Full spectrum camera vs h-a filter on scope

[vertigo262]

oh, i thought you meant, 1200 subs, so i was curious how long, because that would be a lot of shots. 

I haven't seen the california nebula in such detail. But it needs color and then I think it would really stand out.

Can you do longer exposures in ha, due to the mono? or is it the same thing. since most of my shots over expose after 120 seconds?

[Thalestris24]

oh, i thought you meant, 1200 subs, so i was curious how long, because that would be a lot of shots. 

I haven't seen the california nebula in such detail. But it needs color and then I think it would really stand out.

Can you do longer exposures in ha, due to the mono? or is it the same thing. since most of my shots over expose after 120 seconds?

It was originally colour but I changed it to greyscale as that's what you get with a mono camera. You can do very long exposures in Ha/narrowband irrespective of a mono or colour camera. That's because it only lets a very narrow band of light through i.e. not so many photons. But a cooled, mono ccd is the best camera to use, as discussed previously.

Louise

[vertigo262]

ya but you need to do each channel with filters. which is much cleaner, but a lot longer to do

[Thalestris24]

I guess it depends on what your aims are... One option is to combine Ha with RGB. Another is to create images purely from mixes of narrowband eg Ha + OIII + SII. Some people set up multi-imaging rigs (see Gina's thread in the DIY section). A dual imaging rig would be quite good with one scope for osc rgb and another for narrow band. Or you just make do with one scope

Louise

[vertigo262]

I agree... That is why color vs mono seems to be so confusing. Everyone wants the best quality they can get. although that means 4 shoots provided you get all the subs in one night for each shoot. which when I think about it, I want the best quality, but I don't know if I want to put that kind of effort in. But, I haven't made up my mind on that yet as where I am going on that

[Thalestris24]

I've been imaging just over a year but haven't yet managed to produce a decent, finished image yet... Patience is a virtue, they say. No rush!

Louise

[vertigo262]

I wish I had a mono camera to try, to see the results with my own sweat. I've seen other peoples, but that doesn't tell you much... unless you go out and see what you can do with it. although. I've also seen some pretty impressive results with OSC cameras. so it's really hard to know what works for you and provides the results you need.

we show me your best, in color, using a mono. I'm curious to see what you got. and also, know what it took to get it

[kalasinman]

In my limited understanding, the time of imaging issues you mention aren't as clear cut as you might think. Reading the posts of Olly and others, one could generalize that taking an image requires a certain quantity of photons. Photon collection appears to be =  aperture x time - filtering loss. In the case of red, a bayered camera already loses 3/4 of the light in that spectrum, while a mono ccd with filter would collect roughly 4x as many in the same time period , all else being equal.

If one uses a wheel to reduce changeover time, and parfocal filters, mono seems to be pretty much the same, timewise. I've also heard that processing becomes easier with mono and filters.

[vertigo262]

That's all in theory, but really, the question is, what is it taking for people to do.

Example, lets hear from someone who did the horsehead, which is probably one of the easier ones. How long did it take them? I'd be curious to know if someone did that all in one night, with clear, no noise images.

I guess if the exposure time is quicker, and you need less, then that might even things out. but it would be nice to have some in field times from people doing all channels 

also, even though you have a filter wheel, I think you might need to center the scope on a star for refocusing, and then re frame. But I could be wrong about that.

[kalasinman]

That's the point of parfocal filters. The reason I posted the above, is that I've been thinking about getting into NB or LRGB with a CCD at some far future point. I like to do all the reading I can, and I believe it was Olly who brought up the very points about per result, mono being faster.

[vertigo262]

It would be good to get feedback from people on that. I find it hard to believe. But you never know. Although I've read a few articles on mono vs color, and most said it took a lot longer, but the results were way better. It's just most people don't want to deal with all of that and want to just deal with osc with less complexities and quicker. But really, it all comes down to, what is it taking for people to do.

Just off the top of my head, I will take a guestimate for horse head.

lets say I do 30 x 120 seconds because mono should be quicker and get more information

setup time - 1 hr

Ha - 1 hr

R -   1 hr

G -   1 hr

B -   1 hr

changing focus with all 1 hr

calibration frames - 1 hr

well if I do this, 1 night is fine. But, I have no clue if my exposure times are accurate.

Right now, I've been out 2 nights to get 40 subs on the horse

400 x 40 at ISO 200

But this is extremely low ISO. 

So honestly, that is just theory and really doesn't tell me anything. So others feedback on doing HaRGB or LRGB would be helpful on this subject

[kalasinman]

I can see your point on this. Maybe Olly Penrice will weigh in on this.

An hour of focus time with parfocal filters?

An interesting approach is that rather than taking all the subs of one filter in one session, one can take a single sub of each type consecutivly. That way one has a sort of sampler if the clouds roll in to combine and see how things are going. That way color balance can be judged and one always has complete packages at the end of each night.

[vertigo262]

I'm just throwing out guestimates, I'm assuming parafocal means you don't need to refocus, I've never heard of them, but that would save a lot of time. I'm not used to using filters, bought my first uv ir cut filter the other day. struggling and learning.

I guess you could do it that way, but you would have to keep manually changing filters, which would take a lot longer unless the wheel was automated. But to do the actual shoot, I'd think you would have to do 1 filter at a time. 

[kalasinman]

I'm just trying to fill in with what I've learned from the experience of expert imagers here.

Yes, that's exactly what parfocal means.

Even a manual wheel can hold 5-7 filters. It's just a click to the next one. Far easier than taking the camera out and threading a filter in. Yes electric filter wheels are programmable, so ones capture program can pretty much automate the session including filter changes.

I just upgraded to BYN premium, which is the same as BYEOS for camera control. I haven't used it yet, but there is a feature to store a pre-programmed imaging session.

[Thalestris24]

Hi

If doing rgb you can save time by binning each colour 2 x 2 so will only take half the time of luminance subs. It can be argued that processing of separate colours is easier so time saved in that part of the process. I've no experience of processing images from a mono camera - just what I've read. Narrowband is different since that requires different sub lengths for each filter - OIII capture is notoriously slow, so I gather. On the other hand, if lp is bad then narrowband might be the only option. Being in the UK, imaging time can be very limited cos of the weather, so osc seems the best way. However..... When you have bad lp, as I do, you need to capture a lot more data to make a decent image compared to imaging at a dark site. That's one of the reasons I've not yet made a decent image yet - not acquired enough decent data! The 'imaging with the 130pds' thread is a good place to look at various types of images I still live in hope that I'll get my mono 1100d back so that I can have a proper go at narrowband.

Louise

[kalasinman]

If one uses the approach of getting a little of all channels in each session then in daytime or cloudy periods, one could experiment and adjust times for the next session to deal with the way test combinations look in revue. Do you want more or less time with any one channel to give the balance you want? There seem to be several ways of combining channels. One can: use Ha as luminance, blend Ha and luminance, replace the red channel with Ha, blend Ha with red channel, etc.

What one decides as a result of being able to combine after the first session suggests one might save considerable time at the end,  as if one had finished data collection for each before going on to the next, then started processing, one might discover that more data is needed for one channel, in effect wasting imaging time on others, in order to get the desired result after spending a lot of time. (run on sentence forgiven?)

[Thalestris24]

Hi

I don't think I'll ever do rgb - just narrowband or osc. The skies are more often clear around the Full Moon (why is that??) so nb seems a good option. I'm not convinced about filters being truly parfocal. I've recently fitted electronic focusers - they make focusing quicker and better and should enable focusing between filters easier. It's all a learning experience!

Louise

ps you can add more data across sessions - even a year or more apart! I knew when I started that it could take me several years to acquire enough data for particular targets...

[vertigo262]

I thought the moon adds light pollution. When I see a full moon, I can't see much else?

also, isn't OSC RGB? I thought that was just a ccd doing RGB?

I'm on budget, so no auto filter wheels, or auto focus, it would be nice though. But I think those seem to be more for ease of use. I'm guessing the only difference between manually focusing and auto, is you can do it without moving off the computer but you still have to watch the fwhm. or maybe not. Those I can live without until I make my billions and take over the world )

But, things like quality are important too me. and achieving imagery from darker objects. That's where my mind is right now. I don't think I have the patience to wait yrs for my imagery.

I could go for a couple of weeks work to a month. But then the law of diminishing returns kicks in. 

[Thalestris24]

Yes, the Moon, especially, around full, is a severe source of lp. But with care narrowband (at least, Ha and SII) can still be done if pointing away whereas osc or rgb get washed out. osc is a color camera. RGB is done with a mono camera plus R,G and B filters.

I'm poor - my only income is a state pension which isn't very much... Still, I've fitted a Skywatcher 'autofocuser' - they are cheap! About $75? £45 here... It's not really an autofocuser but you can optionally add some electronic motor control and software.  The supplied hand controller is useable and combined with APT's focus tool which gives fwhm values, is a definite improvement over focusing by hand. I have a manual filter wheel - good enough for me! The nb filters are expensive though. Have you looked in the 'imaging - deep sky ' section? There are plenty of examples of images constructed over different sessions, even from different cameras.

Louise

[vertigo262]

I've looked at several images all over. and seen several exposure times.

But nobuddy ever says what it takes to get the whole thing. 

For example,  this picture is,  140 image x 120 seconds. 

but nobuddy ever says, I did an L took this long, and R, a G, and a B, took me 3 days to get the shots. etc

also, I've looked into some LP filters after someone suggested earlier in this post or another after looking at my Horsehead, and seems like a good investment. and the results look significant from the other posts.

I really want to try the Ha, but of course I need a mono camera, and that opens up a can of worms which direction I want to go. and the costs to even try it out. I've seen others Ha's, and they look amazing. But you never really know what is or isn't, until it's you, in the field trying it and seeing what happans. 

So now I am poundering on my next future investment on photography equipment. that was why I want to try a cheap debayered slr. Although I don't know if I can do it for that cheap. I know I can probably find a camera for $100 but finding someone to debayer for cheap. who knows.

but whatever I do, I want my final results in color.

[Thalestris24]

Hi

They mostly do give a lot of detail in the deep sky section: http://stargazerslounge.com/forum/37-imaging-deep-sky/

If you have bad lp, a good filter is worth it. You can do a lot with your full-spectrum camera and a lp filter (if needed) so I wouldn't worry too much about getting a mono/debayering a dslr yet. The good quality lp filters are also UV/IR cut so will serve a dual purpose

Louise

[laser_jock99]

LOL- colour imaging is a lot easier! No filters, no refocusing, one set of darks/bias/flats & less processing time.

My last Horsehead image  (240s with a full spectrum camera & fast Newtonian scope)

[vertigo262]

That is why I am taking it one step at a time. My next step is to try to lp filter on my dslr. I drive out of the city to the suburbs where lp is about 2 - 3

If I want better, it's about a 4 hr drive to to the mojave desert where it is less then 1. but that's a ways away.

but what is driving me crazy is I want to try an Ha filter just to see what happens. Hence the problem because I need a mono camera. But like I said. one step at a time.

because in my readings, the ha's cut past the lp significantly. which would be another reason to go mono. And that's something that they don't talk about when you see all the pretty pictures on atik's website from the OSC's. You have no clue if the person who took it is in the ideal location with no lp. then you buy it and find out you can't recreate what he was using it for.

Laser, that is true, OSC is a lot easier, hence the debate on mono vs color.

your focus looks way off on the horse by the way

[Thalestris24]

I think I'd advise to skip the Ha for now and get what you can out of the modded camera. You should be able to achieve high quality images. Adding an Ha filter will complicate matters - harder to focus, needs much longer exposures so accurate guiding. With just an lp filter you won't get the star bloat

Louise

[redmoo]

Just to chime in again, there seems to be one problem with what you are asking for. You say you want 'good quality images', but you are also on a budget. If you do start looking at some of the images that people post on here, please be aware that not only have they been doing this for a long time, but people can spend tens of thousands of pounds on imaging rigs.

Also, you want to get decent images in as short amount of time as possible, again, this is something that does not come easy. I have been told that for every hour in front of the telescope, you need to spend 4x that in front of the computer in the post processing. 

I bought a set of Narrowband filters about 1 month ago. I am using them with a modified DSLR. I chose the target of the Rosette Nebula, and every imaging session I have had has been targetted on that. In 1 month, I have got 1 set of data for H-Alpha that is useable. We have been hounded by clouds as of late, and with the full moon throwing itself into the mix, even the narrowband runs take a hit on contrast.

My plan is to do 1 filter each night. I get about 4 hours worth of data (got work the next day, so cant stay up till 3am). Using Astrotortilla, I can reframe the image automatically, so I dont really need to worry about that. Because I do not have a filterwheel yet, I am having to refocus with each filter at the start of the imaging session. I have no idea how long it will take me to get a picture that I am happy with, but it is a learning curve, and one thing that has come to my attention very quickly, is that this is not a fast process. 

Trying to get hubble style pictures, on a budget, in a short amount of time, I think you are going to be in for a shock.