Flat Schmidt Camera

Schmidt camera is famous for a extremely wide field camera and less abberation, but it has a field curvature, which is not suitable to CCD camera. I designed a flat Schmidt camera with Meade SN-10, Schmidt newtonian. Schmidt newtonian has huge coma like Newtonian, but it would be a perfect optics potentially.
Coma of the Schmidt newtonian will be zero if the C.P. is located at twice of its focal length from the primary mirror. Fathermore, the field curvature will be reduced if a positive lens is located just in front of CCD. I traced optical rays of the Schmidt newtonian with a lens, and I found a solution.

To remove the field curvature, Petzval condition should be zero. Mirror's power is 1/((-1)*(focal length of the mirror)), and a positive lens' power is 1/(1.5*(focal length of the lens)). In this case, 1/((-1)*(1000mm)) + 1/(1.5( f )) = 0, so f=666mm. The lens is placed at 47mm away from CCD plane, and the correcting plate is done at 1.3 times of the mirror's focal length away, 1300mm. The corrector lens redeces half of coma, so the C.P. should be located 1300mm away from the primary mirror. It also makes the original focal length shorter, and the effective focal length of this optics is 920mm, whose Fno is 3.6.

Meade Schmidt Newtonian ray diagram, D=254mm F=4.0

Meade Schmidt Newtonian spot diagram, 0, 0.5, and 1.0 degree from left
Center square is 10 microns wide.

Flat Schmidt Camera ray diagram, D=254mm F=3.6

Flat Schmidt Camera spot diagram, 0, 0.5, and 1.0 degree from left
Center square is 10 microns wide.

I used a Bord 50ED objective lens, f.l.=500mm, for this, and it is located at 50mm away from CCD.

Flat Schmidt Camera in my observatory

  • First light image by STL-11000XM

  • M42 taken by SN-10
  • M42 taken by Flat Schmidt Camera
  • M45 taken by FSC203, based SN-8

    List of the Flat Schmidt Camera in the world.

    1Kazuyuki TanakaJuly 15th, 2004Tokyo, JapanThe 1st Flat Schmidt Camera
    2Yukinari MashitaniOct. 17th, 2004Nara, JapanEOS Kiss Digital user
    3ZaneUnder constructionSydney, AustraliaMagellan Observatory
    4J.DevauxUnder constructionAlignan du vent, FranceHandmade 350mm Newtonian owner
    5Scott TuckerUnder constructionArizona, USAwww.darkskyimages.com
    6KosakaDecember 1st, 2005Aomori, JapanHis first shot, based SN-8

    Please contact me when you made your Flat Schmidt Camera. I will list you up here.

  • Related site T-Reducer

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