A few images taken with SDM Dob

[alexch]

Hi All,

The Weather Gods were a bit more accommodating this Saturday and sent some patches between the clouds. I've got all the adaptors and couldn't wait to try more imaging with my 22" f/3.6 SDM Dob and Sony NEX-5 mirrorless camera with Paracorr Type II.

I intended to do dark frames in the fridge at home, however it seems that Adobe Camera Raw in Photoshop CS5 deals with hot pixels quite efficiently. Also the Servocat Alt-Az motors want to correct the pointing every now and again and limit the exposure time to no more than 15 seconds.

Full-size images and equipment shots are here:
http://www.terrastro.com/galleries/deep-space-hr/

Low-res images are attached below.

I have a lot to see visually yet so I am doing the imaging just for fun without much skill involved and have no intention to get into EQ platforms or expensive field de-rotators. (Please remind me about that frequently...)

Thanks for looking.
Alex

Omega Centauri (NGC 5139): 3 x 10sec, ISO 3200
Jewel Box (NGC 4755): 3 x 15sec, ISO 3200
Centaurus A (NGC 5128): 17 x 15sec, ISO 3200
Keyhole Nebula (in NGC 3372): 8 x 15sec, ISO 3200
Orion Nebula (NGC 1976): 9 x 8sec, ISO 3200

Processed in DeepSkyStacker and Photoshop CS5

[TrevorW]

I wouldn't complain about those well done Alex (the astroholic)

[asimov]

That is seriously nice work! Well done.

[[1ponders]]

Geez Louise!!! They are Great Alex! What's this NEX-5 camera you talk about???

That Centaurus A shot has some awesome detail in it.






Edit: Just checked out the camera. Your kidding right??? Look out canon!

[mill]

Yep that Centaurus shot is very good :thumbsup:
The rest too :)

[dugnsuz]

Great images for such short exposures - aperture rules in this instance.
Cheers
Doug

[multiweb]

:eyepop: That's awesome. Aperture rules indeed. :thumbsup:

[renormalised]

Geez, Alex!!! Everyone else has to shoot for hours to get shots like that and with uber gear to boot. You do it with a dob, servocat and a few short subs!!!!:):):)

Must be in the wrist:):P

Maybe I'm not poking my tongue at the right angle:):P

Maybe I don't have 22" of mirror:):P

[renormalised]

Just checked out the cameras too....not bad:):)

Not too dear either!!!:)

[alexch]

Trevor, John, Paul, Martin, Doug, Marc, Carl - thanks heaps for the encouraging comments, much appreciated!

[alexch]

Yes I love this little camera for family photos, it is as capable as any DSLR with an APS-C sized chip but much lighter and easier to carry. Not very expensive too.

Working with the live view only and a quirky UI was frustrating for the first few days but then I got used to it. The tilting display is great for waist level shooting.

The only problem I anticipate with it for real astro-work is that live view cannot be turned off (it has no viewfinder). I tend to switch the camera off when not taking images in order not to heat up the chip. Also Sony NEX series are quite prone to getting very warm.

In the image attached below I have NEX-Nikon adapter (Photodiox, $50), Nikon T-Adapter, Televue 2.4" T Ring adapter, Televue Paracorr Type II coma corrector.

Cheers,
Alex

[renormalised]

Is it just the live view heating everything up or does the camera as a whole heat up??

[alexch]

I haven't done extensive testing when imaging through the Dob so not sure. However after 20 minutes of constant live view or video recording the camera feels warm in the hand.
Edit: I mean the whole camera is warm.

[renormalised]

Given that you're only shooting such short subs and getting these sort of results, I don't think you'll be having to worry about heating of the camera.

Helps to have a light bucket, though:)

[mswhin63]

Damn they are really :cool: well done. Aperture rules alright :thumbsup:

[h0ughy]

OMG in only a few seconds.............oh man................

[desler]

By the look of those images Alex, you've done incredibly well.

Wonder if we are about to see another aperture rules uptake!

Darren

[jjjnettie]

LOL You've left everyone with their jaws on the ground with those pics.
Fantastic work!

[DavidU]

:eyepop:How awesome is that ! Neat little camera too. I'm sure some one will come up with a switch to turn off the LCD display that I'm sure is where the heat is coming from.

[Screwdriverone]

Holy Moly!

Who needs EQ platforms and hours of exposures when a handful will do?

Cant wait to see what you get when you arent "doing the imaging just for fun" !!!!

Innovation award me thinks! Doesn't Mr Malin have a category for such a thing?

Damn these are good Alex!

Cheers

Chris

[rogerg]

Wow. I'm stunned at what you're getting for subs of less than 15 seconds. Such light gathering capability. Amazing.

[norm]

That's very cool stuff Alex :thumbsup:

I assume your SDM has servocat installed ?

Man, its damn good!

Cheers, Norm

[alexch]

Thanks again, guys and gal! I was overwhelmed when I saw all the colours after 10-15 second exposures on the camera screen and now I am even more overwhelmed by the warm reception of my humble short-exposure deep-space attempts here.

I've been concentrating on ultra-wide filed astro-terrestrial images but learned a good deal of how deep space images should look by browsing some brilliant work in this forum.

Cheers,
Alex

[alexch]

Thanks, Norm.

Yes ServoCat and Argo Navis come standard on SDMs larger than 20"

Cheers,
Alex

[ChrisM]

Alex - your pics are seriously impressive! Well done.

Chris

[Dave47tuc]

Unbelievable :eyepop:
The way of the future I think. Big scopes quick exposures aperture rules big time. More and more people will be doing this with there motor driven Dob's.

That 5139 is just like in the eyepiece and 5128 :eyepop::eyepop::eyepop: awesome

Great work Alex :thumbsup:

[Scorpius51]

Not too shabby at all Alex! I'd be right chuffed with those pics. Wouldn't mind the 'scope, either! Good one :thumbsup:

Cheers
John

[DavidU]

Alex, does the CMOS chip have the filter on it ???

[Paul Haese]

Looks great. Impressive results for sure. 22" of aperture is always going to rule. Nice.

[alexch]

Yes - like a stock DSLR.

[alexch]

Thanks, Chris!


Thanks, Dave. We need a good night at the Briars or Heathcote so you can look through the eyepiece :)


Thanks, John. I am surprised how well they turned out.


Thanks, Paul. It sure does but only until it is overruled by ... say ... 32" ?

[erick]

Alex, I might have missed it, but are you fitting shorter truss poles to bring the camera into focus?

[alexch]

No I use the longer visual poles. Paracorr helps to bring focus a bit forward.

[erick]

Visual and photography with the same poles - that is neat! They are very nice images, Alex - and such short exposures! Aperture rules, yet again?

[strongmanmike]

Lovely little collection of snapshots there Alex! Drive-through imaging :thumbsup:

That camera looks very similar to my el' cheapo...well they are both black :D

Mike

[asimov]

I'm that impressed I had to come back for a second comment or two!:P

These are just too good to go past, for the mere fact that they are 15 sec. exposures. Gotta love that extra aperture. I can only imagine 'going deep' & pulling REALLY long exposures of a whole 30 secs!!:eyepop::lol:

:thumbsup:

[Jen]

:eyepop::eyepop: wow ALex they are amazing pics in such a short time just gorgeous :thumbsup::thumbsup:

[alexch]

Eric, Mike and Jen - thanks heaps!

[alexch]

I forgot about the three 10-second subs of NGC3242 (Ghost of Jupiter) I took the same night.

When processing the images today I noticed a few fuzzies in the image that look like galaxies nearby (in 10-second subs!).

Attached are the normally processed image and with exaggerated levels to show the fuzzies. One location matches a spiral galaxy at the left of this beautiful image:
http://www.capella-observatory.com/ImageHTMLs/PNs/NGC3242.htm

These are unresized crops of a full size image.

Cheers,
Alex

[Jen]

:thumbsup: kool Alex yep i can see the fuzzies ;)

[erick]

Re that Ghost of Jupiter.

That beautiful image - done and dusted in under a minute - amazing! :thumbsup:

[telecasterguru]

Just amazing. wonder how this setup would work with planetary? Maybe a Toucam or the like?

[alexch]

I have DMK21 with a filter wheel and was planning to give it a go later

[Dave47tuc]

I think the results will be :eyepop: :eyepop: :eyepop: :eyepop: I can not wait to see how it goes :)

[renormalised]

A small, light CCD camera like an Atik 314L+ would be better than the DMK for DSO's, but the DMK would produce pretty spic pics.

Or you could try a Mallincam or GStar camera (good for live viewing).

[iceman]

I'm amazed at how good these are! 22" brings in a lot of light, such short exposures and so few of them!

You're obviously very talented and any sort of photography is no problem!

This is now IOTW (http://www.iceinspace.com.au).

Cheers

[alexch]

Mike, you are too kind.

Thanks for IOTW!

Cheers,
Alex

[Big Dave]

Well done Alex.

[prokyon]

Wow, great! I like the way you make your pics.

[paulF]

Congratrs Alex on those mind blowing images!

[sasup]

ok im blown away.

[Lester]

You are on a winner Alex, thanks for the wonderful views, and all the best for more top images.

[peter_4059]

Impressive for such short subs - well done.

[Satchmo]

I am not a photographer ( and always seeking to clarify what I do know ) , but seems some posters are attributing the depth of the images in such a short exposure being attributable to the 22" aperture.

As far as I know , any lens or scope operating at the same F# ( in this case F 4.14 with the coma corrector) using the same camera , exposure times and stacking and processing techniques would get the same results, albeit with a different image scale. I think it is the image scale of these images ( which is attributable to the 22" aperture) that is impressive about these short exposures.

[strongmanmike]

Oh oooh open a can of worms :lol:

In a nut shell, limiting magnitude of point sources is aperture dependant. Faster focal ratio = higher signal to noise in a given exposure time on extended diffuse objects.

so you want aperture and fast focal ratio :thumbsup:

Mike

[jjjnettie]

Light Buckets Rule!

[Satchmo]

oooh perhaps better in another thread then.

I guess I was referring to the speed of imaging extended stuff. So , with point sources like stars its the increased focal length that allows us to image fainter stars ( I assume that deepest magnitudes can be reached by increasing exposure time for a given aperture ) So given we want as fast a system as possible for extended objects, fainter limiting magnitude at a given exposure is reached via longer focal length gained by keeping F # constant and increasing aperture?

[alexch]

Not quite, as far as I understand with point sources it's the aperture that defines the deepest magnitude and it is independent of focal length. For example my 14mm f/2.8 lens with 90mm front element gets fainter stars than 35mm f/1.4 lens with 55mm front element with the same camera and exposure length (although this is subjective - I have not done any measurements)
Somewhat outdated but still relevant info:
http://www.eskimo.com/~rachford/widefield/calc.html (http://www.eskimo.com/%7Erachford/widefield/calc.html)

[Edit: added another link]
http://starizona.com/acb/ccd/projectsfaint.aspx ("Capture the Deepest Amateur CCD Image" paragraph)
Alex

[Satchmo]

Thanks Alex. Great links. It makes sense as the star is a blob of light at the focal plane that is swollen by seeing , tracking errors and optical errors. At the end of the day its a photon stream that increases in brightness with aperture. Just out of interest what is your scale of pixels /arc second with this camera /scope combination and what sort of FWHM were you getting on the night you took these exposures ?

[clem]

Wow! Aperture envy! Must get to making my own large aperture Dob, pronto! That mirror hanging on the wall in my bathroom must be bigger than 30 inches, I wonder if that will do? :-)

[danielsun]

Love all of your work Alex, from your photos to your time lapses.:thumbsup:

Cheers Daniel.

[alexch]

The FOV calculator tells me I can fit 0.6x0.4 degrees onto SONY Nex-5 chip with Paracorr and 2360mm FL. Judging by the moon it is right.

So I have 4592 pixels covering 2160 seconds of arc, which works out to be 2.125 pixels per arcsecond.

For "Centaurus A" my DeepSkyStacker image parameters were:
FWHM=8.36, Sky BAckground=10.16%

Cheers,
Alex

[alexch]

Dave, prokyon, Paul, Stacey, Lester, clem and Daniel - thanks heaps for the comments!

[toc]

These are amazing!

How long will it track before tracking errors are apparent?

[alexch]

Thanks, Tim.

10-15 seconds before the errors come in, depending on the part of the sky. The closer to zenith the worse.

[CometGuy]

Hi Alex that is great work!

I had a look at your ghost of Jupiter image and the image scale is around 0.5" / pixel. Its impressive your getting tight star images with 10 second exposures (as well as mag 18 stars). All I can say is wow!

Terry

[stutir]

Hi Alex

You have mentioned about SONYNex5 for capturing the images. Please let me know if I can also go ahead and make this investment for astrophotography for my SKYWATCHER 150750 EQ 3-2.

Please suggest.

Thanks and regards

Stuti

[HRJ]

Awesome images Alex.



What does this mean? I am not familiar with Servocat. Does it mean that the tracking motors kick in only once in about 15 seconds? In other words, your sub-exposures aren't tracked and have minute (invisible) trails?

[alexch]

Thanks Terry. My calculations were the same: 2.125 pixels per arcsecond. That large aperture is good to have :)

[alexch]

Stuti, Sony NEX-5 is a good camera, that can do general day-time photography and also used occasionally for astro-photography. However I wouldn't recommend to purchase it just for astro work, because:
1) It does not have an optical viewfinder and. In my 22" the stars are quite bright on the screen but it may not be the case for smaller telescopes
2) The body is small and the sensor is being constantly used for live view and NEX cameras are getting warm very quickly. IT will be a problem with longer exposures required with smaller telescopes.

Hope it helps.
Alex

[alexch]

Thanks.
Servocat is a drive system for Alt-Az mounts and needs to correct for field rotation.