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The "No EQ" DSO Challenge!


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Couple from last night. 

15 sec exposures live stacked in Sharpcap. Bit of processing in Startools.  Such as my ability is with it. Lol

Altair 72mm semi apo, ZWO 178MC, AZGti

M81

2020-04-26_06-53-07.jpg.99afc43f0cb906545919481087049726.jpg

 

M101

2020-04-26_06-53-34.thumb.jpg.fef39514fc3265e3377eb9b6adacac26.jpg

 

 

Edited by Bobby1970
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I'm still fairly new to imaging, but have had a good start with Planetary and Wide Field images. Obviously, like most of us, it's the Deep Sky stuff I'd like to glimpse, but time, location and more im

Assorted shots with a Nexstar 102SLT and a Canon 1000D. 30sec subs at ISO1600. Total exposures range from 5 mins (M20)  to ~1hr (M31). NigelM

this was taken a couple years ago on my AZGOTO mount with 130p...... about 50 x 5 sec subs, no calibration frames

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Some of my early images taken with a Nexstar 8SE Alt/AZ with Celestron Motor Focus (ASCOM), Celestron Starsense, Celestron F 6.3 Reducer/corrector, an Altair 385C (at 115mm from the reducer via a diagonal) over the last week, whilst checking everything was tracking / aligning / focussing and working out how to use Sharpcap properly (HIstogram, tracking and stacking etc). This is a new telescope for me after upgrading from the 4SE. Images are noisy anf far from flawless (Lots of short subs and max exposure just ot get something on the sensor!). Have just watched this you-tube vid so next clear night will be attempting to 'do it properly'. Still, am happy its all working together with not a lot of things misbehaving! hopefully its just a case of learning and refining now. Images exported from FITS to jpeg and spruced up on iPad using built in photo editor so less than flawless and are really just test and 'what does this button do' type images!

 

M51.jpg

m81 cigar galaxy.jpg

M82 .jpg

Stack_12frames_192s_WithDisplayStretch.png

Edited by fluffkat
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Hi Happy-Kat, I wrote it down as M106however not 100% Sure! :p am really quite happy as I have a street light next to the garden an the moon was coming up so far from great conditions! they are M82, M81 and suspected M106 :p (danger of a go-to... I just had it slew to something to make sure it was centering properly!)

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M57.  LX90 with Canon 70d, single exposure. Cropped, resized and brightened a bit is about the extent of processing I did.   I'll have a go at some stacking next.

It's a bit of a learning curve and two things I learnt were:

The focus shift on the scope is a flaming pain and makes it hard to get it 100% so focus is probably slightly off.

Some sort of counterweight at the front of scope probably isn't a bad idea as the scope with camera gear is a bit back heavy.

received_567855097173883.jpeg

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Great to see activity of new images posted on this thread.

LlThat's a super cluster you've got.

M57 you could try stacking multiple frames to tease more from the target.

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Finally started to teach myself some post processing methods instead of using phone apps. Although a bit over done I'm really pleased with the detail in this pic.  M33 captured a good few months ago . Nexstar evolution 9.25 , zwoasi294 Mc , sharpcap and startools. 158x7 second exposures. Darks and flats applied.

PSX_20200522_095038.jpg

Edited by Manners2020
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The whale galaxy, 9.25 Nexstar evolution @6.3 , asi294mc, captured with sharpcap and processed with startools. 27 minutes worth of 16 second exposures, darks and flats applied.

PSX_20200524_090056.jpg

Edited by Manners2020
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M87. Very new to this hobby, so got a lot to learn. ISO 6400, and 15 seconds. Canon t3i. I included the histogram too for the raw pictures, what should I change with the ISO or exposure to reduce the colour noise? Should I use a lower ISO? Also had full sets of calibration frames. 40 lights.

Screen Shot 2020-05-24 at 7.11.58 PM.png

Screen Shot 2020-05-26 at 12.04.02 PM.png

Edited by Heskyyyyy
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You certainly don't need an equatorial mount! I have been very pleased with the results I've gotten with my iOptron AZ Mount Pro and a Celestron RASA 8. 

The camera is a ZWO ASI183MC Pro.

Here's M101 on April 10 with 15 minutes total exposure using Sharpcap:

m101_2020-04-10T23_18_40_Stack_16bits_227frames_908s.jpg.9a2f5848e83c018223e9d15a1482748d.jpg

And here is M61 with its new supernova taken on June 12 using 10 minutes total exposure using Sharpcap:

m61_2020-06-12T22_36_54_Stack_16bits_201frames_603s.jpg.915f2194d5006dbc70bcbc61ba1ea980.jpg

Assuming it's permitted to post a link, I have a blog at https://howardgrams.github.io that shows many more images taken with this combination.

Edited by howardgrams
Added information about camera used.
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@Heskyyyyy what telescope are you using? The high ISO will I think be giving motole trouble, with a t3 I can't use above 1600. But you histogram is not giving much room to play with, are you using a light pollution filter?

@howardgrams lucky you you've captured that super nova, that's great. Agree that much can be done with what equipment already have. Are you using what is being described as 'lucky' imaging? Does your camera also support taking still?

 

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On 26/05/2020 at 19:04, Heskyyyyy said:

what should I change with the ISO or exposure to reduce the colour noise?

The simple answer is exposure. The more lights you can take and integrate, the more you can lift the signal and then deal with any noise in post-processing. The other answer is random dithering but that requires that the mount can be finely controlled between images.

Getting the ISO right can be a bit of trial and error. You're looking for an ISO that minimises read noise without blowing the exposure (which could be a risk in very light polluted or moon-lit skies) and that differs by make/model of camera. There are some good sites that show the read noise curves for cameras. You're looking for the point where there is minimal improvement in read noise when increasing ISO (near the bottom of the steep curve). Don't worry about using lower ISO's. You'll recover the signal through integration and stretching.

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To happy-kat: I had forgotten to mention what camera I use - it is an ASI 183MC Pro.  I've edited the original post to add that information.

The M101 image had Sharpcap stacking 227 separate 4 second exposures, while the M61 image  was a stack of 201 3 second exposures.  So no, this is not "lucky" imaging. (I have played with that to image the moon or planets,.)

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On 26/05/2020 at 19:04, Heskyyyyy said:

what should I change with the ISO or exposure to reduce the colour noise?

 

5 hours ago, Filroden said:

There are some good sites that show the read noise curves for cameras.

For example, this site https://www.photonstophotos.net/Charts/RN_e.htm#Canon EOS 600D_14 where the curve is for the Canon EOS600D, as it is better known on the UK. If you hover your cursor over the data points you can see what the read noise in in terms of electrons rather than its log*. However, the 'dynamic range' worsens as ISO increases (https://www.photonstophotos.net/Charts/PDR.htm#Canon EOS 600D), which means that the sensor is more readily saturated by bright objects at high ISOs.

So there has to be a compromise. This is one of the problems with AZ imaging, that individual sub exposures are of necessity limited and the fact that you need to take many of them you also want to keep the read noise down. It's not clear that from your message that you are stacking lots of image files, but if not, then you should aim for dozens, if not hundreds :icon_eek:. You probably are though, as I see you have used calibration frames.

Ian

*Edit. Below I've plotted the the read noise against ISO, with the ISO scale linear rather than the usual log scale, and it shows more clearly where the read noise levels out.

578546949_ReadNoise.png.20ea4714ce3660cd820eaab5686d975b.png

Edited by The Admiral
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Taken in city lights of Rochester, NY last night.  

90 x 30 sec lights (no filters, no darks, no flats). 

Alt-Az (Celestron Evolution mount). 

Fujifilm X-a10 mirrorless DSLR @1600 ASA (75F), Celestron C6, @ f/4.  Used Starizona Night Owl .4x reducer.

M27-7.jpg

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On 17/06/2020 at 13:47, The Admiral said:

*Edit. Below I've plotted the the read noise against ISO, with the ISO scale linear rather than the usual log scale, and it shows more clearly where the read noise levels out.

 

578546949_ReadNoise.png.20ea4714ce3660cd820eaab5686d975b.png

@Heskyyyyy the short answer (borne out by @The Admiral's graph above) is that most folks use ISO800 for the older Canons.

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