sorting out 135mm SY

[powerlord]

Hi guys, I was wondering if anyone can help with a SY 135mm..

Im using this lens more and more, but with the asi2600 or worse still the FF 6D, the outer part is really not very good.

Have people got any experience with whether this is fixable ? e.g. sending to 'Professor' Reid.. or is it a case of some optics just not very good ?

here's an example stack.

 

 

[happy-kat]

Is this wide open or what's the lens like with a step down ring is it acceptable then?

[powerlord]

that was wide open or stopped to f2.8 I think.

it gets a bit better stopped to f4, but tbh I've not tried much further than that as it'd be a pain to use much slower.

I've found using it with something like my asi533 is more acceptable as I'm only using more of the centre, but I'm sure others have had sharper results so figured it's just the very variable quality control of these... so trying to work out if the quality control is variable in the assembly (and hence possibly fixable) or in the optics (and hence I'm stuffed).

stu

[powerlord]

So - here's a few subs. Ideas ?

These were stopped down to F4

 

 

[powerlord]

Oh, and I should say, I've used the asi2600 on some of my other OTAs, and those show pin sharp stars all over, so it's not tilt on the sensor or something.

[scotty38]

There's a chap on the NINA discord has gone through 2/3 of these trying to find a "perfect" one so as you say I think variable quality is the big reason. No idea if it can be fixed though....

[michael8554]

Coma and Tilt.

But you should be looking at a single short exposure, to eliminate tracking/guiding errors.

Michael