as well - so it is f2.632653 (!!) - f2.6 is close enough for me  

33 minutes ago, malftobe said:

find something suitably sized to pack the height difference out....

I ended up using a thick washer which I had acquired from somewhere over the past too many years of collecting such things in a tin - as you do  

I'm very happy with my imaging train arrangement but less so with my EAF positioning. It works well but has restricted me to having the camera sensor in 'portrait' rather than 'landscape' with respect to the Vixen bar. If I rotate the whole assembly to be in 'landscape' I can't get my filter in and out of the filter drawer. Arghh!! I would like to be easily able to arrange as per my RedCat setup where it is simple for me to rotate the camera through 90 degrees as spacing is not critical. If I introduce a spacer on the SY135+ASI183 to achieve 'landscape' the focus is no longer within the 'L'. So frustrating - I mean challenging.

I need to move the EAF to the side of the lens but it's not easy  

Adrian

[Uranium235]

Just a quick run last night to test the new CCD CLS filter in preparation for the main event.

No calibration, just a quick 3 panel stitch and crop.... picked up a bit of cloud damage on the right side (by that time the moon was coming up anyways).

8x180x3  - Optolong CCD CLS filter (I chose that exactly because it is 2mm thick, I want to standardise my filters for the sake of easier focusing)

Pixel peepers, feel free to inspect I think youll find everything in order

[Uranium235]

Better....

[Grant93]

7 Hours on the Sadr Region Flats and Bias no darks. 2 min exposures with the Lenhance. Stacked and processed in siril.

[Uranium235]

Meet my new friends, Des and Troy.... put them together.. they destroy 😅

[Uranium235]

Had a gap in the clouds last night, so I tested the concept of CCD/DSLR imaging.  Just an hour L on the CCD, but less on the DSLR (about 30min).

ISO kept deliberately low (400) to help retain star colour. Its not narrowband, so youre never going to get the same level of contrast, its a setup more suited to for chasing dust in a dark place - not a light polluted patio 😅

No idea what went on in the bottom left, im pretty sure its either a flare, or a glint off something shiny.

Hit lucky with the alignment, with the DSLR being able to cover the FOV of the CCD despite being off-centre. However, this will need to be addressed at a later date when I switch to identical cameras. Anyways, I'll have another bash at processing it later, id prefer the stars to be smaller (I did no work on those), and the background to be a bit flatter.

 

 

[Uranium235]

Thats better

[woldsman]

Two hours of Ha & O3 & S2 (30 x 120" of each) on the North American & Pelican Nebula. Samyang 135 f2.8 + zwo asi 183 mono. 

 

 

 

 

 

 

 

 

 

 

 

 

Edited August 15, 2022 by woldsman
Edited Astro image.

[symmetal]

On 21/07/2022 at 10:19, Uranium235 said:

No idea what went on in the bottom left, im pretty sure its either a flare, or a glint off something shiny.

That looks like a flare from Deneb. It's outside the sensor area but likely within the FOV of the scope. 🙂

Alan

[LaGuille]

Hello everyone! I enjoy seeing all your beautiful images on this page. I own the Samyang 135, with a star adventurer, and a Canon 1000d. I would like to switch to CCD cameras one day. What would be the ideal setup for you ? With 500-700 dollars? color camera maybe? no problem for second hand (I don't understand much about filters to be honest). Thanks a lot for your answers ! 

[Adreneline]

6 minutes ago, LaGuille said:

Hello everyone! I enjoy seeing all your beautiful images on this page. I own the Samyang 135, with a star adventurer, and a Canon 1000d. I would like to switch to CCD cameras one day. What would be the ideal setup for you ? With 500-700 dollars? color camera maybe? no problem for second hand (I don't understand much about filters to be honest). Thanks a lot for your answers ! 

Welcome to the SY135 thread!

7 minutes ago, LaGuille said:

What would be the ideal setup for you ?

I am pretty happy with the one I've got! Bearing in mind I am a committed mono-camera + filters person I would suggest that is the way to go in the long term. I started with an ASI1600MM on my SY135 and was very pleased with the results. I now use an ASI183MM; I understand the smaller pixels are less senistive but the SY135 sucks up photons at a great rate, even when stopped down to f2.6 using a 49mm step-down-ring. (I now use the ASI1600 on my RedCat 51 - the SY+183 and RC+1600 offer a very similar f.o.v. - great for doubling up). As for filters I would suggest using a 2" manual filter drawer and just start with an Ha filter. You will see many, many mono Ha images on the this thread - Ha imaging is very rewarding and there are a wealth of targets ideally suited to the SY135.

I am sure you will have picked up on the fact that spacing (to within 0.1 mm) between the end of the lens and the camera sensor is essential if you are going to get really good results from the SY135.

This is my current setup:

Good luck! - and enjoy  

Adrian

 

[LaGuille]

Thanks for your tips, which I will treasure! 

I note your choice of the 183mm. And your advice for the filters. 

I understood that you need something between the camera and the lens (back focus?). I'm really a beginner, could you please explain me? 

Your set up it amazing.
I see a system to adjust the focus, could you tell me too?

This material is fabulous.
I only use it at 10% of its capabilities.
I would really like to do better! 
But I'm afraid it's a bit light on a star adventurer, no? 

Thanks you so much !

[tomato]

The SY135 is a great choice for widefield NB imaging. Although a mono camera with dedicated NB filters will ultimately give you the best results, it also works well with a modern sensitive OSC camera and a suitable dual band filter like the IDAS NBZ. 

I use my lens with both types of camera, I think I prefer the OSC set up simply for less mass hanging off the lens and the (relative) ease of aligning the camera, which as @Adreneline points out is critical for good star shapes. Support for the camera is a good idea though, please excuse my very homemade extended lens shield and camera support!

 

[Adreneline]

37 minutes ago, LaGuille said:

I understood that you need something between the camera and the lens (back focus?). I'm really a beginner, could you please explain me? 

The 'nominal' spacing you need to achieve between the back face of the lens and the camera sensor is 44 mm - however! - there are so many variables and the spacing is extremely sensitive if you are to achieve focus with the reference mark within the 'L' on the lens.

I use an AstroJolo M42 adapter on the back of the lens because I do not wish to use my SY135 on a Canon camera. (Some people use the AstroEssential adapter which I believe presents an M48 thread so you would need an M48-M42 adapter). If you wish to continue to use the lens with your Canon camera you will need to use something like this which is designed to be used with the ZWO EFW and an ASI camera with 6.5 mm back focus - like the ASI183 or ASi1600 (i.e. the distance between the front face of the camera and the sensor). The (my) ZWO EFW is 20.3 mm thick whereas my TS-Optics filter drawer is 15.07 mm thick; you would need to make up the difference with M42 spacers/shims. The introduction of a filter will increase the nominal 44mm by 1/3 the thickness of the filter. I use Astronomik filters which are 1 mm thick so I need to introduce (in theory) 0.33 mm of M42 shim spacers to make the gap 44.33 mm. These are all nominal figures and you need to experiment with shim spacers to get the exact spacing for your particular lens, filter, camera combination.

37 minutes ago, LaGuille said:

I see a system to adjust the focus, could you tell me too?

I have made an small plate from aluminium bar (from eBay) onto which I have mounted the EAF. The 'red' focus ring is 3D printed by a friend and the HTD pulley can be purchased off Amazon, as can the HTD belt, although I use a company called Motionco in the U.K. to supply my belts and pulleys. Before getting the red 3D printed gear I attached a length of HTD belt to the focus ring using double sided sticky tape. I have measured the backlash with my system and it is consistently 32 steps of the EAF; you can input the backlash figure into software like NINA or the ASIair-Pro.

Here is a picture of the other side of the SY+183 showing the WiFi access point for the ASIair-Pro

I hope this helps.

Adrian

 

Edited July 29, 2022 by Adreneline
Photo added

[Adreneline]

13 minutes ago, tomato said:

Support for the camera is a good idea though, please excuse my very homemade extended lens shield and camera support!

Do you find the extended lens shield helps? How did you establish how far you could extend the shield - trial and error?

@LaGuille - @tomato makes a very good point about camera support, in fact supporting the whole imaging train - the smallest amout of droop will affect star shapes.

 

[LaGuille]

Thanks Adrian and Tomato ! I'm starting to understand a lot of things now. I'll continue to look into it on my end, and I'll come back to you if I need to. Thank you a thousand times! 

[tomato]

3 hours ago, Adreneline said:

Do you find the extended lens shield helps? How did you establish how far you could extend the shield - trial and error?

@LaGuille - @tomato makes a very good point about camera support, in fact supporting the whole imaging train - the smallest amout of droop will affect star shapes.

 

I have a lot of red LEDs dotted around inside the dome, they all do a good job on indicating the status of various dome control systems, but their light can easily intrude into the lens. I quickly needed a lens shield extension to fix this and the cardboard tube was just the right diameter and the length looked enough to shroud the lens so on it went. Its long enough to eliminate the problem. I have a Sony mount lens (significantly cheaper second hand than the Canon mount) and have access to the tools and expertise needed to make the adapter to mate them to the camera.

The problem is the original screws holding the SY sleeve in place on the lens barrel are not very strong so even my lightest OSC camera option can suffer from sag. The adjustable cradle does the trick to provide support at the rear end. @Tomatobro who has a dual rig SY135 rig using the Sony lenses, uses full circle bolted cradles on the cameras, similar to your set up.

[Phillyo]

Just curious, are most of you shooting with this lens wide open or are you stopping down? If stopping down, how far do you go?

I have the Antlia ALP-T 5nm filter, original version. I hadn't realised at the time that it was designed for use at f3.6 or slower apertures. I'm considering getting the new 'Highspeed' version to replace the one I have so that I can shoot at either F2 or F2.8, but is it worth it? I know for light gathering F2 is amazing, I was shooting at F3.6 using stop down rings so obviously there's less light being gathered but it also means everything is a little 'tighter' than F2. 

Just wondering what the general consensus is with everyone using this lens.

For info I'm shooting with the ASI533 (at the mo, thinking of going up to the Risingcam IMX571 (APS-C) filter).

Phil.