Imaging with the Samyang 135mm f2

[woldsman]

3 hours ago, Phillyo said:

Just wondering, how do you guys rotate your lens and camera to get the correct framing of your target? Or do you just set it and leave it and hope for the best? Any tips/tricks for easy rotation and framing?

Used a ts optics 360 rotator with a zwo ccd. Not sure how to rotate with a DSLR. However, am experiencing tilt. See the photo attached. Think the tilt is due to inaccurate back distance and have ordered a wider range of spacers and shims. Hoping to go back to the rotator as some targets need accurate framing (eg Heart & Soul). Benchmark for tilt is 25% (moderate ) with the DSLR on the bayonet. If I can get this with the ccd & rotator, will settle for it (the majority of Astro images posted have at least moderate tilt if you check them, I think).

Edited January 20, 2023 by woldsman

[Phillyo]

Located in the constellation of Auriga, the Flaming Star Nebula (IC405, SH2-229 or Caldwell 31) is approximately 1500 light years away. The Tadpoles (IC410) are located at approximately 12,000 light years, so despite looking like neighbours, these two are not.

Captured with the Samyang135, Risingcam IMX571c, Antlia ALP-T 5nm filter, EQ6r Pro, NINA, PHD2. Processed in Pixinsight. This is approx 14.5 hours of data. I'd like to have rotated the camera/lens 90 degrees for better framing but it's a faff so I didn't bother  

Thanks for looking.

[Alien 13]

1 minute ago, Phillyo said:

Located in the constellation of Auriga, the Flaming Star Nebula (IC405, SH2-229 or Caldwell 31) is approximately 1500 light years away. The Tadpoles (IC410) are located at approximately 12,000 light years, so despite looking like neighbours, these two are not.

Captured with the Samyang135, Risingcam IMX571c, Antlia ALP-T 5nm filter, EQ6r Pro, NINA, PHD2. Processed in Pixinsight. This is approx 14.5 hours of data. I'd like to have rotated the camera/lens 90 degrees for better framing but it's a faff so I didn't bother  

Thanks for looking.

I think the framing is perfect, a nice portrait of an Alien..

Alan

[Phillyo]

23 minutes ago, Alien 13 said:

I think the framing is perfect, a nice portrait of an Alien..

Alan

You're not the first person to tell me that! That's the first thing my Mrs said when she saw it lol

[ollypenrice]

First light for the setup I share with Paul Kummer and Peter Woods.

Olly

[Space Oddities]

Superb capture Olly! I haven't seen a lot of pictures of Orion's head, but that gives me ideas!

[ollypenrice]

4 hours ago, ollypenrice said:

First light for the setup I share with Paul Kummer and Peter Woods.

Edit: wide open at F2.

Olly

 

[aleixandrus]

And what about guiding camera vs main camera orientation? I know that rotate the guiding camera is not big deal (in most cases) and I suppose having same orientation than the main camera eases guiding math but... it is truly necessary rotate the guide camera when rotating the main camera at this low focal length?

[Adreneline]

I am posting this purely for interest.

I have owned a Samyang 135 for several years and during that time it has been used with ZWO 1600 and 183 cameras. Throughout that time I have gone to great lengths to set the spacing such that the focus point with properly focused stars was within the base of the 'L' on the lens.

Last night, for the first time, I used the lens with a Canon 6D camera and thought I would show the focus position when the lens was focused using AF and then checked with a BM.

I know there is lots of debate on this thread about the ideal focus position. I should stress this is for my particular lens - I am sure there is variation between lenses.

I hope this is of interest.

Adrian

P.S. The whole setup:

 

 

[Gonzo]

Almost there with my OpenAstroTracker setup.

[Gonzo]

And here's a video of it 

 

[powerlord]

wow that's a thing and a half. Does it work ? What sort of length exposures are you getting from it if it is working ?

stu

[Gonzo]

2 hours ago, powerlord said:

wow that's a thing and a half. Does it work ? What sort of length exposures are you getting from it if it is working ?

stu

head over to https://discord.com/channels/693401540744183859/874631941255753778 to see results from many users.

[Gonzo]

Example or what others are capable of capturing with the OpenAstroTracker and this lens.

Edited February 3, 2023 by Gonzo

[SAW]

Just fine tuning my focus with the Samyang 135mm, ZWO2600MM and filter wheel.

Is it 44mm backfocus including the Samyang adapter https://www.firstlightoptics.com/adapters/astro-essentials-samyang-lens-to-m48-adapter.html or is it 44mm from this adapter ?

Thanks.

[Adreneline]

1 hour ago, SAW said:

Just fine tuning my focus with the Samyang 135mm, ZWO2600MM and filter wheel.

Is it 44mm backfocus including the Samyang adapter https://www.firstlightoptics.com/adapters/astro-essentials-samyang-lens-to-m48-adapter.html or is it 44mm from this adapter ?

Thanks.

Including the adapter - from the back face of the lens (the m48 adapter) to the sensor - 44 mm plus 1/3 the thickness of your filters. You want the lens to focus within the base of the 'L' - spacing has to be accurate to within 0.1 mm in my experience otherwise the focus position will be well before the 'L' or you won't achieve focus before hitting the end stop of the focus ring.

If you look back through this thread you will find several images of members holding digital callipers to show the distance from the back of the lens to the camera body.

[barbulo]

First small project with this lens. A classic Heart & Soul. Around 4h of valid data through 3 nights. 180s SHO lights plus 30s subs for RGB stars. Taken at f/2.8 with an ASI294MM and ZWO filters. First time using NINA, so wasted precious time getting grips. Processed in PI. Also first time processing an undersampled image, and I found it a bit tricky. Perhaps more data will help, though I’ll keep on trying. Thanks for watching. 

[SAW]

I'm still trying to get the ideal spacing with the 2600MM and Samyang 135mm. Quick stack of 12x300s Ha tonight. Yeah I know the core is blown out 😆

[SAW]

So I'm in focus but my lens is nowhere near the  infinity mark so I need to add some spacing, but how much ?

[jfrijhoff]

On 20/01/2023 at 14:13, Phillyo said:

Just wondering, how do you guys rotate your lens and camera to get the correct framing of your target? Or do you just set it and leave it and hope for the best? Any tips/tricks for easy rotation and framing?

Like the others mentioned: I have my lens on an astromodified DSLR (canon), and rotate the camera in the lens collar to get the correct framing. The lens is mounted currently on a A001 lens collar off of Aliexpress. It’s not a flush fit though, so I put felts on the inside to make it work. I’m waiting on a WO cat mounting ring that should be a snug fit, then I can also attach the guide cam on top.

[SAW]

Is this where I should be measuring 44mm from ? 

[Adreneline]

4 hours ago, SAW said:

Is this where I should be measuring 44mm from ?

Yes - to the front face of the camera + 6.5 mm.

[aleixandrus]

I bought a set of metal spacing rings from Artesky to add ~1.6mm additional spacing to get reasonably good stars with both ZWO LRGB and Baader Ha filters (I have some tilt in one corner, not sure how to fix that). I also use the M48 adapter and I measure from the face of the adapter, as you show. It is safe to say the focus mark should be near the 'L' mark on the lens. However, as each lens vary, best approach is to try different spacing rings until you get the one best fits your particular unit. It is a bit tedious but it can be done in one night. ASTAP or any other aberration inspector (such as NINA or PixInsight) helps a lot.

In my opinion, in the end what matters is having a 'good looking' image and don't worry too much achieve a perfect 44mm spacing. A 0.1mm spacing difference may have huge impact and it is difficult to handle. In fact, if you mix filters you may be interested in having *less* spacing to get focus with all filters inside the mechanical limit of the lens although you don't get perfect spacing for any of the filters, you know, a compromise solution.

If this helps, my setup is configured in this order:

1. SY135 + M48 adapter
2. 16.5mm ZWO extension tube
3. 1.65 spacer rings
4. 20.0mm EFWmini (+ filter)
5. 6.5mm ASI183MM (without the 11mm ring)

Total: ~44.65mm

Note: Those Artesky metal rings feel a bit cheap and they are not labelled, it's hard to differentiate between 0.1-0.15-0.2mm even with a caliber as they flex a lot. There are better (more expensive) ones but in the end, they do the work... Although the tilt I have may come from them. I don't know for sure 🥲

[SAW]

7 hours ago, Adreneline said:

Yes - to the front face of the camera + 6.5 mm.

I'm using the 2600MM and with the tilt plate removed my sensor is 12.5mm back.

[Adreneline]

45 minutes ago, SAW said:

I'm using the 2600MM and with the tilt plate removed my sensor is 12.5mm back.

Apologies for the misleading advice - I hadn't appreciated you had removed the tilt plate. Good luck.