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DSLR nosepieces


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Hi all,

This is a really noob question, so apologies in advanced!

When it comes to t-thread nosepieces that go on a DSLR, is there any difference if you use a 1 1/4" or 2" nosepiece when it comes to light gathering? Or is there no difference at all because the image is still focused on the same chip?

Thanks :icon_mrgreen:

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I don't notice and vignetting or anything using the 2 different adaptors.  If you're going with prime focus, afocal or what not on the scope and what your imaging you will need certain adaptors to achieve certain things. I must use a coma corrector with my DSLR and Newt for DSO work and must use the 2" tube there.  For the CCD lunar/planetary at prime i adapt the tube to 1.25.  For projection and afocal i use a clamp that attaches to the 1.25 eyepiece extension. Be versatile have all the adaptors and you'll be ready for anything.

Edited by Leveye
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This is assuming prime focus:

The limiting factors will be the light path from the scope, and the size of the sensor, and the distance between the two.

If you have  a narrow light path and a small sensor, then all the light may pass through a narrow 1.25" nosepiece.

If you have a wide light path and a massive DSLR (full frame) sensor, then the smaller nose piece may cut off some of the light and result in vignetting, hence a 2" might be better.

Vignetting is common anyway and may be unresolvable.


Edited by jambouk
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Ah ok, in that case, all my DSO AP is done using prime focus with a 2" nosepiece.

The reason I'm asking is because my H-alpha, OIII and SII filters are 2", and my LRGB filters are 1 1/4". I'm just trying to figure out if I need to invest in 2" LRGB filters or if I can use my 1 1/4" nosepiece with the LRGB filters.

Thanks for the input guys :smiley:

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