M42....First DSO...Comments welcome

[vernmid]

Hi All,

Been lurking on the forum for a few weeks and finally got out last night to take my first DSO.

The attached was taken with 20x30 second unguided subs. Unmodified Canon 350d, Skywatcher 200p + EQ5. All from my back garden in Hampshire.

Stacked in DSS and no further fiddling!

All comments welcomed, don't hold back :-) Can someone tell me why the stars appear to have ghosts and I am surprised to see a star burst effect. How does this happen? I thought it was only JJ Abrams who added these effects ;-)

I had a blast putting this together and almost fell of my chair when I saw the first sub!

Thank you

Vern

[Knighty2112]

5 minutes ago, vernmid said:

Hi All,

Been lurking on the forum for a few weeks and finally got out last night to take my first DSO.

The attached was taken with 20x30 second unguided subs. Unmodified Canon 350d, Skywatcher 200p + EQ5. All from my back garden in Hampshire.

Stacked in DSS and no further fiddling!

All comments welcomed, don't hold back :-) Can someone tell me why the stars appear to have ghosts and I am surprised to see a star burst effect. How does this happen? I thought it was only JJ Abrams who added these effects ;-)

I had a blast putting this together and almost fell of my chair when I saw the first sub!

Thank you

Vern

Not an imager, so can't help there. However, for a first DSO shot this is very good. No wonder you nearly fell out your chair! Well done!  

[frugal]

Nice first image! M42 is such a nice target to begin with, it was certainly my first image.

The starburst effect is a diffraction effect due to the spider vanes at the front of your scope. All images takes with a Newtonian telescope will have them, the longer the exposure the more prominent they become. 

[vernmid]

Hi Frugal

Thank you. That explains the starburst. I am trying to remember my school Physics to understand the effect a bit better ;-)

Cheers

Vern

[frugal]

Effectively Newtonian telescopes have a diffraction grating attached to the front of the telescope. As the light hits the edge of the vane it gets diffracted out at 90 degrees to the vane which is seen as the spike. Bahtinov masks for focusing work in exactly the same way, except that they have the diffraction grating at 0, +30, and -30

[Gerry Casa Christiana]

Really great first shot! Well done! 

[Marky1973]

1 hour ago, vernmid said:

I had a blast putting this together and almost fell of my chair when I saw the first sub!

 

I hope you have a well-stocked wallet to break your fall...welcome to the bottomless pit of astro-imaging! Great first picture though and it does give you the bug. I'm not an expert by a long way, but reckon that the image might just be slightly out of focus. Bahtinov masks were mentioned above and they are a definite investment for imaging - my focus has been much better since I got one! Also, and I don't own a reflector, but the corner stars are most likely suffering from "COMA" so have a look at coma correctors if you want to smooth the corners out - depends how wide your images are and how much you can crop them.

 

Have fun!

[vernmid]

Marky1973

OK, thanks! I wondered what COMA was :-)

Regarding "bottomless pit"...Questions have already been raised concerning the number of Jiffy bags arriving at our front door!!

Thank you everyone for your comments. Really apreciated

Vern

[bobro]

Excellent first image. Stacking in DSS including flats will make for an improved image (you will need to take flats). Also, setting the Saturation to about 20 in DSS before saving the image will bring out the colour.

[vernmid]

Hi bobro

Thanks for that. I did try a few darks but skipped the flats due to lack of preparation!! I just wanted to get outside :-)

I'll try the saturation adjustment as I did wonder where the colours went! 

Thanks again to all

 

[vernmid]

Hi All,

Thank you for all your comments yesterday.

Last night I played around with the stack to see if I could bring out the colours. I guess I over did it but I was curious to see what signal was actually recoverable. I noticed a couple of things and wondered if someone here would be kind enough to confirm my thoughts.

The image shows vignetting when saturation is increased. Is is because I didn't use flats? If I did use flats would the dark ring get lighter or the brighter center get darker?

The starbursts on some stars are doubled. Is this because my focusing was out?

Many thanks

Vern

[happy-kat]

Flats will deal with the vignetting. Be careful not to clip the black point, the background isn't supposed to be black. Great start onwards to the next clear sky.

Your double stars appear to be in the corners where your mirror aberrations will be strongest. Cropping the image is the cheapest answer.

[JohnSadlerAstro]

Hi,

It's always really fun to see someone getting their 1st images--especially when they start off with good, solid equipment setups that will really help them. (I didn't and it was painful ) Coma will be causing uneven focus across the image, so I would suggest focusing at a star about 30% away from the centre, that way you will get the best overall focus. Flats are a must, take them right after your imaging run is finished without moving anything, take LOTS and LOTS of them, also LOTS of Bias frames, I couldn't get the Flats to work if I didn't take enough. (Not quite sure why! ) In fact, although Darks are the most obvious calib frames, I hardly use them at all, just a set I took with a standard-ish expo length a while ago. DSLRs, I found, didn't make too much noise on shorter subs (less than 1:30).

Keep it up!!

John

[bobro]

The end result should be something like this when flats are included. Have fun!

[vernmid]

happy-kat, JohnSadlerAstro, bobro

Thanks very much for the guidance. Really appreciated.

bobro, how did you do that? I guess that's from my image? I can see more sleepness nights coming now!!

Thanks again

Vern

[bobro]

26 minutes ago, vernmid said:

bobro, how did you do that? I guess that's from my image?

Yes Vern, that is your image. Doug German has a great selection of YouTube videos on image processing that are really worth a look. One of these is on reducing gradients  https://www.youtube.com/watch?v=yTEVMH_WE80&index=11&list=PLD1E1162212A88E25. I used this technique with GIMP (2.9.x) to remove the vignetting. Best to do it properly with flats though, especially as flats are quick to take.

What is sleep? 

 

[Notty]

Brilliant first image Vern, I wish my early shots were as good, but I also recall the rush I got when I put it on a screen and started to reveal what was out there.  The trouble is it's more addictive than Meth and if you're not careful you'll end up like me with all the gear, no idea.... and no time!

[Owmuchonomy]

Check your scope is well collimated.  If it is out of alignment it may explain your double 'starbursts'.  With your large DSLR chip you will benefit from a coma corrector too.  Your egg shaped stars are in one axis too.  If you can work out if that was your RA or DEC axis that will tell you many things! And it goes on and on.... welcome to imaging.

[DaveS]

Yes, the double diffraction spikes indicate that you're a touch out of focus, and you could do with a coma corrector, the Baader MPCC is reconned to be the best without going to silly money. Taking flats will get rid of the vignetting, and a Bahtinov mask will nail the focusing. The great thing about a B mask is it will tell you if you've gone through focus which you could miss if you just look at the stars.

[AndyW2008]

Hi Vern

Congrats on your very first image - it is one you will always remember!

What I am finding out is that using the scope and taking the image is only half the battle - learning how to stack and process the image is just as important if not more so. Working the software can really bring detail in an image you never thought was there. And it gives you something to do when the skies overhead are clouded over!. Learning new techniques and applying them to existing images is fun. Honest!

Andy 

[vernmid]

Hi all,

I have been really amazed to have received so many positive comments and good advice. about my posting Thank you everyone. I'm really looking forward to having another crack hopefully this weekend.

Thanks again

Vern

[Swithin StCleeve]

On ‎03‎/‎04‎/‎2017 at 09:21, vernmid said:

 

The attached was taken with 20x30 second unguided subs. Unmodified Canon 350d, Skywatcher 200p + EQ5. All from my back garden in Hampshire.

 

Can I ask what 'unguided subs' means please?

[Swithin StCleeve]

11 hours ago, Swithin StCleeve said:

Can I ask what 'unguided subs' means please?

 

I'm confused because unguided makes it sound like the scope isn't moving, but the OP said they took 20x30 second unguided subs, so that twenty photos with thirty second exposures each? is that what that means?

I'm trying to get to grips with astrophotography but sometimes I find the terminology a stumbling block. I've searched the term 'unguided sub' and there's lots of mentions but I can't find an explanation.

[Davey-T]

You can use a camera on a tripod which is obviously unguided or a camera on a motor driven mount which follows the stars across the sky, this is also unguided.

If you use a motorised mount and another small scope and camera it will control the mount motors to follow the stars more accurately, this is guided.

You can spend loadsa money on a motorised mount with high quality engineering that is capable of following the stars accurately without another small guidescope / camera, this is also referred to as " unguided " but it is being guided by motor encoders.

Dave

[Swithin StCleeve]

So if I polar align my EQ mount, and fit a motor on to follow the stars, this is still 'unguided'. To call it 'guided' that means you need a second camera and mount, and that second camera and mount guides the first more accurately?