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Zwo Pro camera OAG and a single filter between OAG and Camera


volcanotop
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Hi folks,

is there an easy way to get a 2” filter (eg l-enhance) into the imaging train of a zwp pro (eg 071 or 294) where the filter sits BETWEEN  the camera and the OAG.   I can see how to add it to the end of the train (eg to the focal reducer etc) but id rather not guide thru the filter.

zwo dont show this in the 55mm backfocus diagrams.  

Thanks

 

Edited by volcanotop
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I feel the simple answer is no, I have a 071 too. You can buy a sliding filter holder but the one that I have seen that is close to the correct size is rather pricey at 150odd euros, then you require shims to make up the remaining part of a millimeter, I forget how much. I am told Zwo will be bringing out a 2 inch filter wheel soon but this will again be pricey for, in my case the holding of a IR/UV filter or if I buy one the L-enhance.

Alan

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Hi Alan,  thanks for the response.

With reference to the article on the ZWO web site on getting the right back focus.

if there is a filter in the optical train then 56mm seems to be the magic number.

if thats the case are the thoughts below crazy / or missing something?

The Camera eats 17.5mm

The OAG eats 16.5mm

So there is 56-17.5-16.5 = 22mm for a single filter and spacers.  (where the filter sits between the OAG and Camera)

the extenders between the Camera ad OAG are T thread

Astronomik stock T hread filters that are physically 5mm thick

so i need 22-5 = 17mm spacer.

the camera kit comes with a 16.5mm spacer that i dont need because of the OAG.  

so could i just use that supplied 16.5mm spacer with some thin  shim washers to get the last fractions of a mm dialed in?

I appreciate that this wouldn't be as convenient as a filter wheel/draw but with a OSC and light pollution the l-enhance or equivalent might be  permanent part of the train.

 

 

Edited by volcanotop
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On 19/12/2019 at 09:14, volcanotop said:

BETWEEN  the camera and the OAG

Hi

Unless you're using a narrow band filter, there'll be an improvement in star quality (signal to noise ratio?) by guiding through the filter. Tested with a cls when we have to image in non-rural settings. Conclusion: save yourself €silly on a filter adaptor!

Cheers and HTH

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  • 2 weeks later...
On 19/12/2019 at 10:39, alan potts said:

I feel the simple answer is no, I have a 071 too. You can buy a sliding filter holder but the one that I have seen that is close to the correct size is rather pricey at 150odd euros, then you require shims to make up the remaining part of a millimeter, I forget how much. I am told Zwo will be bringing out a 2 inch filter wheel soon but this will again be pricey for, in my case the holding of a IR/UV filter or if I buy one the L-enhance.

Alan

£75 doesn't seem bad for the new filter holder.

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I wanted to install a single (1.25”) luminance filter in front of an ASI 178. ZWO offer a threaded collar which screws into the camera body and hence is after the OAG, and has minimal effect on the back focus distance. This is the link to FLO’s page, however I cannot see a 2” version.

https://www.firstlightoptics.com/zwo-accessories/zwo-t2-to-125-filter-holder.html

In the end it was easier (and cheaper) to make a simple push fit collar to hold the filter central in the optical train and clamp it in place by the adapter that screws into the camera to attach to the OAG, this might be the way to go?

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On 07/01/2020 at 23:35, tomato said:

I wanted to install a single (1.25”) luminance filter in front of an ASI 178. ZWO offer a threaded collar which screws into the camera body and hence is after the OAG, and has minimal effect on the back focus distance. This is the link to FLO’s page, however I cannot see a 2” version.

https://www.firstlightoptics.com/zwo-accessories/zwo-t2-to-125-filter-holder.html

In the end it was easier (and cheaper) to make a simple push fit collar to hold the filter central in the optical train and clamp it in place by the adapter that screws into the camera to attach to the OAG, this might be the way to go?

This adapter  comes with some of the cameras, ASI183MC in my case, I think it is those with smaller chips.

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