ASTROPHOTOGRAPHY WITH THE NIKON D70 DIGITAL SLR CAMERA Last updated: 27 September 2005

Prime Focus Astrophotography
During my 24-25 September 2005 trip to Oracle Observatory I did some LXD55-8"SC Prime Focus astrophotography. As noted on the previous Prime Focus page, when doing prime focus or eyepiece projection on faint objects, in the longer duration shots I had done up to this time had some trailing evident due to tracking errors. So I tried out a solution for that on my last trip to Oracle Observatory.

I took the ETX-90 OTA off the fork mounts and piggybacked it as a "guidescope". Since I had the Meade camera adapter for my 8"SC I decided to try that out. It worked OK except that the ETX "sagged" on the front somewhat so I had to support it using a piece of foam. That seemed to solve the problem. (Of course, a better solution, which I may get at some point, would be to use Losmandy rings. For guiding corrections I used the Shutan Visual Back to attach a reticle eyepiece at the rear port or if more convenient, the reticle eyepiece was placed in the normal eyepiece port on top of the OTA.

This worked fine sometimes. But, depending upon where in the sky I was pointing, I had some drive slippage which caused problems in guiding. Apparently, the ETX OTA, the Nikon D70 DSLR, the Maxview II, and the two counterweights were just too much for the LXD55 drive gears. Also, the mirror "bounce" created image vibrations, even in short (1/60 sec) exposures. I used the "hat trick" method for long exposures but apparently that has to be done even for short exposures. This messed up the planet photos I did. I also had some stray light coming in at the end of the exposures; possibly stray light from my red flashlight during the noise reduction process. There is a cover for the camera eyepiece but I hadn't used that. Guess I will in the future.

M57, the Ring Nebula in Lyra
This is a stack of nine 30 second exposures (no manual tracking corrections) using Lynkeos (Mac OS X). Some editing was done in GraphicConverter. Note that the central star can be seen!

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