M13 - 22 May 2011 00:00 to 02:30 BST

[The Thing]

LX90 8" UHTC Baader Alan Gee II Telecompressor, Canon 350Da, Astronomik CLS-CCD clip filter, Lakeside Focuser, Bahtinov Mask, Dunc's Collimation Mask, Meade 8x50 FinderGuidescope & QHY5, PHD Guiding, APT Astro Photography Tool, DSS Live to monitor and stack subs as they are saved ('cos it's there!). And the main difference - HEQ5 Pro, EQMOD, CdC.

Processed in DSS using groups. 9x300s, 8x120s. 1737 x 1157  Pixels (2.01 MPixels) (ROI from full frame) resampled to 1024 X 682 no sharpening. Still got some rugby balls floating around the sky but that was undoubtably due to the wind and mount niggles (see other thread).

[Fay]

One of your best Duncan!!!!!!

[MarkS]

Very nice Duncan!  Definitely one of your best.

You've captured the different star colours very well without burning out the core.  However, overall I think it is slightly too pink.

A good result for a light-polluted location.

Mark

[Carole]

Thats looking very promising Duncan, you've captured some good colour in the stars.  I think the background needs to be darkened slightly.

Well done

Carole

[The Thing]

Thanks for the kind comments.

I have tweaked the colour and increased the gamma for a bit more sparkle. If I had some decent image software to hand I would give it a little unsharp mask as well. Hope this improves matters! Image processing is such a subjective thing.

[The Thing]

I had another go after 'exercising' the mount around both axes several times - now have a £5 gamepad which make this more fun. Guiding is now better but there are some lumpy areas which must be gungy gears or something.

So here is last nights effort at M13 - 19x300s + 26 x 120s at iso800. Same equipment. Stacked 36 40 frames (2h1220m, 90%) in DSS using groups. I am very pleased with the star colours. However I still have radially elongated stars, they are terrible towards the edges. Would that be the flattener/reducer spacing???

Updated image with better tweaking...

[mickw]

Getting more detail but colours look a bit weird, looking good though

[Mac]

Looking good,

Mac.

[Fay]

well a good basis is there Duncan, that's the main thing, colour is cosmetic................................

[MarkS]

So you have 2 night's worth or data now?  Can you combine it all into a single image?

Radially elongated stars are a feature of SCTs caused by astigmatism.  Most focal reducers make no difference to this. However www.teleskop-express.de do sell one that does make a difference - I plan to order one for my C11.  But it only reduces down from F10 to F8 and you do have to maintain a very precise distance from reducer to CCD.

Mark

[The Thing]

The second image is one nights data, the first a different nights data. I didn't combine them as the firat nights subs were not nearly as good, a couple might be OK.

I may try my Meade focal reducer next time the skies clear.

The colour looks fine to me on my laptop and my Fiona says the colours look fine to her - but I haven't calibrated it since I re-installed Vista so maybe you lot are seeing soemthing different.

[JohnP]

Looking very nice Dunc & colours showing through well. Like you say if you can sort out the elongated stars you'll be there... John

[RobertM]

Tracking looks really good despite what you say.  The core looks a bit saturated but the colours are looking much better.  I think that focal reducer is the main problem now.  Have you contacted Baader to see what results you should be able to get with it ?

Like Mark, I have my eye on the TS 0.8 reducer corrector but it only reduces the focal ratio to f/8 which is still quite slow.

Robert

[The Thing]

The trouble with tracking is you look at the PHD graph and it looks like things are all over the place. One minute there is an rms of .11 then it's .75 and so on. It's definitely cyclical and I won't be happy until I've stripped the axes down, cleaned and re greased the cogs. If it's the same after that I'll know I wasted my afternoon!

[RobertM]

I can't believe it's that bad! I was getting 0.02 pixels at DSC with a finder guider so there must be something else going on.  The usual questions:

Is it balanced correctly
Any breezes at the time
Is everything firmly fixed together
etc, etc...

If you need a hand with the strip down then let me know.

Robert

[The Thing]

Hi Robert,

Tuesday night had very little air movement, I double checked everything was balanced and well done up and that the cables were free and wouldn't catch anything.

I wish I had logged the guiding numbers or print screened the graph, someone might have been able to say - 'Oh yes that's the xyz being unflanged by the doodab' or something. I love these little mysteries, it would be boring if it all just worked perfectly!

[mickw]

Duncan, there is a setting you can/should change in EQMOD that stops weirdfulness happening with guiding

Change the default figure in Ascom Pulse Guide Settings to .5 or 5 (can't remember which) Chris told me so he'll know the correct value

Here's the menu screen - see top right
http://eq-mod.sourceforge.net/eqaindex.html

I

[The Thing]

HI Mick,

I tried upping the setting from the minimum (as it installs) 0.2 to 0.3 and it made things worse! Maybe I wasn't brave enough.

[mickw]

Must have been .5 then.
Definitely improved the wayward guiding issues - IRC the pulse guide setting slows the mount down enough so it receives the command from the guider before moving

[Rocket Pooch]

Hi,

The reason for upping it is to do with calibration and guide pulses, if you galibrate with a higher number in EQMOD the stars move further and the accurate angle and rate of movement can be recorded.  Thats all.

I guess you could fiddle with PHD calibration timings?

Chris

[The Thing]

Hi Chris,

I had already set the PHD callibration timings to 2500ms to compensate for the short focal length (190mm) finder guider scope to get the full 25+ pixel movement required in around 12 steps. Of course that doesn't affect the actual guiding. I will try increasing the EQASCOM setting and see what happens.

[The Thing]

Yet another M13! The setup is the same with 34 of 38 subs stacked, 6x300s + 32 x 120s (EQMOD crashed doing the 300s subs).
The major difference is a 5mm T spacer between the Baader SCT to T mount unit and the Canon adaptor. And lo, there were round stars! (maybe no quite round enough for you perfecionists!). The remaining mis-shappeness I think is now just guiding jumps and jitters as described.

Thanks to Mick and Chris for the EQMOD Rate setting - not 0.2 use 0.5! Makes calibration of PHD a lot quicker too.

Full size image here (1.8Mb)
Here is the same crop as before:

[JohnP]

Wow Dunc - looks tons better - nice one. Bet you are feeling chuffed with that - John.

[Fay]

Great Duncan, I am going to reprocess mine now, as it does not look too good!!!!!!

[MarkS]

Duncan,

That's much better!  Those stars have a much better shape now.

Mark

[Carole]

That's definitely the best one.  The core is showing more detail and the stars are nice and round.

Carole

[mickw]

Much better Dunc

[RobertM]