Author Topic: Another M27  (Read 4279 times)

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MarkS

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Another M27
« on: Jun 09, 2008, 21:46:59 »
Here is M27 taken under less than ideal conditions on Sunday night:
1) M27 was low in the sky
2) The sky was a bit dewy
3) Ambient temperature was 19C (a bit too high for the Canon EOS 300D) -  first day of Summer!!!

120min total exposure in 4 min subs with Astronomik CLS filter.  Final image is scaled by 2/3 and cropped.

This image will be used for comparison purposes once I have modded the 300D.

http://gallery.orpington-astronomy.org.uk/albums/userpics/10046/m27_080608.jpg


« Last Edit: Jul 21, 2008, 22:45:17 by MarkS »

Rocket Pooch

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Re: Another M27
« Reply #1 on: Jun 10, 2008, 08:04:05 »
thats actually a lot better than some mono ccd'ers get, well done.

Fay

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Re: Another M27
« Reply #2 on: Jun 10, 2008, 09:28:37 »
Excellant Mark. Can't believe you got that with your Canon. Obviously good things to come!
It is healthier to be mutton dressed as lamb, than mutton dressed as mutton!

Mike

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Re: Another M27
« Reply #3 on: Jun 10, 2008, 10:00:44 »
Tracking or stacking is off slightly as the stars are ellipses but it's a great image for a DSLR.
We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology. Carl Sagan

JohnP

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Re: Another M27
« Reply #4 on: Jun 10, 2008, 10:25:46 »
Yep - have to agree Mark - that's very nice - John

RobertM

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Re: Another M27
« Reply #5 on: Jun 10, 2008, 11:21:09 »
It certainly is exceptional for an uncooled camera but I'm sure it will be much better after the Ha mod.  I'm really looking forward to seeing the post mod result...

JohnP

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Re: Another M27
« Reply #6 on: Jun 10, 2008, 13:51:56 »
I did a quick test last night with my Atik 16ic on m27 - I took a couple of frames each with CLS & then with Ha - amazing the difference between the two images. I'll post soon.

Cheers,  John

MarkS

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Re: Another M27
« Reply #7 on: Jun 10, 2008, 21:00:26 »
Quote from: Mike
Tracking or stacking is off slightly as the stars are ellipses but it's a great image for a DSLR.

It's the guiding that's at fault - it's not keeping the guidestar precisely central.  It drifts slightly from time to time.  I'm using PhdGuiding and the lead that runs from the serial port to the handset of the EQ6.

Do you think it would it perform better if I used a lead to ST4 port instead via the handset?

Mike

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Re: Another M27
« Reply #8 on: Jun 10, 2008, 22:30:18 »
Are you not able to run a cable directly into the mount?
We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology. Carl Sagan

Ian

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Re: Another M27
« Reply #9 on: Jun 10, 2008, 23:15:23 »
I'm reading it that you're using LX200 guiding commands over the serial link. I had a crack at that with my Vixen but never really had much success. I'm inclined to think that the processing time for the mount to react, and the general lack of precision in the LX200 protocol is getting in the way. I've now gone over to using the st4 port on my art285 connected to the guide port on the SS2K. Seems to react better with that...

MarkS

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Re: Another M27
« Reply #10 on: Jun 10, 2008, 23:33:54 »

Yes I'm presently using the serial link to the handset of the EQ6.  I could try a lead direct to the mount instead (the ST4 port) - I just need to buy one. 

From what you are both saying, it sounds like that would give me more accurate guiding.

Mike

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Re: Another M27
« Reply #11 on: Jun 11, 2008, 14:32:20 »
Probably easier and cheaper to make one Mark. I have a crimper you can borrow.
We live in a society exquisitely dependent on science and technology, in which hardly anyone knows anything about science and technology. Carl Sagan

Rocket Pooch

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Re: Another M27
« Reply #12 on: Jun 11, 2008, 21:24:55 »
Mark,

Go EQMOD you do not need a hand controller and it brilliant, I can guide sub pixel for ever and hop stars etc with it, if you want to have a look pop around.

Chris

Also you do not need a ST4 cable.

And you can control the telescope from 20 meters using a rumblepad.

RobertM

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Re: Another M27
« Reply #13 on: Jun 12, 2008, 09:10:15 »
Another excellent image Mark, you're really on a roll at the moment.  You do need to sort out that guiding, ideally you only want corrections in RA so that means perfect polar alignment.  I'm not sure about EQMOD but some mounts need an ST4 type control connection so the guider can control the mount motors directly.  Reactions are quicker and proportional to the movement needed whereas if you have guide software controling the mount then the correction pulses are for a fixed time/distance movement.  This can lead to over/under correction especially if the mount only accepts guide commands on a periodic basis.  Don't forget that a guide correction is only needed if the guide star has moved and so by definition there will always be some trailing however small and insignificant (which is what you are after).

Robert

MarkS

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Re: Another M27
« Reply #14 on: Jun 23, 2008, 06:47:09 »

I now have an image taken last night with my DIY modded EOS 300D.  Below are the "before" image (on the left) and "after" image (on the right):



Both images are 24 x 5min and I've tried to scale them so the nebulous blue is looks approximately the same in both.

Some comments:
1) In the "after" image I had to reduce the red component by a factor of 2.5 to prevent it swamping the image.
2) The blue looks less noisy in the "after" image.  This is because last night the temperature was cooler (16C vs 19C) and also the wind helped cool the camera.
3) The stars in the "after" image are more elliptical because of the gusting wind last night.
4) All stars appear brighter in the second image - some dramatically so.  It is very noticeable against the nebulous blue.