BACHES Echelle Spectrograph

You will need this adapter, but in addition also our 2" Filter holder M48/SP54
https://www.baader-planetarium.com/en/filters/filter-accessories/baader-dslr-2%22-filter-holder-m48sp54.html

We are NOT RECOMMENDING these filters for solar observation or photography at all! If somebody does this, its on his own risk, it may lead to permanent damage of the eye or the camera/telescope setup. We are warning and recommend not to use these filters as an internal ERF - they are not designed for this use. We have no values for working temperature a.s.o.

This is an empiric value. You need 40mm of distance to get rid of the distortions at the edges with a full-frame-camera; for APS-C, 30mm are sufficient.

We did not notice obvious influences on the image quality by increasing the distance/magnifications, only the exposure times get longer when you increase the distance. Of course, if you are close to the resolution limits of the optical system, too much magnification is not helpful, but but as long as you don't exceed the resolution power of your telescope, it should not matter whether you use 30 or 40mm with APS-C.

The 8" EdgeHD has got a backfocus of 133mm, the SC-Clicklock is 47mm long.
For an APS-C-camera, you can use T-2-adapters without problems and don't need a larger diameter for the adapters. So, you can use the standard T-ring, which gives you 55mm backfocus for the DSLR.

To adapt the APS-C-camera to the 8" EdgeHD with a Clicklock, we'd recommend
- 1x T-Ring Nikon to T-2 # 2408300 (55mm backfocus to the camera sensor)
- 1x Baader VariLock 29, lockable T-2 ExtensionTube 20-29mm with spanner tool, set to 28.5mm, # 2956929
- 1x Baader 2" / T-2 Nose Piece and Camera adapter # 2408150 (total length 2,5mm)
- 1x 2" Clicklock #2956220 (length 47mm, you already have this part)

This gives you a total length of 133mm without a filter.

You can screw any filter with a 2" housing into the 2" nosepiece (just like into any eyepiece). The filter will move the focus outwards by ca. 1/3 of its thickness, so a 2mm filter will move the focus about 0.7mm outwards. If you set the Varilock to 29mm, you are within the 8" EdgeHD's specified working distance of 133.35 +/-0.5mm.

A full-frame camera would require a Wide-T-Ring to make use of the full aperture; for the smallet APS-C, the T-2-combination works fine.

The thickness (optical length) of the ring is 11,8mm. With the delrin compensation ring a filter can be max. 3mm thick, without the ring
it is 4,5mm. Please don´t forget that by refraction filter lay out focus to extra focal about 1/3 of the filter thickness. So a 3,5mm filter will
set it about 1,2mm out. According your question please see following picture:

https://d3gqwrfrlgdnxc.cloudfront.net/media/extendware/ewimageopt/media/inline/99/b/baader-zero-tolerance-protective-canon-dslr-t-ring-t-2-m48-and-2-50c.jpg