Recently I have had a chance to fine tune my imaging setup due to the great weather I had one evening. This finally gave me the opportunity to get various settings of my guider setup sorted. My equipment for imaging is as follows: Celestron CGEM mount on a pier, Orion VX12 Newtonian, Olympus E-PL5 full-spectrum camera, Orion Thin off-axis guider, Lacerta MGEN autoguider, Astronomik CLS-CCD filter and Baader MPCC III coma corrector.
The Lacerta MGEN has been touted as having a very sensitive autoguider camera. So why am I was finding it difficult to acquire stars for guiding when mounting this on the Orion Thin off-axis guider with my Astrotech 8″ Ritchey Chretien F8 telescope. Even after upgrading my telescope to the F4 Orion VX12, I did not see much improvement in this. That tells me that there was something else in my imaging chain which was impacting on the light getting to the Lacerta camera.
It then dawned on me that the Astronomik CLS-CCD which I use to block light pollution is mounted at the end of the Baader MPCC III coma corrector. Thus it blocks some of the light getting to both the imaging camera as well as the autoguider camera. This loss of light including infrared, could be the reason why my Lacerta MGEN is not picking up guiding stars as easily.
Hence I moved the Astronomik CLS-CCD filter to between the Olympus E-PL5 camera and the Orion Thin off-axis guider. Now all the light from the stars including infrared will be able to get to the autoguider camera, which is great. Now I am finding it much easier to find suitable guide stars, and at much shorter exposures.
With this setup, I have managed to get both the Olympus E-PL5 and the Lacerta MGEN cameras to come to focus at the same point, so adjusting the focuser will get the focus for both. So all I need to do is use the Bhatinov mask to adjust focus on the E-PL5 and then it is done.Also, the E-PL5 sensor is at the recommended 55-56mm away from the Baader MPCC III which means it will work properly to correct for the coma of my Newtonian telescope. Great!
The only issue which is outstanding is that the stars in the Lacerta MGEN camera are ovalish due to the coma effect, as the distance of the autoguider camera to the Baader MPCC III is not ideal. But I can live with that as it still guides well. But I am pleased that it is easier to find guide stars now, which makes my imaging setup workable. Now I just need clear skies to be able to use it.