Iris Nebula with Zenithstar 73

[Peter Reader]

First night out with my new-to-me Zenithstar 73 and the 73A field flattener.

76 x 3 min 

I'm not hugely impressed witht he flattener, can anyone else put this performance into contect? Is this the best you can get with Zenithstar 73 in terms of flat field? Sensor is APS-C.

[Stuart1971]

Hi,

Nice image, regards the flattener, have you got the distance between flattener and sensor exactly as it should be, as this is pretty critical for most flatteners, also you have to allow for any filters in the imaging train also, rule of thumb is to add 1/3rd of the thickness of the filter to the backfocus distance…

Looking at your stars I would say you need to move the flattener away from the sensor a tiny bit…

This is not for your flattener, specifically, but may help in reading the star shapes as it applies to most 

 

[Peter Reader]

@Stuart1971 thanks, is it possible that the top of the image is too close (flattener needs to move outwards) and the bottom left is too far (flattener needs to move inwards)? Suggesting some tilt?

[Stuart1971]

1 hour ago, Peter Reader said:

@Stuart1971 thanks, is it possible that the top of the image is too close (flattener needs to move outwards) and the bottom left is too far (flattener needs to move inwards)? Suggesting some tilt?

Yes, more than likely…👍🏼