Using a modified Canon DSLR and Backyard EOS

[AndrewPearce]

Hi All

I'm considering removing the LPF 2 from my Canon 800D to enhance the H alpha in images.  I just wanted to find out of anyone else has done that and whether there was any issues to continue using the camera with Backyard EOS.  I understand that once removing that filter that I won't be able to auto focus.  But is that a problem for Backyard EOS? I'd appreciate any feedback.

Regards

Andrew

[admin]

BYE won't know the difference.

You won't be able to use autofocus with the camera lens only, this is not an issue if you're using the camera with a telescope, and focusing with your telescope will/should not be affected.

Hope this helps.

 

[astroman133]

It depends on what you mean by "autofocus". BYE does not automatically keep stars in focus nor does it have a way to automatically focus the field-of-view. Also when doing astrophotography the field is too dark for the camera's autofocus logic to work. This is true regardless of what filter is installed over the sensor. This is why BYE provides FWHM and HFD focus metrics to help you manually achieve critical focus.

Also, the correct choice of cutoff filter depends on whether you will be using a refracting telescope as the lens or not.  The refractor's lenses are optimized to cause the entire visible spectrum to be in focus at the same time. If you widen the cutoff range to increase the Ha sensitivity you will be letting in deeper infrared light which the scope may not bring to focus at the same point. This is moot with a reflector.

You should tell the filter maker about your setup and let them recommend which filter you should purchase.

[AndrewPearce]

Thanks for the responses, apologies I probably created confusion when I mentioned autofocus.  I just understand you do lose this with removing the LPF2 filter.  However I don't need that functionality for AP.  I have a simple 85mm lens with my Canon 800D and as long as BYE can frame and focus images (via FWHM) just like I've been doing for years with the LPF2 filter in place, then I'm all good.

[astroman133]

Oh, okay. Thanks for the clarification.

Lens autofocus logic is all in the camera, so if the camera cannot autofocus with the filter removed, there is not much that BYE can do to override that. Manual focus with HFD or FWHM is the best alternative.