(I think this meets the price watch criteria; it's not my sale and it's on an external auction site.)

http://www.cloudynights.com/classifieds/showproduct.php?product=103895

Pentax made some legendary telescopes back in the day that could handle a full 6x7 film frame. This would be an interesting companion to test a 645Z's high ISO long exposure capability. The link is for a 100/f4. Telescope specs are stated as width/ratio instead of the usual photo lens length/ratio. This is a 400mm long scope.

[Michal1]

Hi, that ad is mine .
Here is a link to the actualised version of the ad
Cloudy Nights Classifieds (CNC) - Best Offer: PENTAX SDUF II 100/f4 astrograph including accessories - Powered by PhotoPost Classifieds