Imaging with the Samyang 135mm f2

[Elp]

Have you built in some sort of side to side adjustment? I ask as I have my lenses side by side separated by around 3-4mm on the ODs of the lens hoods, but imaging at the same time one lens is off by around 60 arc minutes (enough to cut out half of a large target) if using the same cameras.

[Gonzo]

25 minutes ago, Elp said:

Have you built in some sort of side to side adjustment? I ask as I have my lenses side by side separated by around 3-4mm on the ODs of the lens hoods, but imaging at the same time one lens is off by around 60 arc minutes (enough to cut out half of a large target) if using the same cameras.

The two main brackets holding the lenses are solid pieces. So they are correctly aligned to each other.

[Elp]

Your FOVs won't match up. My last two sessions my two lenses are pretty much parallel and level to each other, the second lens data was pretty much useless as I couldn't use it with the first lens data which was acting as the main lens. I'm looking at getting an adjustment bracket for the second lens so I can do a slight converge on their point of view rather than have them parallel.

[Gonzo]

13 minutes ago, Elp said:

Your FOVs won't match up. My last two sessions my two lenses are pretty much parallel and level to each other, the second lens data was pretty much useless as I couldn't use it with the first lens data which was acting as the main lens. I'm looking at getting an adjustment bracket for the second lens so I can do a slight converge on their point of view rather than have them parallel.

Will test that once it's up and running and adjust accordingly. Thanks for the heads-up.

[Elp]

For reference this is how mines setup atm, waiting on some button head bolts for the clamps, guidescope goes on the left, two asiairs on the right (or leave one on the floor):

[powerlord]

7 hours ago, Gonzo said:

A few pictures of my twin lens system, still a build in progress... but almost there... (waiting for the 2" filter holder to be able to add the second camera and final bracket)

If you're interested in the build https://discord.com/channels/693401540744183859/1016760448764350474

I tried th discord link, but just get a 'nothing to see here'?

Stu

Edited January 11, 2023 by powerlord

[tomato]

On 05/01/2023 at 10:14, ollypenrice said:

Would you experienced users care to comment on this, our worst corner on a 2600 chip wide open and shown here at 100%? The other corners meet the house standard. Our last tweak was a 0.2mm reduction in backfocus and was an improvement. Given that these aberrations are confined to a tight crop of one corner, we are inclined to try an image. Experience with the RASA suggests that a stack has better corners than an individual sub and Blur X might work on a stack. It didn't help the star shapes on this single sub. Seen at 50% we feel the corner looks fine and at 66% it seems acceptable.

 

 

A two-minute cosmetic fix in Ps takes the corner to here:

 

Are we in the zone?

Olly

By my standards I would say you are. With respect to tilt, coupling a Moravian G2-8300 to a Sony version of the lens required a bespoke plate with three threaded studs (made from brass, no less). This had the added advantage of providing total adjustment for both tilt and back focus, a very time consuming exercise but immensely satisfying when I got it right. Sorry but this doesn’t really help you at all.

 

[ollypenrice]

22 minutes ago, tomato said:

By my standards I would say you are. With respect to tilt, coupling a Moravian G2-8300 to a Sony version of the lens required a bespoke plate with three threaded studs (made from brass, no less). This had the added advantage of providing total adjustment for both tilt and back focus, a very time consuming exercise but immensely satisfying when I got it right. Sorry but this doesn’t really help you at all.

 

All information is good. Thanks!

Olly

[Gonzo]

For those of you using an OSC camera on this lens, where is your focus mark on the lens scale?

[Phillyo]

On 12/01/2023 at 12:09, Gonzo said:

For those of you using an OSC camera on this lens, where is your focus mark on the lens scale?

I had to doctor the lens and remove the hard stop to achieve accurate V-curve via autofocus.

[Phillyo]

This is a widefield view of NGC2264, the Cone Nebula. It's forms the top part of a two panel mosaic I'm working on to try and incorporate the Rosette Nebula too. I need more time on the bottom panel though, only 8 hours so far.
This is 15 hours of data shot in 3min subs through my Samyang 135@f3.4 and my Risingcam IMX571 camera, through the Antlia ALP-T 5nm Dual Narrowband filter.
There's a LOT going on in this area, as you can see in the starless version. I'm very tempted to keep adding to this and see how much more I can bring out? I've left the background fairly light here to show the faint details around the main nebula but it does mean there's a little more noise present in the image too.

Phil

[Gonzo]

3 hours ago, Phillyo said:

I had to doctor the lens and remove the hard stop to achieve accurate V-curve via autofocus.

ok thanks, but where is your focus mark? As in, when you've achieved focus, where is the mark on the lens?

[powerlord]

6 hours ago, Phillyo said:

This is a widefield view of NGC2264, the Cone Nebula. It's forms the top part of a two panel mosaic I'm working on to try and incorporate the Rosette Nebula too. I need more time on the bottom panel though, only 8 hours so far.
This is 15 hours of data shot in 3min subs through my Samyang 135@f3.4 and my Risingcam IMX571 camera, through the Antlia ALP-T 5nm Dual Narrowband filter.
There's a LOT going on in this area, as you can see in the starless version. I'm very tempted to keep adding to this and see how much more I can bring out? I've left the background fairly light here to show the faint details around the main nebula but it does mean there's a little more noise present in the image too.

Phil

Lovely work. My neighbours house and some woods stop me getting more than 60 mins in a night on the cone. That really is excellent.

[Phillyo]

4 hours ago, Gonzo said:

ok thanks, but where is your focus mark? As in, when you've achieved focus, where is the mark on the lens?

Ah, well it varies depending which filter I have in. However off the top of my head I don't know lol, I'll check tomorrow when I cover it up again. I use an EAF with it so I never really notice/care any more. Sorry!

[Elp]

Mines barely a 10th or 12th turn from the stop. Different filters changes this but still pretty near.

[Phillyo]

10 hours ago, Elp said:

Mines barely a 10th or 12th turn from the stop. Different filters changes this but still pretty near.

Mine was so close that I couldn't actually achieve accurate focus with one filter, that's why I had to modify the lens a little bit. 

[Elp]

4 hours ago, Phillyo said:

Mine was so close that I couldn't actually achieve accurate focus with one filter, that's why I had to modify the lens a little bit. 

How did you modify it? When I use my o3 filter the stars are awful (too close to sensor somehow) but adding spacing, even like 1mm means the focus is beyond the stop and I can't focus.

 

[Phillyo]

1 hour ago, Elp said:

How did you modify it? When I use my o3 filter the stars are awful (too close to sensor somehow) but adding spacing, even like 1mm means the focus is beyond the stop and I can't focus.

 

I followed a youtube video on modifying the backstop. I added it to another post somewhere else on the forum where Olly was making a new Samyang rig if you can find that? I'll see if I can find it for you. It's very easy to do.

[barbulo]

Perhaps this one?

[Phillyo]

Just now, barbulo said:

Perhaps this one?

Yes, that one. Thank you

[Petrol]

First light with this lens. 2 hours, 120s subs, asi 294 OSC with ZWO dual band filter.

 

[Phillyo]

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?

[Adreneline]

12 minutes ago, Phillyo said:

set it and leave it

That is my preference - with either the long or short side of the sensor perpendicular to the mounting bar. Having invested so much time in ensuring there was no droop or misalignment between camera/filter-wheel/lens I decided that introducing a camera rotation system was asking for trouble - assuming of course there is space to fit such a device and maintain the critical back focus spacing.

[powerlord]

2 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?

I can rotate mine in the 3d printed mount. It does mean I have to focus again, as the focus ring will stay in place as connected to asiair, but it's no big deal really.

If you use asiair, it shows you framing, and has great new angle adjust feature so you can get framing right in a few minutes.

[Elp]

I just unclamp the tube ring and manually rotate it. Of course it'll have to be refocused afterward. It helps if you use telescopius or something to plan first, at least then you can roughly orient the lens/camera prior.