Success! I went back to the telescope and tried to get the guider to plate solve. (See last entry). Unfortunately the peripheral stars in the field I think are too distorted and probably not enough of them to get a consistent solution. I did get it to work sporadically but this was not going to be sufficient to get the job done. Went to plan B which was to remove the spectrograph and put the regular focuser back on, then proceeded with the mount pointing model and polar alignment with the imager, the Atik 460EX. In other words, I did the mount calibration the usual way with the main camera like we do in the case for regular imaging. After we got a decent pointing model and more accurate polar alignment, I reattached the spectrograph. Moving around the sky confirmed satisfactory pointing accuracy. The star shows up in the guider field consistently. Although not centered, it was a simple matter to center the star using the cross hair in the software program. Interestingly, the spectrograph slit in the guider field is easy to see now due to the waxing gibbous moonlight! Thank you Moon! I found it was very easy to place the star onto the slit even if it was slightly off center! Next step was to test the guiding capability . I calibrated the guider on the target star because that is typically the brightest star in the field and the software will default to that if you select a dimmer star. Great! I see the calibration is successful. I select a star in the field other than the target star and start guiding! So the target star starts on the slit and lets see if we can keep it there after 10 minutes. Looks like we can! Now the guiding accuracy is OK. Generally we are staying under a pixel error but because of the moonlight probably there is a lot of noise that perhaps fools the guider thinking those pixels are part of the star (see image below). Looks like we are ready to take our first test spectrum! I slew to a nearby medium bright star, 4th magnitude. I’m not sure about the spectral type but this is a test. The star is centered manually. Guide star is selected and we start the guiding. I start a 10 minute exposure on the imager and wait…………..Image download……….A stellar spectrum is seen on the screen!!! I have never been so excited to see a thin streak of light across a computer screen. It actually works!
So this is a star in the constellation Cygnus which has a Hipparcos catalog number HIP106481 (see below). Turns out it is a “G” type star and as you can see there are lots of absorption lines. For now we won’t worry about what it means but we celebrate a successful spectrum acquisition! Next we slewed to the star Alhena in Gemini which I know from my early spectroscopy experience with a simple grating called a “star analyser” that it is an A0 star with a strong H alpha absorption line. After a 5 minute exposure there I was able to recognize a distinct absorption line which must be what we’re looking for. Won’t know for sure until we process it but I would say we are moving along pretty well now! Looks like we are ready to do a full project including calibrating and processing. Onward and upward!
Thanks for reading!