Weird star shapes

[Ishan Mair]

Hi,

I get these strange star shapes in my subs. The direction of trailiing varies randomly with target position. The polar alignment is not perfect so I am not surprise by declination trailing. But there is lot of RA trailing in most of the 2 min. subs. This problem has appeared suddenly. "star walk" is evident as I go through multiple images. In a set of consecutive images trails are in slightly different directions. RA is very nearly Up-down. Trails go longer with longer subs. Please help with possible reasons or troubleshooting.

Equipment :

Canon 1100D

HEQ5 Pro

Skywatcher 130PDS

A few cropped 2 min subs

Thanks,

Ishan.

[FunkyKoval35]

Backslash.

[Oddsocks]

Hello Ishan,

Your trailing could be because PEC+Sideral is selected but an incorrect PEC program correction is installed or the wrong object tracking rate is selected.

1st place to look is under the handset menu "setup" and ensure you have not accidentally selected PEC+Sideral, lunar or solar tracking rate.

Select standard "Sidereal rate" and try acquiring images again.

If this is better then next, if not auto guiding, is to go back to the same menu and select "Pec+Sidereal" and carry out the PEC programming to reduce RA periodic drift.

If not a handset setup issue then check for a loose RA clutch, loose telescope tube clamps, loose tube mounting to dovetail, loose dovetail puck fixing screws, Loose focuser draw tube, loose camera mounting, ensure no cables are pulling or dragging on the camera or telescope and check the RA worm mesh for backlash, with the clutch tight you should not be able to feel any movement of the telescope when you try to gently rock it from side to side in the RA axis, if there is movement you will need to adjust the RA worm mesh.

 

[glowingturnip]

looks like you've got some vibration in both axes though, judging by the last three frames - is the scope anywhere where it can pick up vibration from people walking past or whatever ?

Are you guiding ?  I presume not

[Ishan Mair]

I will check if there's any backlash.

I am still confused. With nothing changed, I got lot better 3 & 5 min subs (unguided) the previous time I imaged.

Stuart, no I am not guiding.

RA clutch doesnt give enough friction for my mount. I mean the ra axis can be moved(not rocked) easily with a little force. PEC wasnt on...I'll double check and give pec training a try.

Thanks,

Ishan.

[glowingturnip]

RA backlash won't be an issue if you're not guiding, because the RA motor will always be pushing.

I still think you have an external source of vibration from somwhere to get those kind of trails, showing vibration in both Dec and RA.  PEC won't fix any errors in Dec either.

Is the scope properly balanced ?