Star shape with SW esprit 80ed

[Dave kay]

Hi folks,

 

I'm looking for some advice about my SW esprit 80ed. 

I've had it for a few months and have only just started taking longer exposure pictures with my guided mount and the dedicated field flattener. 

I've uploaded two images:

1) my bahtinov mask focus with 30 sec exposure

2) 30 sec exposure of Vega without mask. 

Is there a reason why the stars are not perfectly round? Not sure if it's something I'm doing wrong or one of the lenses is out of line. 

Any help / advice would be much appreciated. 

[david_taurus83]

Are these cropped images? What camera are you using?

[Dave kay]

Yes they are cropped. I'm using a canon 7d mark 1. 

[david_taurus83]

They look pretty round to me. The smaller ones look square and blocky as they are probably undersampled. Have you taken a series of images and stacked them?

[Adam J]

2 hours ago, Dave kay said:

Hi folks,

 

I'm looking for some advice about my SW esprit 80ed. 

I've had it for a few months and have only just started taking longer exposure pictures with my guided mount and the dedicated field flattener. 

I've uploaded two images:

1) my bahtinov mask focus with 30 sec exposure

2) 30 sec exposure of Vega without mask. 

Is there a reason why the stars are not perfectly round? Not sure if it's something I'm doing wrong or one of the lenses is out of line. 

Any help / advice would be much appreciated. 

 

I am assuming that it is the chunks out of the star halo that you are concerned about?

 

[Ken82]

This looks like lateral chromatic aberration to me. 
 

Split the RGB channels and see how they line up. you could then potentially realign to the green channel which should scale the red and blue. 
 

I think you will find red and blue are at different scales (very slightly) 

Can you post a full sub for download? 
 

ken 

[Dave kay]

1 hour ago, david_taurus83 said:

They look pretty round to me. The smaller ones look square and blocky as they are probably undersampled. Have you taken a series of images and stacked them?

Just one off images of Vega. Done some basic stacking of m31. 

[Dave kay]

57 minutes ago, Adam J said:

I am assuming that it is the chunks out of the star halo that you are concerned about?

 

Yes, thought it would be a perfect halo all round. 

 

[Dave kay]

43 minutes ago, Ken82 said:

This looks like lateral chromatic aberration to me. 
 

Split the RGB channels and see how they line up. you could then potentially realign to the green channel which should scale the red and blue. 
 

I think you will find red and blue are at different scales (very slightly) 

Can you post a full sub for download? 
 

ken 

 

[Ken82]

5 minutes ago, Dave kay said:

 

Hi

sorry i meant a fit file or equivalent. 

If you zoom into the image you will see a general rotation of colour around the edges this is the lateral colour. First hand looking at your low resolution jpeg its not too bad but there is clearly a residual chromatism issue with the star in the middle. It could be a combination of a little lateral chromatic aberration and longitudinal chromatism. 

The Esprit scopes are generally excellent for this TBH. Where did you buy it? Its always worth getting ES to check it out at FLO first. It could be a slight misalignment of the triplet lens. 

Ken 

 

[Adam J]

2 hours ago, Dave kay said:

Yes, thought it would be a perfect halo all round. 

 

Well one thing is certain and thats is you have a tone of sensor tilt and so its hard to say. The sensor tilt is most likely causing your elongated stars though. In terms of the dark bands in the halo that is caused by clips in the light path or sometimes on the Esprit 80 its a notch in the lens buffer ring. Either way I would discuss with your supplier as its not normal. The sad thing is I have seen lots of this from the Esprit 80 recently.

Here take a look at this thread.

https://www.cloudynights.com/topic/691489-poor-stars-with-esprit-80ed/

Adam

[Dave kay]

7 hours ago, Adam J said:

Well one thing is certain and thats is you have a tone of sensor tilt and so its hard to say. The sensor tilt is most likely causing your elongated stars though. In terms of the dark bands in the halo that is caused by clips in the light path or sometimes on the Esprit 80 its a notch in the lens buffer ring. Either way I would discuss with your supplier as its not normal. The sad thing is I have seen lots of this from the Esprit 80 recently.

Here take a look at this thread.

https://www.cloudynights.com/topic/691489-poor-stars-with-esprit-80ed/

Adam

Thanks for the advice Adam. Looks like the my scope has the same issue as the one in the thread. I'll be getting in touch with FLO about it to see what they recommend. 

Dave. 

[Dave kay]

Hello again folks,

So I went out again on Monday night and took the following images of Vega. One with bahtinov mask and then three guided images at 30, 20 and 10 secs. What do you think about star / halo shape and possible chromatic aberrations? Thanks for any input you can offer me. 

 

Dave K. 

IMG_6070.CR2 IMG_6069.CR2 IMG_6067.CR2 IMG_6065.CR2

[Synchronicity]

I bought my Esprit 80 2nd hand and it had already been back to FLO for Es Reid to check after the previous owner saw issues.  The attached was Altair taken September last year with my Canon 7d Mk1.
Because it had been checked I assumed that this was something to do with saturating the camera but reading this thread has got me wondering.

Raw file below if anyone wants a look.

 

2019_09_20-800-0004.CR2

 

All the best

Michael