LMC in 3nm NII with New Guiding Method

[avandonk]

I still had slight flexure between the 100ED guidescope and the RH200. It was a slow creep especially near the SCP where the sideways forces due to gravity had the greatest rate of change.

I dug out a TAL finderscope and mounted it directly to the frame around the camera. This finder has a FL of about 180mm and is held in adjustable rings on a single leg. With the Lodestar it guided very well.

Here is the first image 6MB

http://d1355990.i49.quadrahosting.com.au/2012_12/LMC_NII_NG.jpg

As you can see this is about as good as it gets until I eliminate another lesser problem.

10 x 16 minute exposures in NII.

Cannot show you a picture yet as my XP laptop died with a power failure and my Canon 20D software will not run on Win 7.

I reckon I have just about got this system tamed!

Bert

[allan gould]

Great detail in that image Bert, you certainly appear to have the beast tamed and it's a delight to pan around and see exactly what is present. That SN remnant mid LHS really stands out to me and would make a great detailed image on its own.
Many thanks for posting.
Allan

[Martin Pugh]

Not really possible to assess a jpg Bert.

Post a Fit, or tell us what the FWHM was on the best frame of the stack compared to your previous guiding solution

Martin

[avandonk]

Here is the unstretched stack Martin. It is upsized by 1.5x before stacking so it is about 2' per pixel. 27MB

http://d1355990.i49.quadrahosting.com.au/2012_12/LMC_NII_.zip

I thank you before for any advice.

I do not bother with FWHM as it is too arbitrary. When battling with a mix of misalignment, flexure and focus issues I can only nail down one issue at a time.

Bert

[Martin Pugh]

Understand you are still resolving issues, but what metric are you using to assess progress as you continue to fault find if not FWHM and stellar 'flatness' across the ccd?

FWHM is a very close approximator to the seeing conditions at the time. It is irrelevant whether you are imaging at 0.5 asp and your local seeing averages at 2". So, if a 5-10 sec unguided image taken at the RA/Dec of your target yields an FWHM of an on axis star of 2.5", a light frame of 5-10 mins should yield an on axis FWHM of 2.5" +\- 15% with stellar flatness less than10%. That should be your goal. To get there, you have the unenviable task of finding and eliminating the causes.

This is why hi-res astrophotography is difficult and why beginners start off in the low resolution domain

Martin


Martin

[Peter.M]

Assuming same conditions ( sub length, target, ect ) I would have thought relative fwhm values to be a great indicator of individual variables performance.

[gregbradley]

That's a clever guiding solution Bert. Well done.

Greg.

[Regulus]

This is another very good photograph from you. Thanks for sharing it.
Trevor

[Ross G]

A good looking photo Bert.

Amazing detail.

Ross.