Have I got the correct back focus

[KyleStoke]

Hi All 

I am trying to hook a Samyang Canon fit lens to my Atik 428.

currently after a bit of use with a hacksaw I have the following focal distance. 

Atick chip distance 12.5mm (where is this measured from the front of the camera is rounded so I took it as the very front. I then have 32.7mm for the rest of the image train this is to the metal plate at the back of the Lens. 

Sot that is a total of 45.2 I have filters that are 2 mm thick so minus .6 = 44.6 is that still to far over? 

[Adreneline]

This worked/works for me.

Image shows a Samyang 135mm on the left, a TS 2" filter holder centre, and the Atik 428ex on the right. The red tape shows the position of the sensor in the camera (close as I could get it).

I had to mess around with a few custom spacers to get it to focus at f2.

HTH

Adrian

 

[KyleStoke]

Hi Adrian 

If the bit by you red tape upto the block is 12.5mm which Atik stake as the chip distance then yours is actually .9mm longer than mine, how thick is your filter? 

Im trying to use the 16mm version instead of the 135mm but should be the same. 

A second question looking at your equipment how do you find the ASI1600 compared to the 428?

[wxsatuser]

1 hour ago, KyleStoke said:

Hi All 

I am trying to hook a Samyang Canon fit lens to my Atik 428.

currently after a bit of use with a hacksaw I have the following focal distance. 

Atick chip distance 12.5mm (where is this measured from the front of the camera is rounded so I took it as the very front. I then have 32.7mm for the rest of the image train this is to the metal plate at the back of the Lens. 

Sot that is a total of 45.2 I have filters that are 2 mm thick so minus .6 = 44.6 is that still to far over? 

The back focus is measured from the chip to the front face of the camera housing, should be 13mm.

You then have 31mm to make up with whatever but add 0.6 for the filter, so 31.6mm to make up.

[KyleStoke]

4 minutes ago, wxsatuser said:

The back focus is measured from the chip to the front face of the camera housing, should be 13mm.

You then have 31mm to make up with whatever but add 0.6 for the filter, so 31.6mm to make up.

Hi Mike 

Always had it at 12.5 but can see 13mm +- .5 so im either at 45.2 or 46.2 or somewhere in between 

according to the adapter sizes I am eos to m48 10mm m48 to T2 3.5mm filter wheel 19mm filter wheel to camera 0. so would not be possible. 

what is the tolerance at F2 

[wxsatuser]

3 minutes ago, KyleStoke said:

Hi Mike 

Always had it at 12.5 but can see 13mm +- .5 so im either at 45.2 or 46.2 or somewhere in between 

according to the adapter sizes I am eos to m48 10mm m48 to T2 3.5mm filter wheel 19mm filter wheel to camera 0. so would not be possible. 

what is the tolerance at F2 

45.2 should be ok it allows for the filter and +/- 0.5.

I would try it and tweak from there.
 

[KyleStoke]

Thanks Mike, ill try tonight if a get a clear patch, hope it needs to go out because apart from getting new really thick filters I can shave any more distance off 

[Adreneline]

30 minutes ago, KyleStoke said:

how thick is your filter?

Hi!

I'm really not sure to be honest. Every time I put together a new arrangement my experience tells me that trial and error is the way to go. I've read all the theory and all that stuff and then find that spacers never go together quite as you think, or they engage too much in the filter holder and stop you withdrawing the filter, or something. The end figure is never far from the theoretical figure but then Atik quote a tolerance on the exact position of the sensor (I read +/- 0.5mm somewhere) so trying to come up with the perfect theoretical spacing is not necessarily going to work either!

34 minutes ago, KyleStoke said:

how do you find the ASI1600 compared to the 428?

I'm still getting used to the ASI1600 but so far I like the fact that I can get very rewarding results with much shorter exposure times so I get less wastage due to aircraft (which regularly take off or land over the house). Not surprisingly I spent an age sorting out all the spacing again because the back focus on the ASI is 6.5mm. Joy!

Good luck with your trial and error

Adrian

[wxsatuser]

I got my Atik 383 to about 45mm and it seems to work ok with Astrodon filters.

[KyleStoke]

Thanks Adrian Ill report back. 

That extra 6mm ish does seem to help a lot 

[KyleStoke]

4 minutes ago, wxsatuser said:

I got my Atik 383 to about 45mm and it seems to work ok with Astrodon filters.

Might work out cheaper to get a new camera, as much as a set of Astrodon filters is very tempting 😁

[wxsatuser]

I have'nt got a full set of Astrodons just the Ha and the RGB set, got em cheap secondhand.
Cost to much new make my wallet wince. 😉

[KyleStoke]

definitely one id have to smuggle past the wife

[KyleStoke]

Sadly the distance needs to be reduced. From what I can tell I have 3 options. 

1. Probably most sensible save up for a new camera. 

2. The thread from the eos adaptor to m48 adapter is too long there is a mm minimum that could be shaved off somehow. 

3. Perhaps the most drastic remove the thread entirely and glue it directly to the front of the filter wheel. 

[KyleStoke]

Right I have got my spacing fixed, think im actually under now, but it is my understanding that this is ok because I can just focus past infinity.

My issue is now tilt of some variety, what do you guys think and if it is how do you fix it, this is one frame stepped down to F2.8 just starched and converted to PNG

[wxsatuser]

Mine ended up with very slight tilt, hardly noticeable on a widefield image.
It's there but I was willing to accept it rather than mess about.

If yours is tilt it's more than just noticeable.
Whats the quality of the EOS adapter, any slop in it, would have thought any T2 threads should be ok.

[KyleStoke]

I think it will be from where I had to chop the end of the thread off to reduce the distance, the eos adapter feels pretty solid