Imaging with the Samyang 135mm f2

[tomato]

A recent image taken with my SY135/RC571c had some terrible star shapes caused principally by camera sag with the weight hanging off the lightweight SY Sony plastic adapter. I did make a makeshift support but it wasn’t suited to fine adjustments of the support needed to minimise tilt:

 

So an hour or two in the workshop has produced a 360 ring with 3 support bolts at 120 degrees. This is mounted onto a longer dovetail with thicker rod, with the added bonus that the whole lens/camera assembly can now be removed from the mount without taking the saddle off.

Sure, a full collar would be more stable but adjustments would be a lot harder and this rig comes on and off the mount quite frequently.

Just need some clear sky time to see if I can dial out the poor star shapes…

[Adreneline]

A clear night and an opportunity not to be missed.

I've fitted the ASI1600 back onto the Samyang 135 with my Antlia 3nm filters - lens shut down to f3.0 with a step-down-ring - not sure whether that is totally necessary but f3 is still pretty quick.

Centred on Zeta Cephei:

... 15 x 300s of S, H and O.

Adrian

 

[900SL]

My 135 took a knock a while back, I thought I'd test it last night, not looking too good

At f2.8:

Backspacing is accurate, I'm using the ZWO Nikon adapter and a 533 MC Pro so small sensor, lens is mounted in a Redcat ring and a secondary ring supports the camera so I think this is decentering rather than tilt. ASTAP reports >40% and 'severe' into one corner

Is the quick way to check for tilt to rotate lens and camera 90 degrees in the rings? 

 

[Adreneline]

2 hours ago, 900SL said:

I think this is decentering rather than tilt

I am trying to get my head around de-centring. How is it possible for the sensor not to be central with the OTA axis assuming (a) all the connecting adapters are concentric, and (b) the sensor was centred correctly in the camera body at the time of manufacture?

As an aside I have a similar problem with a Samyang 85mm lens but I have no doubt about the cause of the problem - it became detached from a Geoptik EoS mount one night and bounced its way around the stone paved patio  

I wonder if/fear your lens may be out of alignment as is my 85mm lens.

[Elp]

It's an issue with camera lenses in general, some copies are better than others. Samyangs are known for their QA if you read any number of online reviews from buyers.

[900SL]

17 minutes ago, Adreneline said:

I am trying to get my head around de-centring. How is it possible for the sensor not to be central with the OTA axis assuming (a) all the connecting adapters are concentric, and (b) the sensor was centred correctly in the camera body at the time of manufacture?

As an aside I have a similar problem with a Samyang 85mm lens but I have no doubt about the cause of the problem - it became detached from a Geoptik EoS mount one night and bounced its way around the stone paved patio  

I wonder if/fear your lens may be out of alignment as is my 85mm lens.

Decentering refers to possible movement or tilt between the individual lenses inside the lens (collimation), not the sensor alignment

[Elp]

10 minutes ago, 900SL said:

Decentering refers to possible movement or tilt between the individual lenses inside the lens (collimation), not the sensor alignment

It's amazing they even make a complete product, most modern lenses have 8-10+ pieces of glass in them.

Edited August 10, 2023 by Elp

[aleixandrus]

Some posts ago, after dealing and (mostly) resolve backfocus issues, I said I deserve some fun with the Samyang. Well, this is my upcoming project:

The pic above is just a test-shoot to make sure I can fix anything in planning prior to the actual shooting. This is a 4x3 mosaic with just 1x300s Ha, calibrated with darks and processed with Pixinsight (GradientMergeMosaic, DBE and manual stretch). It went much smoother than I expected... which scares me as hell as it could be just good luck 😅 The initial plan is to add 12x300s per filter (SHO) per panel (4x3=12). This is 36h total to build a 'base' mosaic and, then, add more integration where needed up to 3h/filter (108h).

What do you think? Any advice from those with more expertise? It seems ambitious for my skills -never did a mosaic before-, for my sky conditions -clouds and rain most of the year- and many things may go wrong but... hey! it seems fun!

[Laurin Dave]

Dusty Cepheus including the Rotting Fish (LDN1251) The Dark Shark (LDN1235) the Wolf's Cave (VdB152)/Ced201/Barnard175), Dengel_Hartl-5 (LBN538) planetary nebula and an ancient supernova remnant. Two panel Samyang135/ASI2600mc mosaic 17.5 hrs total integration time also 10hrs Ha through Askar200QHY600 over the lower panel. But still nowhere near enough!.   Processed in Pixinsight and Photoshop... extensive use of Croman Tools!

Thanks for looking 

Dave

[symmetal]

Most impressive. 🤗 I've done the Dark Shark and Wolf's Cave area separately with my RASA 11, but it's nice seeing them all together.

Alan

[Laurin Dave]

4 minutes ago, symmetal said:

Most impressive. 🤗 I've done the Dark Shark and Wolf's Cave area separately with my RASA 11, but it's nice seeing them all together.

Alan

Thank you Alan, weather permitting I shall be looking at them again in higher in a months time when we get back form France

Dave

[ollypenrice]

On 12/08/2023 at 14:03, aleixandrus said:

Some posts ago, after dealing and (mostly) resolve backfocus issues, I said I deserve some fun with the Samyang. Well, this is my upcoming project:

The pic above is just a test-shoot to make sure I can fix anything in planning prior to the actual shooting. This is a 4x3 mosaic with just 1x300s Ha, calibrated with darks and processed with Pixinsight (GradientMergeMosaic, DBE and manual stretch). It went much smoother than I expected... which scares me as hell as it could be just good luck 😅 The initial plan is to add 12x300s per filter (SHO) per panel (4x3=12). This is 36h total to build a 'base' mosaic and, then, add more integration where needed up to 3h/filter (108h).

What do you think? Any advice from those with more expertise? It seems ambitious for my skills -never did a mosaic before-, for my sky conditions -clouds and rain most of the year- and many things may go wrong but... hey! it seems fun!

That is a truly magnificent framing.

Olly

[aleixandrus]

I had acquired some data to start building the large mosaic I mentioned a few post ago. I focused in O3 to take advantage of the past moonless nights but I also added some Ha and S2 to one particular panel. This way I can build the mosaic while having some data to fully process individual tiles and show some progress.

Well, this is my first image it deserves to be shown. The Crescent Nebula region, ~8h with the Samyang 135mm @ f2.8 + ASI183MM Pro 300s + SHO 6.5nm Baader filters. This is also my first "properly processed" SHO image, this is, using PixInsight and the "correct" steps and a repeatable workflow. I know I have a loooong way to go but it is a first step. For instance, I have some issues with star processing I must deal with (check that dark halos around many of them) but I think the nebula it is reasonably accomplished (to my untrained eye). Please, feel free to C&C and point out any aspects that could be improved!

[ollypenrice]

45 minutes ago, aleixandrus said:

I had acquired some data to start building the large mosaic I mentioned a few post ago. I focused in O3 to take advantage of the past moonless nights but I also added some Ha and S2 to one particular panel. This way I can build the mosaic while having some data to fully process individual tiles and show some progress.

Well, this is my first image it deserves to be shown. The Crescent Nebula region, ~8h with the Samyang 135mm @ f2.8 + ASI183MM Pro 300s + SHO 6.5nm Baader filters. This is also my first "properly processed" SHO image, this is, using PixInsight and the "correct" steps and a repeatable workflow. I know I have a loooong way to go but it is a first step. For instance, I have some issues with star processing I must deal with (check that dark halos around many of them) but I think the nebula it is reasonably accomplished (to my untrained eye). Please, feel free to C&C and point out any aspects that could be improved!

Splendid. Well done.

Olly

[powerlord]

very nice. my only comment would be, you've got some wierd blending going on with the stars. Not sure how you've done it in PI, but something like an overlay mode works well usually. see here:

[aleixandrus]

Thank you for pointing that issue, @powerlord. Yeah, I know stars are a mess but I couldn't get them better and I'm not sure where the problem is. I build the master S+H+O, do a ChannelCombination for SHO, apply BlurXT+NoiseXT+StarXT in linear phase. I think nebulosity processing comes just fine but I struggle to move the stars image from linear to non-linear (using Hyperbolic Generalized Stretch, with Color+Arcsin method). I also use the Bill Blanshan script for star reduction and star blending and there is a (very probable) chance I'm using it wrong. Any tip is welcome!

[Laurin Dave]

Posted separately in the Deep Sky section, link below

Dave

 

 

[Swillis]

Hi all,

I'm wanting to tap into the wealth of knowledge of everyone in this great thread. What are your experiences with 3d printed mounting brackets? Are some better than others (astrojolo, astrokraken, other?)

I have the lens on a canon 600d, and attach this to the mount via the WO redcat ring. I now want to attach my guidescope and had considered the WO handlebar but the 'nose' (where the built-in flash pokes out) would get in the way. Obviously I could just rotate the camera but wanted to see what others experiences are with the 3d printed mounts which could be more suitable options, certainly where rotation is concerned but maybe the WO ring and handle bar is more secure?

Thanks 

Simon 

[Chris-h]

I had the Astrokraken, which was fine at first, but broke in the end. I now have one from Astrodymium (FLO sells it), and it is WAY better. Very solid. easy to attach a ZWO EAF, and you can mount a guidescope at the top or on the side.

https://www.firstlightoptics.com/adapters/astrodymium-ring-system-with-zwo-eaf-asiair-mount-for-samyang-rokinon-135mm-f2-lens.html

[Elp]

I'd err caution with anything 3d printed, especially if it's going to hold up hundreds/thousands in value of equipment, it's just not worth trusting them. A, has the item been designed by someone whom has experience with engineering and knowing how to design in strength, B, has the item been printed with suitable mechanically sound material (abs, petg, nylon), C, do you need the lightness, D, in what way is a 3d printed solution better than putting together a metal constructed solution which will be a lot more secure (you know, why are tube rings made of aluminium/metal)? I understand the need for a custom and available solution, but you'd have to weigh up the pros and cons.

[Swillis]

Thanks @Chris-h I knew there was an obvious one I'd forgotten. 

@Elp that would be my main concern too. At least from a sample size of one it sounds like the astrodynium one would likely be a bit more reliable. The fact that FLO stock it is hopefully reassuring as to its quality. But that said I am starting to lean towards the WO handle

Thanks both

[Elp]

When I was putting my dual rig together the WO cat tube ring seemed to be the one to fit the diameter but I never bought it. I managed to find a sigma lens rig which fitted my video lenses, not sure it the photo lens has the exact same outer profile/OD sizes. The benefit of the WO one is that you can mount things on top of it whereas mine you can't.

[Space Oddities]

Simon,

If I were to do it again now, I'd get the Astrodymium. It seems solid and well thought out indeed. i tried the Astrokraken one, but it actually didn't fit my camera, and didn't feel very solid.

I went the BlackCat mount way, which was originally intended to work with the RedCat 51 telescope (which I also own - although mine has a rare white fur for some reason!). The advantage was that I could switch that mount from the Cat to the Sam rather easily.

The downside of this solution is the 3D printed gear that wraps around the lens. You need a custom made one, since the RedCat has a slightly different close though). Also, the toothed gear attached to the EAF eventually cracked and I haven't been able to use it since. Finally, although the RedCat's rube ring is a good fit, it's not perfectly snug. I can feel the lens very slightly moving. 

So I switched to a belt system which is much better IMO (another advantage for the Astrodymium). I found a free model of a GT2 ring, an aluminium pulley and then found a perfectly sized GT2 belt. Works like a charm! I'll do the same on my RedCat I think.

At the end of the day, this cost me more than the Astrodymium solution, which didn't exist at the time, sadly... So I guess that's the best option on the market right now!  
Anyway, I'm glad my Samyang is fully operational again, can't wait to have a go at those big nebulae again!

à

[aleixandrus]

A vote to Astrodymium ring system. I'm quite happy with it despite I had to make some modifications to attach more elements as I'm not using the AsiAir but a MiniPC + PegasusAstro Powerbox. Oh, and I had to contact with the manufacturer (I broke a screw head, totally my fault) and he was very helpful and considerate providing a replacement, worth to highlight this.

If you plan to attach additional devices to the lens (specially the EAF), one of these 3D printed rings really worth it. If not, a solution as the RedCat51 ring may be more robust in the long term. However, when using 3D printed accessories is very important to not over tighten the screws as the printed material will suffer from microcracks with will lead to major fails without notice. Tightening enough is... enough.

Side note:

Nowadays my major complain is not being able to rotate the framing easily as the focuser and the lens are coupled to the 3D rings. I would like to rotate the lens after loosen up the rings but the EAF do not allow turn the motor by hand. To be fair, this is a common issue with most 3D printed rings for the Samyang. I've 'resolved' this issue by moving the focus ring to the middle with the EAF, way out of focus, and then I loose up the rings to freely rotate the lens while keeping the focus ring and the belt carefully in position to do not damage the EAF motor. If I need a precise rotation angle, I move the focuser close to infinite again and do a plate solving... I have to repeat this procedure until I get the desired angle. Despite I know approximately the camera rotation checking the back of the camera body, it is quite annoying. I know I can attach a rotator but I don't change framing too often, a rotator may introduce some tilt which at f/2.8 may be a problem, flats are more fussy, I don't have too much free backfocus space and I'm tired to deal with stars in the corners. Maybe in the future...

@Space Oddities: Could you please share which rotator model are you using? Thanks a lot.

Edited September 12, 2023 by aleixandrus

[Space Oddities]

@aleixandrus I'm using this rotator from TS Optics: Teleskop-Express: TS-Optics Rotation Adapter, Filter Holder and Quick Coupling - M48 to T2 thread

It's available in different formats for both the camera and telescope side: M48, T2, M42x1, Canon... depending on what you need. The good thing about it is that it can be used as a 2" filter holder as well (the part attached to the camera has 2" threads on one side), which is great considering the rather short flange distance of the Samyang. My adapter itself is 19mm thick, so that's too thick to add a filter slider as well.

I found the thumb screws too short and impractical, so I got some longer one.