Santa Cruz Astronomy Club

At tonight's regular Bonny Doon star party, I was tired, so I only shot one series of 20 1min exposures of m13 with my DSLR through the celestron/vixen 80mm super-polaris.... half were sketchy (elongated stars at a pixel level), so I know I definitely need to come up with an autoguider. but the other 10 were good enough, albeit somewhat underexposed, that I was able to stack this, with a bit of contrast curve adjustments (black stayed black, white stayed white, I just steepened the curve a lot at the dark end)

Continuing with my adventures in beginning astrophotography, on the last new moon night at Bonny Doon, I shot a series of piggyback exposures with various camera lenses on my EOS 60D.

The final pics are here, with comments explaining whats what. I included some of my 'raws'. None of the stacked pictures used any dark frames

The Canon EOS 60D

• 22.3 x 14.9mm CMOS sensor
• 5184 x 3456 pixels
• 4.3 micron square pixels

with a 900mm focal length, thats 1.4 degree wide field of view, with 1 arcsecond pixels

with a 200mm focal length, thats a 6.3 degree wide field of view, with a 4.4 arc second pixel

with a 20mm lens, its a 63 degree slice of the sky.

so, while waiting out this interminable cloudy/rainy weather (not one clear night since March 9th?!?), I started hacking on a homebrew autoguider.

I acquired a celestron 9x50 straight through finderscope in trade for an old eyepiece I don't use, and I scored a 'golf ball' logitech webcam, which I promptly gutted after determining that it functioned, reducing it to a little 1.5 x 1 inch PCBA with the camera chip on one side, and the USB cable on the other side.

Astrophotography... I resisted the lure of this for years, knowing I'd be sucked into a spiral of spending money on toys :)

Last episode, I got my hands on this lovely old Celestron-Vixen C80-SP, a nice Made-in-Japan 80mm f/11 achromat on a Super Polaris mount with a heavy duty wood tripod. Right now, I'm mostly using it for piggyback photography with a DSLR.

The SP mount had no polar alignment scope, but I read on a forum that the current Celestron CG-5 / Synta EQ5 polar scopes fit. So I ordered a polar scope off ebay, and it works perfectly. Like it was meant to fit there. I guess Synta really did copy the SP and GP right down to the thread sizes. The mount is much easier to align now, I got polaris in there just so, and I had minimal drift error over 15 minutes on Orion.