M51 - RGB - First Test DSO from MN190

[Chris]

Well done for getting what you did Gina, your certainly tenacious, always out grabbing data even when there are slim pickings:D I'm sure you'll be producing M51's like Komet once you've got everything sussed out and perhaps a better guide cam like you say.

Theres always the next bit of kit isn't there Gina:D

Chris

[Gina]

Thank you Chris Seems to me that if you don't grab what you can when you can these days you'll never get anything

Yep! There's always something else

[Gina]

Had another go last night with some clear spells but nothing to show for it Well not quite nothing - some experience but no M51 images or any others. There may have been thin high cloud or the wind and I don't think the moon helped. I had a severe background sky gradient. The stars looked quite bright though. I had trouble with several things - AstroTortilla wouldn't solve my images from last time or ones of M51 from the web but it did solve last night's star collection - no good without a reference to know where to go though. I believe you can use CdC to get the goto info but I'm darned if I can find it. As a result I never found my target. I did manage to get the half moon in the frame though and prove my focussing system worked fine - this scope and camera produce lovely sharp moon pics with the moon being just less than the frame width (a full moon would need a 2 panel mosaic).

As for guiding, I got PHD to calibrate on a bright star using 3s exposures in 5 steps in each direction but it refused to guide properly on it. Later I shut PHD down and started it up again. I couldn't see any stars, only hot pixels but still decided to try the auto star selection (grabbing at straws) and it found what it thought was a star (looked the same as the hot pixels to me). It calibrated in 6-7 steps per direction and proceeded to guide on it beautifully. Almost a flat line with regular spikes either way on both RA and dec. Then I noticed I'd forgotten to up the integration time and it was running at 1s Maybe I've been trying to guide on too bright a star

By 1am I decided that I wasn't going to find my target - I even tried other targets such as M13 and M101 but no joy with those either - so decided to call it a night. When I looked at the sky a few small clouds had come in, so that was that. We're forecast a clear sky tonight - all night - so I shall try again if the forecast comes true. Meanwhile I need to sort out AT.

[Komet]

Keep going Gina .... just remember and give thanks for the fact that you will always have to "fettle".

[Gina]

Thank you Mick - I will

I've managed to get AT to solve a previous M51 image taken a couple of months ago with the ED80 I used the luminance stack from DSS. I saved the solution in the Bookmarks so I should be able to use that to set the co-ordinates for AT to use tonight, weather permitting.

[nytecam]

Very nice Gina - keep up the good work

[Gina]

Very nice Gina - keep up the good work

Thank you I shall certainly try

[Gina]

More success tonight AT worked well and I got M51 nicely in the frame. Getting guiding to hold onto a star was tricky. Started off fairly well but then lost the star and putting it back onto the star didn't help - it moved away again. So I moved M51 in the frame until I got a better star in the QHY5/PHD frame and it's now quiding reasonably on that one. Nothing like as good as I got the guiding last night according to the graph but I couldn't find my target last night. I'm running 5m RGB subs which is producing an ADU around 40,000 on the brightest galaxy centre. The histogram in FITS liberator shows plenty of headroom too so I shouldn't be overexposing.

I think I've sussed out the reason for the gradient from top to bottom - shadow of the OAG prism and its holder - too far in

[Gina]

Here is the result of last night's imaging. I managed an FWHM of mostly just under 2 representing a resolution of around 2.5 arcseconds - reasonable for UK skies I gather. I left it going and went to bed around 1am, got up at 4am to find that the scope had passed the meridian and had collided with the pier. As a result I'd lost 5 sets of subs but still had 15 x 5m subs in each of RGB or 75m per colour (total 3h 45m). I'll set up some limits to stop slewing before this happens if I can work out how to do it.

Each colour stacked in DSS, colours aligned in RegiStar then loaded into PS for combining and further processing. Apart from levels, curves, colour balance and saturation, a small amount of sharpening was applied and the image was cropped for appearance and framing. (Framing unbalanced to get a guide star in the OAG.)

If the sky is clear tonight I might grab some Ha subs to bring out the star forming regions a bit more.

[Komet]

Slight collimation issue there I think .... good luck with that. Getting there though - well done.

[JohnC64]

Cracking image there Gina. Looks like you have the MN190/Atik314 combo working pretty well there

John

[AndyUK]

Hi Gina - You've got some very good detail that goes right down in to the core... I'd say that for your first full LRGB image with the MN190 - and using the new OAG - you should be very happy with that !

[Mark72]

Nicely done Gina;

Great details; may be the color is a bit to the pink in the core.

Mark

[starman1969]

That is a beauty. M51 is fast becoming my favourite sight in the night sky.

[nytecam]

Excellent image Gina - I like my images large and detailed just like that

[Gina]

Slight collimation issue there I think .... good luck with that. Getting there though - well done.

What can you see that indicates a colllimation issue Mick? I can't see anything. When defocussed the stars appear as a nice symmetrical doughnut. I'll take a defussed image tonight if I get a chance. Yep, getting there

[Gina]

Cracking image there Gina. Looks like you have the MN190/Atik314 combo working pretty well there

John

Thank you John Have to say I'm pretty happy with that as a start

[Gina]

Hi Gina - You've got some very good detail that goes right down in to the core... I'd say that for your first full LRGB image with the MN190 - and using the new OAG - you should be very happy with that !

Thank you Andy Yes, I'm happy with that start

[Gina]

Nicely done Gina;

Great details; may be the color is a bit to the pink in the core.

Mark

Thank you Mark

Nicely done Gina;

Great details; may be the color is a bit to the pink in the core.

Mark

Thank you Mark Yes, I think you're right - it is a bit pink

[Gina]

That is a beauty. M51 is fast becoming my favourite sight in the night sky.

Thank you It's been my favourite for some time now

[Gina]

Excellent image Gina - I like my images large and detailed just like that

Thank you Same here

[Komet]

You have triangular stars ..... I have suffered from this to varying degrees. Defocused stars look great but once you focus, there they are.

I say collimation but I "think" it is more of an issue with the secondary not being perfectly aligned. As it is attached to the corrector it is quite tricky to get it aligned totally accurately. Rotating it is easy as long as you slacken off the clamping nut but doing that up often rotates it once more. As I said, awkward. I believe I have mine sussed now but some of the star shapes on one side of the frame can be a bit pointy. I am learning not to bother about it too much now (bearing in mind that the stars through my ZS66SD have "character" all of their own anyway and I am comfortable with those now).

For collimation I use a Cheshire and I have modified a generic laser collimator to take a bigger laser as the diddy things they come with flatten the batteries in the cold in a few minutes. My bigger one uses rechargeables. I use the laser to align the secondary now and it seems to work very well - time will tell though, the next time I don't use the Mn190 for a whilst the little refractor is on the mount.

Anyway the point is that a nice round doughnut on a defocused star is no guarantee of perfect collimation on this scope. Still a great scope though.

[Gina]

Thank you Mick I don't think I'm going to worry about it too much

[Ewan]

Very nice Gina, can you send my clear skies back when your done with em :-)

[Gina]

Very nice Gina, can you send my clear skies back when your done with em :-)

Thank you Ewan Looks like the clear skies are going from here but whether they'll be with you next I wouldn't know