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First light (ever)


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Evening/Morning all, managed to get my very first DSO tonight, after much faffing with polar alignment, I managed to get a good bit of time on M27, but unfortunately lost a good few exposures to dew :icon_sad: rookie error! 

It's far from perfect and I have work to do on gear and processing, but this is where I'm at:

C6 SCT @ F6.3

Unmodified Canon 550D 

approx. 90 x 30 second exposures @ ISO 1600, 20 darks, no light added yet.

 

 

 

M27.jpg

Edited by Martyn87
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Very good for a first attempt. Way better than my first go.

Just an observation, you appear to have a lot of "walking noise" in the image. You should consider dithering between your subs, that will take care of it.

It's a long time since I used a DSLR for deep sky imaging but I remember having to do the Holy Trinity of darks, flats and (for the DSLR especially, bias frames).

It's nice to get an image in the bag though, very well done 👍

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4 hours ago, Hals said:

Very good for a first attempt. Way better than my first go.

Just an observation, you appear to have a lot of "walking noise" in the image. You should consider dithering between your subs, that will take care of it.

It's a long time since I used a DSLR for deep sky imaging but I remember having to do the Holy Trinity of darks, flats and (for the DSLR especially, bias frames).

It's nice to get an image in the bag though, very well done 👍

Thanks @Hals! Am I right in thinking I need to be guiding to dither? If so, I'm not quite there yet, I have an OAG waiting to go but no guide cam to put in it.

@Vroobel I haven't added flats or bias frames. Looks like I should be able to do some flats today but I might have missed the boat on bias frames as they have to be done at the same temperature as lights...? 

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55 minutes ago, Martyn87 said:

Thanks @Hals! Am I right in thinking I need to be guiding to dither? If so, I'm not quite there yet, I have an OAG waiting to go but no guide cam to put in it.

@Vroobel I haven't added flats or bias frames. Looks like I should be able to do some flats today but I might have missed the boat on bias frames as they have to be done at the same temperature as lights...? 

Yes, you need to be guiding to dither. You can do it manually by moving the RA and DEC by hand, but you have to sop imaging, move it, reestablish guiding and then start imaging each time. Not ideal. I tried it once with a star adventurer 2i, never again! 

No, dark frames should match the temperature of the lights. Bias are captured at the fastest shutter speed (say 1/4000th second) with the lens cap on. Easy to do, and can be done at any time. They can also be reused for future sessions.

Thats a great first image, coincidentally I was also imaging it for the first time last night 😊

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Posted (edited)
35 minutes ago, WolfieGlos said:

Yes, you need to be guiding to dither. You can do it manually by moving the RA and DEC by hand, but you have to sop imaging, move it, reestablish guiding and then start imaging each time. Not ideal. I tried it once with a star adventurer 2i, never again! 

No, dark frames should match the temperature of the lights. Bias are captured at the fastest shutter speed (say 1/4000th second) with the lens cap on. Easy to do, and can be done at any time. They can also be reused for future sessions.

Thats a great first image, coincidentally I was also imaging it for the first time last night 😊

Thanks @WolfieGlos, dark frames were done immediately after my lights last night / this morning, so should be OK. I've taken some flats and bias this morning but they don't seem to have made a noticeable difference, maybe I did something wrong, or just have no idea what I'm looking at 😂

Guiding is definitely on the cards, just as soon as I make a decision on a guide camera! After last night though, I think I might have to sort some dew prevention first, I lost a good half of the frames I'd taken because the corrector was covered... 

How did your image come out? 

Edited by Martyn87
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24 minutes ago, Martyn87 said:

I've taken some lights and bias this morning 

Do you mean flats? Lights are your captures of the target.

24 minutes ago, Martyn87 said:

, I think I might have to sort some dew prevention first, I lost a good half of the frames I'd taken because the corrector was covered... 

Good idea! I use Amazon specials that run off of a USB power bank, cheap enough but proper dew straps with a regulator would be better. I’ve got by so far, but it’ll be upgraded at some point. 
Have you got a dewshield at all?
 

24 minutes ago, Martyn87 said:

How did your image come out? 

Errr. I didn’t stack after the session due to our newborn waking up. So I fed her, slept, and now typing whilst feeding again whilst the wife readies the house for visitors today! So won’t be until later at least.

I only dedicated half of the session to M27, I’m intending to add more tonight with our predicted 3rd night running of clear skies 🤩 Possibly Monday night too if the forecast holds true.

Edited by WolfieGlos
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Posted (edited)
6 minutes ago, WolfieGlos said:

Do you mean flats? Lights are your captures of the target.

Good idea! I use Amazon specials that run off of a USB power bank, cheap enough but proper dew straps with a regulator would be better. I’ve got by so far, but it’ll be upgraded at some point. 
 

Errr. I didn’t stack after the session due to our newborn waking up. So I fed her, slept, and now typing whilst feeding again whilst the wife readies the house for visitors today! So won’t be until later at least.

I only dedicated half of the session to M27, I’m intending to add more tonight with our predicted 3rd night running of clear skies 🤩

Sorry, I did indeed mean flats! I'll get my head around these calibration frames eventually! 😂

I'm thinking I might grab one of the celestron heater rings and aluminium dew shield. I think I have a power supply that will do the job already. 

Ah I'm glad those days are behind me now 😂 fingers crossed for tonight! 

Edited by Martyn87
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3 hours ago, Martyn87 said:

Am I right in thinking I need to be guiding to dither?

Depending on your set up you can manually dither every few frames - but it is a faff. Also, so software allows you to dither without guiding. If you are just using an intervalometer with the camera, then manual it is!

Personally, I am impressed with anyone who images during the summer. I am waiting for astro darkness to return with the cloud and rain🤣

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23 minutes ago, Clarkey said:

Depending on your set up you can manually dither every few frames - but it is a faff. Also, so software allows you to dither without guiding. If you are just using an intervalometer with the camera, then manual it is!

Personally, I am impressed with anyone who images during the summer. I am waiting for astro darkness to return with the cloud and rain🤣

I'm using NINA for setting captures rather than an intervalometer, but I guess it's basically the same thing! Once I'm guiding, I'll definitely enable dithering. 

Looking at my subs, there's a clear difference in background brightness between the first and last, quite looking forward to astronomical darkness coming back! 

I'm already getting the itch to buy a better camera, even though last night was the first time I used this DSLR 😂

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41 minutes ago, Clarkey said:

Personally, I am impressed with anyone who images during the summer. I am waiting for astro darkness to return with the cloud and rain🤣

Thanks very much 😉

Luckily we've had an hour of astro-dark here for about a week now, but I'm still gathering data in nautical darkness.

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10 hours ago, Martyn87 said:

Canon 550D

Excellent shot.
To minimise noise, banding and colour artefacts use, light and flat frames ONLY:
550D?,Therefore  ISO800 with no in-camera dark or bias frames; simply subtract the offset. Method here.
Cheers and HTH

Edited by alacant
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24 minutes ago, alacant said:

Excellent shot.
To minimise noise, banding and colour artefacts use, light and flat frames ONLY:
550D?,Therefore  ISO800 with no in-camera dark or bias frames; simply subtract the offset. Method here.
Cheers and HTH

Thanks for this! I'm not seeing those settings in Siril but I'm sure I'm just missing it, but I was using ISO1600 which may have introduced some noise. Back on it tonight at 800!

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I'm not seeing any of those tabs to be honest. Is this part of the stacking process? I'd stacked in DSS but I've tried doing it again in Siril but it's asking for SO much disk space! 
image.png.926ebd78cf5855bb286fb52b5e02dcc1.png

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That is a superb first shot, well done.

I echo the advice about dithering and only flats as calibration frames. About not seeing the tabs, they might just be hidden. Click the little arrow to the right of the screen to reveal the tabs, and you can also drag the screen more to the left to have it take more space so you can see the tabs.

For Alacant's method you need to stack manually instead of using the script, which i am assuming you used since you get the "Error in line 64" log message, meaning you are executing a script with many lines. You can also change the working directory to a drive other than C, if you have multiple drives in your computer. If you cant get more space on some other drive you'd have to do the stack the dataset in smaller chunks, and then stack the stacks. Its not as good as stacking all the data in one go, but its possible.

Another method is to crop stack, although now you have to jump through some hoops. You would calibrate a portion of the data first, then crop those images to a smaller size since you dont need all of the sensor area to cover this target - after which you delete the uncropped files to save space. Then those cropped files take a small fraction of the total disk space and you can probably stack everything in one go.

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23 minutes ago, ONIKKINEN said:

That is a superb first shot, well done.

I echo the advice about dithering and only flats as calibration frames. About not seeing the tabs, they might just be hidden. Click the little arrow to the right of the screen to reveal the tabs, and you can also drag the screen more to the left to have it take more space so you can see the tabs.

Thanks @ONIKKINEN
I'd totally missed the arrow on the right hand side... there were the missing tabs. Told you it would be me! :D 

I was indeed using the script. I'll give it a go manually later today and see how it goes. I managed to get the script to work by moving to another drive, Managed to use 89Gb in 7 minutes which is quite an achievement

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1 hour ago, Martyn87 said:

the script

Ah, OK.

The scripts are quite restrictive. Perhaps learn how to use Siril manually first, especially with a 550. 


 

Edited by alacant
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6 hours ago, Martyn87 said:

I've taken some flats and bias this morning but they don't seem to have made a noticeable difference, maybe I did something wrong

A newbie error is to take flats too long and then they don’t work.  They need to be around 25,000 adu.  If you don’t have a way of measuring this then examine the histogram. The dark part should be between one third and under half way across.  
 
Great first image by the wsy.  
 

Edited by carastro
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Thanks @carastro, I used the NINA flats wizard which let's you set a target for adu, but I didn't really know what I was aiming for so just left it at default values. I can check later and take these again if needed. 

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I know some-one who used the flats plan in another software and it did not work for him, but using the method above it worked fine.  If you can set the ADU with that Nina Plan that should work.  Personally I normally use about 22,000 ADU.  

Dithering as stated above will definitely help but I know where you are coming from, I did everything one step at a time too and your first image is far far superior to my first efforts.  

Edited by carastro
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