Imaging with the Samyang 135mm f2

[barbulo]

I'm thinking of buying a tilter adjuster like this to tackle both spacing and tilt.

[Elp]

You could try one of the cheaper ones FLO sell, that one seems expensive, you'd also have to consider the backspacing distance but if you're using a canon lens with a simple ring adaptor (not the filter drawer types) you should have plenty of space.

[barbulo]

4 hours ago, Elp said:

You could try one of the cheaper ones FLO sell, that one seems expensive, you'd also have to consider the backspacing distance but if you're using a canon lens with a simple ring adaptor (not the filter drawer types) you should have plenty of space.

I use the M48 lens adapter so I believe I'll have enough space for the tilt adjuster. I point at that one, even though there are cheaper, because the adjusting screws are on its side instead of the front.

[SAW]

Just redoing the spacing on my set up.

I have the Samyang Lens to M48 adaptor, so from this I need 44mm spacing to the sensor ?

I have the 2600 with the tilt plate removed so that mean the sensor is 12.5mm back from the camera face ?

I then have a filter wheel, 20mm.

Which means including the M48 to M42 adaptor https://www.firstlightoptics.com/adapters/astro-essentials-m48-to-m42-t2-adapter.html i should need about 11.5mm of spacing ?

Is that correct ?

[Elp]

I've always done the backspacing starting from the flat face of the bayonet fitting (where it sits flush against any mating adaptor) so you have to include the adaptor thickness into the backspacing.

[Adreneline]

10 hours ago, SAW said:

even just adding 1mm of spacing then through the focus back the other way where it was in focus before the L mark.

I'm not sure why you are not following the advice I gave you on the 28th May; you need to make incremental changes of 0.1 mm not 1 mm. 

[SAW]

1 minute ago, Adreneline said:

I'm not sure why you are not following the advice I gave you on the 28th May; you need to make incremental changes of 0.1 mm not 1 mm. 

Where do I get 0.1 shims ? Smallest I have is 0.5mm.

[Adreneline]

7 minutes ago, SAW said:

Where do I get 0.1 shims ?

Ebay.

[powerlord]

Or just get a sheet of 0.1mm a4 abs or petg. And just cut your own out.

Stu

[SAW]

I'm almost there 😀 need some of those 0.1mm shims now. The white marks are where I've been getting focus using different shims. 

[aleixandrus]

On 06/06/2023 at 11:54, geeklee said:

The filters may be parfocal but the Samyang lens is not bringing all wavelengths of light to focus at the same point.  

My Ha and OIII are at least 100 steps apart I'm sure.

This is a very good point. I was aware of that and I get this quote from the seller, which also point in this direction:

"How much chromatic aberration has your Samyang? Did you tested it with a color camera? I believe the filters are right and not mixed. I think your Samyang is tuned for the OIII (501nm) and Ha and SII (656, 672nm) are focused a little fair away on the focal plane. as well because it is intended to be used in daylight use with color cameras, that are cutted around 650nm, so maybe it's the design who doens't take care to give a good correction on bandwidth after 600nm. This is my idea, based on what I saw with photo lenses."

The key is knowing if my filters are ok or not... and it seems they are just fine. Not a big problem as I have autofocus but this is a bit disappointing. I suppose I have to live with it. So now I need to check the "signal weakness" issue, I need a clear night to add more subs and make some actual measurements.

21 hours ago, SAW said:

 With the correct spacing it would focus way past the bottom of the L mark, even just adding 1mm of spacing then through the focus back the other way where it was in focus before the L mark.

It's a pain trying to get it adjusted as I am using the Astrodymium mount so I have to strip eveything off just to adjust the spacing !

If you use NINA, you can try the Hocus Focus plugin. It provides some measurements of backfocus and tilt you can use for fine tuning. I'm still testing how it goes... However, the procedure @Adreneline indicates seems the best to me: start from scratch and add different spaces until you past 'perfect' focus. This may be where you focus with your Canon camera or not, just check your images and use the backspace you see it performs better, whatever the focus mark is in the L mark. I also have the Astrodymium mount but I also add the focuser, filter wheel, a mini PC and a powerbox. For these tests I also removed the guidescope. So... I know disassembly everything so I temporally move to a laptop and a mess of cables, it is a pain in the ass but you only have to do it once. I did it with my LRGB filters, I will do it again with my SHO (if weather helps, I was waiting for 2 months )

11 hours ago, Adreneline said:

Ebay.

I bought a similar kit from Artesky but I don't quite happy. I suspect I have some tilt issues due to poor construction, but I'm not sure. In addition, they are not labelled so it is not easy to figure out the thickness of the thinner even with a caliper. There is a similar kit from Baader which seems more user friendly. Just my 2ct.

[Adreneline]

Sadr taken mid-May, presented at 1:1 : 12 x 300s of S, H and O:

Just the edge stacking effects cropped reveals the stars look pretty good all the way to the corners:

Processed to tame Sadr and reveal the heart of Sh2-108

Don't you just love the Samyang 135  

[SAW]

I've got my focus correct now so it's at the base of the L mark but the stars in the top left and right are slightly elongated. I have some tilt shims 01, 0.2 & 0.3mm, do I need to shim the top where the stars are elongated or the opposite side ?

[aleixandrus]

 These corners make me VERY jealous, @Adreneline 😁

@SAW: I think it depends on the direction of the elongation... If the stars are elongated towards the edge, you are probably too close so you can add some shims in that corner. However, if the elongation is perpendicular to the corner-to-center direction, you are too far away... which is more difficult to address as you need to 'subtract' distance and you will mess up the other corners. If they have a good shape, maybe you can live with one ugly corner. Do you have some pic to show?

[SAW]

Out of interest what cameras are people using with the Samyang ?

I'm thinking of buying another one but this time a OSC, normally use mono.

[SAW]

On 12/06/2023 at 10:39, aleixandrus said:

 These corners make me VERY jealous, @Adreneline 😁

@SAW: I think it depends on the direction of the elongation... If the stars are elongated towards the edge, you are probably too close so you can add some shims in that corner. However, if the elongation is perpendicular to the corner-to-center direction, you are too far away... which is more difficult to address as you need to 'subtract' distance and you will mess up the other corners. If they have a good shape, maybe you can live with one ugly corner. Do you have some pic to show?

Here is a single 120s image all I have done is a EZ Soft Stretch in Pix.

[Petrol]

5 hours ago, SAW said:

Out of interest what cameras are people using with the Samyang ?

I'm thinking of buying another one but this time a OSC, normally use mono.

I started with a ZWO 294MC Pro using the bayonet adapter. The results were just OK. The 294 packed up so I replaced it with a Player One Poseidon-C Pro (IMX571) and ran into a few problems using it with the Samyang lens. In particular elongated stars at the corners. Big chip camera with a wide angle lens means bigger problems from what I can gather but after taking a lot of advice from  @Adreneline particularly replacing the bayonet with a screw on M42 adapter and proper back focus setup, I'm getting close.
If you get the back focus right and add a filter you will need to re shim. You really need to shim to 0.1mm tolerance and its trial and error to get it right. It's been a lot of messing about but the combo of a big chip and a wide angle lens means mega widefield images which is what I'm hoping for. It's also a good time of year to get the rig sorted out.
This is 20X 120s lights, flats and a quick process in PI. I'm also using 2 filters - an IR/UV cut and a dual band. The problem with OSC and dual band filters is halo's around stars of certain colours. That's why I'm using an IR/UV cut filter as well to reduce star bloat.
HTH
Pete

[Adreneline]

6 hours ago, SAW said:

Here is a single 120s image all I have done is a EZ Soft Stretch in Pix.

Just eye-balling the image the stars on the right look 'bigger' to me than on the left of the image - that might suggest there is a bit of tilt from left-to-right - maybe?

 

[aleixandrus]

I have taken the liberty of playing a bit with your shots. I'm not an expert by any means and take this with a grain of salt but, to me, while the shot from @Petrol seems quite nice by my standards, the one from @SAW has some lateral tilt. Based on star shape, to me, right side is too far from the sensor while left side is too close. I concur with @Adreneline

This is the star elongation direction I see (by eye) in the corners:

While ASTAP provides some actual measurements, which seem to confirm the same tilt orientation:

 

Considering @Petrol shoot, tilt is just perfect to me. Also, star size, they are smaller so maybe you can double check total backfocus besides tilt (although using different cameras, sensor size and already stretched images may misrepresent this conclusion).

 

Hope this helps. I also need to address the same issue as I get new SHO filters and all my image train has changed. But I was hoping for a single clear night one month ago with no luck and next weeks prediction is just awful

Oh, by the way, I shoot with an ASI183MM Pro but maybe an ASI533MC could match well. Many people says wanders about that sensor.

[Petrol]

On 07/06/2023 at 20:26, SAW said:

Where do I get 0.1 shims ? Smallest I have is 0.5mm.

Might be worth a mention but I have a few of the 42mm gaskets that came with various cameras and accessories. They vary in thickness quite a lot and you can mix and match to get the right back focus.
I also checked the tilt using the SY and Zwo 294MC camera and it was quite a long way out. It was the same on my RASA
The tilt is a lot less on all my rigs with the Player One camera and from what I can gather, the sensor is very well aligned during manufacture.
My advice would be to get the back focus sorted before moving on to tilt adjustements. It's also important to understand that any slop in the bayonet adapter will cause problems. I would also measure any filter holders, shims or adapters to make sure they are absolutely straight. You might be suprised how some components are poorly made.
The bottom line here is we are pushing the boundries of everything to the absolute limit. That said, I have every faith in this lens and some of the images posted here are testament to that.
Hope that helps @SAW  I was at the point of giving up but after following @Adreneline advice, I'm sorted

Clear skies
Pete

[Elp]

Or you can temper expectations and usually crop unless there's excessive tilt. It's down to how self satisfied you'll be with the end result, I personally don't bother too much, it's bad enough trying to get the right backfocus distance (I chop and change equipment and setup every time so know how annoying this can be) without then driving yourself nuts with tilt adjustment (it's necessary for solar to avoid newton Rings but for night maybe not so much). Larger sensors obviously exasperate the issue.

[Space Oddities]

Just received this nice 3D printed toothed ring for the Samyang. I had some issue with the toothed gear and ring that came with my BlackCat mount, but then I found this aring on Thingiverse. Cost me 16€ to get it printed, I think the quality is just great. I'll have to add a belt, but hopefully I'll have autofocusing again soon for my next project  

 

The added bonus is that I can add the lens hood backwards, the ring is slim enough for this! I couldn't before, so, that's neat for travel and storage!

Here it was before:

Edited June 27, 2023 by Space Oddities

[Len1257]

On 27/06/2023 at 15:28, Space Oddities said:

Just received this nice 3D printed toothed ring for the Samyang. I had some issue with the toothed gear and ring that came with my BlackCat mount, but then I found this aring on Thingiverse.

Pierre, do you have a link for the ring on Thingiverse please? I'm confused which one it might be.

Thanks

Len

[Space Oddities]

I found the link on Astrobin, but can't remember where. I saved the STL file though, maybe that will help!

I printed it in PLA Pro, 80% fill, 0.1mm resolution. I don't know anything about 3D printing but that seemed fine!

6485c7fcc370e_9cb257b709c87bd2122436b5c6f0058c.stl

[emyliano2000]

Cygnus mosaic (18 panel) in SHO-RGB

This is the first time I properly use my Samyang 135mm F2 lens with one of my mono cameras and I thought it would be a good opportunity to take on a big project that I've been planning for quite a while.

Because of the lack of astronomical darkness in the UK during the summer months, a lot of people stop imaging but I never do, and despite that, I used the lens wide open at F2 to collect a lot of data in a short period of time. Most of the panels are done in a single night, because a single panel has 2 hours and 45 minutes worth of data and the nautical darkness only lasts for about 3 and a half hours.

I shot 10 subs for each filter, 5 min for the narrowband and 30sec for the RGB stars.

I initially started with the Sadr region which was processed separately, and after seeing how easy it is to collect the data during a single session, I started adding panels to make my largest mosaic to date.

Equipment used:

Mount: Dark Frame hypertuned EQ6

Samyang 135mm F2 lens

QHY294M Pro Cmos camera, cooled at - 10°C

QHYCCD QHYCCD CFW3M-US 36mm filterwheel

antlia 36mm 3nm Ha, Sii and Oiii filters

antlia 36mm RGB filters

Deep Sky Dad AF3 autofocuser

Qhyccd QHY5L-IIM guide camera

Qhyccd Polemaster

Software used:

Eqmod, SGP - Sequence Generator Pro, PHD2, Stellarium with stellariumScope, SharpCap for polar alignment

Date: 20.05 to 26.06.2023

Location: Hemel Hempstead, bortle 5

Frames:

Antlia 3nm Narrowband H-alpha 36 mm: 180×300″(15h)

Antlia 3nm Narrowband Oxygen III 36 mm: 180×300″(15h)

Antlia 3nm Narrowband Sulfur II 36 mm: 180×300″(15h)

Antlia V-Pro Blue 36 mm: 180×30″(1h 30′)

Antlia V-Pro Green 36 mm: 180×30″(1h 30′)

Antlia V-Pro Red 36 mm: 180×30″(1h 30′)

Integration:

49h 30′

Stacked in AstroPixel Processor and processed in Pixinsight and Photoshop CC 2023

I hope you like it.

Emil

Edited July 2, 2023 by emyliano2000