A question of length...and also, who's good on deep space quirks?

[Tim]

Firstly, hope everyone has a successful new year. (When I say 'everyone', I dont mean any passing axe muderers, perverts, ASBO collectors or VAT inspectors).

It's nice to be back in a way after an extended winter break (-5 in a caravan ) and I did manage a little imaging while I was away, but mainly spent the time testing the little Off Axis Guider from TS. Full report to follow when i've caught up with a bit of work, but I have a question in the meantime.

Am I right in assuming that the focal point will always fall at the same distance from a focal reducer or other lens, even if you split the image, and if the chip sizes are different?

In simpler terms, will the spacing to the imaging camera be identical to the spacing required to a guiding camera to make them parfocal? I think they will, but the spacing is hard to measure, and I'd like to know that I am starting on the right foot to begin with!

Also, whilst taking a widefield sequence of the cone nebula area, I noticed a couple of objects that I cant out what they are. The images arent processed yet, but as you look at the cone and have it pointing 'west', there is a small triangular object to the south, looks a bit like a comet but doesnt appear to have moved. Also, if you follow the point of the cone and go off way past the fox fur bit, there is a largish (bigger than the blue reflection part of the cone area) bluish round nebula, very similar to something I have picked up on the edge of the Rosette. Anybody happen to know the area at all? I appreciate that its difficult without a pic, so it will be along soon, I just have too much to do in the meantime

Cheers

TJ

Oh, pikeys too. (Excluded from opening salutations)