Gina

But the Borg homeworld never looked like that when I saw it!

This Samsung lens would appear to move lens groups relative to each other and only produce a flat field, properly corrected across the entire field, when both internal distances and the back focus is right. The lenses I use which were produced by the Asahi Company of Japan move the entire lens set to focus - there is no internal relative movement between lens groups. This make setting up simple - slightly wrong back-focus is corrected by focussing. The 135mm lens I use is smaller aperture of f2.5 rather than f2 so the Samsung passes nearly twice the amount of light. For those interested, these Asahi lenses were produced for Pentax cameras and with versions of Takumar, Super Takumar and Super Multi-Coated Takumar (SMC Takumar) as lens coatings progressed. They come in two mount versions M42 1mm pitch thread and (later) bayonet mount. The M42 thread is slightly different pitch from T2 which is 0.75. A so-called "Russian Adapter" converter can be bought for a few pounds, though in most cases the Pentax thread will engage several turns in T2. Back-focus of the thread mount lenses is 45mm. These lenses are available from that well known auction site at prices ranging from around £50 to £100. Focal lengths in general go from 28mm to 200mm and occasionally 300mm telephoto lenses are available. I'm talking prime lenses here - I don't use zoom lenses for astro imaging

I've seen that myself.

I've been very pleased with the ZWO ASI1600MM-Cool cameras since upgrading from Atik 460EX.

Thanks @RadekKI'll try that.

Oohh I don't know, we get a couple of hours of darkness in summer and TBH that seems to be all we are getting in winter!!! I may concentrate on solar Ha in the summer.

Long time no see Martin... How are you?

Very nice indeed!

Surprise, surprise!!!

Yes, I plan to.

Yes, really substantial hardware that! I have the same.

Now printing the focuser parts for the second lens.

A couple of photos of the part completed rig. Needs focus mechanism for LH lens and dew shield also the extra electronics for the 2nd camera & focuser. Then I need to add dew heaters to both dew shields.

I've ordered the 16 heavy duty 500mm square grids to make up the yellow path in the diagram.

GASP GASP 🤣

The camera without a filter wheel will have a 1.25" filter mounted in an adapter right on the camera. All these parts are supplied with the camera. Next to the camera, 7, is a ring with internal T2 (M42) thread. Inside that goes an adapter, 6, from M42 to the 1.25" filter thread and inside that a standard 1.25" filter, 5. In this case an Astrodon 3nm OIII filter. The filter couldn't be any closer to the camera so vignetting will be minimal (even better than with the ZWO EFWmini on the other camera).

Errr... Yes... I rolled into it! I guess I could move it...

I had to do that with my build. I bought two in fact - the first wasn't big enough. Tied mine on with rope and used lengths of timber to support it/them. Yes, they were cheap and didn't last long but long enough to do the job. I spent many days (weeks, months) under tarpaulin building my observatory. You can't rely on good weather in this country!! ('Tis true 🤣)

One thing to consider with lenses intended for terrestrial photography is that they are not fully apochromatic (APO) into the deep red where Ha and SII wavelengths lie. This means that you need to change focus when changing filters. For RGB you may notice a change in focus for the Red whilst the Luminance image looks rather soft.

If we get a break in the rain over the next few days I may bring my imaging rig indoors as it needs work on it. Otherwise I shall probably be staying indoors.

Absolutely!! Very much so!!

Yes, me too. As I think I said in the other thread.

"Mud, mud glorious mud - nothing quite like it for cooling the blood" 🎶 GROAN!!!

All stop now I imagine

No good for me - my night vision has almost disappeared! I can only see Orion's belt with averted vision.