RASA 8 2" filter holder urgent help please

[symmetal]

My RASA 8 Starizona 2" filter holder for 17.5mm backfocus cameras arrived today and was hoping to try it with an NBZ filter tonight, but the filter projects out the back of the adapter far too much and when you fit the whole assembly to the RASA with the RASA locking ring, after 1 turn the filter mounting ring hits the knurled ring on the front of the RASA, as shown on the first image, and jams.

I have removed the RASA glass filter locking ring and the clear filter as required from the front of the RASA but it seems I have to remove the large knurled locking ring too for the NBZ to fit into the space left, but this looks like it is what is holding in the front corector lens. 😬

Without the filter installed it all fits together like the original RASA M42 adapter, with the correct camera spacing, but I can't see any other way to fit the filter, as there is only one 2" filter thread, and when fitted with just one turn available on the locking ring, it puts the camera about 6mm further forward than it should be.

How are other peoples 2" filters fitted. I know some of you have the Artesky adapter but any help with this dilemma and whether the large knurled ring need removing is appreciated. None of the instructions imply that it does, just to remove the clear glass filter for correct optical spacing with an external filter.

Starizona adapter on the right

Alan

 

Edited September 16, 2022 by symmetal

[symmetal]

I've highlighted the knurled ring on this image from the RASA white paper and it doesn't appear to clamp the corrector lenses as they butt up against the flange behind it. The ring just seems to hold the clear glass. Shall I remove it? 😖

Alan

[symmetal]

Eventually found a topic on CN concerning the glass filter and helpful images confirms that the outer knurled ring is just part of the filter assembly and can be removed without affecting anything else.

Currently outside with original setup imaging RGB but will try removing the 'whole' filter assembly later and try some NB when the Moon gets higher. 🙂

Alan

 

[symmetal]

Starizona adapter with NBZ fitted easily once 'complete' clear filter removed. 😊 Focus was significantly out after changing so expected to have some odd shaped stars requiring a shim spacer but good stars all over after refocusing and still no tilt. 🤗

5 min exposures gave a sky background ADU of 711 where 717 ADU is the point where the read noise is swamped by 5, though there is a partial moon so on moonless nights 6m may be better.

Alan

Edited September 17, 2022 by symmetal