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Thread started 12 Jun 2016 (Sunday) 09:42
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Deep sky attempts: M13 and M57

 
pulsar123
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Canada
Post has been edited over 1 year ago by pulsar123.
Jun 12, 2016 09:42 |  #1

Still learning the ropes of deep sky photography. My earlier attempts a few years back were not very successful, so I upped my game by (a) buying a collimator tool for my 6" Newtonian and doing a proper collimation job, and (b) doing a very careful job with polar alignment of my mount. At the end I improved substantially quality of my un-guided deeep sky photos (in the prime focus of the telescope): now 30 seconds exposures are good most of the time.

Here are the two examples from the night before: globular cluster M13 and planetary nebula M57:

IMAGE: https://c1.staticflickr.com/8/7782/27327167040_8ea5e3ba5a_b.jpg
[IMAGE'S LINK: https://flic.kr/p/HCNS​Gq] (external link)Globular cluster M13 (external link) by SyamAstro (500,000 views - thank you!) (external link), on Flickr

IMAGE: https://c1.staticflickr.com/8/7450/27588618176_87429bf2ce_b.jpg
[IMAGE'S LINK: https://flic.kr/p/J2UT​1C] (external link)Space fluorescent bulb (external link) by SyamAstro (500,000 views - thank you!) (external link), on Flickr

I used multiple 15-second exposures at ISO 3200 on my Canon 50D. The M13 shots was stacked from 20 exposures, the M57 shot - from 100 exposures. I used electronic shutter (FRSP) under Magic Lantern for shake-free shots. (And hence the 15-second exposures: unfortunately FRSP doesn't work at >16s.) I used 20-shot dark frames, and did the stacking in DeepSkyStacker.

What was surprising that both shots have the same limiting apparent magnitude - 16.2m, despite the factor of 5 difference in cumulative exposure. I realized I still have to learn quite a bit about DSLR usage in astrophotography (my prior astrophotography experience was from the old film days.) From reading a couple of articles (like http://dslr-astrophotography.com/i​so-dslr-astrophotography/ (external link) ) I realized that my choice of ISO (3200) is likely the worst possible for my camera; ISO 1600 should be much better. I'll give it a try next time. Also, the 15 second exposure could be the fundamental reason I can't go beyond 16 magnitude, regardless of the number of shots, as there are simply not enough (or none at all) photons in many short exposure shots, so stacking won't increase the sensitivity anymore. The proper solution would be longer exposures, which might mean the need for an auto-guider and for a better location (my city has really bad light pollution problem; I can do maximum 30s at ISO 3200 at f/5 before the background overwhelms the photo.)

Here is a specific quote (http://www.covingtonin​novations.com/dslr/new​dslr/) (external link):

"The best ISO for deep-sky work with most Canon DSLRs, and indeed most DSLRs of all brands except the very newest, is around 1600. ... With most Canon DSLRs (such as the 60D) that is around ISO 1600. Shooting at more than ISO 1600 does not record any more light; it just loses dynamic range."

6D, Tamron 24-70 f2.8 VC, 135L, 70-200 f4L, Laowa 15mm 1:1 macro, 50mm f1.8 STM, Samyang 8mm fisheye, home studio

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troypiggo
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Jun 13, 2016 18:52 |  #2

I think you've done well. Maintaining star colours etc. 15s is pretty short and I'd like to push that a bit harder - with my 5DII I do subs around 4m to 8m long, but admittedly that's guided and at dark sites (don't tend to use my DSLR at home) - I think you said you weren't guiding? Might need to look into that ;) What mount are you using?
ISO 1600-3200 should be fine with newer cameras.


"Interesting. You're afraid of insects and women. Ladybugs must render you catatonic." - Sheldon
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pulsar123
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Jun 14, 2016 08:34 as a reply to troypiggo's post |  #3

Thanks for the feedback. Yeah, I wish I had skies dark enough for 4-8 minutes exposures :( Going somewhere darker is currently not an option, and I suspect (still trying to figure out the technical details) that with my polluted skies autoguiding would be a waste - but I can just try it for the heck of it, because I like technical challenges. My mount is fully capable of autoguiding - Celestron GT5 with a dedicated autoguiding port, also fully controllable from my laptop (Stellarium, ASCOM) via USB-serial adapter connected to the NexStar remote. My hope is that a program like PHD2 can control my mount via ASCOM driver -> USB-serial adapter -> NexStar controller, so I don't even have to find the way to use the autoguiding port (I have Arduino experience, so if I have to I can put together an adapter for that). My idea is to get a cheap small second hand telescope on kijij (I see 70-80mm options for under 50$), piggyback it on top of my C6-NGT reflector (my mount is rated for much larger telescope than my 6"-er, so should be okay), attach a web camera to it, and run the whole thing using PHD2 on my laptop.

Trying to deal with the sky light pollution, I just ordered a cheap (20$) Orion SkyGlow filter knockoff from China. Supposedly it can improve contrast for nebulae by a factor of three, likely less for continuous spectrum sources (stars and galaxies). With this filter I will likely need autoguiding.

I also ordered a camera adapter for eyepiece projection photography. For now I only have the direct focus option, where my Canon 50D pixels are too large to get to the diffraction limit of my telescope. With my 20mm eyepiece this should give me ~3x longer effective FL (from 750mm -> 2300mm), reducing the skyglow by a factor of 10, which again would be an interesting case for autoguiding.


6D, Tamron 24-70 f2.8 VC, 135L, 70-200 f4L, Laowa 15mm 1:1 macro, 50mm f1.8 STM, Samyang 8mm fisheye, home studio

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troypiggo
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Jun 15, 2016 00:42 as a reply to pulsar123's post |  #4

PHD2 and ASCOM definitely the way to go. Guidescope and camera - I use a little Orion finder guider and QHY5 guide cam (something like this: https://www.optcorp.co​m ...i-autoguider-package.html (external link)).
Skyglow filters etc - careful of your whitebalance. My experience was that they throw the spectrum out and found it hard to whitebalance.
A CCD camera will tolerate LP better than a DSLR, but I know it's a cost thing. You can work up to that in a couple of months :)
I've never done EP projection photography - reckon prime focus as you're doing now is the best quality.


"Interesting. You're afraid of insects and women. Ladybugs must render you catatonic." - Sheldon
Flickr (external link) | Gear List | Macro Rig | Astro Rig | Astro Software Post

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Celestron
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Jun 25, 2016 19:14 |  #5

Guess I missed this post . Good captures on both images .




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pulsar123
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Post has been edited over 1 year ago by pulsar123.
Jul 24, 2016 17:16 |  #6

I got recently a dedicated astro-camera (ToupCam, 1.3 Mpix, 3.75 um pixels, mono, 75% quantum efficiency; was on sale for 180$; http://www.ontariotele​scope.com ...ith-ST-4-Port_p_631.html) (external link), and redid M57 last night with this camera as its first DSO test (10 exposures x 15 seconds) - again in the prime focus of my 6' f5 Celestron. It looks substantially better than my previous attempts using Canon 50D (perhaps my focus wasn't precise): one can see stars down to 18th magnitude (the two circled stars are ~18m), and much more detail:

IMAGE: https://c4.staticflickr.com/9/8701/27906250283_c1eed6d32d_o.jpg
[IMAGE'S LINK: https://flic.kr/p/JvYP​Yg] (external link)M57 with ToupCam (external link) by SyamAstro (500,000 views - thank you!) (external link), on Flickr

6D, Tamron 24-70 f2.8 VC, 135L, 70-200 f4L, Laowa 15mm 1:1 macro, 50mm f1.8 STM, Samyang 8mm fisheye, home studio

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Celestron
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Jul 24, 2016 17:39 |  #7

Congratulations on the new camera . It's very sensitive . I can see that companion galaxie slightly to the right lower of M57 . Not really much detail but enough to tell it's suppose to be there . When you get more images to stack it may show up better . You can see it in this image on APOD : http://apod.nasa.gov/a​pod/ap030516.html (external link)




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pulsar123
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Jul 24, 2016 20:07 as a reply to Celestron's post |  #8

Thanks - indeed, there is a galaxy there! It only has integrated magnitude of 15.5m, but I can already see something - cool!


6D, Tamron 24-70 f2.8 VC, 135L, 70-200 f4L, Laowa 15mm 1:1 macro, 50mm f1.8 STM, Samyang 8mm fisheye, home studio

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Toxic ­ Coolaid
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Jul 25, 2016 14:49 |  #9

Nice shots. Takes me back to one of my 1st DSO of M57. It was cool to see the ghostly Ring appear in the first shot.

I've had great luck with cheap timers off ebay for $10-15. for the price you can order 2 and have a back up, or one for another camera. The only timer I've ever had fail was an $80 canon timer.

http://www.ebay.com ...3b177f:g:YaEAAOSw-zxWmMRz (external link)




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pulsar123
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Jul 25, 2016 15:26 |  #10

Thanks!

With Magic Lantern I think there is no longer a need for external timers in Canon world. The last M57 photo was made with ToupCam (no DSLR involved; direct recording to my laptop).


6D, Tamron 24-70 f2.8 VC, 135L, 70-200 f4L, Laowa 15mm 1:1 macro, 50mm f1.8 STM, Samyang 8mm fisheye, home studio

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Toxic ­ Coolaid
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Jul 25, 2016 18:54 |  #11

I've have used Magic Lantern in the past. I thought you said you were limited to 15 seconds using it. I have found old school stuff helps add less clutter to the already complex task of shooting Astro.




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pulsar123
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Jul 25, 2016 20:02 |  #12

Toxic Coolaid wrote in post #18077502 (external link)
I've have used Magic Lantern in the past. I thought you said you were limited to 15 seconds using it. I have found old school stuff helps add less clutter to the already complex task of shooting Astro.

No, it's only in the FRSP (electronic shutter) mode I am limited to 15s. With a regular shutter I can run intervalometer with arbitrary exposures under ML. And once you get used to setting it up it is actually very convenient - no additional cables to be bothered with.


6D, Tamron 24-70 f2.8 VC, 135L, 70-200 f4L, Laowa 15mm 1:1 macro, 50mm f1.8 STM, Samyang 8mm fisheye, home studio

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pulsar123
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Jul 26, 2016 11:01 |  #13

More testing of ToupCam from last night:

IMAGE: https://c2.staticflickr.com/9/8312/28565670545_560c7b1876_b.jpg
[IMAGE'S LINK: https://flic.kr/p/Kwfw​D8] (external link)Near Galactic centre (external link) by SyamAstro (500,000 views - thank you!) (external link), on Flickr

IMAGE: https://c1.staticflickr.com/9/8631/28533151136_a9193e07ea_b.jpg
[IMAGE'S LINK: https://flic.kr/p/KtnR​KE] (external link)Globular cluster M13 with ToupCam (external link) by SyamAstro (500,000 views - thank you!) (external link), on Flickr

IMAGE: https://c6.staticflickr.com/9/8821/28565669805_7fab897081_z.jpg
[IMAGE'S LINK: https://flic.kr/p/Kwfw​qn] (external link)Spiral galaxy M51 with ToupCam (external link) by SyamAstro (500,000 views - thank you!) (external link), on Flickr

I am trying to autoguide my Celestron AG-5 mount with PHD2 software, to get beyond ~30s limit I have now, but it looks like my mount is not behaving. Perhaps it needs "hypertuning", which is a risky stuff.

6D, Tamron 24-70 f2.8 VC, 135L, 70-200 f4L, Laowa 15mm 1:1 macro, 50mm f1.8 STM, Samyang 8mm fisheye, home studio

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pulsar123
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Sep 25, 2016 14:35 |  #14

Another one, from last night. I definitely need shorter FL and color here...


IMAGE: https://c6.staticflickr.com/9/8408/29839225501_6b5823c8b1_b.jpg
[IMAGE'S LINK: https://flic.kr/p/MsMQ​ac] (external link)Center of the Andromeda galaxy (M31) (external link) by SyamAstro (500,000 views - thank you!) (external link), on Flickr

6D, Tamron 24-70 f2.8 VC, 135L, 70-200 f4L, Laowa 15mm 1:1 macro, 50mm f1.8 STM, Samyang 8mm fisheye, home studio

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TCampbell
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Sep 26, 2016 10:27 |  #15

pulsar123 wrote in post #18076507 (external link)
I got recently a dedicated astro-camera (ToupCam, 1.3 Mpix, 3.75 um pixels, mono, 75% quantum efficiency; was on sale for 180$; http://www.ontariotele​scope.com ...ith-ST-4-Port_p_631.html) (external link), and redid M57 last night with this camera as its first DSO test (10 exposures x 15 seconds) - again in the prime focus of my 6' f5 Celestron. It looks substantially better than my previous attempts using Canon 50D (perhaps my focus wasn't precise): one can see stars down to 18th magnitude (the two circled stars are ~18m), and much more detail:

QUOTED IMAGE
[IMAGE'S LINK: https://flic.kr/p/JvYP​Yg] (external link)M57 with ToupCam (external link) by SyamAstro (500,000 views - thank you!) (external link), on Flickr

Sometimes it isn't necessarily the focus, but how well the atmosphere decides to cooperate. It can also be a question of how high the object is in the sky when you do the imaging. Objects near the zenith mean you are looking through less atmosphere than when the object is lower.

I find that the M13 globular cluster is a good test of atmospheric stability. On nights when the seeing is poor, it appears as a fuzzy patch on the sky with a few stars that can be resolved. On nights when the seeing is excellent it appears as thousands of stars and I don't see it as a fuzzy spot on the sky.

Where you are is also a big factor. Earlier in the season M13 is in the southeast section of the sky during peak observing hours, I can set up my scope on the northwest shore of Lake Erie and now I'm viewing it across miles and miles of very cold, flat water. This really calms down the atmosphere because it promotes a smooth laminar airflow with no thermals to create turbulence. If I wait until later in the year when it appears in the southwest, I have to view it over warmed land and this creates more thermals and blurs the object.




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Deep sky attempts: M13 and M57
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