something wrong with my askar120apo

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MING ZIWEN avatar
My ASKAR120apo in that case of use a 2600mc camera, the star point is large, and detection by an astronomical box is usually about 4 pixel, and the star point average size is about 3.2 pixel even at the best sight. I don't think this should happen. I need some other user data to compare and communicate with the official customer service. If anyone has some information I need, please let me know. Thank you very much
andrea tasselli avatar
At f/7 it is normal to have a FWHM of that size given that the scope is a refractor. And the seeing isn't that great.
Adam Cox avatar
Hi Ming,

I'm in a Bortle 4-5 location and my FWHM is around 3" on average when shooting in mono with my 2600mm Pro. I can get down to 2.5" in good seeing and 4-5" in bad seeing.

Regards,
Adam
Well Written Concise
Tony Gondola avatar
Welcome to the reality of astrophotography.
Aquawind avatar
Adam Cox:
Hi Ming,

I'm in a Bortle 4-5 location and my FWHM is around 3" on average when shooting in mono with my 2600mm Pro. I can get down to 2.5" in good seeing and 4-5" in bad seeing.

Regards,
Adam

I am about the same with the 2600mc. My focus changes more than my 80ED did so an Electronic focuser is needed.
Tobiasz avatar
3.2 pixel at best with 0,91"/pix sampling is ~3" FWHM. I don't think the telescope is broken, your seeing is just average/below average. Keep in mind there are many factors affecting star size and introducing blur like the quality of your lenses/mirrors, your tracking, guiding and (back-)focus. 

Less expensive refractors introduce softer stars (there is no free lunch). Just check out the spot diagrams of different refractors of different price points and you may see a difference.
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Niels_L avatar
I'm also at around 3" on my 120APO with 1x flattener and 294MC.  On good seeing it is around 2.7" at best, bad seeing it gets to 4".
MING ZIWEN avatar
Tobiasz:
3.2 pixel at best with 0,91"/pix sampling is ~3" FWHM. I don't think the telescope is broken, your seeing is just average/below average. Keep in mind there are many factors affecting star size and introducing blur like the quality of your lenses/mirrors, your tracking, guiding and (back-)focus. 

Less expensive refractors introduce softer stars (there is no free lunch). Just check out the spot diagrams of different refractors of different price points and you may see a difference.

But my actual test FWHM is around 7.5, and 3.2 is just the average star point size shown in the astronomical box
MING ZIWEN avatar
Adam Cox:
Hi Ming,

I'm in a Bortle 4-5 location and my FWHM is around 3" on average when shooting in mono with my 2600mm Pro. I can get down to 2.5" in good seeing and 4-5" in bad seeing.

Regards,
Adam

I am about the same with the 2600mc. My focus changes more than my 80ED did so an Electronic focuser is needed.

I use pixinsight the actual detected FWHM is about 7, and the guidance star and the vision on that day are both very good
Tobiasz avatar
MING ZIWEN:
Tobiasz:
3.2 pixel at best with 0,91"/pix sampling is ~3" FWHM. I don't think the telescope is broken, your seeing is just average/below average. Keep in mind there are many factors affecting star size and introducing blur like the quality of your lenses/mirrors, your tracking, guiding and (back-)focus. 

Less expensive refractors introduce softer stars (there is no free lunch). Just check out the spot diagrams of different refractors of different price points and you may see a difference.

But my actual test FWHM is around 7.5, and 3.2 is just the average star point size shown in the astronomical box

What is your Median FWHM if you check your subs with Subframe Selector? Or when you run the script "FWHMEccentricity"? To be honest I do not know what you want to say with "astronomical box".
andrea tasselli avatar
MING ZIWEN:
Tobiasz:
3.2 pixel at best with 0,91"/pix sampling is ~3" FWHM. I don't think the telescope is broken, your seeing is just average/below average. Keep in mind there are many factors affecting star size and introducing blur like the quality of your lenses/mirrors, your tracking, guiding and (back-)focus. 

Less expensive refractors introduce softer stars (there is no free lunch). Just check out the spot diagrams of different refractors of different price points and you may see a difference.

But my actual test FWHM is around 7.5, and 3.2 is just the average star point size shown in the astronomical box

*Can you post a screenshot of a star field at full resolution. That should clarify where you are.
Aquawind avatar
MING ZIWEN:
I use pixinsight the actual detected FWHM is about 7, and the guidance star and the vision on that day are both very good


I do not use PI atm. I watch it in NINA and the numbers are similar in Siril and APP.
MING ZIWEN avatar
Tobiasz:
MING ZIWEN:
Tobiasz:
3.2 pixel at best with 0,91"/pix sampling is ~3" FWHM. I don't think the telescope is broken, your seeing is just average/below average. Keep in mind there are many factors affecting star size and introducing blur like the quality of your lenses/mirrors, your tracking, guiding and (back-)focus. 

Less expensive refractors introduce softer stars (there is no free lunch). Just check out the spot diagrams of different refractors of different price points and you may see a difference.

But my actual test FWHM is around 7.5, and 3.2 is just the average star point size shown in the astronomical box

What is your Median FWHM if you check your subs with Subframe Selector? Or when you run the script "FWHMEccentricity"? To be honest I do not know what you want to say with "astronomical box".

the midian FWHM is 7.5.
And the astronomical box is ASIAIR
Tony Gondola avatar
If you suspect the optics why not do a star test, that will tell you a lot and is easier than ever to do it digitally.
andrea tasselli avatar
MING ZIWEN:
the midian FWHM is 7.5.
And the astronomical box is ASIAIR


*That's pretty bad if this is the best you can achieve. I'd certainly return the scope if that would be the case.
Well Written
MING ZIWEN avatar
OKeveryone I use the pixinsight did a test in. Here's the test report
Tony Gondola avatar
That's great but posting a full resolution sub frame would tell us a lot more.
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