In the previous post I suggested a configuration to use in mating DSLR lenses to the ASI 2600MM camera + ZWO 7x36mm EFW. A first test of this has been done, with good results. Here's a simple stack/stretch of some Heart Nebula H alpha data taken using an old Olympus lens with a Canon adapter, mated to the ASI with a thin Canon to M42 adapter + thin spacer rings for 1.4mm
Things to be aware of are
- The wind was gusting to 30mph the entire time data were being collected.
- North is to the right; you can see a substantial drift in RA probably because this is a temporary rig and utterly out of RA balance (PHD was squawking a lot)
- Focus was far from perfect
- This was 2x2 in-camera binned and roughly calibrated using dark frames from 10C cooler calibration, no flats, no bias.
- Stretch was just the PixInsight STF
Evidence of the drift is seen along the top (west) edge of the image where there is a thin band of partial coverage. As a result of the probable bouncing due to PHD's problems we expect stars to elongate in RA during the ten-minute exposures, and that's just what we see in this composite image of the center and four corners:
The center shows the poor focus and evidence of the RA drift. (RA drift is in the vertical.)
Stars at the corners compare well with the center stars. While they show the same soft focus and RA elongation, there's no evidence of aberrations resulting from improper spacing between lens and sensor.
Sharper focus might well show defects, but this is not bad for a windy night, no balance, and a $40 Olympus 200mm f/4 lens (stopped down to f/5.4).
And one last little observation about the pricing of astro gear. The Canon lens adapter for my SBIG ST-8300 cost me $300. Things were far less expensive for the ASI. The Canon/M42 adapter plus the thin spacing rings came to $75. Over half of that was for the general purpose rings that will see duty in additional ways.
