The "No EQ" DSO Challenge!

[The Admiral]

1 minute ago, Nigel G said:

Ian, it's the other way round, without flats much worse 

Nige

Doh! Why didn't I read it properly?

Ian

[Victor Boesen]

1 hour ago, Nigel G said:

really noticeable difference!! the second image is way more sharp and more natural

[The Admiral]

3 minutes ago, Victor Boesen said:

really noticeable difference!! the second image is way more sharp and more natural

Yes I agree, there seems to be so much more contained in that second image, different processing not withstanding. Looks like that filter could be a winner.

Ian

[Nigel G]

2 hours ago, The Admiral said:

Yes I agree, there seems to be so much more contained in that second image, different processing not withstanding. Looks like that filter could be a winner.

Ian

Thanks guy's,  when I first saw the difference between the M33 exposures I thought I had made a mistake buying the filter even while I was taking the M31 subs the visual difference between previous exposures appears doubtful.  Once I started processing the difference become very apparent.  

I was sweating for a while. 

Cheers 

Nige.

[Graptharshammer]

New to astroimaging and have been following this post with much interest because of the Alt/Az component.  I have a question though, much talk has been made about L subs, subs...What is a sub if you can spare a second to educate a Noob on some of the slang?

[happy-kat]

sub = a single exposure

L generally short for a light exposure rather than a calibration frame

Edited October 30, 2016 by happy-kat

[Chris]

Hi, subs are sub exposures, so if you take 10 x 30 second exposures you have 300 seconds total exposure, but the inidividual 30 second exposures are the subs if that makes sense?

Edited October 30, 2016 by Chris Lock

[Nigel G]

5 minutes ago, Graptharshammer said:

New to astroimaging and have been following this post with much interest because of the Alt/Az component.  I have a question though, much talk has been made about L subs, subs...What is a sub if you can spare a second to educate a Noob on some of the slang?

Hi there.

Welcome. 

Subs or light frames are individual photos taken of your chosen object, so 50 subs x 30 seconds is 50 photos,  offset frames are to reduce camera noise and telescope anomalies like hot pixels on your camera sensor etc.

 Offsets include dark frames, flat frames and bias frames.

Dark frames are exactly the same settings as the subs or light frames but with the lens cap on so no light reaches the sensor,

Flat frames remove the effects of the telescope or lens, (darker around the outside of the image), a flat frame is taken using the same ISO setting but with camera set on  AV mode pointing the scope or lens at an evenly lit surface like a white computer screen.

Bias are taken with camera cap on, same ISO setting,  but shutter speed fastest possible. 

An example,  say 100 lights or subs at 30 seconds , iso 1600 would need around 50 or so darks at 30 seconds and iso 1600, 50 or so flats iso 1600 and 50 bias iso 1600.

adding the offsets helps in processing a lot removing noise vignetting etc.

Darks and lights should be taken during your imaging session ideally but bias are re usable needing updating around 6 months.

Hope this helps a bit.

cheers 

Nige 

[Graptharshammer]

Thank you Nigel, Chris Lock and Happy-Kat!  Light bulb started to go on after reading your explanations.  I'm fascinated by the idea of taking so many short exposures and coming up with something as awesome as the photos on this thread.  Really amazing stuff people are doing with stacked images.  I appreciate you taking a few minutes to educate the newbies like me on terms that might not be readily obvious in their meanings.  You guys are great!

[sheeprug]

Hi Everybody.  This is a really really interesting thread, so thanks for all the images and conversation, and as a result I want to play too.

Now regarding kit, I have an 14" OO dob, but as it stands no suitable camera. However, there will be budget for one by Xmas so research is already under way. Normally my inclination would be to go to Canon since (a) I've always used Canon cameras and (b) I gather they have better support/features for astro.  However, in another thread on the 'cameras' part of this site it has been pointed out that the sensors used in Nikon cameras have a better noise performance.  

Now I appreciate that the Nikon vs Canon debate is well documented on this site, but I'm wondering if in the alt/az scenario, where exposures are shorter then than for eq, does the low noise performance become assume a greater importance?

Secondly, regarding the scope, i'm assuming a 14" aperture is good, but a FL of 1600mm may be a little long.  Is that too long in practice? 

SR.       

[jimbo747]

39 minutes ago, sheeprug said:

Hi Everybody.  This is a really really interesting thread, so thanks for all the images and conversation, and as a result I want to play too.

Now regarding kit, I have an 14" OO dob, but as it stands no suitable camera. However, there will be budget for one by Xmas so research is already under way. Normally my inclination would be to go to Canon since (a) I've always used Canon cameras and (b) I gather they have better support/features for astro.  However, in another thread on the 'cameras' part of this site it has been pointed out that the sensors used in Nikon cameras have a better noise performance.  

Now I appreciate that the Nikon vs Canon debate is well documented on this site, but I'm wondering if in the alt/az scenario, where exposures are shorter then than for eq, does the low noise performance become assume a greater importance?

Secondly, regarding the scope, i'm assuming a 14" aperture is good, but a FL of 1600mm may be a little long.  Is that too long in practice? 

SR.       

Does the mount track? 

[Nigel G]

Hi SR and welcome to our playground

As Jimbo asked is your mount motorised.

If your mount and scope are balanced and smooth tracking then I can't see a problem. Ideally motorised mounts are better as they track but it is possible to get DSO images with 1 second exposures, just loads of them, you would be restricted to brighter DSO's with no motors. There's still plenty of them to capture though.

Camera choice I can't really help there, I have only owned canons, the noise levels are not to bad considering the short exposure side of things, I just bought a clip in Light pollution filter which has made a big difference reducing the noise levels.

Another thing to look out for is to make sure your scope with a camera connected at prime focus can actually focus on the target. I had to modify my telescope to be able to connect my camera as the focuser would not travel in enough to focus.

Cheers

Nige.

[sheeprug]

25 minutes ago, jimbo747 said:

Does the mount track? 

Sadly, no. I'm assuming I'll have to do manual tracking, and s/w alignment.

SR

[Filroden]

59 minutes ago, sheeprug said:

Hi Everybody.  This is a really really interesting thread, so thanks for all the images and conversation, and as a result I want to play too.

Now regarding kit, I have an 14" OO dob, but as it stands no suitable camera. However, there will be budget for one by Xmas so research is already under way. Normally my inclination would be to go to Canon since (a) I've always used Canon cameras and (b) I gather they have better support/features for astro.  However, in another thread on the 'cameras' part of this site it has been pointed out that the sensors used in Nikon cameras have a better noise performance.  

Now I appreciate that the Nikon vs Canon debate is well documented on this site, but I'm wondering if in the alt/az scenario, where exposures are shorter then than for eq, does the low noise performance become assume a greater importance?

Secondly, regarding the scope, i'm assuming a 14" aperture is good, but a FL of 1600mm may be a little long.  Is that too long in practice? 

SR.       

Welcome also and I hope we can get you started!

You scope is quite fast, f4.5 I think. And it gives a reasonable field of view (i've used my DSLR, a Canon 60D, to illustrate what your scope could image).

One thing to remember with field of view with alt-az imaging is that because of field rotation you will need to crop quite a bit of the edges of any image once integrated, so your target ideally needs to fit within about 70-80% of the frame or you could produce a mosaic.

Your biggest issue will be tracking. Even if motorised, your focal length will reduce what you can reasonably achieve. When I first started I was using an f10 9.24" SCT, i.e. with a 2350mm focal length. I was easily getting 8s exposures and was just started to get confident I could achieve 15s most of the time and 20-30s occasionally. That meant bright DSO like M42 or M57 were within its reach. Since then I've moved to a smaller and much faster scope so 30s is now at my lower end of easy. I suspect, with tracking, you could easily achieve 20s and maybe 30s. That's enough for all the targets we've seen in this thread.

Camera choice should probably be driven by its main purpose. If you want a DSLR for daytime photography, get the one that best suits that need. All DSLR could be used for astrophotography and I doubt the different noise levels will make too much of a difference. That said, if you can get a less noisy camera it will help with the processing! Colour DSLR suffer an inherent reduction in sensitivity due to the way it captures colour, using a RGGB matrix. It means at best you're capturing 25% of the available red and blue data (both important) and 50% of the green (not as important except in a few cases). It also introduces colour noise. Field rotation means you're aligning different pixel positions with each frame, so you could be merging blue data with green, etc. It shows in the noise as colour speckles that seem to 'walk' across the image and needs to attention to reduce in processing without losing signal.

However, a DSLR will work! In the meantime you could always try eyepiece projection and capture images using any camera, even one on a phone, by positioning it where your eye would be. It's not as good but it still feels like progress (and when you do get the DSLR you get that feeling of more improvement again!).

 

[Filroden]

12 minutes ago, sheeprug said:

Sadly, no. I'm assuming I'll have to do manual tracking, and s/w alignment.

SR

I've not had to manually track but I've seen some cracking images on here of aircraft at 33,000ft taken with a manually tracked dob. I think, with practice, you will be able to achieve longer and longer manually tracked images. As above, even sub-10s exposures can, if enough are taken, show some great detail in brighter objects. Also, a simple wedge might make tracking easier as you're mainly tracking in one direction (dec) with small corrections in RA because of poor polar alignment. I remember building one for an old film pentax camera with 50mm lens from a couple of pieces of plastic, hinges and some nuts and bolts. I had to rotate a handle at the same speed as the second hand on a watch and I was achieving 10 min exposures. Now that's a much wider field which is more forgiving, but the principle is the same!

There is also the option of using just the camera with lens too for some wide-field imaging.

Edited October 31, 2016 by Filroden

[Nigel G]

8 minutes ago, sheeprug said:

Sadly, no. I'm assuming I'll have to do manual tracking, and s/w alignment.

SR

Don't give up hope, with a photon hoover like yours and quite dark sky's of Woodbridge ( Suffolk I guess ) you can get a lot with 1 or 2 second exposures stacked, it might take quite a few but certainly possible.

Nige.

PS, quite often sail to Woodbridge in Suffolk,

[jimbo747]

14 minutes ago, sheeprug said:

Sadly, no. I'm assuming I'll have to do manual tracking, and s/w alignment.

SR

at 1600mm FL I personally wouldn't bother with a DSLR - thats even assuming you can achieve focus without modifying the scope or changing focuser, you're limited to very short exposures, a few seconds at best before trailing ruins the image (the dslr has tiny pixels) and you'll need thousands of images and if its anything like my canon 1100 it'll be noisy. By all means get one and do some wide field shots but I don't think sticking it on a manually tracked dob will get you the images you're hoping for. There are some images around with someone using a huge dob and 1 second exposures using a low noise camera like a asi 224mc which look amazing, and it'll be perfect for planetary, lunar and solar imaging too.

 

[Stub Mandrel]

2 hours ago, sheeprug said:

Hi Everybody.  This is a really really interesting thread, so thanks for all the images and conversation, and as a result I want to play too.

Now regarding kit, I have an 14" OO dob, but as it stands no suitable camera. However, there will be budget for one by Xmas so research is already under way. Normally my inclination would be to go to Canon since (a) I've always used Canon cameras and (b) I gather they have better support/features for astro.  However, in another thread on the 'cameras' part of this site it has been pointed out that the sensors used in Nikon cameras have a better noise performance.  

Now I appreciate that the Nikon vs Canon debate is well documented on this site, but I'm wondering if in the alt/az scenario, where exposures are shorter then than for eq, does the low noise performance become assume a greater importance?

Secondly, regarding the scope, i'm assuming a 14" aperture is good, but a FL of 1600mm may be a little long.  Is that too long in practice? 

SR.       

There's an astro-modded 450D with very low shutter count in the classifieds. While not the ultimate imaging camera the 450D is capable of great results (IMHO).

[sheeprug]

9 hours ago, jimbo747 said:

at 1600mm FL I personally wouldn't bother with a DSLR - thats even assuming you can achieve focus without modifying the scope or changing focuser, you're limited to very short exposures, a few seconds at best before trailing ruins the image (the dslr has tiny pixels) and you'll need thousands of images and if its anything like my canon 1100 it'll be noisy. By all means get one and do some wide field shots but I don't think sticking it on a manually tracked dob will get you the images you're hoping for. There are some images around with someone using a huge dob and 1 second exposures using a low noise camera like a asi 224mc which look amazing, and it'll be perfect for planetary, lunar and solar imaging too.

 

Thanks Jimbo, interesting points to think about.  Re the asi224mc, it has a small 6mm sensor, so probably a too small angle of view for deeper sky stuff where I think the most interesting work will be.   Are there any larger sensor cameras around in a similar price bracket? I can't see any, but I've not tried very hard yet.  

We

 

[sheeprug]

10 hours ago, Nigel G said:

Don't give up hope, with a photon hoover like yours and quite dark sky's of Woodbridge ( Suffolk I guess ) you can get a lot with 1 or 2 second exposures stacked, it might take quite a few but certainly possible.

Nige.

PS, quite often sail to Woodbridge in Suffolk,

Yes, Suffolk. If you see a yellow/grey laser dinghy give me a wave and pop into the Deben Yacht clubhouse for a beer!    Skies here are pretty good looking north, but the sky glow from ipswich and Felixstowe's washes out a lot in the south.

SR.

 

[happy-kat]

Got a day off tomorrow and for a very rare change it is clear. (due to get cloudy soon) Was tonight sucessful... pass a beer!

Set the virtuoso up from scratch, nice and level. Re-aligned from the start and finished with Polaris right in the centre of the camera lens. Expect to be all good to go.

Tracking, absoultely no tracking occuring star trails on 30 seconds were the same length as if the mount was off. I had used a brand new set of batteries, yes batteries but we are only talking of carrying 1 kilo of weight and the camera was balanced and only uising the 40mm pancake lens and I slew by hand.

My next thought is to dig out my Astroboot synscan v3 handset I bought last year and rather than manually align to actually do a star align (wont be easy as can only see N through W to SW) and see if that is better. If that fails I will go back to my barn door until a future point where I 'might' get a battery for the mount but that defeats keeping it light.

 

[The Admiral]

Sorry Happy-kat, I didn't quite follow that. I presume that you didn't use Polaris as one of your alignment stars?

Ian

[Filroden]

9 hours ago, happy-kat said:

and I slew by hand.

You had me confused for a second! Just checked the mount specs and it has "A great feature of the Virtuoso is the patented Freedom-Find dual-encoder technology which allows the telescope to be moved manually in either axis without losing alignment or positional information. This gives the user enormous convenience and flexibility during observing sessions."

I'd love that for my mount. It's the noise from my slewing that means I don't like setting up too late.

Does it hold an accurate alignment after a lot of manual slewing?

[happy-kat]

The freedom find is now also used in the star discovery mount the one Nige uses. I had thought so that yes it does carry on tracking. It's great having the ability to disengage the clutches.

Ian, I have not yet use my synscan unit with the mount, the mount can be aligned manually to Polaris to engage just tracking which is what I do.

[The Admiral]

1 hour ago, happy-kat said:

Ian, I have not yet use my synscan unit with the mount, the mount can be aligned manually to Polaris to engage just tracking which is what I do.

Hmm, that's interesting, I can't see how that works with an Alt-Az. I guess it must assume that the mount is perfectly level, and then if it knows where Polaris is it can make the 'scope rotate around it. I think I'd prefer the synscan unit with it, at least then if you align to a couple of stars it'll take account of any mount not quite levelled. Still, that wouldn't account  for the apparent complete lack of tracking. Any ideas why? Do you have a mains power supply you can check it with?

I had a quick look on t'internet for this mount, but it doesn't seem widely available, and only then with a 'scope.

Ian

Edit. Ah, I've just looked at the manual for your scope. I see it depends on setting it to point to true north and the 'scope levelled prior to switching on. So I see what you were saying, that it pointed to Polaris OK after starting, indicating that it had got its alignment right.

Edited November 1, 2016 by The Admiral