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Pages: 1 AstroMan0 member Reged: 06/19/12 Loc: Massachusetts Focusing Through Deep Red Filter       #5494715 - 10/29/12 02:07 PM Edit   Reply   Quote Quick Reply   Does anyone have any tips on focusing though a deep red filter (Wratten #29)? I couldn't even see the brightest stars through it. All I could see to focus on was the moon. I know I can't focus without the filter and then put it on, because then the focus will change. Also, I am using a fast achromatic refractor, so the deep red may come into focus at a different point than the other colors. What should I do? Edited by AstroMan0 (10/29/12 04:48 PM) Post Extras:       Michal1 sage Reged: 07/25/10 Loc: Czech Republic, Central Europe Re: Fucusing Through Deep Red Filter [Re: AstroMan0]       #5494873 - 10/29/12 03:51 PM Edit   Reply   Quote Quick Reply   Noah, focusing on the camera's focusing screen isn't recommended even without any filter. There are many methods that are more convenient here, see e.g.: http://www.astropix.com/HTML/I_ASTROP/FOCUS/METHODS.HTM I suggest making a parfocalized eyepiece (described in the link). Once you have an eyepiece parfocalized with the camera + filter, you can use it to focus on a star. I use the combination of a parfocal eyepiece and a Hartmann mask. If you found something unclear, don't hesitate to ask. Post Extras:       AstroMan0 member Reged: 06/19/12 Loc: Massachusetts Re: Fucusing Through Deep Red Filter [Re: Michal1]       #5494930 - 10/29/12 04:26 PM Edit   Reply   Quote Quick Reply   Thanks for the reply, I would use a parfocalized eyepiece, etc. But the problem is that my setup is based on 2 inch accessories, such as a 2" off axis guider, 2" adapters, 2" filters, etc. (1.25" adapters gave me severe vignetting). I don't currently have any 2" eyepieces, and from my experience, they are pretty expensive. Post Extras:       Michal1 sage Reged: 07/25/10 Loc: Czech Republic, Central Europe Re: Fucusing Through Deep Red Filter [Re: AstroMan0]       #5495054 - 10/29/12 05:40 PM Edit   Reply   Quote Quick Reply   My parfocal eyepiece is 0.75" (image). I found a paper tube that firmly holds the eyepiece and tightly fits to a film container. I have to focus with a 2" to 1.25" adapter, then unscrew it and mount the camera instead of it. Post Extras:       Pages: 1

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