are my stars too large

[iwols]

well just moved over from my 400mm scope to my 2032 mm c8 edge which might not help ,do you think my stars are large or is it that im just used to my 400mm scopes images,scope was focused well ,any comments please,its a 300sec lum sub stretched  thanks

 

[ollypenrice]

Yes, they're a bit big and a little distorted, probably just because collimation needs a tweak. It should be easy on an SCT with spherical primary. They are slightly cometary with upward pointing tails. For some reason most SCTs used for DS imaging do produce rather large stars but they can be held down in processing. Here I tried to reduce their size and render them round using a couple of Photoshop tweaks. This is just from a screen job so it could be done much better on the TIFF.

Olly

 

[iwols]

thanks olly,still trying to get the collimation bang on ,would you say my backfocus  and focus look ok though,will give it another go tonight.Just looked on astrobin and seems common with the c8 edge on the cigar galaxy size wise

 

 

Edited May 6, 2021 by iwols

[rickwayne]

It does look a bit soft to my eye, I  don't see doughnuts but I do wonder about the focus. Are you using a quantitative metric for that?

Just for kicks and giggles, I also  took a run at the  JPEG, using Topaz Sharpen AI and  pulling the  slider over till it screamed "please don't  hurt  me". It did yield a bit more detail, at the cost of my burden of guilt.

[ollypenrice]

On 06/05/2021 at 14:22, iwols said:

thanks olly,still trying to get the collimation bang on ,would you say my backfocus  and focus look ok though,will give it another go tonight.Just looked on astrobin and seems common with the c8 edge on the cigar galaxy size wise

 

 

Until you have collimation nailed I don't think it's possible to comment on focus but I don't see any reason to doubt backfocus here.

Olly

[Alien 13]

Its odd but looking at the realy dim stars some looked to have focus nailed and some off...

Alan

[michael8554]

Simple answer:

The same star with your 400mm scope and with your 2000mm scope, the star in the 2000mm scope will be 2000/400 = 5 times larger ?

I know all stars are point objects to our measly little scopes, but optics come into it too.

Michael