Imaging with the Samyang 135mm f2

[Adreneline]

13 minutes ago, woldsman said:

Thanks! Do you use a guide camera? Just wondering where it would go. Having the EAF mounted below on the dovetail would free up a perch for a guide scope on top. 

[nephilim]

23 hours ago, woldsman said:

Thanks! Do you use a guide camera? Just wondering where it would go. Having the EAF mounted below on the dovetail would free up a perch for a guide scope on top. 

@woldsman Here is my Samyang setup. I'm also looking at ways to mount the EAF. I'm posting this to give you another idea of Samyang/Guidescope mounting options.

Steve

[Swillis]

@woldsman I think the astrodynium ring system has a mount for an EAF.

https://astrodymium.com/products/astrodymium-ring-system-with-zwo-eaf-adapter-for-samyang-rokinon-135mm-f-2-lens

Not sure if anyone has experience with this or not?  I don't have one myself, don't even have a Samyang 135 (yet)!

Good luck with finding something that works for you

Simon

[Richie092]

Tried the new noise Xterminator in Pi On my flaming star and quite pleased with how it turned out. 
 38 5 min subs at 2.4 with Idas NBZ

2600mc on Gem45 with ZWO filter draw adaptor  

Edited May 25, 2022 by Richie092

[Stickey]

3 hours ago, Richie092 said:

Tried the new noise Xterminator in Pi On my flaming star and quite pleased with how it turned out. 
 38 5 min subs at 2.4 with Idas NBZ

2600mc on Gem45 with ZWO filter draw adaptor  

That's stunning 👏 Richie.

[Richie092]

Thanks Stickey. I still have a long way to go with my processing capability but I was really pleased with it. 

[geeklee]

13 hours ago, Richie092 said:

Tried the new noise Xterminator in Pi On my flaming star and quite pleased with how it turned out. 

2 hours ago, Richie092 said:

I still have a long way to go with my processing capability but I was really pleased with it. 

That's come out well @Richie092  Something to keep an eye on is the stars - not sure what process has created the effect (I've seen these with Topaz and other things), but they start to join together and become strange shapes.

  

[Richie092]

Thanks for the feedback, it is much appreciated. I'm happy with my setup and capture, it is all about nailing the processing now.

[900SL]

533MC and SY 135, 2hrs & a quick process of Rho in Siril

Getting some odd diffraction around Antares, the mount did a flip 2/3 way through. f2.8

 

[900SL]

Veil, 3 hrs, Vixen SXD2, 533MC Pro, SY 135

0 gain 120s exposures

 

[aleixandrus]

Hi! Well, it took a while but I managed to read all the 42 previous pages of this mega-thread :) There is a lot of very valuable information. Most of the notes I took were related to the mechanical assembly as it was the first problem I had to tackle. Now, I'm checking for narrowband filters. What I found is many of you just simply use 'conventional' filters but others use 'CMOS optimized' filters or even 'High Speed optimized' filters for f2-f4 scopes (such as the Baader High Speed 6.5nm Narrow Band Filter - CMOS Optimised). No consensus here.

I have an ASI183MM Pro and I don't plan to go crazy with 3nm filters but 6.5nm or even 12nm wide. I guess the wider the band is the less important redshift is. I also plan to add other scope in the future but as it will be slower (it's hard to go faster than f2!), I don't want to buy an additional filter set. How critical is redshift for this lens? Should I go for 'high speed' filters or may I go with 'conventional' ~12nm or ~7nm filters? In your experience, is there any specific filter or brand I should run away from? I want to buy once, but buy well.

Thanks a lot!

[geeklee]

On 22/06/2022 at 08:12, aleixandrus said:

In your experience, is there any specific filter or brand I should run away from? I want to buy once, but buy well.

You're right @aleixandrus there isn't a consensus and you'll see plenty of the Baader 7nm Ha being used without a problem - whether this loses a little signal, I'm not sure.  Some of us also stop down the lens a touch too which would help.

I personally have the Astronomik MaxFR Ha and OIII - these are rated for fast systems but also claim to go up to F8.  I emailed Astronomik recently and they confirmed that while each filter has a specific transmission, the aim is to get a certain percentage peak transmission at each end.  For example, my Ha is Tmax 95.9% and states F6.1 - F2.2.

I also use a normal 6nm Astronomik SII filter and this states on the back Tmax 93.6% and F-infinity - F2.3!!

It's very confusing as this would indicate that if you get lucky you could get a normal 6nm filter that'll work well at high speed too.  Their marketing doesn't help!

A wide filter - like 12nm - should have even less issues.

I typically shoot my Samyang stopped down ~F2.6 (and also used a 183MM).

Hope this helps.

Edited June 23, 2022 by geeklee
clarification

[aleixandrus]

Thanks a lot! I think I'll go for 6-7nm filters, seems the best compromise. In addition, O3 suffers more from light pollution so the more restrictive the better (please, correct me otherwise). If those Astronomik work well for fast systems, I think they may perform better than the Baader. I'll have to check this carefully.

Any comment about filter size? I know 1.25" are enough for my ASI183 and I don't plan to go further in the mid term (maybe a ASI294 in the long run, but even 1.25" seems to be acceptable). I have the ZWO EFWmini filter wheel and the documentation says:

The distance between the filter and sensor is around 10mm when you connect it to ASI1600. So 1.25″ filters won’t have vignetting up to F5 focal ratio scope and 31mm filter won’t have vignetting up to F2 lens

I suppose I should go with 31mm unmounted to avoid issues...

[geeklee]

15 hours ago, aleixandrus said:

If those Astronomik work well for fast systems, I think they may perform better than the Baader. I'll have to check this carefully.

I've also found my Ha & OIII MaxFR have no halos or reflections in the Samyang -> spacer -> EFW -> 183MM solution.  

15 hours ago, aleixandrus said:

Any comment about filter size? I know 1.25" are enough for my ASI183 and I don't plan to go further in the mid term (maybe a ASI294 in the long run, but even 1.25" seems to be acceptable).

I have the 1.25" in the EFWmini and they are fine for the small sensors, but as mentioned in your quote, won't be ideal with the next step up (1600/294) at high speed.  I'd probably have got the 31mm if I could go back   I've seen the 1.25" used with the 1600 (perhaps stopped down a touch) and they calibrate fine (again, are you losing a little signal with this? I'm not sure).

[Adreneline]

I have used a Baader 1.25" 7nm Ha filter with my Samyang 135mm and ASI1600 and the results were great. In fact initially I used using all Baader NB and LRGB filters. I've now changed to Astronomik NB but still use the Baader LRGB in a ZWO EFW.

Adrian

[aleixandrus]

9 hours ago, geeklee said:

I'd probably have got the 31mm if I could go back

31mm then! :) Cost is not very different.

3 hours ago, Adreneline said:

I have used a Baader 1.25" 7nm Ha filter with my Samyang 135mm and ASI1600 and the results were great. In fact initially I used using all Baader NB and LRGB filters. I've now changed to Astronomik NB but still use the Baader LRGB in a ZWO EFW.

Why did you switched brand? I'm between Baader and Astronomik filters...

[Adreneline]

2 hours ago, aleixandrus said:

Why did you switched brand? I'm between Baader and Astronomik filters...

I purchased a 2" Astronomik Ha 6nm to use with my Samyang 135mm and convinced myself I could see a difference between the 7nm Baader and the 6nm Astronomik. I then decided to switch from Baader to Astronomik but only NB and only my 1.25" set. I have since purchased a 2" SII but still use my Baader 2" OIII. Is one better than the other? I am happy I changed to Astronomik NB - I have no intention of changing from Baader LRGB.

[emyliano2000]

Cygnus at 135mm

 

Test of my iOptron Skyguider Pro with results that didn't disappoint. I used my astromodified canon 6d and my Samyang 135mm f2 lens and I chose Cygnus as the target.

 

Only 22 x 60sec exposures, ISO1600 @f2.8

 

Emil

 

 

[Uranium235]

Waiting to try that part of the sky this year... ive got a plan for it...  not long now.... not long

[Zummerzet_Leveller]

I've been playing with a set up for the Samyang 135mm, I have the cine version.  Here's my first effort with the new rig configuration. I need to sort out an aperture mask rather than stopping down about one step.  Have some squiffy stars in one corner but pretty pleased with this considering it's been taken over the last week with no astro dark, a fair chunk of moon, no filters and all manual focus.

9.5hrs in 5min subs on the AVX with the 2600MC pro.  Processed in Siril, GIMP and Topaz.  If viewed on a calibrated lower backlit monitor some of the subtle Ha is more visible.

[malftobe]

Good evening,

 

I’ve finally in the samyang 135 club (but not quite imaging just yet!). I was lucky to get one second hand with the m48 adaptor. 

 

I’m having a problem with backspacing. After a quick test on Thursday at f2.8 I can’t quite achieve critical focus or go past infinity focus with my setup. 

 

Will going (quite a way) under the backfocus distance of 44mm still achieve infinity focus, but simply  result in infinity being somewhere else on the focus ring? @Adreneline talks of his focus being 3mm before the L with one of his spacings.

 

From front side of filter wheel back to sensor I have 39.5mm. To get to the 44mm backfocus, This should leave 4.5mm (or 5.5mm as I use 3mm thick filters). 

 

I have tried an m48-m42 adaptor, which has an external size of 4mm, but when added to the thread on the camera side adaptor the total extension is 5.8mm. This puts the total back focus at 45.3mm which I think is where my problem with focus lies. 

 

I’ve been in touch with The seller of  the 42mm samyang bayonet replacement, which should solve my problem. Threading it directly into the filter wheel would give me back focus of 39.5mm. 

 

I have a 3mm and 5mm m42 extension and shims. But I may be in same position as before  if I try to add an extension piece as the minimum length will be defined by the thread length on the bayonet replacement (4.8mm).  

 

Will going with a backfocus distance of 39.5mm  still achieve infinity focus?

Edited July 9, 2022 by malftobe
Spelling

[woldsman]

First test image with the Samyang 135 paired with the ZWO asi 183.  Ha 30 x 120" and O3 30 x 120".  Bining 1x1. Three queries in case anyone has views.

1) The stars look OK despite the oversampling (imaging scale is 3.77) probably because the ZWO asi 183 has such a small pixel size (2.4). 

2) To get the histogram closer to 1/3r distance from the x-axis, I varied the gain & offset: gain 56 & offset 10 for Ha and gain 111 (unity) & offset 15 for O3.  Is this bad practice or OK?

3) Is there a camera rotator that is an option for this lens & camera pairing?

Thanks for reading!

 

 

[geeklee]

1 hour ago, woldsman said:

2) To get the histogram closer to 1/3r distance from the x-axis, I varied the gain & offset: gain 56 & offset 10 for Ha and gain 111 (unity) & offset 15 for O3.  Is this bad practice or OK?

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?  

If you do the above, you'd need a set of darks for each gain/offset pairing.  While this isn't difficult it seems like added complexity for no gain (pardon the pun).  You'd have to be extra careful, not only during calibration but every time you connected the camera to make sure the gain/offset was set just for the filter you were using.

When using this combo (Samyang+183) I kept things simple - unity gain and the default offset.  That way I knew whichever program, set of darks, flats etc I was using, it was all going to match up with the lights.  I don't think tweaking the offset would have been a deciding factor in any part of my finished image 🙂

1 hour ago, woldsman said:

3) Is there a camera rotator that is an option for this lens & camera pairing?

What rig do you have holding this combo and what sort of room is free in the imaging train?  I had mine in a set position and didn't change it - the FOV was typically wide enough even with this small sensor to work around.  In addition, the Samyang requires precise backspace setup and I was loathe to change anything when I had it set 😅

[Adreneline]

 

On 09/07/2022 at 21:56, malftobe said:

Good evening,

 

I’ve finally in the samyang 135 club (but not quite imaging just yet!). I was lucky to get one second hand with the m48 adaptor. 

I’m having a problem with backspacing. After a quick test on Thursday at f2.8 I can’t quite achieve critical focus or go past infinity focus with my setup. 

Will going (quite a way) under the backfocus distance of 44mm still achieve infinity focus, but simply  result in infinity being somewhere else on the focus ring? @Adreneline talks of his focus being 3mm before the L with one of his spacings.

From front side of filter wheel back to sensor I have 39.5mm. To get to the 44mm backfocus, This should leave 4.5mm (or 5.5mm as I use 3mm thick filters). 

I have tried an m48-m42 adaptor, which has an external size of 4mm, but when added to the thread on the camera side adaptor the total extension is 5.8mm. This puts the total back focus at 45.3mm which I think is where my problem with focus lies. 

I’ve been in touch with The seller of  the 42mm samyang bayonet replacement, which should solve my problem. Threading it directly into the filter wheel would give me back focus of 39.5mm. 

I have a 3mm and 5mm m42 extension and shims. But I may be in same position as before  if I try to add an extension piece as the minimum length will be defined by the thread length on the bayonet replacement (4.8mm).  

Will going with a backfocus distance of 39.5mm  still achieve infinity focus?

Will going (quite a way) under the backfocus distance of 44mm still achieve infinity focus, but simply  result in infinity being somewhere else on the focus ring? @Adreneline talks of his focus being 3mm before the L with one of his spacings.

It may do - depends how much I suppose.

My understanding is that this lens 'focusses beyond infinity' - wherever that is! I have no idea. All the advice seems to be that you should aim to achieve focus with the reference mark somewhere within the base of the 'L', and that is what I try to achieve.

I have found that introducing a spacer as thin as 0.1 mm has a significant effect on the focus position relative to the 'L'. The difference in thickness between may Ha Astronomik filter (1 mm) and my OIII Baader filter (2 mm) produces a significant change in the focus position - in my case the Baader OIII focusses about 2-3 mm in front of the 'L' - so that is the same effect as introducing a 0.33mm spacer into the imaging train.  

I have my imaging train optimised for my Ha filter and accept the compromise when using the OIII - one day I'll buy the Astronomik OIII to go with my SII  I feel my OIII images are not as consistently sharp as my Ha or SII but that maybe due to it being 8.5nm and not 6nm like the Ha and SII. The FWHM figures for the stars are comparable with the Ha and OIII filters. Maybe it's just my OCD getting the better of me.

I guess if the lens is producing acceptable results with focus at some other point and not within the base of the 'L' then that's good!

If it works for you then it's best left as is  

Adrian

 

[woldsman]

1 hour 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?  

If you do the above, you'd need a set of darks for each gain/offset pairing.  While this isn't difficult it seems like added complexity for no gain (pardon the pun).  You'd have to be extra careful, not only during calibration but every time you connected the camera to make sure the gain/offset was set just for the filter you were using.

When using this combo (Samyang+183) I kept things simple - unity gain and the default offset.  That way I knew whichever program, set of darks, flats etc I was using, it was all going to match up with the lights.  I don't think tweaking the offset would have been a deciding factor in any part of my finished image 🙂

What rig do you have holding this combo and what sort of room is free in the imaging train?  I had mine in a set position and didn't change it - the FOV was typically wide enough even with this small sensor to work around.  In addition, the Samyang requires precise backspace setup and I was loathe to change anything when I had it set 😅

Many thanks for responding. Agree best not to over-complicate. NB I was careful to use the right darks from the darks library to match gain & offset. Also histograms are not just for DSLRs & unless you clip data, there are pros and cons to a range of histogram points.