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FORUMS Photography Talk by Genre Astronomy & Celestial Talk 
Thread started 25 Jun 2016 (Saturday) 16:39
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What to photograph tonight??

 
davidmtml
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Jun 25, 2016 16:39 |  #1

Hey everyone!

I just received my iOptron Skytracker (3302B) and need something cool to shoot tonight (besides the Milky Way)! I will definitely still be testing it out for some widefield Milky Way shots, but would like to try some sort of DSO as well. I see lots of talk of the Orion Nebula for a good entry-level DSO to photograph, but that isn't visible in the sky right now. Maybe Andromeda??

I've got about 2.5 hours from sunset to moonrise...so...what should I shoot? Any other recommendations for good "entry-level" DSO photography? I will be shooting with a 6D and 5d III, and I have a 85 F1.8, 135 F2, 70-200 F2.8, and Sigma 150-600C (which the skytracker seems to handle to my surprise) at my disposal.

Thanks!!




  
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Celestron
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Jun 25, 2016 18:57 |  #2

Personally with those lens I'd leave the big lens home. Your 85 is a good size but I would favor the 70-200 or the 135mm . Try a WF shot of M8 region or Scorpion's head shot . Lots' of good objects in the MW region .




  
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davidmtml
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Jun 25, 2016 19:42 |  #3

Celestron wrote in post #18049913 (external link)
Personally with those lens I'd leave the big lens home. Your 85 is a good size but I would favor the 70-200 or the 135mm . Try a WF shot of M8 region or Scorpion's head shot . Lots' of good objects in the MW region .

Thanks Celestron! I'm sure I will mostly use the shorter lenses, especially since it's my first time out...but I'm sure I'll bring the 150-600 in the car...just in case :)




  
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davidmtml
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Jun 26, 2016 11:19 |  #4

Well, I got out to try it last night, and overall I am impressed! I was running a little later than I wanted to, and knew the moonrise was coming within a couple hours, so I just did a very rough alignment. It will definitely take some practice to get good with the polar scope. I was still able to get pretty decent tracking, did a few ~4 minute shots at 14mm, 38 seconds at 135mm, and 28 seconds at 600mm. There's definitely a tiny bit of error which would most likely be corrected with a better alignment, plus more patience! I set my intervalometer to take 15 shots, but I kept going over and grabbing it to look and see how it was doing, definitely adding a bit of shake! I found this random nebula(?) in the Milky Way, so that's what I tried to shoot. I still haven't figured out DSS, and at this point, a single image is way better than what I get with DSS. Here's a small sample! Flickr is giving me grief uploading, so using the POTN uploader, which limits to 2 per post.

(This is untracked, but caught the moonrise)


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This is a crop from a 178 second exposure with the Samyang 24mm f1.4


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davidmtml
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Jun 26, 2016 11:20 |  #5

38 seconds at 135mm


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28 seconds at 600mm


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Celestron
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Jun 26, 2016 12:51 as a reply to  @ davidmtml's post |  #6

Both turned out very well ! Nice job on captures and edits . Next time you get a chance go for m6 & m7 , both very nice open clusters . That 135mm would be your best option for those and maybe you can get both in the same FOV . Look forward to more images. The moon comes up 30+ mins more later every night . Won't be long til a new moon night then you'll have lots of time with dark nights .




  
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TCampbell
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Jun 26, 2016 14:44 |  #7

Unfortunately Orion isn't currently visible. The sun is currently in that section of the sky. You have to wait for winter months for the Earth to swing around to the other side of the sun in order to view it.

But there are lots of interesting objects in the band of the Milky Way... region (most of the interesting stuff is near the band of the Milky Way).

For example...

M8 (Lagoon Nebula) and M20 (Trifid Nebula) are very close together (they could both be framed in the same image using a 500mm or wider lens). Using a 300mm focal length you could easily fit M8, M20, and M21 (an "open cluster" of stars) in the same frame.

M16 (Eagle Nebula) and M17 (Omega Nebula) are also very close and could easily be framed using a 300mm or wider lens.

The North American Nebula (NGC 7000) is quite high in the sky just near the tail of Cygnus the Swan -- it would nearly fill the frame of a 500mm lens (or scope).

The Veil Nebulae (Western and Eastern Veil) are NGC 6960 and 6992 and also would fit in the frame of a 500mm focal length lens.

The Antares / Rho Ophiuchi region (in Scorpius) is very colorful at about 135mm (low to the horizon for Northern Hemisphere observers.)

If you stay up late enough you can image the Andromeda Galaxy (the galaxy is about 6x wider than the width of the full moon -- so it occupies a larger piece of sky than you might guess). Things tend to image better if you wait for them to rise high enough in the sky (usually at least 30º above the horizon... or even 40º). Not all objects rise this high (the core of the Milky way doesn't get very high up for those living at northern latitudes) but Andromeda does get quite high up if you wait. If you wait until 3am it's quite high... or you can just wait until, say, August or September to image it and then it'll be quite high without having to wait so late in the AM.

There are several types of "nebulae" including "emission nebulae" (gases that are glowing), "reflection nebulae" (gases that are not glowing but reflecting the light of nearby stars), dark nebulae (black clouds that aren't glowing or reflecting), and "planetary nebulae" (really the shells of gas expanding outward from stars that have died -- these tend to be very small and need long focal length telescopes to see them. I have a photo of the Dumbbell Nebula that I've posted here but that was taken through a 14" aperture Celestron C14 which has a focal length of 3910mm -- so you won't see those in wider field camera images because they are too small.)

I mention these types because of these, "emission nebula" tend to be dominated by gases glowing in the Hydrogen alpha wavelength -- which is a red color. Hydrogen is the MOST dominant atom in the universe (by far)... roughly 90% of all normal matter is hydrogen atoms. This is why astro-imagers want cameras that are sensitive to that particular wavelength of light. But Humans are visually not particularly sensitive to reds... so a typical photographic camera has a filter in front of the sensor which trims the wavelengths of light that can pass in order to imitate the sensitivity of the human eye. An unfiltered camera is somewhere around 4-5 times more sensitive than a filtered camera. So... these cameras that are modified for astrophotography tend to be about 4x more sensitive to these reds (that would be like taking an exposure which is 4x longer).

Canon's model was the Canon 60Da but they ran out of the supply of those. Nikon introduced the D810a (but it's expensive.)

What most people tend to do is get a used or less expensive DSLR and then modify it by doing surgery on the camera and replacing the internal filter.

Hutech sells a version of the camera 6D which has been modified for astrophotography and the advantage of the Hutech version is that they're (so I'm told) an authorized Canon service center... so if Hutech does the modification it doesn't void the warranty.

The modified cameras do a much better job imaging these areas (and the exposure time required is significantly less) than using a standard (unmodified) camera.

You can use astrophotography software to help you determine what's up in the night sky and even how it will frame through a telescope or camera lens.

I use Starry Night Pro Plus 7 (the "pro plus" version is about $250, the "pro" version is about $150) to do this. It lets me enter my equipment list of telescopes, cameras, eyepieces, etc. It doesn't specifically support camera lenses but you can enter a camera lens as if it were a telescope and it'll calculate the accurate frame of view (the area of sky visible) through that lens with any given camera.

You can do this with Stellarium (Stellarium is free software) too. It's not quite as advanced as Starry Night but you can't beat the price.

A few other tips... you'll typically be shooting at higher ISO... e.g. 800 or 1600. But noise is higher at these high ISOs AND it builds up over the long exposures. To combat the noise, you can take LOTS of frames (e.g. say 25 frames) of the subject. Take about half as many frames with the lens capped (e.g. put the lens cover on and take 13 more frames -- these are called "dark" frames). Using the same ISO, but the fastest shutter speed, take the same number of frames (e.g. 1/4000th sec exposures at the same ISO you used for your "light frames") and these are called "Bias frames" Lastly, you typically want something called "flat frames" and to take those you need something which is PERFECTLY EVEN illumination in front of the camera lens and then just take a middle exposure (you could hold an iPad with an "all white" screen in front of the camera lens and take another 13 exposures metered so that those images are middle-gray).

All of these are combined in a program such as the free "Deep Sky Stacker" (you may hear people mention "Registax" or "AutoStakkert2" -- Registax and AutoStakkert are for "planetary" imaging -- not deep space. Registax and AutoStakkert use the round shape of the planet to register (align) the frames for stacking... Deep Sky Stacker uses the positions of bright stars to register (align) the frames for stacking. You feed Deep Sky Stacker all the data and it'll combine to produce your image.

The combined (fully calibrated, registered, and integrated) image then still requires some post processing to stretch the image data and tease out the beautiful details.




  
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davidmtml
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Jun 27, 2016 16:41 |  #8

I'm thinking my photo may have been of the lagoon nebula...can anyone verify??




  
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TCampbell
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Jun 27, 2016 17:01 |  #9

davidmtml wrote in post #18051608 (external link)
I'm thinking my photo may have been of the lagoon nebula...can anyone verify??

The larger nebula at bottom is the Lagoon (Messier 8). Near the top of your image, the red/blue is the Trifid nebula (Messier 20).




  
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davidmtml
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Jun 27, 2016 17:24 |  #10

TCampbell wrote in post #18051631 (external link)
The larger nebula at bottom is the Lagoon (Messier 8). Near the top of your image, the red/blue is the Trifid nebula (Messier 20).

Perfect, thank you for that, and for your detailed post before!!




  
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What to photograph tonight??
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