Takahashi 0.73x Reducer Spacing

[SyedT]

Hi all,

I've been fighting a losing battle with figuring out spacing between my Atik 490EX and the Takahashi 0.73x reducer. I have an FSQ85-EDX and am using the 0.73x reducer with it. The reducer requires a spacing of 72.2 mm, plus 1 mm added to it to compensate for 1/3 of my filter thickness, giving a total of 73.2 mm. My imaging train and measurements from camera to reducer are as follow:

490EX backfocus 13 mm + Atik EFW2 22mm + Atik OAG 24 mm + M54 male-male adapter 2 mm + M54 5 mm extender + Tak CA35 adapter 7.2 mm = 73.2 mm.

This gives me a radial star pattern which indicates that the distance is too much (first set of images below with corners). The issue is that I had previously tried this without the 5 mm extender as I had left it out by mistake (which would give me a spacing of 68.2 mm). This still gives me a radial pattern which indicates that the spacing is still too much (second set of images), which doesn't make any sense as the spacing is actually less than optimal! Exposures are 300 seconds in H-alpha. Any guidance would be appreciated, as I'm pretty close to just giving up on the reducer and going with the native FL.

Spacing 73.2 mm

 

Spacing 68.2 mm

 

 

Edited March 6, 2020 by SyedT

[Guest]

Hello

I have the same reducer, and according to specs, the ideal work distance for the reducer from the M56 thread"adapter is 72,2mm

https://teleskop-austria.at/TKA36580_Takahashi-Reducer-QE-073x

To be honest and since you are also using a FILTER within the lght path " since you have a Atik EFW2 " then with the spacing you have with 73.2mm is correct, since you should ADD 1mm for the FILTER LIGHT PATH in your calculation..

Regards

 

Martin

 

 

[SyedT]

On 07/03/2020 at 08:57, artem said:

Hello

I have the same reducer, and according to specs, the ideal work distance for the reducer from the M56 thread"adapter is 72,2mm

https://teleskop-austria.at/TKA36580_Takahashi-Reducer-QE-073x

To be honest and since you are also using a FILTER within the lght path " since you have a Atik EFW2 " then with the spacing you have with 73.2mm is correct, since you should ADD 1mm for the FILTER LIGHT PATH in your calculation..

Regards

 

Martin

 

 

Thanks, I was sure I had it right! Having done some further imaging, I think it may be a case of tilt. I'll keep adjusting parameters and seeing where it takes me I guess!

[Kinch]

Yes - looks like your spacing is correct. The only thing I can think of is perhaps pinched optics; i.e. things just screwed together too tightly. A bit of a long shot.....but I do believe that it happened me once.  Unfortunately I cannot confirm that I had the exact same problem show in the subs......but I do know I had problems of some sort in the corners.

[Guest]

Hi, since you mention " think it may be a case of tilt " and you may have right.. there are many threads related to 0.73 Reducer, just try to google for them.

Good luck

Martin