what is this mess?

[matt-c]

Hi everyone i've had my first clear free night since September!!! and finally able to try my new ccd

the only problem....it was a total disaster.

I tried a 15 min sub of the horsehead region and got this 

 

can someone diagnose this disaster? i have my suspicions that its gear related as i heard  a few weird clunks that i hadnt heard before.

My gears been left dormant so maybe i need to strip it down and regrease.

 

any help appreciated, thanks.

[michael8554]

Hi matt-c

Which mount, OTA, guidecam? OAG or guidescope? What guiding software?

Haven't seen "seagulls" like that for a long time.

From the orientation I'd say that your imaging camera was in Portrait?

So Dec is Left - Right in this exposure, and has drifted the width of the wingspan, I'm not clever enough to tell you if this is just poor Polar Alignment.
RA has Periodic Error shown by the sinusoidal shape of the up-down motion.

Guiding this poor would have shown up on the guide graph if you were using PHD.

Noises from the gears may be due to poor balance.

Michael

[matt-c]

Thanks Michael I'll have a double check over the balance and perhaps my polar alignment was off aswell.

 

Weird thing was in PhD I had an initial trace of RA and DEC then it vanished for the rest of the night so I can't even tell you what the graph looked like. 

It showed that the mount was giving constant corrections but no matter what settings I gave It, it wouldn't not come back.

[Tinker1947]

That looks like imagine with a AZ Mount, Redo your PA a couple of times, balance the scope left right and center twice, make sure every thing is tightened down.....the PHD trace goes off the plot when its either or both things out.....

[matt-c]

Thanks tinker that's actually reminded me I didn't complete my polar alignment with eq mod. Im an idiot.

I'd slewed to the correct position but didn't place the star in it.

 

Do you think this could have caused those weird seagulls? I would have though I would just get star trails.

 

Thanks

matt

[Tinker1947]

i would think its a lot of Dec and RA movement like a AZ mount would move, it can only get better......

[opticalpath]

Matt, when diagnosing guiding/ tracking problems, I think an important first step is to get an assessment of how your mount is behaving with guiding switched OFF.  Once you start guiding, it can be difficult to distinguish between problems related to guiding (software settings, cables, flexure, etc), and those arising from basic mechanical problems to do with the mount (polar alignment, backlash, periodic error, gears, cable snags ....) 

I don't use PHD but I'm sure there must be a way to set it tracking a guide star and logging the x-y displacements, but not sending any corrective impulses to the mount.  Then you can look at the 'guide' graph or log to see how your mount is tracking without guiding.  If that reveals any major problems, you need to address those first, before switching on guiding and assessing any guiding-specific issues.

Adrian

[michael8554]

I agree with Adrian.

You could repeat your 15 minute exposure on a bright star with guiding off.

Michael

[matt-c]

Thanks for the comments I'll try that out when I next get some clear skies. 

I'm thinking there maybe something serious at play because I had no RA and DEC readings on the graph.

I also examined it in daylight  and noticed the noise I could hear was the cog actually jumping and hitting the box.

I plan on stripping it tonight cleaning and re greasing it all, fingers crossed.

[ollypenrice]

It looks as if the mount drifted on one axis, had a big nudge in the other axis and then continued to drift as it had done originally. (We have two trails going from lower left to upper right with a kink at about 90 degrees heading down and right. 

It's always best, when framing allows, to align the chip along RA and Dec either in landscape or portrait. Apart from making it easier to add data another night it also makes it easy to see which axis is giving you which problem. Still, can you tell which trail belongs to which axis? (I'd put a loseable sum of cash on the trails aligning with the axes but not a sum I couldn't afford to lose!!)

This has the look of something catastrophic rather than of a steady drift due to polar alignment or unresponsive guiding. I'd be looking for major backlash, for instance, or cables dragging and/or snagging. Some kind of nasty contamination in the gears might also account for it but it seems that you have a problem in both axes. Testing without guiding is, as the others have said, a good idea because it could also be caused by sudden and unwanted guide inputs. Bear in mind that you might have two problems here, not just one.

First off though, how do RA and Dec align so far as the two trailing directions are concerned? This is vital to know.

Olly

[Dave In Vermont]

There should be some sort of award for a picture that bad!

Wow! Thanks for sharing. That took guts!

Dave

[ollypenrice]

17 minutes ago, Dave In Vermont said:

There should be some sort of award for a picture that bad!

Wow! Thanks for sharing. That took guts!

Dave

Awe... I used to like you, Dave!!!! *

Olly

* Still do... 

[matt-c]

Thanks olly I think catastrophic is a good word! 

I stripped my mount tonight and I think (I hope) I've found the problem. My RA gear had some how moved and wasnt meshing correctly causing it to flick itself up into the casing causing the clinking noise I described. So I'm hoping this explains why regardless of sub length I got the same seagull shape. It's all greased and running smooth again just needing a clear night.

 

 

And dave.....thanks.....I guess

[ollypenrice]

I only meant 'catastrophic' as an alternative to 'gradual' since both are out get you when they can! Good to hear that you've found a credible explanation. It sounds plausible to me.

Olly

[matt-c]

Just for anyone having anything similar to this i think the strip down and re alignment of the gears has worked. 

I managed to get 3x15 mins subs this the other night ( i was gonna put it in the deep sky section but i want my first ccd image to be better ) )

 

and also one with a huge stretch showing all my lovely imperfections 

Still not happy with the star shapes but PHD was being a royal pain to calibrate, perhaps due to pointing straight up 

anyway an overall improvement from the horsehead i opened with.

Thanks for everyone's input!!!