I plan on purchasing, in the near future, a QHY9 set (camera + FW + filters) and am trying to work out what spacers i will need.
I just received my Televue RFL-4087 FF and need to purchase the T-ring adapter for it.
I know the FF needs 55mm of back focus, but i cant find any mention of how this back focus is calculated.
By this i mean: The TRG-1072
) will add some focus distance - or has Televue already considered this in its calculations of needing 55mm back focus?
So with the adapter on the FF, will i need to make up the 55mm or will it only be 51/52mm (55mm negative whatever the distance of the t-ring adapter is)?
Secondly, i have found an estimate of the amount of focal distance of all the QHY equipment combined over here: http://qhyccd.com/ccdbbs/index.php?P...2&topic=2011.0
So roughly 50mm. Thus i need to make up 5mm.
Televue have two spacers available in the 2.4" format, a 6.4mm spacer
and the 1 & 2mm set: http://www.optcorp.com/product.aspx?...kw=spacer&st=2
The 6.4mm is obviously going to put me over by 1.4mm. Is this going to be a big problem, or is it manageable?
If the back focus calculations do not include the t-ring adapter then i guess it will be the 1 & 2mm adapter set.
If anyone happens to have an exact measurement of the QHY9 set, that would help.