I wanted to put out some info on PVS-4's with MX11620 Gen 3 tubes. PVS-4 is a variable gain device. The trick to variable gain is being able to turn down the gain a little and greatly reduce noise. As a result, contrast is improved by the cleaner background space afforded by less background noise.
These are large devices and come with 4x catadioptric lenses with very good mirrors. The lens section can be completely removed though and an adapter put in place to fit various SLR lenses or a nosepiece fitted to go in a larger telescope able to balance heavy 2" eyepieces.
The tubes are 25mm and offer a much wider view than 18mm devices.
Adapters - c-mount adapter would need to be custom made. NAIT has designed a T2 adapter I just tested tonight. This is a flush fit adapter with deep enough threads to accomodate any T2 accessory.
The good - so close a fit that putting 2" nosepiece with 2" .5x reducer still leaves plenty of focus room.
The temporarily bad - SLR lenses do not come to focus as it is too close a fit
The solution - I used a 5mm + 10mm T2 extension coupled with T2 to Nikon F mount adapter. This put the 135mm F/2.8 lens I was trying right at perfect length to allow both close focus and infinity with spare focus room on either side of close or infinity.
The Ability to add by extension to achieve focus is great, provided you have some extensions lying around like I did, or order some up. Much better to need to add vs out of luck because you can't take away length. This is a great adapter. Custom contoured to match the shape of the PVS-4 and uses the same screws that you take out to remove catadioptric lens. Anodized in black.
I am going to email NAIT tomorrow to let him know this adapter coupled with some T2 extensions for SLR lenses or without for work in a scope with focal reducers, is a great design. Flexible and very professional looking.
These devices are very good for astronomy. They have enough oomph to handle narrowband filtering also.