M101 and general updates
June 3rd, 2009
My latest and I think my best effort is M101. The pinwheel galaxy is a face-on spiral galaxy about 27 million light-years away in the constellation Ursa Major.
This images is comprised of 1 hour 38 minutes of data, so 47×2 minute exposures (maths not my strong point) taken at ISO 1600, equipment used as per normal :
- Orion Optics Europa 250mm F4.8 Reflector
- Vixen Sphinx SX Mount Unguided
- Canon EOS 1000D Unmodified
- Skywatcher 2″ Light Pollution Filter
I started imaging at about midnight and got to bed some time around 4am, time I think well spent. I made some modifications to my processing technique this time round, in DSS I increased the saturation to 15% and matched the RGB levels prior to saving the stacked image to tiff.
This made life much easier I found in photoshop to get the black levels correct. Colour however remains a problem. The biggest issue with colour is the loss of reds due to the IR cut filter installed by default into the DSLR camera. Modification is possible but I think it will sit further down the shopping list for now as I’d rather get a Baader MPCC (Multi purpose coma corrector) first to remove the stretching of the image caused by the concave primary mirror.
Tracking remains somewhat of an issue, it’s still not staying as true as I would like. I noticed last night whilst taking some pictures of the moon that the target was visibly shifting in RA between frames, not good. In order to try and improve this I’m going to try the techniques for CCD/DSLR drift alignment as detailed here. Hopefully I should be able to improve things.
I’ll leave this for now, I will update on the improved drift align method after I’ve tried it, also I’m making and improved mounting plate for the scope and I have a Philips SPC900NC webcam on the way, so I’ll update on that when it turns up.
