Paul Haese
11-09-2018, 05:00 PM
This is a little off the beaten track. I had a bit of a search on the net and could not find many images of this galaxy and I know why with that whopping great O star (Alnair) in the field.
It took a fair bit of work to get any detail out of this galaxy, as the light from Alnair floods the entire field; that is sort of interesting in itself but not ideal. Though I am quite pleased at the resolving power of this mirror. It seems not to be a lemon from OOUK.
Last night I drove to the observatory and made some changes to the scope setup. First up I changed the Cats Eye collimation triangle to one of the new perforated ones (nuclear symbol). While I was at it I removed the oval shaped edge mask they had on the primary. Its clearly for turned edges but I don't think this mirror has a turned edge. I suspect the shape of the mask was inducing some astigmatism into the mirror cell. Then I reduced the sensor to corrector distance by half a turn. Finally collimated and then did a test image. Interestingly it appears I am very very close to having round stars across the field now. I don't know what sorted the problem but most likely something of each. I then proceeded to do an imaging run on this target.
I had already collected data on this object and had cropped the data because of huge halos and an odd flare in the opposite corner to Alnair. So I added the data I collected last night to the previous data and it resulted in this image.
Click here (http://paulhaese.net/NGC7213.html) for 100% crop.
It took a fair bit of work to get any detail out of this galaxy, as the light from Alnair floods the entire field; that is sort of interesting in itself but not ideal. Though I am quite pleased at the resolving power of this mirror. It seems not to be a lemon from OOUK.
Last night I drove to the observatory and made some changes to the scope setup. First up I changed the Cats Eye collimation triangle to one of the new perforated ones (nuclear symbol). While I was at it I removed the oval shaped edge mask they had on the primary. Its clearly for turned edges but I don't think this mirror has a turned edge. I suspect the shape of the mask was inducing some astigmatism into the mirror cell. Then I reduced the sensor to corrector distance by half a turn. Finally collimated and then did a test image. Interestingly it appears I am very very close to having round stars across the field now. I don't know what sorted the problem but most likely something of each. I then proceeded to do an imaging run on this target.
I had already collected data on this object and had cropped the data because of huge halos and an odd flare in the opposite corner to Alnair. So I added the data I collected last night to the previous data and it resulted in this image.
Click here (http://paulhaese.net/NGC7213.html) for 100% crop.