Whats wrong with my stars?

[simmo39]

Hi

went out again last night to have another go at M57, Im happy that my imaging is improving but my stars seem to have grown ears! does anybody know what the cause is. is trails or vibration or bad collimation?

http://i242.photobucket.com/albums/ff7/simmo_simmons/starz_zpsewn5jmgc.jpg

[peem]

Hi  It looks like coma to me  Ian

[ollypenrice]

That looks like a crop from the shape of the frame. It would be best to post four corners and a centre.

Initial thought for me is collimation but also, perhaps, pinching of the primary?

Olly

[steppenwolf]

I'm on an iPhone so can't see what gear you may be using via your signature. Can we see the full frame and have a description of your imaging train please?

Sent from my iPhone from somewhere dark .....

[MarsG76]

You didn't leave your bahnitov mask on the objective, did you?

[simmo39]

Hi all

my set up is SW 130 pds on a HEq5 mount with a 600d modded camera. im already using a SW coma corrector. here is the hole image:

http://i242.photobucket.com/albums/ff7/simmo_simmons/IMG_0414_zpstipc68km.jpg?t=1440173617

[steppenwolf]

Unfortunately, I can't tell much from this resolution image but based on the first image and from the little I can see in the full frame image, I'd be tempted to check the collimation. The 130 PDS is capable of capturing terrific images with good star shapes and the HEQ5 mount is an excellent match for it so I would expect much better results than those shown.

If the collimation proves to be fine or after adjustment, the problem continues then pinched optics could well be a factor here. This is easy to correct by simply loosening the clips that retain the primary mirror in its mounting cell.

Good luck.


Sent from my iPhone from somewhere dark .....

[simmo39]

Hi.

Will try collimation again and see if its any better, just need a good night to try again.

thanks everyone  for the pointers.

[wimvb]

Hi,

did you solve your problem with the "pointed stars"?

I was just browsing the forum and found this:

http://stargazerslounge.com/topic/251060-solved-round-stars-and-other-recent-learning/

As the stars have a shape similar to yours, I thought it might originate from the same problem: pinched primary mirror.

Regards,

Wim

[StargeezerTim]

Hi,

did you solve your problem with the "pointed stars"?

I was just browsing the forum and found this:

http://stargazerslounge.com/topic/251060-solved-round-stars-and-other-recent-learning/

As the stars have a shape similar to yours, I thought it might originate from the same problem: pinched primary mirror.

Regards,

Wim

The other thing worth trying is using 'mirror lockup' if you don't already.Tim.

[simmo39]

Hi,

did you solve your problem with the "pointed stars"?

I was just browsing the forum and found this:

http://stargazerslounge.com/topic/251060-solved-round-stars-and-other-recent-learning/

As the stars have a shape similar to yours, I thought it might originate from the same problem: pinched primary mirror.

Regards,

Wim

Hi,

havent solved it tottaly but getting better, see here:            http://stargazerslounge.com/topic/251504-had-another-go-with-s-130-pds/  

Will do another colimation and see what that brings (weather permitting ) then failing that look at the primary.

thanks for the pointers

Andy

[Uranium235]

Yep, might be worth a little tweak of the primary. Its not such a scary thing to do, its just a case of leaving a very small space in between the clip and the mirror - as small as the thickness of a cigarette paper (but thats no good reason to take up smoking!).

But other things to check may be the mounting of your camera - is it connected solidly enough? As sometimes it can "pop out" a little when youve tightened up the two thumbscrews. The solution to that is to drill and tap for a third thumbscrew - so you have three 120^o apart. StargeezerTim has done all of this and no longer has any dodgy stars.

[simmo39]

Think Ill have a look and adjust as necessary, Well a least it will give me something to do while the weather is so pooh!. Thanks

[lensman57]

Check the primary retaining pads are not putting too much pressure on the mirror but the scope should be roughly in the same orientation as when you imaged as these look pinched to me . Once this is done you have to do a proper collimation.

PS: Also make sure that the CC-  camera set up can not move under their own weight in the focuser, this may not be so evident as in the beginning of imaging they look solid .

A.G

[simmo39]

Will check them when too, thanks everyone for all the hints and tips. Hopefully will be able to get some good shots as soon as it stops raining.