Funny/Weird stars? - (coma? Collimation? guiding?

[tingting44]

Hi since i have been guiding i have been looking back on my subs and all the starts seem to have this weird trailing in them, at 1st i thought it was down to collimation as it was well out, but i have now collimated it nicely and still getting this same effect no matter what the exposure or ISO i use. I am using a DSLR with SW 130-pds (no coma corrector), HEQ5, EQMOD, PHD (QHY5L-ii)

Here is a whole frames

5min

5 min sub by tingting44, on Flickr

Here are some crops

15sec top left

funny stars - Crop (top left corner) - 15 sec ISO6400 by tingting44, on Flickr

5min top left

funny stars - Crop (top left corner) - 5 min ISO200 by tingting44, on Flickr

10min top left

funny stars - Crop (top left corner) - 10 min ISO100 by tingting44, on Flickr

10min center

10 min sub - (Center crop) by tingting44, on Flickr

as you can see exposure makes no difference, if any one can shed any light on to this situation it will be most grateful

[Knight of Clear Skies]

Looks like coma to me, as the trails are more extreme towards the edge of the frame and all point towards the centre.

[Uranium235]

No coma corrector = loads of coma (which is what you have there!)

Get a corrector, its mandatory for imaging with a newt (even with small cameras), SW or Baader its up to you.

Edit: But I would lean towards the Baader, since it offers more connection options.

[tingting44]

so this is what coma looks like then.............? lol great, thanks guys, *note to self* GET COMA CORRECTOR lol

[Pete Presland]

i felt my 200 PDS was un-usable without a coma corrector, i purchased the sky watcher coma corrector which is produced specifically for this range of scopes.

[tingting44]

i felt my 200 PDS was un-usable without a coma corrector, i purchased the sky watcher coma corrector which is produced specifically for this range of scopes.

yes its pretty unusable with subs like this now that ive got past the 1st stage of getting guided subs, i want decent guided subs now lol

CC's are not cheap tho, is the SW 0.9x one ok?

http://www.firstlightoptics.com/coma-correctors/skywatcher-coma-corrector.html

[Pete Presland]

yes its pretty unusable with subs like this now that ive got past the 1st stage of getting guided subs, i want decent guided subs now lol

CC's are not cheap tho, is the SW 0.9x one ok?

http://www.firstlightoptics.com/coma-correctors/skywatcher-coma-corrector.html

thats the one i use, i was pretty dissapointed to have to spend another £100 to make the scope usable

[glowingturnip]

yep, I have exactly the same, stars look like little Pacman ghosts in the corners, hopeing for a CC for my birthday...

[tingting44]

thats the one i use, i was pretty dissapointed to have to spend another £100 to make the scope usable

yes there not cheap are they with postage and M48 ring its nearly the same price as the 130-pds

yep, I have exactly the same, stars look like little Pacman ghosts in the corners, hopeing for a CC for my birthday...

the DREDDED pacman nightmare isnt it, how long you got to wait till your birthday? get me one too lol

[Knight of Clear Skies]

As a workaround, you could centre your target and crop heavily. Depending on what you are imaging that could work well.

[laser_jock99]

Good coma correctors (well astrophotography in general) are not cheap I'm afraid- if you're planning to use a Newtonian for AP then you need to budget for a coma correct AND good quality collimation tools.

On the plus side a quality coma corrector (and the collimation tools) are like eyepieces and could be used in different scopes if needed. I'm able to use mine in my different Newtonians.