Hi Peter i agree with what you say but at the end of the day its the imager who has to be happy with what they have. I myself tend to process my images to get then close to what the colour should be. But i don't get myself work up over the colour if its a bit off, as long as i am happy with what i have, that's the most important thing to me. I sometimes find the processing of these photos harder then taking then.
Phil
There has been a lot of rumination over what I would have thought was a pretty straight forward suggestion, in metaphorical terms: the emperor has no clothes.
NGC2070 can be mooted to be various shades of red.
But most certainly, it is not blue/cyan..and if we want to argue the Physics...come in spinner!
Artistic license aside....and sure your can make the sky look green with Photoshop or a badly calibrated camera....emission nebulae are red, red, red, just as the sky is blue.
Where is the problem with this patently obvious observation?
Artistic license aside....and sure your can make the sky look green with Photoshop or a badly calibrated camera....emission nebulae are red, red, red, just as the sky is blue.
Where is the problem with this patently obvious observation?
The problem is that someone assigned an arbitrary primary colour to Ha. The red part of the spectrum contains every shade of red there is. Infra red is not red, it is below red and has no colour that the eye can really perceive. Some night vision goggles assign green to infra red and this is just as correct as assigning red.
Ha accounts for a tiny wavelength of the red colour of the spectrum, at the most it is a very very very dark shade of red.
The hubble palette is just a convention and i reckon assigning Ha to red is just a convention as well.
As far as artistic license is concerned. Well, shooting DSO's is like someone who just likes to shoot a small subset of say cat's. There are only so many and they get done over and over and over and over again and again the same one. Fine, i like doing this, and if my tarantulas come out blue, well i like that ghostly look.
The reason i am posting this is again you have made a value judgement. You havn't just said hey i think nebs are red and left it at that, you are trying to force your opinion down everyones throat. Well good luck to you. I got what you wanted to say in the first post, so cant you just leave it at that?
H-alpha has a wavelength of 656.281 nanometers. This is not my opinion.
It just is. If you've ever looked through a H-Alpha solar telescope, the colour is vivid red, and quite striking, but just a heck of a lot brighter that
your average emission neb.
I am not suggesting we should legislate to ban the blue ghostly look
If you are happy with that look, then good on you.
Quote:
Originally Posted by Zuts
you are trying to force your opinion down everyones throat. Well good luck to you. I got what you wanted to say in the first post, so cant you just leave it at that?
[quote=Peter Ward;287395]From my short time on ISS, I have to say it is an very enthusiastic group, polite, but often not very critical. By critical I am not suggesting you go around calling someone a boof-head!
When I look at a deep sky image the things I like to see are, excellent focus (this is the one thing you can nail every time), excellent tracking (i.e. round stars) accurate colour balance.
There are other aspects, but for now the above three really are essential to a good image.
Hi Peter, Just reading your initial statement again (This has definitly gone off track) I notice you say we are not very critical and items such as round well tracked stars and excelent focus. This to some extent may be true but to some degree you are missing your own point. Most of us here are fairly new to imaging and rely on people such as yourself for constructive criticism. I would be most helpful if the likes of yourself were to actively criticise but also to give some pointers or ideas on how these faults can be fixed.
I for one have been trying very hard to produce good images. I have spent many sleepless hours attempting to get tracking and guiding correct. Focus is also a problem I have spent hours working on. I am now starting to produce reasonable images (fantastic for me) but from a semi professional view point probably quite poor.
I think the views and almost war scene in this thread are based on these facts.
1. We can't all afford the pro type setup.
2. We are all trying very hard to achieve our best.
3. We are all very proud of our improvement.
4. We find it dificult to get real help with the problems listed above.
5. Equipment is expensive and even the semi pro dealers such as yourself don't provide sufficient information or advise on equipment.
Most of us have equipment bought from retailers tha now lives in a box and will probably never be used again because it is not suitable for our equipment.
6. A lot of passed on knowledge on sites like this is from someone who knows as little as you do.
Peter it is pleasing to get criticism but please attempt to assist with a fix or some ideas of a fix.
To turn a thread like this into a war is of no benifit to anyone and some look back a previous posts could give some ideas as to why this has happened.
The knowledge you possess is what most of us are after. Please don't just be critical but try to help as well.
Woah...slow down there...The whole point of my initial post was to do exactly what you allude to, by simply giving constructive criticism, plus a fix, instead of albeit an encouraging "that's great/nice/stick with it" I'd suggest will help people improve their imaging efforts.
I have gone to some lengths to say this is not an equipment issue, the fix being simple & cheap. I even posted a succinct PS tutorial to clarify the method.
Some thought this was a sleight of some kind, and there was clearly another agenda. I certainly took issue with that!
I agree, anyone can be a critic and I certainly would not endorse that alone. Constructive criticism, by way of, "how 'bout trying this, or that"
will give us all a leg up
Quote:
Originally Posted by Hagar
Peter it is pleasing to get criticism but please attempt to assist with a fix or some ideas of a fix.
To turn a thread like this into a war is of no benifit to anyone and some look back a previous posts could give some ideas as to why this has happened.
The knowledge you possess is what most of us are after. Please don't just be critical but try to help as well.
I've read through all of the posts in this thread but want to stay away from the controversy. I used Peter's suggestion of modifying the red curve properties in photoshop as I had used a 350D to photograph eta carina nebula and had noted how "blue" it looked. After PS I find that the Bok and other features look better. As a scientist I understand the arguements but must admit that there is "more" information for me to see in the PS adjusted photo.
Thanks for the suggestion Peter and admit that I prefer the "redder" photo as a personal taste. Surely cheaper than modding the 350D but I think I will be getting a 40D as it certainly looks great.
This one is 4:25 hours and needs more luminance and some more red or Ha.
One point I may make generally speaking now- with DSLR images, often the images are very "short" exposures. By that I mean less than a hour.
Almost any object will look great with enough exposure. A rough rule of thumb is a minimum of 2 hours total.
DSLRs have the ISO setting so you can adjust the sensitivity whereas CCD cameras that gain is set by the manufacturer. This means you can artificially crank up the camera and it can invite you to take less exposure time than is really required.
With DSLRs one rule of thumb is to set your sub-exposure time to below where the sky glow becomes intrusive. If you live in a light polluted area (most would) then an light pollution filter helps. You can even do Ha with a DSLR although it requires a 2 inch screw on type (more expensive).
ISO 800 is often quoted as a good sensitivity. I always used 1600 or 3200.
Another thing that might help with DSLR imaging and this may be a more advanced technique. To take a short exposure for the stars only and longer for the main object. Photoshop allows you to remove the stars from one image and blend in the stars from another. DSLR images often have white stars with no colour. This is the most obvious difference between DSLR and CCD images. The CCD camera can expose longer without spilling over than most DSLRs (although the Caon 5D has lower noise and higher almost everything than an STL11).
The new breed DSLRs are now 14 bit and extremely low noise (Canon's at least - not sure about the Nikon's). The gap is narrowing especially now CCD cameras have a range of one shot colour cameras available and seem to be increasing in popularity. Apogee Ascent series are a lot cheaper and closer in price to DSLR top range and Sbig is bringing out a 10.5mp CCD camera shortly that is supposed to be fairly "cheap".
For autoguiding there are heaps of options now. The Orion Starshoot, the Meade DSI, the Celestron Neximage, The ToUcam (modified) and a hot one is the QHY 1.3mp CMOS chipped autoguiding camera which is US$245. That's a real bargain and use it with PHD guiding software (free). It may or may not need a Shoestring Astronomy adapter for your mount depending on what you are using.
Ye PS curves really worked well in Allans Eta Carina image for sure.
I agree with Greg, 2 hours is a good imaging time, though I guess for very fast systems shorter will do. As for length of subs, for me, I try to get the histogram about 1/3 the way across from the left, showing the sky background has well and truly been reached. For me in Newcastle an image throuhg my 10 inch f5.6 scope and modded 350D using just the IDAS uv/ir filter, I cannot go more then 5 to 10 mins @iso400. With the UHCS filter I can go 1/2 hour subs, but in my uncooled camera I performed a test which showed I get less noise taking 3x10 mins rather then a single 30 minute sub.
I believe most dedicated CCD camera users dont normally do more then 10 minute subs anyway? I believe SBIGs can do up to 1 hour subs?
What Id do if I was the owner of SBIG was approach Canon to see about buying a run of their SMOS sensors but without the bayer filter array, ( in otherwords a mono chip) and tee that up to a 16 bit ADC. I could then sell a 10 megalixel dedicated astro camera for less then half the price of an STL11 with similar overall performance but considerably less dark current and absolutely positively no blooming.
Nice M45 shot Greg too, and thanks for the tip re the guide cameras. The QHY6 looks like a great buy, $300 here
Scott
Someone earlier in this thread mentioned about false colour. Interestingly when the ST4 and ST6s were first released some years ago I remember looking at some demo shots, some taken in false colour. But for some reason this doesnt seem to have been very popular in amateur circles - although it does bring out detail very nicely sometimes.
Does anyone know of any software capable of this?
By the way, there are some great images on this post. I'd be quite proud of the green tarantula. Guess thats what your eye would see via the eyepiece (if it were brighter). Obviously in addition to Ha there is a fair amount of emission in the green part of the spectrum too which is quite interesting to me (In fact I was discussing this only a few nights ago with a friend).
Thanks Scott for the IRIS hint. Also increasing the red channel does work well to enhance the Ha Peter when your sensor is not very red sensitive.
i think if you have a modded dslr or some form of astro ccd then yes you should get the colour balance 'right'
but to me, for an unmodded dslr its just rediculous even saying that the colour isn't right because its not red, of course it isn't because its not picking up anywhere near the amount of Ha as an astro ccd or modded camera and i don't think saturating the red channel is a real solution to this because you just wont have the Ha data there with an unmodded cam.
Im sure its easy for someone that has all the fancy gear to tell someone that struggles with lesser equipment that this and that is wrong with their image but noone gets out there with the intention to take an out of focus or poorly tracked or even the most disastrous, wrong colour image.
all you can do is get out there and give it your best shot and if thats not good enough for some people then i guess its bad luck
i just find it horrible that people spend hours capturing an image that they get told they got horribly wrong when they have done nothing wrong, it is just a limitation from their equipment.
I understand that the Un-Modded DSlR has its limitations in picking up the HA in any deep sky object, however I am quite amazed that my Canon 5D actually picks up a considerably amount , and this has been commented on buy some of this group.
Although my images are sometimes struggling to be up there with some of the others posted . I am very happy with the results.
To be able to capture these wonderful objects at all is just awesome.
