Solved! Round stars and other recent learning....

[StargeezerTim]

Just checked my subs from last night and discovered some round stars, not oval, or square or triangular but round! I seem to have tried all sorts of things to cure this but it turns out it was my primary mirror being too tightly held in by the three screws. I slackened them off yesterday (they may be too slack now) and...Voila.. round stars this morning!

I will go ahead and put another screw hole in my eyepiece holder, as advised here, not least because I ordered the screw tap and and a workmate bench (with doubled up tesco clubcard points!). Never thought that simple round stars could make a 60 year old geezer so happy. 

I wait to see if slackening the screws also cures my rogue diffraction spikes, though that is a minor issue.

I have also learnt recently that, for me at least, 12 X 5 min subs is much better than 40 X 90 sec subs. iso 1600 is OK to use, and including cloud affected subs in a stack has a disproportionate effect on the final image. I hate doing it, but being severe on leaving out sub standard subs really improves the final image.

The last bit of recent learning is not to always blame new bits of equipment for problems. I thought my star issue was to do with a faulty coma corrector but turns out it was nothing to do with it.

And I won't even start talking about the weather! Must process my first round starred image soon. It feels like having a new scope!   Tim. 

[Scott]

glad things are working now Tim. In my experience, it's more oft a faulty operator thanfaulty equipment

[Astrosurf]

Excellent! It feels so good when things start working.

Alexxx

[Tinker1947]

Nice to see the plan coming together, well done.

[ollypenrice]

As a rule of thumb pinched optics give triangular stars. There are other effects too but, as a rule of thumb, it's a good one.

Olly

[Leveye]

Got to love it when things just work!. My Newt had pinched optics and I ended up removing the clips altogether and siliconing the primary onto the basket. It cured the issue 100 percent. No mirror flop either and having to re- collimate so much.

[StargeezerTim]

Got to love it when things just work!. My Newt had pinched optics and I ended up removing the clips altogether and siliconing the primary onto the basket. It cured the issue 100 percent. No mirror flop either and gaging to re- collimate so much.

What a great idea!

[MarsG76]

Yeah, I know the warm and fuzzy feeling when you solve a issue that was bugging you for a while... I agree with the longer exposure subs being better then the many short subs... The longer exposures is how the photos reflected from the fainter matter is captured... No amount of stacking or gain can compensate for that.

[Pete Presland]

Always nice to read a good positive experience!

Sent from my GT-N7100 using Tapatalk

[Shelster1973]

Congrats on solving this.  I had similar after removing my primary for cleaning and re-spotting.

Didn't think that I had over tightened but had

[Shelster1973]

Got to love it when things just work!. My Newt had pinched optics and I ended up removing the clips altogether and siliconing the primary onto the basket. It cured the issue 100 percent. No mirror flop either and having to re- collimate so much.

 You sir are a very brave man...although I am now tempted to try this, but am a wee bit scared to give it a go as do not want to bork the primary.

Which silicone did you use and how much.....