Reecntly a problem with 120 format Tech-Pan film resurfaced on the APML. The printing on the paper backing prints through on to the film during the hypering process. With tech-pan being the only known B&W film with excellent red response this print through poses problems for medium format shooters on the list.
It was and is  well known  that Ilford SFX-200 film straight out of the box was not worth the effort to load it in the camera for astrophotography.
This has been proven by Rober Reeves film test where the reciprocity failure rate is in excess of 2.5 F-stops in 120 seconds. This puts the projected film speed at under ISO 30 after just four minutes, not very long for Hydrogen-Alpha photography. Also Bill Mattil from the list ran a roll through his camera with absolutely dismal results which matched up with Robert Reeve's test results. And matched with Ilford's own comment that the film is best suited for direct sunlight.
The only teaser with this film is Ilfords claimed red response of 740 nm,  very appealing when shooting through a hydrogen-alpha filter.
Not having my hypering system up and running I looked for an alternative to sensitize the film. Numerous articles have been written about preflashing the film to increase its sensitivity. I built a low level light source with an array of red leds, these were then housed in a can and a diffusion filter placed infront. The idea was to expose the film just enough to fog the film base and then continue the exposure on the stars.
Initial tests of the preflash unit with SFX-200 showed that with a half second exposure at f/22 with the H-A filter installed there was a slight fogging of the emulsion. At the same time it showed a very uneven distribution of light from my light source. A second sheet of drafting velum was added as a diffuser and spaced aboutan inch from the first sheet. The light was again measure with the camera light meter and showed a drop in light by three stops. This resulted in my making two errors.
 I changed a variable in the test (2nd diffuser) and did not retest to check its impact. Instead I calculated the increased amount of time based on the number of f stops.
This was the source of my second error as I felt the problem with the film lay in getting past the toe by fogging and into the linear region of the film. My 3 stops was based on no reciprocity losses.
In any case, here are the results using a 50mm lens and a lumicon hydrogen alpha filter with two seconds of preflash at f/22 pointed  at the Cygnus region.

A few lessons learned.
1) I need to be more careful about the centering of the preflash unit, the dark corners are the result of it not being centered.
2) 2 seconds of preflash is not enough.

The negatives are very thin and the fogging is just barely perceptable when looking at the negative backlit with a 60 watt lightbulb ten feet away even on the 25 minute exposures.
I will redo the test next clear sky keeping the 25 minute exposure time for each frame and double the amount of preflash on each consecutive frame. The film may need a higher level of preflash/fogging before it yields results. Or it may just be that the film is truly useless for AP no matter how you treat and process it.

As a side note, the LED method/concept of pre-flashing could possibly be expanded to red/green/blue LEDS under micro controller or laptop control to allow for colour correction of films which are more sensitive to specific colours or which exhibit different reciprocity rates for the different layers. This would require extensive testing of each film and a lookup table for preflash. And the number of LEDs for objectives over six inches would be high.