M20 Trifid Nebula

[Startrek (Martin)]

Finally Imaged M20 last night after an aborted attempt the previous night due to very poor seeing and heavy dew etc
75 x 2 minute dithered guided subs
20 x darks
6” f6 Bintel newt on a HEQ5 mount
Canon 600D with Baader coma corrector
PHD2 guiding ( 1.30 to 1.50 arc sec error )
EQMOD and Stellarium for Goto and tracking
BYEOS
Stacked in DSS
Processed in Startools

Finished at 1.30am this morning
I noticed my focus drifting towards the end of the session when my scope was pointed West about 20deg above my neighbours roof line.They leave their Air con running all night so I assume there is some residual heat rising from the house ( a big 2 storey brick home ) I noticed my focus was drifting off a bit on the last 10 subs. I assume it might be due to the heat rising off the house as M20 was still at around 45 deg when I finished. Maybe ? Who knows?

Thanks for looking, comments most welcome

[xelasnave]

Very nice Martin.
I think you are probably correct as the the neighbours but it could be just because you are plowing thru more atmosphere.
Anyways very well done and goes to show again what a great night you have there with your scope.
Alex

[muletopia (Chris)]

Hello Martin,


Nice picture but I am taken aback by your guiding RMS size, I think you had to work pretty hard in Star Tools.
Your subs are much shorter then the PE cycle for your mount (to 6 minutes?) so PE jumps should not effect many frames.


It takes extremely poor seeing to generate such large errors, another cause can be poor polar alignment.
I don't know how you polar align but my path on this subject is as follows.
A HEQ5 with EQMOD & Stellarium. I had no joy with PHD2's polar alignment so I went to DARVE drift alignment. This took half an hour to achieve a reasonable alignment an an hour + to get a good alignment. PHD guiding assist then approved of the alignment.



Then a revelation, Polar Align tool in Sharpcap. Ten minutes with reasonable seeing to have a combined RA error of 15 arc seconds, quite possible to reduce this but it is seeing limited.


This good alignment has two benefits, the guiding corrections do not have to correct for large PA error and thus The RMS is smaller leading to tighter stars. Secondly I find no discernible field rotation in two hour + imaging runs.


Typically my RMS values are in the range .35 to .45 arc seconds . On good nights it can be as little as .25 and on bad nights up to .65. If it gets up to .7 arc seconds I give up on photography for the night and do visual on bright objects.


I fond setting up Stellarium and Stellarium Scope a chore and much prefer to use Cartes du Ciel as my planetarium for go to, it has extensive catalogues which can be added to. I never did use the electronic setting circle goto with EQMOD but I have used the equivalent in my mount control software (sidereal technology servo controler2) for objects not in the loaded catalogues.


This is from a beginner who has much to learn but I hope it helps somehow.


Chris

[Startrek (Martin)]

Thanks Chris
I’ve never guided on my HEQ5 mount mount below 1 arc sec total even on a great night of seeing and all my subs have nice round stars to edge of field
I don’t start getting distorted star shape until I’m up over 2 arc sec error
I use the Syncan polar alignment function which takes anywhere from 10min to half an hour to get PA. Star stays in target crosshairs for 3 or 4 minutes before get noticeable drift
EQMOD and Stellarium is great for me , I can find objects in minutes , it’s so accurate , only takes me 1 minute to connect
Startools is great to , easy to use , I use short subs in Sydney due to the light pollution, I dont do narrowband or use filters, Startools wipes away most of the gradients and vignetting etc...

Thanks for your comments

[Startrek (Martin)]

Chris
Here’s some photos of my M42 capture earlier this year in Sydney
PHD2 guiding 1.50 to 1.70 arc sec error
2 minute subs
Image of M42 nice round stars

What scope are you using ?

You mentioned you would give imaging away after 0.70 arc sec error

That’s strange because I’d give anything to get under 1 arc sec

Note we do have a high Jetstream running across Sydney during winter months sometimes up to 125kt which does have an affect your guiding


Cheers

[Jasp05 (Aaron)]

I can also vouch that getting under 1 arc sec RMS on the HEQ5 seems quite tough to do at times.

My best guiding was at 0.7 RMS but generally average somewhere between 0.8 and 1.2.

I have spent a considerable amount of time playing with my mount, regreasing, new bearings, worm mesh etc just to get to this point.

and by all my research done, you must be extremely "lucky" and got a very good set of worm and ring gears to run that low.


I would like to know if you use a guidescope or are you off axis guiding? Also how old is your mount?

but if that's what your mount is guiding all I can say is - I'm a little bit jealous of your results.

Edit: I just checked your profile to see what gear you use Muletopia (Chris) - A Mesu 200. I would probably be disappointed if my mesu was guiding at 0.7 arcsec RMS also

[Startrek (Martin)]

Aaron
Mount is 2 years old
I use an Orion 50mm guide scope with helical focuser which replaces my finder scope when I’m guiding
My guide camera is a ZWO ASI120 MM

[muletopia (Chris)]

Martin,


Scope Mewlon 210, focal length 2415 mm.

As it has moving mirror focus I use off axis guiding with a zwo 120mm
Imaging camera Canon EOS 60Da.


My recent post (here in beginners) of HCG 63a wast taken with RMS between .28 and .34 arc seconds, the subs are 16 minutes long. Plenty of coma from the uncorrected Mewlon but round stars away from the edges.


I found my RMS decreased to its present level when I went to off axis guiding.


Chris

[Startrek (Martin)]

Chris
You have some very good equipment there so I can understand your achieving such good guiding figures , almost flat lining
My set up is basic entry level
Scope $299
Mount $1200
Camera $0 my wife’s Canon 600D
Guide camera $230

Under $2000

With such a budget set up Im extremely happy with my images so far and can only improve as time goes on

Cheers

[muletopia (Chris)]

Martin,
Yes good gear sure helps but I set out with a HEQ5 PR0 and even with EQMOD I found it frustrating. The Mewlon was just too heavy for it . My wife built herself a wooden 6 inch f5 newtonian, perhaps 1 third the weight of the Mewlon,total cost two mirrors and a focuser from Bintel.


That now rides on the HEQ5 and the mount handles it with ease, but she is not into asto photography (just woodwork) so I can't give an RMS figure for this setup. But PA with Synscan 3 star and polar alignment is easy.



The other thing which helps no end is a pier, it makes for an absolutely steady scope.
My pier is described at
http://www.iceinspace.com.au/forum/s...d.php?t=135400



A neighbor supplied the steel and built it for me at no cost, I had helped him significantly in the past!


It took time to arrive at this configuration, my active limit now is my lack of processing skills.


Chris

[Startrek (Martin)]

Chris
Give Startools a try , you really can’t go wrong with it , there’s no levels and curves and histograms to tweak and you always get a reasonable result
I like how you you can go back and forth and sweeten your processing to taste
It’s definitely not a sophisticated program and designed to get beginners up and running but also some very advanced features also. It also has some higher level modules to use if you want
Check some of my image posts in beginners over the past month or so , all processed in Startools
Cheers