Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Astrophotography and Sketching >> DSLR & Digital Camera Astro Imaging & Processing

Pages: 1 | 2 | 3 | 4 | 5 | (show all)
srosenfraz
Post Laureate
*****

Reged: 03/06/11

Loc: United States
Re: I am doing something very very wrong new [Re: shawnhar]
      #6127591 - 10/09/13 06:19 PM

The new bias frame you posted still doesn't look right. Its level is at 56, where it should be at 0. Now, its possible that the bias is ok, and what you're posting has had some stretch applied, but there's something not right about the Master offset file you posted. That may or may not be the issue, but I think you'll want to resolve the discrepancy.

@Shawn - since you're familiar with DSS, would you mind giving ICallHimGamblor directions on how to save an unstretched Master offset tiff file?

@ICallHimGamblor - Would it be possible to post a raw sub (the .cr2 file itself)? That will give us a much better idea as to what your raw data looks like before anything is done to it.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Rankinstudio
Carpal Tunnel
*****

Reged: 04/05/08

Loc: Southern UT
Re: I am doing something very very wrong new [Re: srosenfraz]
      #6127737 - 10/09/13 07:43 PM

I've been having a lot of issues with DSS as well. It looks to be reversing my flats at times, hollow stars, ect. I have found a few settings that seem to help get consistent results.

Under registration
Check automatic detection of hot pixels
Under advanced, reduce noise using median filter
Then adjust the slider and do multiple test runs until you end up with a number of stars that looks like what is in your image.

In the stacking tab use "Standard" under Result
Do a Median combine for lights, darks, flats, bias
Under alignment choose Bilinear
Under cosmetic, uncheck everything

For the best stretch, I save it out as 32bit rational then do a linear stretch before converting it to 16bit.

Seems to make it work right for me for some reason.

Cheers,


Post Extras: Print Post   Remind Me!   Notify Moderator  
ICallHimGamblor
super member


Reged: 06/24/13

Re: I am doing something very very wrong new [Re: Rankinstudio]
      #6127972 - 10/09/13 10:02 PM

Thanks, everyone... everyone is being so helpful.

Scott: I uploaded a single random sub here: https://docs.google.com/file/d/0By0hG91nGRL9WkZoUFFwRWQ3SEE/edit?usp=sharing

David: Thanks.. I will try restacking and re-saving tomorrow when I have a little more time.

Right now, I'm going to try stacking in my Nebulosity trial to see if it makes a difference.


Post Extras: Print Post   Remind Me!   Notify Moderator  
shawnhar
Post Laureate
*****

Reged: 06/25/10

Loc: Knoxville, TN
Re: I am doing something very very wrong new [Re: srosenfraz]
      #6128534 - 10/10/13 08:43 AM Attachment (3 downloads)

Quote:


@Shawn - since you're familiar with DSS, would you mind giving ICallHimGamblor directions on how to save an unstretched Master offset tiff file?




In the folder where your flats are, DSS will generate a master flat when you stack them, same with the darks and bias, but that ain't the problem.
Your single sub has those crazy gradients as well.
What is the light like around you? Streetlight behind some leaves shining in the scope? Gotta figure this out 1st...


Post Extras: Print Post   Remind Me!   Notify Moderator  
ICallHimGamblor
super member


Reged: 06/24/13

Re: I am doing something very very wrong new [Re: shawnhar]
      #6129860 - 10/10/13 08:57 PM

I am in the city, and there are definitely streetlights around, though none with any direct light. There is one nearby behind some leaves.

However, due to trees I am shooting mostly straight up. I bet I started my imaging of this set at 85 degrees above the horizon.

Am I basically just screwed completely because I live in the city? I am pretty sure there are folks on this forum getting decent results in metropolitan areas.


Post Extras: Print Post   Remind Me!   Notify Moderator  
pfile
Post Laureate


Reged: 06/14/09

Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6129962 - 10/10/13 09:46 PM

you may need a light pollution filter, in which case you should be able to get images of emission nebulae at the very least. i have taken these images with a modified DSLR + lenses and telescopes as well, in what is a red zone according to the maps:








i used the Astronomik CLS filter. it is pretty unkind to galaxies, because it "deletes" a lot of wavelengths that galaxies emit. so with CLS it's easier to stick with Ha/OIII rich targets.

it can be done, don't give up

anyway, those gradients look like clouds or even dew on your scope/lens; i don't think i've ever seen such a complex gradient in any of my subs. usually the gradient is mostly linear in nature.

rob

Edited by pfile (10/10/13 09:49 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
ICallHimGamblor
super member


Reged: 06/24/13

Re: I am doing something very very wrong new [Re: pfile]
      #6129987 - 10/10/13 10:01 PM

I have uploaded a random sub from a week earlier on a completely different target, Hickson 93.

https://docs.google.com/file/d/0By0hG91nGRL9clVEX25QUFFCakk/edit?usp=sharing

Does it have the same issues? If so, we can eliminate clouds and dew and stuff, right?


Post Extras: Print Post   Remind Me!   Notify Moderator  
srosenfraz
Post Laureate
*****

Reged: 03/06/11

Loc: United States
Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6130039 - 10/10/13 10:22 PM

Suggestion - you're trying to image some very challenging targets from very light polluted skies. While its possible to do, it might serve you better to start with some brighter targets and refine your routines and techniques for image capture and processing. Targets like Stephan's Quintet and Hickson 93 can make for some beautiful and impressive images. But, they also demand tight focus to capture the small details plus a lot of exposure to give a good SNR due to their relatively low surface brightness. When you're imaging from light polluted skies, you'll typically need to increase that total exposure time to many, many times what it takes at a dark sky (i.e., a target I can capture well in 1 hour from my blue/green zone sky will take 8 hours for comparable SNR in a red zone). As such, if you try working more with objects with a higher surface brightness, you can capture them in a more reasonable amount of time and start seeing some positive results.

You're not completely screwed because you're in the city, but it does make things more difficult. Still, there's a long list of bright targets (high surface brightness) that should be comparatively easy for you to capture (Mr. Messier developed a pretty good list for starters).

Hope this helps...


Post Extras: Print Post   Remind Me!   Notify Moderator  
ICallHimGamblor
super member


Reged: 06/24/13

Re: I am doing something very very wrong new [Re: srosenfraz]
      #6130082 - 10/10/13 10:43 PM

Scott: I completely understand what you are saying, and I agree. I just have very little interest in those targets. I don't mind at all spending 8 hours on a neat Hickson group, as long as I know something useful will come out of it.

I do have some subs of the Deer Lick Group and NGC 6946 that are equally as disappointing in my opinion, and those are pretty bright, large galaxies. In fact, NGC 6946 came out worst of them all.

If the answer to all my problems is just "you need more exposure time", then that's fine. I'm good with that. But it sounds like I'm doing something wrong if my bias frames don't come out black and I'm getting psychotic gradients on three minute subs.

But while I'm learning, I will also seek out some easier targets. Your advice is definitely taken.


Post Extras: Print Post   Remind Me!   Notify Moderator  
pfile
Post Laureate


Reged: 06/14/09

Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6130242 - 10/11/13 12:26 AM

so just as a sanity check, did you stack without any calibration frames and check the results?

it is hard to see the gradients in a single sub. what i can see though is that the vignetting in each channel is very different, which is a little strange for a reflecting telescope. still there are refracting elements in an SCT which might account for that.

also your camera temperature is way up there at 97F (36C). this can really make it difficult to collect dim targets. you may want to investigate building a cooler box to keep the thermal signal down.

rob


Post Extras: Print Post   Remind Me!   Notify Moderator  
shawnhar
Post Laureate
*****

Reged: 06/25/10

Loc: Knoxville, TN
Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6130486 - 10/11/13 07:29 AM Attachment (1 downloads)

Quote:

I have uploaded a random sub from a week earlier on a completely different target, Hickson 93.

https://docs.google.com/file/d/0By0hG91nGRL9clVEX25QUFFCakk/edit?usp=sharing

Does it have the same issues? If so, we can eliminate clouds and dew and stuff, right?



Seems to have the same gradient.
Take a raw with the lens, pointed at a surface that is uniformly colored, like a wall and see if it still has it.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Tonk
Postmaster
*****

Reged: 08/19/04

Loc: Leeds, UK, 54N
Re: I am doing something very very wrong new [Re: shawnhar]
      #6130554 - 10/11/13 08:39 AM

That look like plain old vignetting as far as the brightness drop off to the corners is concerned (that's sorted by flats) - the dark band along the bottom is often due to the spongy strip padding that runs on one edge to damp out the mirror slap - that too is cured by flats

- or are you referring to the weak coloured gradients on top. No idea what doing that and flats would not likely solve those


Post Extras: Print Post   Remind Me!   Notify Moderator  
ICallHimGamblor
super member


Reged: 06/24/13

Re: I am doing something very very wrong new [Re: Tonk]
      #6130730 - 10/11/13 10:27 AM

Oh man.. I really hope we are back to just having a problem with my flats.

Post Extras: Print Post   Remind Me!   Notify Moderator  
shawnhar
Post Laureate
*****

Reged: 06/25/10

Loc: Knoxville, TN
Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6130832 - 10/11/13 11:21 AM

It's the color gradient that is causing the issue. I am not really sure what is causing it or how to deal with it, never seen gradient like that on one sub except shooting through clouds. The gradient appears to be the same on each non-calibrated exposure, suggesting it is internal to the camera or the scope.

Post Extras: Print Post   Remind Me!   Notify Moderator  
ICallHimGamblor
super member


Reged: 06/24/13

Re: I am doing something very very wrong new [Re: shawnhar]
      #6130950 - 10/11/13 12:09 PM

Is there a camera setting that could affect this? That might also explain why my biases are not black.

Post Extras: Print Post   Remind Me!   Notify Moderator  
srosenfraz
Post Laureate
*****

Reged: 03/06/11

Loc: United States
Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6131234 - 10/11/13 02:12 PM

I have a feeling your bias problem is in how your processing/posting it in DSS. Could you post one .CR2 RAW of a bias frame? That will help us ensure that your bias data is good and its the processing/posting of the bias is why we're not seeing a black master bias

Post Extras: Print Post   Remind Me!   Notify Moderator  
ICallHimGamblor
super member


Reged: 06/24/13

Re: I am doing something very very wrong new [Re: srosenfraz]
      #6131405 - 10/11/13 03:31 PM

One raw bias frame coming up: https://docs.google.com/file/d/0By0hG91nGRL9REQzNHpBNnFtVFk/edit?usp=sharing

Post Extras: Print Post   Remind Me!   Notify Moderator  
srosenfraz
Post Laureate
*****

Reged: 03/06/11

Loc: United States
Re: I am doing something very very wrong new [Re: ICallHimGamblor]
      #6131527 - 10/11/13 04:30 PM

Ok, so the good news is that your bias raw looks like a nice, normal 0,0,0 all over the place bias frame. My gut suspicion is that when you're saving the .tif out of DSS, your applying a stretch to it and that's why it doesn't look normal. I would assume for the time being that DSS is actually applying it as a very dark bias frame when its using it to calibrate the flat.

Again, perhaps someone familiar with DSS can explain why his normal looking bias ends up in a Master Offset .tif that is clearly not dark?

For the time being, let's assume your bias is OK (sorry if I had led us astray). As I look through this thread, I noticed that I and others have been referring to your filter as a CLS filter. My assumption was just that - that it was the Astronomik CLS-CCD filter. However, I notice that you keep referring to it as an LP filter. So, clearly its a filter other than the CLS-CCD filter.

Which begs the question - exactly what LP filter are you using? Specifically, brand and model?


Post Extras: Print Post   Remind Me!   Notify Moderator  
shawnhar
Post Laureate
*****

Reged: 06/25/10

Loc: Knoxville, TN
Re: I am doing something very very wrong new [Re: srosenfraz]
      #6131563 - 10/11/13 04:53 PM

I think Scott is on to something.
You need to take it back to the lowest common denom.
Start with the camera, no filter, and a lens. Take a RAW pic of something uniform in color like a blue wall. Gradient?
Add the filter, take same pic
See the gradient yet?
If not add the scope, indoors, aim at wall, take pic, see the gradient yet? etc...etc...


Post Extras: Print Post   Remind Me!   Notify Moderator  
ICallHimGamblor
super member


Reged: 06/24/13

Re: I am doing something very very wrong new [Re: shawnhar]
      #6131599 - 10/11/13 05:10 PM

Unfortunately, I have absolutely no Canon lenses. I bought the camera body from Canon Direct knowing I would not be using it for any other purpose.

Scott: The LP filter I bought is the Orion SkyGlow imaging filter. There was another thread on here somewhere where that was what I was told to buy.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | (show all)


Extra information
16 registered and 36 anonymous users are browsing this forum.

Moderator:  Dave M, fishonkevin, WOBentley, tecmage 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 1910

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics