Stacking comet lovejoy in DSS-cant see enough stars to stack my images

[richardalan]

Hi, I wonder if anyone can help me. I have taken about 30 shots of comet lovejoy tonight using a canon 1100D, 6" (F12)maksutov on unguided heq5 pro. I am trying to stack them now in deep sky stacker, Ive loaded 26 lights and 3 darks, when I register them the scores are quite low (30 ish) and when I stack them after registering them, it says "only 1 frame will be stacked" and "try adjust the star settings". I have adusted this from 2% to 98% and it still does not see enough stars to align the frames. Ive attached one of my frames, you can see a few stars, but obviously with my scope being a F12 there isnt that many stars to pick from! I would've thought you can select the comet itself as a stacking reference point / alignpoint, (like u can in registax) but I cant figure out how to do it, or even if you can. 

Any advice would be much appreciated!

Thank you.

Rick

[carastro]

There is a comet stacking option in DSS, I only tried to use it once, but my data was rubbish anyway.  

Load up your images into DSS and then click on the top image.  A box will come up on the side with a red cross and a green "comet".  Select the "green comet" and then I believe you have to mark the position of the real comet on all the images.  Pretty tedious IMO but I think that's the way to do it.

If any-one knows better I'd be glad to know as hoping to do the comet myself soon.  

Carole 

[richardalan]

Wow thank you carastro! I will try again tonight and let u know how i get on.

[richardalan]

Hi Carole, I did as you said and sure enough when I clicked on my first light frame, and clicked the green "comet" icon on the righthand toolbar, i was able to place an alignpoint right on the comet. However, it still said there was not enough stars to stack, so I altered the star detection threshold to 2% (so it picks up the faintest stars) and still the same result. So I wasn't able to stack my images, I think maybe if I wait till the full moon disappears, my Mak might pick up more stars. Its either that or buy a faster scope ED80 I think! Thanks for your help, its a tough learning curve isn't it, but a rewarding one

Rick

[carastro]

That's annoying, sounds like the comet alignment didn't work as it's not supposed to align on stars only on the head of the comet as the stars will come out as trails.  Might be worth another crack at it in case you did something wrong, otherwise I think Registax has a comet stacking option, though I have never used it.

Carole 

[jgs001]

You could try selecting the comet in each frame and see if that will stack. 

See if this tutorial will help any

http://www.cowboywithacamera.com/comet-stacking-tutorial-using-dss/

I do wonder if, at f/12, and unguided (therefore presumably short subs) if you've actually captured enough data, but give the full comet stack a go and see what the results are like... you never know...

[richardalan]

Hi Carole, when i selected each frame and highlighted the comet, i noticed that the few stars i had in each frame had tiny circles around them , the comet had a larger circle round it. I did the same with all the frames and saved them all. In the settings , i also selected to align on the comet only (so the stars wud trail). There are other 2 settings , one to align on the stars n not the comet, and lastly to align on the stars and the comet which somehow freezes the stars and on this one everything is in focus. But I'll have another bash after work tonight , thanks for your advise !

[richardalan]

Hi jgs001, i did highlight the comet on all the frames but noticed it picked up a few stars and circled them with smaller circles too. The exposure times were short , 15-25 secs , so as u say prob not enough time to gather enough photons. I think my scope is the cause , maybe I'll just save it for the planets ! I'll have abother go though , thanks for ur help , i will look at the link after work. Ta !

[dph1nm]

DSS needs at least 8 stars in each image. I am not sure I can see 8 on your example frame! There are a couple things you can do in DSS at long focal length - one is ro use "superpixel" mode, which usually help with star detection (at the expense of halving the resolution), and the other is to try the star editor, which lets you select stars manually (this only helps if DSS has spotted something there in the first place but has not recognised it as a star).

NigelM

[richardalan]

Hi Nigel and thanks for your help, The most dss could find was 5! I have seen lots of close up comet images where there are many stars in the picture, like u say I need to capture more stars, I think the issue is my F12,5 opticstar mak. The field of view is far too small, and best I keep that just for the planets and close ups of the moon, Orion nebula etc. I have nearly saved up enough for a SW ED80 apo, which I cant wait to get my hands on, just hope the comets still around when I do!! If I up the iso on my dslr, all I get is more LP and all the shots are orange, plus there was a near full moon which doesnt help. I will try that superpixel mode you mentioned and I will also give the star editor a go too and let you know, thanks again for your advice!!

Rick

[Patrick in memphis]

Try to move the slider down...the lower the value the more stars it finds.I'm still learning dss.I have about 150 shots of lovejoy anywhere from 50mm-300mm-450mm and when I runs dss it fonds roughly 1500-3400 stars per pic I mainly shot a 6400 is and I pushed the shutter speed at 2.5-5 sec...so on close exam there is a little star trail but live able .I've been out shooting the last two nights but too cold tonight 1 degree with wind chill.if someone wants to play with nef/raw files I can send them.and where is the button to add pics (new to this website)

[richardalan]

Thanks Patrick, I put the slider down to 2% as low as it will go and struggled to get 8 stars, Its the 1st time ive tried to image a comet, so really its trial and error. I need to up the iso a bit or try expose a bit longer, its just the LPollution then becomes an issue! Since that night I took all those frames it has not been clear, cloud and constant rain where I live, I hope I get to see it again, while its still bright or I'll be gutted! I cant wait to get my ED80, that will mke things a bit easier I hope!

[richardalan]

This is the result, only 2 stacked, bit embarrassed to post it really but at least I managed something!!   F12.5 is not a winner for comets i think!  

[Patrick in memphis]

I was gonna upload a couple shots but not obvious how to do it

[Patrick in memphis]

Ok I think I figured it out...anyway these are single shots nikon d5000 I have to ck exif but I think 5 & 15 sec ss...f/1.8 & 6400 iso???? On 50mm & 300 mm lenses ...Going off memory....anyway I have about 150 of them

[Patrick in memphis]

Heres another one

[Patrick in memphis]

Sorry

[redfox1971]

I have exactly the same problem not enough stars to be able to stack in image and my star detection slider was at 2% think I will up the exposure length from 30sec to maybe 90 seconds if I get a clear night again that may brighten the faint stars in the images.

[richardalan]

Has anyone ever tried a focal reducer on a maksutov ? If it works i would have more stars in view. I know you use them on refractors but not sure with maks ? Its been another day of cloud in Bolton so wont be going out again. Frustrating!

[gkec]

I has this problem photographing comet lovejoy with not enough stars and very low "scores" in DSS. I had fairy short exposures due to the scope being buffeted occasionally by the wind.  Also DSS didn't "recognize" the comet so I was unable to mark it in DSS.  I eventually managed to get better scores and to stack more than one image by removing the dark frames.

The final result was a bit disappointing

. 

[Patrick in memphis]

I have a Meade sct and I can use a focal reducer...I believe it works the same on a mak

[richardalan]

Thanks for posting your pics Patrick and gkec, & i will take my darks out and retry it tomorrow again, but i think the main issue is light pollution and me not guiding & extending my subs to get more stars.

[richardalan]

Hi Patrick, which one is it and does it give you a much wider field of view ?

[Dave 2112]

I had a load of trouble stacking this in DSS, I couldn't get the reticule to lock on the head of the comet and every stack looked like a huge blob. I ended up removing all the stars I could using the "edit stars" button, stacking without using the comet tool.

and no matter how much I fiddle with the image size in my gallery it still posts a tiny version.

[Davey-T]

and no matter how much I fiddle with the image size in my gallery it still posts a tiny version.

You need to resize it in an image editing program, lost detail though, resizing upwards is not good

Dave