SteveNickolls

Hi Ken,

I'm going to have a ponder and pass on that one then. I'm just about getting me 'ead round dark frames :-) Maybe someone else on SGL knows the answer to this one?

Cheers,
Steve

40 minutes ago, Filroden said:

Looks like you have a strong gradient from the bottom. How good is the wipe tool in StarTools for removing this?

And that raises my next question: as altaz imagers, we have to deal with rotation. But that also means that when we stack images, any linear gradient that appears in each frame slowly becomes rotated through our stack created a non-linear gradient in the final stack. Does that mean we should be removing gradients from each frame before stacking?

Hi Ken,

The image had WIPE carried out on it, I think the gradient is there because there aren't enough frames to make the data good enough for ST to work adequately and you get blocks of off-colour and gradients appearing. Sometimes you can crop a larger image down and 'fool' ST into thinking the data is better than it is and you can then use modules such as COLOR properly. I put last night down to a learning experience :-)

In DSS field the stacked rotated images take up a 'bow tie' appearance over time on the master image but the software automatically rotates individual frames for you. ST then only has to remove gradients once.

Cheers,
Steve

And here is part of the spider hijacked NGC 7000. I managed to crop out the part where the arachnid had left its shadow on the images. What's left is the top most part of the object. I think I will have to get something like a 200mm camera lens to do the object justice. StarTools didn't like the lack of data (there's only x39 fifty second frames at ISO 1600), plus x50 dark frames, flat frames and bias frames. Images taken using the SkyWatcher Startravel 102mm refractor, Synscan Alt-Az mount and Canon 600D DSLR. Images stacked in DSS and processed using StarTools.

Cheers,
Steve

Here's last nights M29 taken with the SkyWatcher 102mm Startravel Refractor, Synscan Alt-Az mount and Canon 600D DSLR. The image is made from x39 fifty second light frames combined with x50 dark frames, x50 flat frames and x50 bias frames. Frames stacked in DSS and processed using StarTools. The stars of M29 are set in a haze of nebulosity.

Cheers,
Steve

I feel like a criminal after last night's Alt-Az imaging session. OK, I'll come clean and tell the whole story.

You have to remember everything was running well; I'd planned to set up extra early and like Ken on SGL had advised, I did the dark frames first. Alignment went swimmingly, first Vega then Regulus, return back to Vega and wait until any mount movement ceased. Vega remained bang in the centre of the eyepiece and none of the usual minor adjustments were needed. Tonight was going to be a steal.

Focusing too with the Bhatinov Mask went without a hitch. If I'm being really honest there was a little wind to spoil the mood and I had to wait a few minutes for the sky to darken once slewed to NGC 7000. At fifty seconds Live View was just a white-over but things got quickly better as the sun finally sank below the horizon.

Fifty frames later and how glad am I now that I decided to hedge my bets and next image M29. I wonder did I have an intuition?

Just before the witching hour I honestly thought I'd got away with it, no problems, no major hitches. I was soon packed away then gone like a thief in the night. The perfect imaging job.

Nemesis swiftly followed the hubris of the night before when, processing my images the next morning, a strange blob appeared on all the light frames. Oddly they were only on the first set of frames used for NGC 7000, M29 was fine. Whatever was the cause? The investigation didn't take long and I realised I hadn't got away with things at all, I'd been caught by Spider, man he'd been hiding in the dew shield all along! Here's the evidence-

It's a true story, honest. I'll post my M29 image soon :-)

Cheers,
Steve

Hi Ian,

Thanks for your post regarding the image with and without dark frames. I've had a day questioning what I do and seeing the effect of not using dark frames was one of them :-)

Cheers,
Steve

35 minutes ago, Filroden said:

Yes. For the ZWO I have darks in 5C bands and multiple gains. For the Canon I only keep one set as it seems to settle to a standard temperature after about 30 minutes after aligning. 

That's very helpful to know Ken, it will certainly make imaging a lot simpler with the Canon and free up time for the important light frames :-)

Regards,
Steve

1 hour ago, Filroden said:

The one advantage of British weather is that our night time temperatures are fairly stable. I find my Canon starts at around 26C as I use live view to align and focus, and cools to about 16C where it stays for the entire imaging session regardless of actual outside temperature. That makes it easy for me to build a dark library.

So do you have dark frames arranged by temperature to use off the shelf Ken?

Cheers,

Steve

Good going nige, well done. The cerise hue in the first image comes across brighter on my hudl but both are very good indeed. I fancy attempting this target but no way could I stay awake till the birds wake up. Good for those who can.

Good luck to all who image tonight.

Cheers,

Steve

Hi Ken,

Thanks for this, I have tended to take the dark frames sometime during the imaging session to have the same temperature and the bias and flats the morning after. I agree though that taking the dark frames sometime before imaging is a good idea to make best use of the night time for taking light frames and will put it to use tonight if conditions improve-cheers :-) 

Steve

Hi Ken,

I can't imaging how good your NGC 7000 will be after x200 more light frames, very good luck with the project :-) Thanks too for showing the rest of us that it can be imaged. Yes it is quite low down as an object right now, from here it's ranging from 16 degrees at 10.30 PM  to 27 degrees around half past midnight.

Thanks too for your comment on the M57 images, it has me seriously wondering if I should bother taking dark frames as they do take up a lot of valuable imaging time of a night time. Decisions, decisions.

Hmm SGL is acting odd saving things today...

Cheers,
Steve

Hi Ken,

Thanks for posting the two versions of NGC 7000, you have been busy. Have you any plans for further imaging the object? I was tinkering with the idea of trying to image either this nebula or the cocoon Nebula tonight if it is clear and the wind drops here.

I was just posting Ken notifiaction of yours came in. 

I attach my coffee-paint scheme colour chart showing the light pollution to be contended with here. I have also been experimenting with omitting to use dark frames in DSS to see what happens. Please find below two images of M57 using the same x16 sixty second exposures but the first with x50 dark,bias and flat frames and the second image without the dark frames. There certainly seems less background stars and some of the red stars have stayed red and not turned white. Stacking in DSS and processing using StarTools.

First with darks-

The second without-

Cheers,
Steve

Canon EOS 600D 5to80s.pdf

26 minutes ago, LukeSkywatcher said:

Hands up anyone who is using an Astro trac or barn door system!!!!!!!.

They qualify as an EQ system.

Anyone!!!!! 

Not me, not me. I leaves all moi tractors in the barn.

Cheers,
Steve

6 minutes ago, The Admiral said:

My two-pence worth anyway. Have fun going through all the options, dreaming, and window shopping.

ian

And how absorbing window shopping can be-there's reading all the reviews, the comparing and finding out from others the up's and downs, and getting the best price before coming to your decision. Enjoy every moment of it Nige.

Cheers,
Steve

Hi Nige,

Regarding getting a refractor it's really what you feel you can 'put up with' in terms of CA and field curvature with cheaper OTA's. I have the f/4.9 102mm Startravel from SkyWatcher, it came with the mount and was a snip from FLO at £289. You can get the 80mm Startravel but same issues. StarTools will help moderate the purple halo caused by the doublet optics, see my images. Now I know I like imaging I'm saving up for a 'better' refractor which will give me sharper stars, I'm contemplating the f/5 Espirit 80ED Pro with the field flattener but it will cost a fair bit and is a heavy beast that should just be carried by my existing mount. There were a lot of others I considered and discounted along the way. Have a look in FLO. Can't advise on a reflector, sorry.

Cheers,
Steve

Hi Ken,

Thanks so much for your post. I like your image of M56 and with NGC 7000 it shows what is possible from 45 second exposures, well done as a proof of concept for us all to try. Your Kenyan blend was a good choice btw :-) It's one of the troubles with Alt-Az imaging-you need a low enough object to work with field rotation but that means you image through the worst of the atmosphere. Nonetheless were getting decent results from modest equipment.

Cheers,
Steve

Hi Ian,

Well done you should be proud of that image, I compared it to one on Wiki and yours is better! You have everything in. Are you proposing to add more frames another night? What do you use Lightroom specifically for can I ask?

Cheers,
Steve

5 minutes ago, Filroden said:

Could you paint my fence in the 70 sec exposure?

 

He, he a pleasure Ken you are obviously a man of great taste, both of coffee and paint.

Cheers,
Steve

7 minutes ago, Filroden said:

Both M56 and M57 should be able to take very long exposures before you see rotation as they are very low and moving round to almost due East. I might give them a shot tonight and see how far I can push it. The killer for me is light pollution which limits my total exposure. I think my peaks were almost 2/3rds across the histogram after 45 seconds at that altitude. I might drop down to ISO800 or even 400 just to test.

Hi Ken,

Yet I forgot to mention light pollution, it's bad here you can usually see stars to Mag 4.3. I made a series of exposures of the night sky on a moonless night from 5 to 80 seconds, it resembles a colour chart from Dulux in their coffee range :-) Unless your frames are whited out you should still be able to pick out signal fram noise but it will degrade the detail. Wouldn't it be great to have darker skies.

Here's the colour chart!

Canon EOS 600D 5to80s.pdf

Cheers,
Steve

Hi Ken,

Lovely image of M5 you have :-) Sorry you had so much trouble getting any decent frames of M13. I'm intrigued at your 9.25" SCT and what it can do.

Good luck imaging tonight.

Cheers,
Steve

Hi All,

Last night I attempted taking 60 second exposures of M56 and M57 with my Synscan Alt-Az mount, partly to see if the mount could do it and to try and compare the resulting image of M57 at 60 seconds from one taken in April at 30 seconds. I've never observed or imaged M56 before so it's a nice small globular cluster to add to the astronomy log. All the frames were stacked using DSS and images subsequently processed in StarTools.

The mount proved able to provide images with sixty seconds exposure albeit with different percentages of frames acceptable to use by DSS; for M56 11/11 frames (100%) and for M57 16/29 (55%).

First M56 from x11 light frames at 60 seconds ISO 1600 plus 50 dark frames, x50 flat frames and x60 bias frames. Equipment used, a SKyWatcher Startravel 102mm f/4.9 refractor, Synscan Alt-Az mount and Canon 600D DSLR.

Secondly M57 from x16 light frames at 60 seconds ISO 1600 plus 50 dark frames, x50 flat frames and x60 bias frames. Equipment used, a SKyWatcher Startravel 102mm f/4.9 refractor, Synscan Alt-Az mount and Canon 600D DSLR.

And one of M57 taken in April this year using the same equipment, ISO 1600, x50 dark frames, x50 flat frames and x50 bias frames. On this occasion x51 light frames of thirty seconds each were used.

The sixty second image shows more detail and is sharper despite taking a shorter amount of total exposure. As Ian has pointed out to me in a PM the different star colours in the sixty second image could reflect saturation or perhaps just old StarTools :-)

I would heartily recommend everyone with an Alt-Az mount to try longer exposure frames where the object can take it (field rotation effect) and see what a difference it can make.

Cheers,
Steve

You've some really nice stars there Wappmupp and a great first try. I think globular clusters and even open clusters by their nature of being points of light can be well imaged with not so many exposures. Sometime I'd like to improve my stars as the telescope I currently have suffers from 'star bloat' a lot but that's ok while I'm learning the ropes. Good luck in your future imaging sessions.

Cheers,
Steve

5 hours ago, Nigel G said:

Going to bed now,  after 180 lights 50 dark I'm leaving it stacking over night hopefully a good image to work with.  

Zzzzzzzz

He he wish I had the resources to stay up so late 'erm I mean so early Nige. Looking forward to your images.

Cheers,
Steve

38 minutes ago, Nigel G said:

Some of these images considering how small the field of view is contain a huge amount of stars, until you see this with your own eyes it's hard to appreciate just how many there is above our heads. I give a big smile when developing an object within or close to the Milky Way  with StarTools. Thousands of star's appear.  ?and that's just from a tiny piece of sky about a thumbnail or so at arms length. 

Nige

Thanks Nige, Ian and happy-kat. Nige- couldn't agree more about the mind blowing number of stars in what, looking up with your own eyes, is a tiny area of light polluted sky-absolutely brilliant. 

There's the last half verse in a poem by Ralph Hodgson, 'The Song of Honour' that's appropriate-

I stood and stared; the sky was lit,

The sky was stars all over it,

I stood, I knew not why,

Without a wish, without a will,

I stood upon that silent hill

And stared into the sky until

My eyes were blind with stars and still
I stared into the sky.

Cheers,
Steve

At the end of April I took 40 second ISO 1600 exposures of three objects in the Cephus/Cassiopeia region. The equipment used was my SkyWatcher Startravel 102mm f/4.9 refractor, Synscan Alt-Az mount and Canon 600D DSLR. The first is a two for one image of the Fireworks Galaxy NGC 6946 and nearby open cluster NGC 6939, x98 light frames, x50 dark frames, x50 flat frames and x50 bias frames. Stacking in DSS and subsequent processing in StarTools.

And a close up of the galaxy with better colour-

And the Pacman nebula NGC 281 using x96 light frames, x50 dark frames, x50 flat frames and x50 bias frames. Stacking in DSS and again subsequent processing in StarTools.-

Cheers,
Steve