My first DSOs, a dream came true

[Archonom]

Last night one of my dreams came true when I managed to obtain my first DSO shots. I am still a bloody beginner and just started in February this year. Since then, I focused on planetary imaging because decent results could be achieved easily. But my biggest goal is to learn how to image Deep Sky Objects, so I started practicing with my equipment and 3 star alignment.

Last night, I tested some new settings with the guiding, and although alignment was poor, I was able to capture a few things. I live in a very light polluted area, so I am glad that at least the brightest objects are visible on cam.

Unfortunately, the pics seem to be out of focus and the starts are not dots, but small eggs or lines. But still, I am very happy and it was definitely worth it staying up until 4 am. 

As usual, I would be very happy if you have feedback for me. When I view the images you guys post here, I am very fascinated of how professional they look. I can only imagine how many hours of work you put into a single picture, and I keep on being motivated by seeing this level of dedication.

Let's start with the Andromeda Galaxy:

 

And the fishhead nebula:

Wow, the Orion Nebula looks so awesome when shutter is greater than 2 seconds!

 

Plejades, single shot, 30s:

And finally, the horse head nebula, only few shots with 30s each and ISO 1600:

 

 

Next goals: Better Andromeda and horse head images. What would you say: In a light poluted area, how would you shoot those two objects?

I just started with 3 stars alignment and guiding, but I imagine it is better to shoot something like 10x5m than 20x2,5m?

Thanks for your time!

 

[Demonperformer]

I would concentrate on M31 first rather than HH. Presume you are using a DSLR - has the IR filter been removed (modded)? This will make HH shots much easier (you get more light from the bright nebula increasing the contrast with the dark nebula.

As regards sub length, if you LP will allow 5m subs they will probably help, but if the subs start getting fogged, drop them down a bit. You also need to consider how good your guiding is. At the end of the day it is the integrated (total) time that is important - longer total time = more photons = better results. 

[RolandKol]

Nice start! Much better than my first attempts! Jealous a bit!

In your case, I would start from proper Polar Alignment, it will alow you to make subs around 2 min exposures with Canon ISO800 and  in quite heavily light poluted area.

Always keep an eye on the Histogram, with heavily Light Poluted skies, try keeping the peak in the middle or two thirds from the left. Only histogram will tell you what exposure time to choose.

Your main testing ISO should be 800 and go lower or Higher later to see if you get better results.

Stay on ISO 800 or 1600 (depends on guiding, the better guiding you will achive, the lower ISO you can hit, but I would not go lower than 400).

Also, I would check the colimation... Your star spikes look very odd... 
Leave the Horse Head for the future, focus on Andromeda and Orion as your Canon 1200D is too week in HA spectrum for Horse Head, and if it's not too late, you can try Eagle Nebula also, you will get quite nice images with Canon.

 

P.S.

What software do you use for guiding and imaging?

By all means, Learn about PlateSolving and Dithering, - it will make your life Much Much easier!

[Vox45]

Nice shots

I would recomend that you learn about plate solving (using astrotortilla just to name one but there are others) that will save you a lot of time and put your targets dead center. Also, I see that you went for 3200 ISO is there a rational for this setting ? I usually go for 1600 ISO on my modded 1000D.

[alacant]

Hi. Great start:) You've simply missed focus a bit. One of these with the telescope pointed at say Deneb would help you perfect focus.

HTH and clear skies.

[Rodd]

Its funny, but I have always thought that Planetary imaging is MUCH harder than deep space imaging.  Maybe because seeing is so important to planetary, an my seeing is typically terrible.  But even on nights of decent seeing when I am able to take pretty sharp lunar images, decent images of the planets elude me.   But I know exactly how you feel--it was a dream of mine since middle school--long  before the invention of the CCD/CMOS or the computer.  

Your off to a great start.  Keep at it.  Start with "easier" targets (targets that do not have huge dynamic ranges that require HDR approaches..that is multiple stacks of various exposure lengths.  I agree that PA is important, but its not critical to get sub arcminute accuracy right off the bat.  Get to know your camera and your scope, so you can find the sweet spot of exposure duration, and the number of exposures you need.  Focus IS critical.  But good results can be had with a B-mask (an electronic motorized focuser is best--even if you use it manually with a hand controller).  The BOSS II kit I have has a temperature probe and after you make a model for a specific scope/camera, you may only have to focus once or twice per night as temperature related focus shift is linear.  Any way--keep up the good work.  There is an entire universe out there waiting for you 

Rodd

[Archonom]

Wow, so much feedback! Thanks, this is highly appreciated! Regarding the things you asked:

Yes, the Canon EOS 1200 DA used for this photo session is astro-modded. @Demonperformer, you mentioned that what counts is the total time of light. However, I started to wonder if it is really the same if I do let's say 10 x 30s shoots or 5 x 1m shoots. I have the feeling that one needs a certain minimal shutter. E.g. it was not the same when I shot 30x2s Andromeda and stacked it compared to 2 x 30s.

 

@RolandKol Thanks so much! I would love to do polar alignment, unfortunately I never discovered Polaris in the night sky. I am a bit ashamed, but I guess that the sky is too light polluted in the northern direction where Polaris should be, so I never was sure about what star is Polaris and what might be just a neighbour.

ISO is 1600 or 3200 because I felt the high sensitiy is needed for my light-polluted site. But I will try 800 next time, thanks! I will also check the colimation.

I ordered a MGEN II, so no software is used for guiding. Dithering is something I want to do when I learned to align properly. I wonder if plate solving is possible when I don't want to use a Notebook?

 

@alacant, @Rodd:

Thank you, your comments are really helpful and very motivating!

 

 

 

 

[Archonom]

Thanks for the hint regarding collimation. I took a look at my Newton today, and well, what could I say, some work needed to be done : - )

Now looing forward to seeing some decent spikes!!!

[Stub Mandrel]

?

If you have a choice of possible pole stars, you have reasonably good skies! It's a good evening if I can see Kochab in Ursa Minor and few times a year when clear skies and well dark adapted I get to see virtually all the constellation.

[Demonperformer]

On 22/09/2018 at 21:16, Archonom said:

@Demonperformer, you mentioned that what counds is the total time of light. However, I started to wonder if it is really the same if I do let's say 10 x 30s shoots or 5 x 1m shoots. I have the feeling that one needs a certain minimal shutter. E.g. it was not the same when I shot 30x2s Andromeda and stacked it compared to 2 x 30s.

Well, what really counts is getting the highest SNR (signal to noise ratio) possible. There are at least 4 sources of noise, some of which can be mitigated by taking calibration subs (bias & darks). There are others on SGL [@vlaiv springs to mind] who can give you much better explanations of the intricacies of this than I could ... and have done so on other threads.

The "minimum exposure" debate rages ... some would say that, if an object (or part thereof) results in only one photon capture per minute, then any exposure less than a minute will not get it. Others would say that if you take two 30s subs, the odds are that at least one would get it ... either way, one photon in a minute ... which is a pretty small number and likely to be lost in the noise. In general, the longer the subs you can get the better will be the results, but I have seen an image (years ago on SGL ... really wish I had kept a note of the thread) of HH made up of about 2000* 2s subs (just over 1h integrated time), so it can be done, but it is not the easiest way ... I would go for 40* 100s subs over 2000* 2s subs any day.

[Stub Mandrel]

5 hours ago, Demonperformer said:

2000* 2s subs

Trouble with that is you are thrashing your shutter count!

With 5-minute subs you are considerably extending the life of your DSLR, if you use one!

[vlaiv]

In very high LP, single exposure length won't matter much, but total imaging time is most important thing.

Exposure length is tied to read noise and it's scale compared to other noise sources (well, there are many factors in choosing it, like target saturation, guide performance, but lets address SNR here). In heavy LP, by far the most dominant noise source is sky shot noise (same noise you get from target, but this one is related to background glow that does not contribute to image in any way as sky glow gets removed in processing).

Use exposure length that is most "comfortable", rather than concentrating on very long subs. Choose it based on how good your guiding is, how much data you are willing to store and process, if you are doing DSLR imaging, do count in number of shutter releases (as it is mechanical thing and wears out as has been suggested).

Looking at the images and star shapes, I would recommend (as others have done) collimation of the scope. Next would be proper coma corrector spacing and resolving any tilt - if you observe your images, apparent defocus is different in different parts of the image - this is due to field curvature and collimation rather than poor focus itself.

LPS filter can help quite a bit. Do also pay attention to target selection for a particular night. Look at your LP in the sky and see if there are "darker" zones of the sky - shoot the target when it is in darker area. Shoot the target when it is at highest altitude. Choose the night of higher transparency for imaging of DSOs.

Calibration of frames with DSLR can be tricky since there is no temperature control. Probably best way to calibrate DSLR subs would be (although others may not agree with this, and use other techniques):

Use bias, dark and flat files, correct flats with bias only, correct lights with bias + optimized darks (software tries to guess correct scaling factor for dark current, because this changes with temperature and there is no way to guess correct value) and flats at the end.

HTH

[Archonom]

Thank you @vlaiv , your hints helped me alot during the last nights!