A few newbie questions

[forum8fox]

I am somewhat new to learning about what a lot of people seem to consider "Real" astrophotography.  However I have been shooting the stars for years, mostly in the form of single frame images, long exposures or stacks of shorter exposures to create star trails.  I have known about dark frames since the beginning but mostly never shot them because the plugin I use in PS to stack startrail images creates it's own dark frame somehow. I went to college for professional photography and I sell fine art landscape work at art galleries.

I've been wanting to learn to optimize the non-trailing star images and so I've been doing an ton of reading on the different types of noise and sub frames that people shoot. I got a better low light camera (6d instead of my 7d) to pull more detail from the stars and foreground on really dark nights, and a couple fast lenses (rokinon 14mm 2.8 and canon 24-70 2.8ii) and recently picked up a 50mp 5dsr and a 150-600mm lens.  At this point I'm still shooting on a fixed tripod but considering picking up a tracker eventually (astrotrac or skytracker pro).

So for now I am still primarily interested in wide field astro-scapes instead of just the stars. I took a few single frames of m42 for my first time to test out the new lens at 600mm and 25k ISO-102k ISO 1/13 of a second to remove trailing and was seriously dissappointed and disheartened. Also I recently did a shot that I shot darks and bias subs for but still no flats.  The questions I currently have is what should I learn to do with PI to get the most out of my astroscapes? I have stacks of images I shot for star trails, is there any benefit to stacking them in alignement without subs? I was going to try batch preprocessing on the image I do have subs for but I'm getting a script error so that's out for now.  Also is slight trailing a problem? some of the shots I did recently on my 5dsr have slight trailing at 24 seconds on a 14mm, and the same thing but perhaps less surprising at 24mm.

I am surprised by how many scripts, processes and features the program has and I have no idea what 97% of them do, or how they work. seriously intimidating. but I want to learn my way around the program and not be so clueless about all the features.

Thanks for any and all advise.

[pfile]

i think if you want a good introduction, it's worth investing in Warren's book (Insight PixInsight). that will help immensely with the learning curve.

having said that, wide-field images are kind of an advanced topic in astrophotography. wide angle lenses always have a good deal of distortion, and zillions of tiny stars. PI can definitely handle that, but by default it's more set up to handle "traditional" astro images, say those taken with a 500-2000mm focal length. the star trails and lens distortion will probably require you to tweak the StarAlignment parameters, meaning that BatchPreProcessing is probably not the right way to go, as BPP's control over the finer points of the StarAlignment process are limited.

at 600mm you need really short exposures to eliminate trailing. it's probably better to save that focal length for when you have some kind of a tracker. keep in mind though that the small trackers are not designed for those long, heavy lenses. maybe the astrotrac can handle it, but i don't really know for sure.

rob

[bulrichl]

I agree to Rob that a 600 mm lens is not suitable for astrophotography with a fixed tripod - indeed I think this lens is not suited for a beginner in astrophotography at all. Forget the 600 mm lens for the beginning. If you try to get that working, I fear you will give up the hobby soon. By the way, for astrophotography there are better and less expansive refractors in that focal length range. If you don't use the 600 mm lens for daylight photography I would sell it.

When starting with digital astrophotography (Canon 20D) I used the lenses that I had. The 17-40 mm f/4L II was proper for for the milky way, the 50 mm f/1.4 images of constellations (e. g. Orion). Later I bought the really fine 200 mm f/2.8 L II for bigger objects like M 8 or M 42.

But you certainly will not get happy without tracking with shorter lenses either. Get a mount (perhaps a used Vixen GP-D or something similar) and try astrophotography with exposure times of 1 - 5 min. Calibrate (at the beginning you will not need flat frames), register and integrate the subframes. Probably you will also find out that you need to guide.

One important thing is: do you take the photos from your home or do you have to drive to a dark site (fixed or mobile setup, power supply, etc.)? This has to be considered from the start.

Best regards,
Bernd

[forum8fox]

Thank you guys for your responses.

I live at 9500' in the foothills to the west of Denver Colorado but I'm mostly surrounded by trees on my property. There is a relatively open meadow just a few miles from me and a very large open meadow closer to the actual town (Evergreen) about 2000' below me. Also I can drive to the top of a 14'000 mountain with an observatory by continuing 15-20 miles up my road (Mt. Evans).  I also have a friend that lives way the F out in the middle of nowhere who's husband has a scope (not sure of focal length but he has to stitch to get a full frame of M42) and she said I could hook up sometime. To be very honest I'm not really looking to expand my equipment past anything I can hike around with so a mount that I need a computer for is beyond my scope currently. From the research I've done it seems the astrotrac should be able to do about a 5 minute exposure at 600mm. the Skytracker is more of a gamble for the big lens but seemingly much more affordable when I factor in the scope and probably a wedge for the astrotrac.

I bought the 150-600 because I didn't have anything for full frame past 70mm and I figure at times I'll want more, it was just a hopeful bonus that I might be able to shoot some deeper space objects with it. I am almost certain I will find it useful for sports and wildlife shots so I'll be keeping it I think.

Sounds like perhaps you guys advise sticking more with the wide field astro-landscapes and perhaps some pure wide field astrophotography for now? I can be agreeable with that as I figure at this point in time I'm probably going to sell more landscape based astrophotos in my niche than I would images of just galaxies, clusters, nebulae etc.Though I've read when buying a mount you'll probably buy more than one if you try to start with something cheap. I'm surely open to advice on which affordable tracking mount would be best for me but since this is a PI forum I don't expect it nor wish to sway the discussion from the software.  Though that does spur other questions,like how can one stitch panoramic astro landscapes when tracking without worrying about paralax error? Is it possible to use a Panoramic head on a tracking mount? I've also been thinking about filters and or modification to help pick up more color, what do you guys advise on that? Seems people like the clip in filters but the thought of having to fiddle around inside my camera with the lens off makes me uneasy, though so does modifying a camera for astro use and hoping I can use filters to preserve it's normal use without sacrificing IQ.  So much to learn, digest and process, astrophotography seems like a significant step up in technical ability and knowledge.

So for wide-field astro-landscapes is PI going to be a useful software for me to pursue and if so what features, scrpits, processes, best practices etc. should I be researching and perfecting? Also just purely out of curiosity does or has anyone use it for regular photography for any reason? If PI isn't going to be the software to best suit my needs what would be better? I was originally looking into DSS but it's not supported on Mac and I don't want the headache of running bootcamp or some other Windows program on a Mac workaround. I currently use LR6 and PS6. Thanks again and I look forward to hearing more from everyone.

[pfile]

i don't know much about landscape astrophotography - obviously you have the added complication of parts of the frame moving and parts of the sky not moving; assuming you are able to align the images (which i think is likely with enough tweaking), the stack is going to have a smeared-out earth component that will have to be composited back, which will likely be easier with "some other" tool (generally discussion of other astro or non-astro image processing software is frowned upon here, but people do discuss equipment).

if you are serious about "traditional" astrophotography then the best advice i've heard time and again (and i believe) is to spend most of your budget on the mount. you're probably talking about $7k to start for a mount that's going to track and guide reliably with a "real" telescope and camera package on-board. if you're not into that then i think the smaller trackers are OK, but really only for shorter focal length. at 600mm the polar alignment error of an astrotrac or similar is probably going to show up fast, and with no guiding, there's nothing there to correct it; the end result is not necessarily star streaks, but definitely oval stars. i guess you can autoguide an astrotrac, but i think it's RA only (no dec guiding).

i have used PI for "regular" photography, mainly experimenting with noise reduction and deconvolution. i think for any astronomical purpose PI is the best software available, but it does require an investment from the new user in time and effort.

the below attached is an example of iOptron skytracker + unmodified 5d3 + thrifty fifty at f/6.3. at that FL i had no issues with tracking or oval stars even with 420s sub-exposures. getting the thing polar aligned and getting the pointing set up was a real chore - with my "real" setup i just tell it to point to something and it happens. here i was on the ground peering up thru the polar scope, then discovering that the whole thing sagged with the weight of the camera on it, then re-aligning (more difficult with the camera attached), then trying to figure out the framing and rotation angle by taking test shots, etc. etc. i used a ball-head mount to point the camera. if the camera were modified then the nebulae would stand out way more - a non-modified camera cuts the red light from the Hydrogen-alpha line by about 80%! i would not worry too much about the clip-in filters; they go in in front of the mirror so there's no chance you're going to drop something on the sensor. however with the dark skies you have you probably don't need to use any filters at all; mainly people use the clip-in filters on DSLRs for light pollution.

by parallax error do you mean distortions caused by nearby objects shifting as the camera pans?

rob

[pfile]

oh i forgot to mention that Astrobin is a pretty good resource - you can search for images made with various equipment and see what people are doing with astrotrac or whatever, just to get an idea of what's possible focal-length wise...

rob

[forum8fox]

By parallax error i am refering to the shifiting of objects of different distances in relation to one another.
I used astrobin to see what had been done with the 150-600 before I bought it.

The advise about the mount is what I had heard too, though there is no way I could justify spending that much on a mount. My car only cost $4k, and I had a real hard time justifying the $6.5k I just spent on cameras and lenses. I've read the breakdown on potential top of the line astro setups costing in the $100k range which is completely insane to me. I seriously wonder how anyone can justify it though I'm no millionaire.

I am not surprised talk of other software is frowned upon however if it's software that does something that PI doesn't what's the harm? I was just under the impression it was implied perhaps there might be something that might work better for my specific application. It was my assumption that anyone had specific software in mind. No worries if we can't touch base on that here, though if anyone feels like sending a private message if that's not frowned upon I would appreciate that too.

So in terms of PI I understand to get the most of it is going to take research and practice which I am ok with. However with such a dense program I could waste a ton of time trying to figure out which features I should learn and perfect them, let alone all of the purposes of all the features available.  I'm currently on the trial version so I'd like to get the most of it to determine if it's something I even need so buying a book and reading it cover to cover doesn't seem the best option. It's not that I don't have other software that has worked for me up to this point but I am hopeful this software, subs, and maybe a tracking mount will elevate my work to a level that I can justify the expenses.

In terms of the clip in filters, I guess I was wondering if anyone could speak to having a camera modified for astro work (removing the sensors extra filters) and using the clip ins to be able to still use it for regular imaging without losing image quality. I realize I probably wouldn't benefit from the light pollution cut filters, though I wonder if they could be good for actually getting stars to show up in cityscapes.

I surely appreciate you taking the time to help me out. Though I still have no idea what to do with the program to even give it a test.
I'm sorry if I'm barking up the wrong tree here, if that's the case could someone point me in the right direction for where to seek advice?
Thanks again!

[pfile]

oh - yeah i have a modified canon 50d, and you can get a clip-in IR cut filter from astronomik. i do have one but it proved mostly worthless as i eventually bought a 60d for terrestrial work (and then the 5d3 much later). from what i understand many people just set a custom white balance with a grey card and that largely undoes the red-heavy response you get after removing the IR cut filter. so i'm not sure if the clip-in filter is a necessity.

100k is for sure easy to hit, but you can probably do excellent work with $10k worth. i think even that level is more than a lot of people spend; an Atlas mount and a small refractor + DSLR costs much less.

if you don't want to invest in warren's book, i guess you should look at Kayron's tutorials ("light vortex") and maybe david ault's website if you want to see how PI is used for astroimage processing.

rob

[bulrichl]

Rob summarized it quite right. Therefore only some supplementary remarks:

Good astrophotos can be obtained with short focal lengthes too. There are a lot of objects large enough for short focal lengthes (up tp 200 - 300 mm). With short lenses you keep the weight low. So you don't have to spend $7k for a mount - the expense for the mount is exponentially proportional to the weight of your equipment. Moreover you don't absolutely need a notebook for guiding. There are computer independent solutions for guiding, e. g. MGEN.

I recommend you to look for an astrophotography association near your location. Talk with the members or even better maybe you can take a look over someone's shoulder when taking astrophotos. Or join in a telescope meeting. You can get a better understanding and learn what you want to do when you see directly what's going on and put your questions. Direct communication with others is important if you want to avoid a costly bad buy.

Bernd