Recent Problems

I bought myself a new scanner for the same price I would pay for 40 1200-dpi slide scans.
That means my Canon 8400F should be paid for in 2 or 3 rolls of film :) Oh, and I get 3200 dpi, which should be enough..
In fact, it was enough for me to spot a few problems in my astrophotos.. I found out that I have a drif of 49 arc-seconds in my recent (July 30th) pic from M101, shown here.

It may have several origins:

• Guidescope slipping off place during exposure (it is currently attached to the main scope, and not directly to the mount)
• Guidescope's focuser moving during exposure (the equivalent of mirror slop in refractors :))
• Imperfect mount alignment, causing field rotation as I was guiding on a bright but distant star. (unlikely the case, as the trail measures 0,145mm (49") on all corners of the 6x6cm frame)
• Too large guiding tolerance (not the case: I use 5"~10" guiding accuracy, this is a 49" trail)

Anyway, I've digitized only 2 slides, and found problems on these 2 only. I still need to digitize 38 more to pay for the scanner, and to find out if other photos suffer from the same problem :) scnning older photos, from when I had a slightly different guide-scope setup, may help in determining the cause and nature of this problem..