Our Beautiful Universe - Photos and Videos

[Devin-M]

Sort of a preview... I managed to get about 8x 10 minute shots through the hydrogen alpha dslr clip in filter of the Spaghetti Nebula (Simeis 147) tonight, which is a supernova remnant that spans about 3 degrees across the sky at about 3000 light years distance, roughly 150-200 light years in diameter... this is one of the unstacked, uncropped, histogram stretched subs (300mm f/4.5 1600iso 10 minute full frame dslr).

Here's a quick and dirty composite of 1 Ha frame and 1 RGB frame (histogram stretched)

 

[Devin-M]

I goofed & forgot to take off the Bahtinov focusing mask while I was shooting the RGB... at least makes for nice artistic effect...

Center (RA, Dec):	(84.525, 26.413)
Center (RA, hms):	05h 38m 05.919s
Center (Dec, dms):	+26° 24' 47.894"
Size:	82.3 x 54.9 arcmin

 

[bruha]

Hello, can I just ask what is mean this 0.75 Hours if noted for. example : And the Sunflower galaxy (M63), 800/5.6, 0.75 hours; 100% crop: ? or resp. sometimes is noted integration time - XX hours. It is exposition time (continual) or what.?
Thank you very much for answer and pardon for ignorance

 

[DennisN]

Hello, can I just ask what is mean this 0.75 Hours if noted for. example : And the Sunflower galaxy (M63), 800/5.6, 0.75 hours; 100% crop: ? or resp. sometimes is noted integration time - XX hours. It is exposition time (continual) or what.?
Thank you very much for answer and pardon for ignorance

I think it is total exposure time for a photo (that is the result of stacking multiple photos into one):

total exposure time = exposure time for one photo * number of photos taken and put in stack

And I expect @Andy Resnick, @collinsmark or @Devin-M to correct me if I'm wrong.

Edit: On a second thought, maybe it isn't quite correct to call it "total exposure time", since stacking multiple photos is not for increasing brightness as such, but for controlling the noise in the photos. Maybe that's why it's better to call it "integration time".

 

[Devin-M]

Hello, can I just ask what is mean this 0.75 Hours if noted for. example : And the Sunflower galaxy (M63), 800/5.6, 0.75 hours; 100% crop: ? or resp. sometimes is noted integration time - XX hours. It is exposition time (continual) or what.?
Thank you very much for answer and pardon for ignorance

Typical exposure times for individual astrophotography pictures of nebulas and galaxies are 1-5 minutes. The more light pollution you have the shorter the individual exposures will be before the image becomes over exposed (overexposure means highlights become white and dark areas show sky glow). The problem with using a single image like this is there will be a lot of temperature dependent sensor noise in the image (the higher the outside temp, the more noise). Since the thermal noise is random, it turns out that “stacking” multiple exposures removes this noise by averaging the pixels from multiple images (it doesn’t make the image brighter although it allows you to brighten the image in post-production without revealing sensor noise). I can’t recall but I think I read somewhere every doubling of the number of exposures halves the noise— and usually at least 60 exposures removes a lot of the noise but but sometimes people take hundreds... the more you take the clearer the subtle details will become. So if you take 60x 1 minute exposures, that’s an hour or 60x 2 minute exposures is 2 hours etc.

There is also non-random sensor noise (hot pixels, amp glow, etc), and this is removed by taking a large number of “dark frames” with the lens cap on and the same exposure settings as the “light” images so any non-random noise in those images is subtracted from the “light” image.

There is also variation in brightness across the image (called vignetting) which is caused by the lens which becomes a problem when you go to brighten up (histogram stretch) the image in post production. This vignetting is removed by taking another 60 or so “flat frames” and stacking these into the image as well. The way I do flat frames is I literally stretch a white plastic bag over the lens and hold it on with rubber bands, then I set the camera to daylight white balance and auto-exposure and take 60 or so pictures pointed at the sky and or a bright light. The white balance of these is adjusted to look as white as possible and at this point you know any variation in brightness across the image is caused by the lens vignetting. So then you stack these into the image as well and it removes the lens vignetting from the astro-photo.

Typically if I’m shooting RGB of a nebula with my dslr in low light pollution I’ll do 60x 2 minute shots of the image (2 hours) to remove the random noise, and 40x 2 minute dark frames with the lens cap on to remove the non random sensor noise, and 40 flat frames with a plastic bag over the lens towards a light to remove the lens vignetting (flat frames don’t take long because the exposure times for each are hundredths of a second).

Shooting flat frames:

PS... the smaller the f/X.X number (ie the bigger the aperture) of the optical tube assembly, the less time it takes to achieve the same exposure on the image sensor. So ultimately having a low f/ number allows you to get a less noisy image in the same amount of time because you can take a greater quantity of separate exposures in the same amount of time.

 

[bruha]

Hello , aha ok, thank you for clearing this question

 

[bruha]

Hello, still one sun green filter image (ISO 300, exp. 1/20 s) , I found better then opposite etc. high ISO, and shorter exp.t)

 

[Andy Resnick]

Hello, can I just ask what is mean this 0.75 Hours if noted for. example : And the Sunflower galaxy (M63), 800/5.6, 0.75 hours; 100% crop: ? or resp. sometimes is noted integration time - XX hours. It is exposition time (continual) or what.?
Thank you very much for answer and pardon for ignorance

What I mean by the term '[xxx] hours' in the image specification is the total integration time and is a sum over all the many (many, many, many...) individual frames.

My individual exposure times depend on the lens focal length and object declination, and limited by my imperfect polar alignment. For me, individual exposure times when imaging at 800mm are generally 10-15 seconds, imaging at shorter focal lengths increases the exposure time. I'm hopeful that I can increase the individual exposure time by enabling 'periodic error correction' as the weather warms up and I can spend time training the motors.

Providing the 'integration time' is simply a metric that can be used to correlate with the signal-to-noise ratio of the final stacked image.

Does that help?

 

[bruha]

Hello, thank you it is clear now (I was not sure, if it is not continual individ. exp. time).
Can I ask what is maximum possible individ. exp. time for drive you have (with respect to drive error?)
Thank you and lot of succes

 

[Devin-M]

This is an animated GIF of supernova remnant Simeis 147 (distance 3000 ly, diameter 150 ly), combination of 1 minute RGB frames with a 10 minute hydrogren alpha frame (6nm narrowband), shot w/ 300mm f/4.5 lens on full frame dslr (d800 @ 1600iso) in bortle 2, sequence played in reverse, star removal performed on later frames via dust and scratches filter (adobe photoshop).

 

[Andy Resnick]

Hello, thank you it is clear now (I was not sure, if it is not continual individ. exp. time).
Can I ask what is maximum possible individ. exp. time for drive you have (with respect to drive error?)
Thank you and lot of succes

As I said, it depends on the lens focal length and object declination: shorter lenses = longer exposure times, closer to the poles = longer exposure times.

For example, the past few nights I have been imaging M101 @ 800mm with 20 second exposure time and keeping 40% of the acquired frames. By contrast, when I image M96 @ 800mm, if I want to keep at least 40% of the frames I must shorten the exposure time to 10 seconds.

For comparison, when I image regions of Cygnus @400mm, I can expose for 20 seconds and keep most of the frames. Imaging Orion or Markarian's chain at 400mm, I have to shorten the exposure to 10 seconds or so: my exposure limits @ 400mm are about double that @ 800mm (as makes sense).

At this point I am 'PEC-limited'; I've figured out how to polar align to approximately an arcminute or so, so the largest error source right now (for me) is the worm gear.

Imaging @ 105mm or 15mm, I can set my exposure time to 30 seconds (or longer, using an external intervalometer) without too much problem. With those lenses, I am limited by light pollution rather than misalignment.

 

[Devin-M]

@Andy Resnick I was wondering do you convert straight from RAW to 16 bit tif with noise reduction disabled, then stack along with dark, dark-flat, flat & bias calibration frames (also converted from raw to 16 bit tif), then histogram stretch the resulting tif? which software do you use?

 

[Devin-M]

I spent a while today trying to do the final processing on this image of Simeis 147. Most complicated processing I've done so far. Here it is. Oddly, the data from the Ha filter looked better from a single subframe than after being stacked (had a gradient after stacking that made it hard to stretch the histogram). The final is a stack of around 30x 1 minute RGB shots (with about 20 darks and 40 flats), a single 10 minute shot through the Ha narrowband filter with stars removed composited over the RGB star field (no darks or flats with the Ha).

100% Crop:

 

[Devin-M]

I just had an idea: Try the filter on the cloudy sky.
Maybe it can filter out the clouds and yield a clear view through them.

(Directed at the Internet in general):

There is a bunch of anti-light pollution filters available on the net.
We don't need any more of those, thanks!

Can someone please develop an anti-cloud filter for us`?

they’ve finally done it...

 

[Andy Resnick]

@Andy Resnick I was wondering do you convert straight from RAW to 16 bit tif with noise reduction disabled, then stack along with dark, dark-flat, flat & bias calibration frames (also converted from raw to 16 bit tif), then histogram stretch the resulting tif? which software do you use?

Good questions! For stacking software, I used Deep Sky Stacker for many years until I needed more and recently migrated to Astro Pixel Processor. I'm not entirely sure how either one converts the RAW files into 16-bit TIFFs, but in any case, I learned a lot about flat/dark/bias frames from using DSS and recommend that package to anyone starting out. I typically stack somewhere between 100-200 images at a time, resulting in a 32-bit/channel FITS image that I histogram stretch/compress down to 16-bit/channel TIFF.

I have a set of master flat/master dark/master bias/bad pixel images for each different lens (400/2.8 FX and 400/2.8 DX, 800/5.6 FX, 105/1.4 and 15/2.8, both FX) that I use as opposed to acquiring those frames every time I image. Something I struggled with for a looooooong time was getting a good flat: as the f/# gets lower, performing a flat field correction becomes more and more difficult. When I stop down a lens, say 400/4 or 105/2, I don't need to use flat files. In the end, I acquired my flats by imaging a computer display, about 40 frames per. Dark and bias frames were done with the lens cap on, also about 40 frames per. All calibration frames were obtained using the lowest ISO setting.

Fortunately, with APP I don't need 'perfect' flat files- APP has a clever post-processing step that I use after stacking called "remove light pollution". Working with the 32-bit/channel FITS image, 'remove light pollution' is flat-field correction on steroids- think of it as iteratively burning and dodging the background until it's flat to within 1 part in 10^8 (limiting case, my stacks are around 1: 10^6) or so across the entire frame (it also corrects for vignetting). This step can take several hours, but most of the time the software is chugging along in the background.

At this point, each target now has a set of corrected FITS files, one for each night of imaging (for example, I have images of M51 going back to 2015). As I acquire additional nights of imaging, I stack those FITS files to get the final stack, perform a quick 'remove light pollution' again, and I have the final image.

Then, I save the stretched 32-bit/channel FITS as a 16-bit/channel TIFF and perform additional post-processing as needed: noise reduction (I use Neat Image), background subtraction and color correction (I use Fiji or Preview), etc. etc.

Looking back over this post, I think I should also mention the need to have a highly organized file system!

 

[bruha]

Hello, Or. nebula -Bohmerwald Sunday 4/4 from 21-21.30 hod.
This photo is stacked from 20 exposures (30s) with Registax +contr. and sharp. increased..
Camera: Nikon D600
Lens: Tamron 70-300/4-5.6

 

[bruha]

Hello, this is still once image of Orion trapezoid by SV Ebony Camera Gimp corrected -(increase exposure and shadow/highlights adjusted)

 

[Devin-M]

+contr. and sharp. increased..

-(increase exposure and shadow/highlights adjusted)

You can get better or worse results depending on the details of how you stretch the histogram.

I made an animated GIF of histogram stretching a stacked 16bit tif of the Horsehead & Flame Nebulas in Adobe Lightroom (60x 2min 1600iso 600mm f/9 ff-dslr + 40 darks & flats, bortle 6):

 

[bruha]

Hi, two sun green filter images (with increased and decreased exposition in Gimp).

 

[DennisN]

I tried out one of my medium tele lenses in the afternoon on the Moon with some buildings in the foreground a couple of days ago. I noticed there were some small black spots in the photo close to the Moon, so I digitally magnified the photo to see what it was:

Ordinary birds, or... much worse? To my eye some of them look suspiciously similar to Klingon Warbirds.

 

[Andy Resnick]

I tried out one of my medium tele lenses in the afternoon on the Moon with some buildings in the foreground a couple of days ago. I noticed there were some small black spots in the photo close to the Moon, so I digitally magnified the photo to see what it was:

Ordinary birds, or... much worse? To my eye some of them look suspiciously similar to Klingon Warbirds.

Heh: "moonwatching".

http://www.eebweb.arizona.edu/courses/ecol484/images/MoonWatchInstructions.pdf

https://ca.audubon.org/news/moon-bi...ittle more information,by some: here and here.

 

[Andy Resnick]

Had a few clear nights, here's M101 @800/5.6, 3.6 hours, (near) full frame image:

and a 1:1 crop:

and a 2:1 crop of NGC 5474:

Not as good as this one, but not bad for urban astrophotography...

 

[Andy Resnick]

And here's the Sunflower galaxy (M63), also @ 800/5.6, 1.8 hours integration time:

 

[Keith_McClary]

SkyGems "preview" of M104 (Sombrero).
Observatory: Hakos iDK 20"
Filter: Luminance
Duration: 800 seconds
Charged with: 4.228 points

Due to a software issue the raw data was lost on the way from Namibia, so they refunded me. So now I have 6 points (need more suggestions).

There are some nice examples on their Results page, they are not just pretty pictures .

 

[bruha]

Hello, this is Registax 5 images stacked+Gimp sharpening and light/shadows little adjusting (older images).
Here in Prague is almost two weeks bad weather -heavily cloudy

 

[DennisN]

Hello, this is Registax 5 images stacked+Gimp sharpening and light/shadows little adjusting (older images)

Very nice!

 

[bruha]

Hello, here is Sun green filter with SV Ebony eyepiece camera .. maybe little better granulation imaging then with mobile camera ...
Have nice day

 

[DennisN]

Earth Restored

Only 24 people have journeyed far enough to see the whole Earth against the black of space.
The images they brought back changed our world. Here is a selection of the most beautiful photographs of Earth — iconic images and unknown gems — digitally restored to their full glory.

Photo page with many fine photos is here: http://www.tobyord.com/earth

Example (what a photo! ):

 

[Devin-M]

 

[bruha]

Hello, this made yesterday again by SV Ebony eyepiece camera-I have some problem with focusing...

 

[Andy Resnick]

Markarian Chain and surroundings in Virgo @ 400/2.8, 4hr integration time:

(part of a plane trail in upper left corner)

Astrometry.net output:

 

[bruha]

Hello, here is Arcturus by SV Ebony eyepiece camera Capt 00001: exp.t. 31 ms, Capt 6: 125 ms, gama and gain cca 100.

 

[Keith_McClary]

Skygems found my m104 data (along with 55GB of other peoples!). I (over)stretched it using GIMP.

 

[bruha]

Hello, here is sunspots (green filter) from yesterday+highlighted by GIMP
lot of succes

 

[Keith_McClary]

xkcd

 

[bruha]

Hello, I would like to ask ..I have problem to upload image 640 kB its reported "too big". Do you know what is size limit for attachment?

thanks and lot of succes...

 

[bruha]

And 209 kb is too big as well...

 

[bruha]

Hello, I attach two sun images from today -one sunspot appearing...
Lot of succes

 

[bruha]

Hello, I attach two moon image ( corrected by affinity photo.. I think better thean Gimp software), second is
with added artificial light source...

 

[bruha]

Next I attach three Spica images (all is made with eyepice SV Ebony webcam) while last one is with removing background (Afinity function)...

 

[bruha]

 

[bruha]

Hello, it is two sunspots from yesterday (Gimp corrected. ..)Although is clear sky nowadays is bad condition for observing as astronomical night is very short...

 

[bruha]

And some with green filter.. here is only one but more significant,,,

 

[bruha]

Hello, I attach sun spot images from today (on second white I got little different shape)

 

[chemisttree]

What was your shutter speed for the white? The green? What time of day do you take your images?

 

[bruha]

Hi, it was about 4 afternoon and made by SV EBONY eyepiece camera with exposure adjusted on cca 2.0 ms
and very low gain cca 2 for all images. Subsequently I made little sharpening and highlighting of spots in Gimp.

 

[DennisN]

China on Mars...

Source: China's Zhurong Mars rover takes a selfie
https://www.bbc.com/news/science-environment-57441757

By the way, I'm looking for more powerful tele lenses.
I am thinking of something like this :

 

[DennisN]

A slice of the Moon

I saw a nice, small Moon yesterday evening, so I fetched my gear and took some shots before it disappeared behind the trees, using my vintage Tokina 400mm f/6.3 tele lens (set at f/8). Camera settings: ISO 1600, shutter speed 1/500 s.

The Moon before it disappeared behind the trees:

 

[bruha]

(I plan moon images too but unfortunately getting quite low horizont already after sunset...)

 

[bruha]

Hello, here is sunspot from today (original and Gimp corrected) as seen spot has structure with dark core and brighter outer area )