Primary baffle reducing performance?

[Pitch Black Skies]

I have a primary baffle fitted to my 130P-DS and I'm wondering if it would actually be better to remove it.

The baffle is designed to cover the 3 primary mirror clips and it does an excellent job at that.

However, there is another method to remove the interference from the primary mirror clips and that is to fix the primary mirror to the backplate with silicone adhesive, and ditch the clips completely (credit to Alacant for this idea).

This method has the added benefit of also preventing lateral movement from the mirror cell.

The main reason I am wondering about whether to remove the baffle is because it is increasing the telescope's focal ratio, consequently slowing the telescope down.

 

With the baffle fitted, I have calculated the focal ratio to be 5.45.

Focal length ÷ aperture = focal ratio

649mm ÷ 119mm = 5.45

 

Without the baffle, I have calculated the focal ratio to be 4.99.

Focal length ÷ aperture = focal ratio

649mm ÷ 130mm = 4.99

 

This means that without the baffle, the telescope is 84% faster for the same SNR?

Focal ratio^ ÷ focal ratio^ 

5.45 × 5.45 = 29.7      4.99 × 4.99 = 24.9

24.9 ÷ 29.7 = .84

 

For 10hrs of data with the f5.45

I would only need 8.4hrs with the f4.99

 

 

Apologies in advance if this has baffled anyone

 

 

Edited April 9, 2022 by Pitch Black Skies
Added pic

[alacant]

We found 2 issues with the baffle:

It makes for fatter stars

It does nothing to prevent lateral movement of the mirror as the mount tracks.

Our optics guy tells me the former be due to the difficulty in producing a perfectly defined circular knife edge aperture. Most 3d printers leave the baffle with an irregular 90° edge which no amount of matt black will cure 

I don't think the advantage would be the extra speed, rather the improved star shapes and the ability to hold collimation through all angles. Although of course, every photon you can lay your hands on can't be a bad thing.

If you have a cheap refractor, there's a good case for stopping down the aperture. With a reflector, there's nothing to be gained by doing so. Why have a 120mm reflector when you could have a 130mm for no extra cost?

Our advice is to go with the silicone. Keep the mirror clips in case you decide to ship the telescope.

Cheers and HTH

 

Edited April 9, 2022 by alacant