FSQ106 coma?

[HunterHarling]

I finally got a chance to test my scope with full frame, and it looks like there is some coma or something. Here is an aberration spotter image...

The brighter stars have spikes also. Does anyone know what this is, or is this normal?

Thanks

[HunterHarling]

Here is a different field after stacking:

It looks acceptable to me, but given that the FSQ has an 88 mm imaging circle, should this be better?

[Rodd]

I had allot of trouble with mine--Things I considered

1) spacing

2) tilt

3) collimation

 

If the stars are deformed toward (or away) from the center in the corners--it is likely spacing.  Tilt of coma would be the same direction across the FOV.  In the end, I sent my scope to TNR and they told me it was miscollimated and they recollimated it.  Even though it passed a star test.  I took a picture of a star and the diffraction rings were concentric and not distorted.  But the test is no where near as accurate as the bench test they do with a laser.  Don't settle.  If it ain't right--it ain't right. People told me that it was so minor that most said they wouldn't bother.  But it ate away at me.  I know it is terrible, but send it in to get fixed.  Was it new--so under warranty?  they like to say that collimation is not covered, but I argued that if a scope arrives new and it is not collimnated--it definitely should be covered--I won that one and they did not charge me except shipping.  They will let you pay using the company account so it will be cheaper--and insured.

I always found that the final images looked much better--you could still see the stars but after integration and channel combination they were much less obvious.  Definitely possible to live with (not for me though). 

Unfortunately, I can't report on the success of the adventure as the scope is still in the box.  But they did a star test and said it was dead on now, so I am not too worried.  I am having too much fun with the TOA right now to make the switch-the FOV will call me though when the big nebulae come back around.

Anyway Hunter-Good luck.  having been there I do not envy your position. 

Rodd

[Tom OD]

I m having issues with mine, but they are different to your problems.

The stars look pinched and distorted. I wonder is something too tight, or maybe a part protruding into the light path?

Do you have a reducer in the path etc..?

The light houses are familiar with the N version, I dont know which one your is. I dont see those lighthouses around the ED versions though.

Tom

[HunterHarling]

Thanks, Rodd and Tom.

It turns out that the adapter I was using was not suitable for a 43 mm sensor. The adapter extended into about 3mm of the light path causing the strange spikes, vignetting, and possibly the pinched stars. Anyway, I have switched back to my ZWO sensor and the stars are perfect. I'm going to stack some images and keep looking...

[kirkster501]

I get this problem too when I am using the reducer - implying the spacing I have is not quite correct.  Without the reducer it is perfect.   TBH, with so few clear nights in UK, I am abandoning using the FSQ reducer and I am going to sell it and the adapters.

For wide field I have moved to Samyang lenses.

[Rodd]

On 03/07/2019 at 16:24, HunterHarling said:

Thanks, Rodd and Tom.

It turns out that the adapter I was using was not suitable for a 43 mm sensor. The adapter extended into about 3mm of the light path causing the strange spikes, vignetting, and possibly the pinched stars. Anyway, I have switched back to my ZWO sensor and the stars are perfect. I'm going to stack some images and keep looking...

See....spacing!!!  I wish that was my problem.  Oh well--all fixed now (I hope).  Full frame must be a dream.  That's teh one advantage of a DSLR--

Rodd