Imaging with the Samyang 135mm f2

[ollypenrice]

2 minutes ago, geeklee said:

Thanks Olly.  I had spotted some clipped nebulosity when I went to look at the data again wondering if I'd been too hasty resampling it (I hadn't). 

In trying to balance the faint stuff so much I made a classic mistake of forgetting another key element of the image.  If there are other points clipped, do call them out so I can review 👍  It was the eastern Veil I was thinking - it has some tricky ranges.

I think that a tweak with the highlights filter in Ps Highlights and Shadows at a late stage in the stretching would be all you'd need - or a curve which flattened a little earlier.

7 minutes ago, Adreneline said:

Recognising when you can push data and just how far is a skill hard learnt and one I have yet to master; I bow to those who have mastered the skill and know exactly how far you can go.

Adrian

 

Indeed, spotting it is the thing. Regular checks zoomed in to 100% are essential. Personally, I don't process for pixel-peepers so I check at 100%, not more. Another key technique is to apply noise reduction only where it's necessary, in the faintest signal.

One more thing, too. For some time I have been halting my Levels stretches once the background sky is up to my desired brightness. After that, I pin the background and stretch only above it.  I see no reason to drag the background towards the noise floor.

Olly

[ollypenrice]

False click. Sorry.

Edited November 27, 2022 by ollypenrice
Typo

[gorann]

Since I just found this thread and posted my first images, maybe I also should post images of my current set-up with the Samyang piggybacking one of the RASA8 on a Mesu 200. My guide scope (an SW Evostar 72) is piggybacking on the other RASA8. The holder for the Samyang is from Astrokraken.fr which includes a fine focusing ring. The camera is an Omegon veTEC571C, and in between is the ZWO filter slider. It is all attached with a SW adjustable guide scope mount which appears steady enough and allows me to adjust the framing.

Cheers, Göran

Edited November 27, 2022 by gorann

[Gonzo]

So due to some hardware fault on my two Player One cameras, they've gone back to them to be exchanged.

I have also recently secured a second Samyang 135mm lens for my twin imaging train. Should be there by this week-end...

[gorann]

34 minutes ago, Gonzo said:

So due to some hardware fault on my two Player One cameras, they've gone back to them to be exchanged.

I have also recently secured a second Samyang 135mm lens for my twin imaging train. Should be there by this week-end...

Fault on both - that is a bit worrying for this brand that looked very promising. What happened?

Edited November 30, 2022 by gorann

[Gonzo]

1 hour ago, gorann said:

Fault on both - that is a bit worrying for this brand that looked very promising. What happened?

There is nothing to panic about, just a small batch got some banding issues.

Text from PlayerOne:

Recently we received feedback from 3 customers, the issue behavior is some horizontal bandings on the top of the image. 
After we repeat this issue, we notice that one batch of Uranus-C camera has possibility of this hardware issue.
(This batch start from Sep. 1st 2022, end at Oct. 25th 2022)
Here is the settings for checking your Uranus-C camera:
Cover the camera to take dark frame, full resolution, Exposure time: 20ms , Gain: 600, offset: 10
Cover the camera to take dark frame, Resolution: 1280*1024, Exposure time: 20ms , Gain: 600, offset: 150

But there's the coolest thing about it:

We will send you the replacement camera once upon we got the tracking number from you. We will also refund you the shipping cost based on your receipt  ; )
Please let us know how much it cost you for the import tax when you receive the replacement camera, we will refund you the money,  the same way as the shipping cost ; )

 

so yeah, no stress, no panic, poops happens and Player One have taken care of the issue.

They are truly a great company to deal with. I'll spare you the details of the issues I had with the useless UK courier companies... while Player One sorted out the return label within hours of me asking them for help.

 

[900SL]

If you have the Nikon F mount version of this lens and you would like to have a dedicated M48 adapter to connect an Astrocamera, kindly let FLO know here  

 

 

[Gonzo]

I have received the second lens for my twin system...

(thanks @odyseus10)

 

[Adreneline]

Will this be the final, final version of my SY183 setup - it has been through so many iterations and derivations.

The only feature not apparent is the 77-49mm step down ring taking the lens down to ~f2.6; helps a lot with peripheral star shapes and avoids the multiple diffraction spikes around bright stars.

The EFW contains Astronomik L2, Ha, OIII and SII 6nm filters - and a blank for darks!

The wires offend my OCD'ness but they don't foul on anything. The whole lot weighs in at 3.85 kg and needs just a single 12V supply connection, although I also choose to connect a wired network cable. It's just lacking the final dew heater for the guide scope - there's always just one more thing!

Adrian

[Gonzo]

Looks like a nice compact setup, I would definitely tidy the wires...

[Adreneline]

6 hours ago, Gonzo said:

Looks like a nice compact setup

Thank you!

6 hours ago, Gonzo said:

I would definitely tidy the wires...

I've shown you mine ... 🤣

[Adreneline]

Are cable ties the greatest thing ever invented?

 

[Adreneline]

10 Cas is not the first thing that comes to mind when composing an image; taking advantage of the slightly wider field of view offered by the Samyang 135 with ASI1600MM and Astronomik filters.

 

[Space Oddities]

Great setup and very nice wide field view!

Have you tried the mosaic tool in the ASIAIR? I'd love to try a mosaic of Orion this winter, if weather allows... I've setup a secondary rig with my AZ-GTi, I thought the Samyang would be perfect for this task.

[Adreneline]

4 minutes ago, Space Oddities said:

Great setup and very nice wide field view!

Have you tried the mosaic tool in the ASIAIR? I'd love to try a mosaic of Orion this winter, if weather allows... I've setup a secondary rig with my AZ-GTi, I thought the Samyang would be perfect for this task.

Thank you! 🙏

I’ve done lots of mosaic with the SY+183 but not tried the ASIair tool yet. I’ve only used Telescopious in the past but recent mosaics have not worked well; it doesn’t seem to cope well with field rotation near the zenith.

Sounds like the SY+GTi could be a great lightweight match. 👍

Adrian

[Space Oddities]

I have used the Telescopius method as well, it worked really well with my newtonian. The built-in tool in the ASIAIR makes it even easier, but at 135mm I'm not sure what to expect. Let's see!  

Yes that's a great portable system, although now that I have my own terrace, portability isn't much of a concern anymore... Plus, I don't have to freeze my butt in public parks too!

[Adreneline]

1 hour ago, Space Oddities said:

Telescopius method as well, it worked really well with my newtonian

It worked well for me at lower elevations - my recent efforts with Cepheus have been a challenge.

1 hour ago, Space Oddities said:

I don't have to freeze my butt in public parks too!

I'm far too old for that! ASIair + iPad + nice warm fire and a coffee - perfect!

[Adreneline]

1 hour ago, Space Oddities said:

the Telescopius method as well

This was my last SY + 183 mosaic - O3 of part of Cepheus - with a 20% overlap!

The Telescopious plan looked fine on paper/screen but in reality it didn't work out too well. I think field rotation was perhaps a factor but I don't know.

It will be interesting to see if the ASIair gives the same result - hopefully it will be better. Just need some clear skies!

[odyseus10]

On 02/12/2022 at 13:27, Gonzo said:

I have received the second lens for my twin system...

(thanks @odyseus10)

 

You are welcome  I look forward to seeing your full dual setup :)

[powerlord]

Hi chaps,

in case of use to others - I've found using my EFW with asiair and the 135 a bit hit and miss due to the focal point being so near the max end stop. The asiair starts autofocus by going beyond where you've placed it, then moving slowly back till in focus. If it hit the stop it can't do this and gives some 'abnormal focus' messsage and quits trying.

This is aggrevated if using a NB filter as it pushes the focal point even closer to the max.

This, by the way is with a standard ZWO M42 to EF lens adapter.

However, if you use the shorter adapter (I've got the old one which was a separate adapter, but I think the v2 is one thing in 2 parts), which is supposed to be so that you can add a filter wheel into the mix (but we don't here), then you bring the focal point into the middle of the focus ring range - and EFW has no problems.

However.. and again, this might not be the case with the V2 adapter - I don't have one to check - the short adapter does not have an internal thread for mounting 2" filters unlike the longer one. So - where to put a filter ?

So - I designed and printed an adapter that clips into the inside M38ish hole in the short adapter and provides an M48 thread to screw your filter into.

At the mo I've got the internal part as 1.5mm (so reducing the 38mm hole to 35mm.. not sure if that matters light gathering wise, but might try printing it at 1mm thickness to gain another 1mm circumference.

Anyway, works a treat - shown here with just a clear UV filter as an example.

Proof in the pudding will be trying it tonight as looking good weather. I'll be using with an L-ultimate.

 

Edited December 7, 2022 by powerlord

[Adreneline]

10 hours ago, powerlord said:

However, if you use the shorter adapter ....... then you bring the focal point into the middle of the focus ring range

Forgive me if I am misunderstanding what you've described but to me this seems to be exactly the wrong thing to do.

All camera lenses, but let's just stick with Canon, are designed to work optimally when the spacing is an exact value between the back of the lens and the camera sensor. The front face plate of a Canon dslr camera is an exact and carefully controlled distance in front of the sensor - the end plate of a Canon (fit) lens is specified as an exact distance from the last lens element within the lens. When the lens is fitted to the camera there is an exact optimal distance between the camera sensor and the last element of the lens. When focussed at infinity the registration mark on the lens should be positioned within the base of the 'L', whether the camera is a Canon dslr or a cooled astro camera.  If the spacing between the last lens element and the camera sensor is incorrect the registration mark will be be either before the 'L' or after it. There are countless references on the web to ensuring that at focus the lens registration mark is within the base of the 'L' whether it be a Samyang, a Canon, or whatever the make of lens. That's one reason why we all want to know the exact back focus on an astro camera.

I understand fully your comment about the EAF driving the focus ring into the end-stop (not good for the EAF or the lens) but that is easily fixed on the ASIair by 'reversing' the direction when the EAF first offsets the focus to start to generate the 'V' curve. When I AF my Samyang the EAF moves the focus ring way round to before the 10m mark and then progressively comes back to the 'L' and just slightly beyond; it does not come up against the end stop.

As I know you know spacing is so critical on the Samyang 135. It was equally so on my Canon 200 mm lens although the focus ring on the Canon 200 had like a 'slipping clutch' so that if you attempted to rotate the focus ring beyond the infinity mark it would effectively slip and not come up against a hard stop. Changing the spacing by as little as 0.1 mm can make a significant change to the focus position. Until recently my biggest challenge has been ensuring that I can focus my 1mm thick Astronomik Ha and SII filters 'within the L' whilst achieving a focus position with my 2mm thick Baader OIII that was as close before the 'L' as I could manage. The 1mm difference in thickness requires a change in spacing of 0.33 mm - that is huge for a Samyang 135 lens. If the spacing is incorrect then star shapes are likely to be compromised especially toward the periphery of the image.

Please tell me if I have completely misunderstood your post above and you are indeed still achieving focus with the lens registration mark within the base of the 'L'.  

[powerlord]

Hi, so firstly - I did not know about the reverse setting !! that makes a difference! And does somewhat make my filter holder a mute point.

So thanks for that. And therefore, it was all for nothing.

Hmm, I admit I was thinking camera lenses like the SY135 were immune to a particular backfocus similar to something like my redcat - petzval designs.

Or, say my newts - where unless using a flattener there is no real concept of optimal back focus, provided it can reach focus.

It sounds like I'm mistaken and most camera lenses are not petzal types then ? That does, I have to say tie in with my test tonight, when I found massive what looked like coma around the sharp centre when I tried it.. though as I've seen this before using my only L-extreme at correct back focus, I assumed it was something to do with fast lens vs filter and decided to image with the redcat tonight instead.

I did find when I tried it a few weeks or so ago though that with the L-ultimate I really was right on the end stop. i.e. might have been better beyond it.. so not being able to reduce the BF a bit might still be an issue at least with my SY135 but in that case, I can try spacing out my attempt above to 43mm or so and try.

thanks for the info - u live and learn. I will try the next night with the regular zwo adapter with L-ultimate and reverse enabled and see what it looks like.

stu

 

[Adreneline]

5 hours ago, powerlord said:

It sounds like I'm mistaken and most camera lenses are not petzal types then ? That does, I have to say tie in with my test tonight, when I found massive what looked like coma around the sharp centre when I tried it.. though as I've seen this before using my only L-extreme at correct back focus, I assumed it was something to do with fast lens vs filter and decided to image with the redcat tonight instead.

Hi Stu.

The SY135 is a great lens but it a real challenge to set it up with an Astro camera and filters. My thinnest spacer is 0.1 mm and I wish it was 0.05! I’ve even been known to try tissue paper spacers - not recommended! All my experience with this lens tells me achieving focus with the registration mark within the base of the L is essential. It’s also very beneficial to stop the lens down with a step-down-ring - I step down to 49 mm giving an effective aperture of about f2.6 - it really helps with peripheral stars and the reduction in aperture/speed is a small price to pay.

I also have a RedCat and what a joy it is to use. My ASI1600 on the RedCat has a very similar f.o.v. to the ASI183 on the Samyang - a great combination.

Good luck with getting optimal spacing on the SY - the pain is definitely worth the gain.

Adrian

[barbulo]

A couple of questions regarding step down rings: Is it a good idea to 3D print them? Where should they be placed? Any example would be more than wellcome.

Thanks in advance.

[Adreneline]

43 minutes ago, barbulo said:

Where should they be placed? Any example would be more than wellcome.

They screw on as would any end of lens filter.

I bought one of a well known online supplier!

44 minutes ago, barbulo said:

Is it a good idea to 3D print them?

The thread might be a bit tricky and you really need a very clean edge on the inner diameter.

HTH