taking long exposures with heavy light polloution

[Alien 13]

Thanks for the confirmation, so both the 600 and 650 cause DSS problems,

daughter will be pleased to know that it isnt just her !

And your stacked pic : that's good news

In the style of the Beatles "It's getting better all the tiimeee, getting so much ,,,  "

I use the 650D with the normal version of DSS no problems at all it detects thousands of stars.

Alan

[Ptarmigan]

There is the start of another wee mystery then !

I have not looked recently but DSS used to use DCRAW and daughter would have downloaded the latest DSS.

So it must be finger trouble somewhere !

[Thalestris24]

Ah thats why they are coming out monochrome thanks for that

Here's a dss tutorial (there are a number of them on youtube): https://www.youtube.com/watch?v=4oIRIPg_QKw

Make sure your camera is in focus before taking any pictures! Focus on a bright star then lock the focuser. Um you'd need an awful lot of subs to make a decent image using very short subs. At, say, 2s/sub then even 60 would still only give you a total integration time of 2 minutes - which is not very much in return for a lot of dslr clicking. 4 x 30s subs would be a lot better!

A lp filter is really valuable if you're stuck with bad lp.

Louise

[Alien 13]

I would agree with Louise 20 seconds or so is the point when you start getting good data and colour information.

Alan

[laser_jock99]

Another strategy for coping with light pollution is to limit the FOV. Wide angle work doesn't suit light polluted sites, longer focal lengths and bright subjects like star clusters, globular clusters work well- but the tracking needs to be spot on. I have seen some good work done from the cities using the right equipment and picking the right targets. The other path is narrowband filters but not all targets suit this.

[oldpink]

really helpful information here thanks to all for your contribution
 

I did some more playing about earlier and discovered my first run in DSS was flawed as I added the Raw blacks not the Tif conversions
when I redid the run it did a lot more processing and gave me a lot better result than I had before
but with only 40 subs out of focus that wasn't bad
 

I did try to focus before I ran them but the LP was obliterating any view I had through the viewfinder, I should set focus on something in a very dark region first
then slew to my tareget

unfortunately the weather has closed in so I can't get out to experiment but I am heartened that I could get some info out of what I thought were a total loss
so I will not give up and I think a clip filter is a must if I'm going to do anything from home, so beans & toast for a month
I doubt my cheap SW LP filter is any use as I can't mount it to the Canon without using a nose cone though I will try that option out
but on my jupiter shots I felt it added some colour in the blue / purple range that didn't seem natural

[oldpink]

thanks for the video link Louise
there is a bit where you can select your camera, I took the rebel XTi option but still my Raw files say no stars but the Tif's work ok

only issue is my tif files are 102mb each from a 18mb raw, processing 45 files from Raw to Tif  crashed my system
so I had to run them in batches of 10 at a time

[Thalestris24]

really helpful information here thanks to all for your contribution

I did some more playing about earlier and discovered my first run in DSS was flawed as I added the Raw blacks not the Tif conversions

when I redid the run it did a lot more processing and gave me a lot better result than I had before

but with only 40 subs out of focus that wasn't bad

I did try to focus before I ran them but the LP was obliterating any view I had through the viewfinder, I should set focus on something in a very dark region first

then slew to my tareget

unfortunately the weather has closed in so I can't get out to experiment but I am heartened that I could get some info out of what I thought were a total loss

so I will not give up and I think a clip filter is a must if I'm going to do anything from home, so beans & toast for a month

I doubt my cheap SW LP filter is any use as I can't mount it to the Canon without using a nose cone though I will try that option out

but on my jupiter shots I felt it added some colour in the blue / purple range that didn't seem natural

Hi again

As I said, focus on a bright star then lock the focuser - but double check you're still in focus. If you have one, a laptop running APT is a huge help as you have a big window with liveview that has a x5 and x10 zoom. Unfortunately it's a fact that good lp filters are very expensive. I can't say anything about the 'cheap' SW one but it will probably help a bit so do try it. Any colour cast should disappear with stacking/processing. There would be vignetting with a 1.25" attachment/filter but you can remove that by taking flats and including them with darks during the stacking - you should do that anyway. As you can see from my example sub above - they come out bright blue! But that disappears with stacking and processing. I'm still a processing beginner but from what I've seen it's amazing what can be done with some time and effort.

I did this last month. It's not brilliant but I was quite pleased with it!

http://stargazerslounge.com/topic/209258-im-into-star-clusters/?hl=thalestris24#entry2231174

Louise

[oldpink]

the main reason I bought the SW 1.25 was it was compatible with my lens and could attach to my ASI nose piece primarily for Planetary work
I always knew the DSO side was another money pit but for future expansion with expensive lenses needed, hell I don't even have a standard lens to take day time shots
the 600D was bought primarily for DSO so I knew it would need more money spent at some point
I think I'm going to go with the Astronomik CLS CCD deep sky / LP filter for the modded camera as it seems to be the best choice for the money
with the added bonus it acts a s a dust shield

I was impressed with DSS when I gave it the right files
it took out the orange glow and gave me an image I could recognise but just lacking in detail due to the fast shutter speed and lack of frames
just need to wait till the weather gives me a chance to get out and experiment more and try the SW while I scrape up the money for the Astronomik clip filter

[Thalestris24]

I have a cls-ccd clip - it's served me well A Hutech idas D1 might be better but sooo expensive!

AP is an expensive hobby... Glasgow is probably not the best place for it either. Oh well, hope the weather clears again soon.

Good luck with your efforts.

Louise

[oldpink]

louise  and the others in this thread I can't thank you enough
what I thought was a load of Rubbish and waste of HD space turned out to be a useful learning tool
I ran the data from my 40 exposures a few times each time learning by my previous mistakes and did a star map
moved over to PS CS6 with no idea what I was going to do but decided to merge the starmap and stacked raw and got this
 

considering I was shooting in the dark and not focused with 20 0.8s and 20 x 1.6s and 5 x 0.8s blacks
I'm well chuffed

[Ptarmigan]

Great news !

Bet you cant wait for the next clear night !

Just a little question ( cos I lost it somewhere along the line ) what software did you end up using to generate the TIFFs was it DCRAW or your bundled Canon sw ?

[oldpink]

used the canon software as it what I had installed

[Ptarmigan]

Thanks.

I'm puzzled, a few stars are nearly in focus but some are blobs ! wonder how that came about ?

if you had two batches taken at different times with a focus jog between, then I would have expected superimposed images, but the two sets are distinct , , , odd ?

[oldpink]

most likely due to two exposures of 0.8 and 1.6 second with blacks at 0.8

just messing around finding my feet

[Thalestris24]

Hi again

You might like to have a look at this thread:

http://stargazerslounge.com/topic/205586-only-stacking-one-pic-in-dss

There are a number of threads in the forums discussing various DSS problems

Hth

Louise

[ardbeg74]

Hi Guys,

Been following this topic avidly. Fantastic posts guys! Pretty much sums up and answers all the problems ive been having with LP and DSS with canon raw files.

The links about taking shorter subs is so counterintuitive to everything ive read before, but yet makes perfect sense. Now bracing myself for the results of testing my sky quality...  15hr integrations to follow im sure    

considering I was shooting in the dark and not focused 

I've found a bahtinov mask has eliminated my focus worries, and its quick and easy to recheck between sets of subs. With bright stars its a doddle in live view zoom, but even with quite low mag stars a 10 sec jpg at max iso and manually zooming into the image works great for me. While everything else tends to go wrong when im out there, focus isnt an issue ( well except couple of nights ago when i forgot to take it off    10 x 45sec of perfect focus   )

All the best and clear skies to you all

Mark

[dph1nm]

I find DSS is quite unforgiving when it comes to out of focus stars. However, you can use superpixel mode for the bayer interpolation. This shrinks the image 2x2, but does seem to make the stars easier to detect (essentially it doesn't do any interpolation but just uses each colored pixel to form the image).  DSS needs a minimum of 8 stars to be able to stack by the way.

NigelM

[dph1nm]

Yes, indeed. However, the sub I posted does look the same in RAW

But to view a RAW image your software has to convert it. If you use the Canon DPP it certainly applies some default non-linear scaling it when you do this (there is a checkbox you can apply  somewhere which says use linear scaling - this usually makes the image vanish!).

NigelM

[lensman57]

this is my problem

My heart goes out to you but this is "dark site" compared to what I have to put up with.

Regards,

A.G

[Ptarmigan]

just messing around finding my feet

Yes, arnt we all ! and good fun it is too

My problem is that my experimental time with light pollution problems has been severly curtailed.

Whereas the light from a moderately distant town was not a big problem,

my research time has now been dramatically reduced by the council switching it all off for 1/2 the night !

Now that is just plain inconsiderate, sorry !! lol!

[wxsatuser]

Hi Guys,

Been following this topic avidly. Fantastic posts guys! Pretty much sums up and answers all the problems ive been having with LP and DSS with canon raw files.

The links about taking shorter subs is so counterintuitive to everything ive read before, but yet makes perfect sense. Now bracing myself for the results of testing my sky quality...  15hr integrations to follow im sure    

I've found a bahtinov mask has eliminated my focus worries, and its quick and easy to recheck between sets of subs. With bright stars its a doddle in live view zoom, but even with quite low mag stars a 10 sec jpg at max iso and manually zooming into the image works great for me. While everything else tends to go wrong when im out there, focus isnt an issue ( well except couple of nights ago when i forgot to take it off    10 x 45sec of perfect focus   )

All the best and clear skies to you all

Mark

The best way I have found is the Bahtinov, use a bright star.

I have marked my focus tube where the focus is near as good then each session

just use Bahtinov to tweak......simple takes no time at all.

[ardbeg74]

 I found this interesting, using a custom white balance, not tried that yet (ive no idea what im doing i just got my camera ), may help. 

Hi Dubhar, good find mate! This really helpful. 

Not sure what camera you have but In return, this is how you set it up on a canon 600d. I guess its probably very similar on other cameras.

Going to try this out tonight weather permitting (yea i know full moon ) and see how it goes. Just wish id bought that cls clip filter

Hopefully with the orange taken care of its just down to integration integration integration   

Clear skies

Mark

[oldpink]

very interesting reading
I knew about setting a custom white balance to offset the Mod's to the camera for daytime
what I didn't realise and if I read correctly if I point at the sky and get the orange glow I can use that to set the Balance

and remove a lot of it before I even attach a filter

[ardbeg74]

yep, question is, do you do it with the camera off the scope or on the scope pointing at the region of sky you want to image???

If the latter works then maybe the WB can be redone every say 20 subs so as the target rises or sets into different LP bands so overall balance is kept the same. Hmm.

What i found particularly interesting was adding the filter then doing the colour balance which is like a win win scenario.

TBH im shocked at the level of LP in Glasgow. Im from there but didnt take up astronomy till after i moved to London. (Kicking myself for not taking it up when i used to go camping on the west coast, wonderful dark skies in ardnamurchan... when its not raining )

Time to nip out for a smoke and take a look at what the clouds are doing... desperate to get out and test all these new ideas

All the best

Mark