Zwo ASI1600MM Spacing

[Skywatcher 200]

Hi All,

I got my Zwo 1600 MM a few weeks ago, and the suggested spacers this morning.

However i can't seem to achieve the 56mm that i was told i needed, 

The Set up is ;

Skywatcher 0.85 Reducer -  M48 to T2 -  Atik M54 to M42 M-F -  Atik EFW2 -  11mm Zwo spacer -  ZWO 1600 mm

Now, assuming that i am measuring from the correct points (see Pic) and have things in the correct positions,

Do i need to add another spacer between the FR and EFW2 ?

 

Thanks for any help

Andy

[ultranova]

Hi Andy, you will need to add the extra 5.5 mm to the optic train to get the best possible results

you could probably get away with +/- 1mm , but its always best to try and get it spot on.

welcome to the wonderful world of spacers.

Paul

 

[Skywatcher 200]

Thanks Paul

i have just placed an order for the required spacer, i was hoping that amongst all my bits and bobs, i would have had one, but, alas no,

Yet another 'bit' to add to the list of 'bobs'  lol

Andy

[Gina]

To have the spacer you require is a rare event indeed!!

[groberts]

16 hours ago, ultranova said:

Hi Andy, you will need to add the extra 5.5 mm to the optic train to get the best possible results

you could probably get away with +/- 1mm , but its always best to try and get it spot on.

welcome to the wonderful world of spacers.

Paul

 

Can you please explain how you arrive at this number?

[Zakalwe]

Unless you are using 36mm or 2" filters I would suggest removing the female T-thread coupler from the camera and screw the camera directly onto the filterwheel. The ASI has a big sensor and 1.25" filters just clear it as long as they are mounted as close as possible to the sensor.

Add T-tubes between the focal reducer and filterwheel to get the correct spacing. You may need to buy some adapters- get used to having a drawer full of expensive bits of aluminium tube, half of which are stuck together and none of which are the correct length!

https://www.firstlightoptics.com/adapters/baader-t2-extension-tube.html

[ultranova]

On ‎16‎/‎10‎/‎2016 at 14:51, groberts said:

Can you please explain how you arrive at this number?

Yes I can, Andy is 5.5mm short od his required 56mm back focus on his f/r , he wants 56mm at the moment  he has

50.5mm so another 5.5 mm is required hope that helps

Paul 

[Skywatcher 200]

Hi all, Sorry for not keeping up to date on this thread, due to Mum, ending up in hospital after suffering a Heart Attack

thanks for the info Zakalwe,

I shall look again at the way i have my spacing arranged as i do have 1.25 filters in the EFW2

Thanks again

Andy

[sloz1664]

You have also got to consider if you place any filters in the imaging train they will effect the spacing distance.

Steve

[groberts]

On 25/10/2016 at 20:52, ultranova said:

Yes I can, Andy is 5.5mm short od his required 56mm back focus on his f/r , he wants 56mm at the moment  he has

50.5mm so another 5.5 mm is required hope that helps

Paul 

OK thanks I get that but was really trying to understand how 56mm is arrived at?

[KyleStoke]

11 hours ago, groberts said:

OK thanks I get that but was really trying to understand how 56mm is arrived at?

I believe that focal reducer is optimised for a Cannon DSLR which attached to it has a back focus of 56mm

[Gina]

I think you'll find it's 54.9mm.

[groberts]

Thanks, got it now.