Quote:
Originally Posted by Peter Ward
A great wide field eta..seeing doesn't affect the data much at 300mm. Sadly for me there is not enough back focus with the STX to use it with camera glass.
BTW I used the Taka 0.73 reducer on the BabyQ recently, which pulls is down to around 300mm as well...have to say the stars from the Pentax glass are very comparable  |
Thanks Peter.
The Pentax 67 and 645 as I recall (I can look it up) have a lot of backfocus for a camera lens. From memory its something like 85mm or more. One of the longest of all lenses which I think is another reason why they have been popular for astrophotography.
Good to know about the lens performance. I have a step down ring on it so its doing F5.17. F4 is fine except I was getting some odd shapes in the blue channel.
Greg.