M42 Pentacon F1.8 50mm - now what?

[Dazzyt66]

Hey,

I got this lens used in vgc as I didn't have a 50mm for very widefield shots - and its fast.

The thing is, I had a quick try with it last night using my usual autofocus setup in Ekos - I realised pretty quickly that the AF was not going to work properly at 1.8, it would get close but then fail. Clouds then came in so had to abandon. That said, the single frame I did get off was excellent - if a little out of focus.

So, my questions are:

Is it better to set the lens at say f4 to get a good focus and obviously the wide view (when using the Ekos autofocus) or step down (up??) even more?

I'd also like to try and take some non tracked shots of Orion (as I need to do this away from my HEQ5 setup) on a tripod. I'm going to go for 8s exposures. Can I go f1.8 like this or again is it worth stepping down (or up??) again? 

Sorry if I got 'step up/down' confused - I'm not much of a photographer (but you'll know what I mean)! 🤣

Cheers

Daz

[FenlandPaul]

Hi Daz

I’m by no means an expert, but I definitely wouldn’t use autofocus for night shots. There are almost no DSLR autofocus systems that work reliably and consistently with stars, so much better to focus manually (ideally using live view) on a bright star / planet/ distant streetlight (😱).

In theory there’s nothing stopping you getting decent focus at f/1.8, but it’ll depend on the specific lens. Using f/4 will probably be sharper,  it you’ll lose a lot of light at that ratio, negating the benefit of your fast lens. 
 

8s at f/1.8, though, should get you some cracking shots!!

[Dazzyt66]

11 minutes ago, FenlandPaul said:

Hi Daz

I’m by no means an expert, but I definitely wouldn’t use autofocus for night shots. There are almost no DSLR autofocus systems that work reliably and consistently with stars, so much better to focus manually (ideally using live view) on a bright star / planet/ distant streetlight (😱).

In theory there’s nothing stopping you getting decent focus at f/1.8, but it’ll depend on the specific lens. Using f/4 will probably be sharper,  it you’ll lose a lot of light at that ratio, negating the benefit of your fast lens. 
 

8s at f/1.8, though, should get you some cracking shots!!

Thanks Paul. I've been having some great success with the AF module in Ekos - it's not the same as using the camera AF (which I couldn't do with the M42 lenses anyway on my EOS) - the module works brilliantly with my 135 & 200mm but for some reason couldn't achieve the last final steps with the 50mm. Although I didn't really have much time last night to try tweaking it - maybe the star selected was towards the edge of the field... anyway I digress... 🤣

Thanks for confirming - I'm hopeful that the non tracked shots will be good at 8s - it looks like it might be clear(ish) here around 4am so I'll give it a shot! 🤞

[FenlandPaul]

6 minutes ago, Dazzyt66 said:

Thanks Paul. I've been having some great success with the AF module in Ekos - it's not the same as using the camera AF (which I couldn't do with the M42 lenses anyway on my EOS) - the module works brilliantly with my 135 & 200mm but for some reason couldn't achieve the last final steps with the 50mm. Although I didn't really have much time last night to try tweaking it - maybe the star selected was towards the edge of the field... anyway I digress... 🤣

Thanks for confirming - I'm hopeful that the non tracked shots will be good at 8s - it looks like it might be clear(ish) here around 4am so I'll give it a shot! 🤞

Ah, I hadn’t come across Ekos - sounds very impressive (and I feel a bit silly now! 🤣)

I reckon you could get potentially decent shots at 10s if you’re at reasonable declination.  Definitely worth experimenting - the pixel-peepers might not be happy but just think of that light!!!

[Dazzyt66]

1 hour ago, FenlandPaul said:

Ah, I hadn’t come across Ekos - sounds very impressive (and I feel a bit silly now! 🤣)

I reckon you could get potentially decent shots at 10s if you’re at reasonable declination.  Definitely worth experimenting - the pixel-peepers might not be happy but just think of that light!!!

No need to feel silly - I originally got Ekos to control my scope and with a bit of DIY I built an autofocuser - and then decided to modify that to fit my DSLR lenses. Up until last night it was working fine which is why I thought the faster lens may have been an issue. I know next to nothing about photography except basic stuff.

I'm not worried about pixel peepers - any image that looks OK is good enough for me! 🤣

Its currently bucketing down with rain so a clear sky at 4am might have been optimistic! 🤣