dawson Posted November 9, 2012 Share Posted November 9, 2012 (edited) Having just read an article in Novembers issue of Astronomy by Tony Hallas on using a digital SLR and only a telephoto lens to do some imaging of DSOs, I emailed him to seek clarification on what lens he used, and if this would be possible with a non-equatorial mount. His initial reply is below, but I wonder if other members have done much imaging with just a DSLR? ----------- Hi James, You will need an EQ mount unfortunately ... to take untrailed images of the night sky you must follow the stars! May I suggest the Vixen GPD2 mount as a good choice? Not terribly expensive, very high quality where it counts, and very basic in design. I was shooting with a rather exotic ( and expensive ) lens ... the Canon 200mm f/2 L, but you don't need to use something quite that fast. The important thing to research is how much false color does the lens have ( usually big red or blue circles around the brighter stars ... you want as little of this as possible ). The important thing is to get that mount ... you can then spend a lifetime trying out various imaging systems on it, and taking it to dark places since it is supremely portable. It comes with a "battery pack" but I would cut the wire noting which is the "+" side, and attach alligator clips. You can then use a rechargeable auto battery ... make sure the "+" side of the wire goes to the positive terminal on the battery! Hope this helps, Best, Tony --------------- James Edited November 9, 2012 by Brantuk Link to comment Share on other sites More sharing options...
+RonC Posted November 9, 2012 Share Posted November 9, 2012 He's absolutely right James, you can take shots like the Moon rising (and setting!) constellations but after that you need an EQ mount. I did some nice pics at Kelling using a 200mm on a standard Canon 1000d on an EQ5 mount, did multiple exposures of 30-50 secs and used Deep Sky Stacker (Freeware) to make a finished photo (see my gallery pics). So I'm afraid your very restricted for content without an EQ mount. (Not an Alt/Az mount either!) Cheers Ron Link to comment Share on other sites More sharing options...
Perkil8r Posted November 9, 2012 Share Posted November 9, 2012 Sheila has done some I believe. There was a very nice picture of Andromeda from Kelling earlier in the Autumn that Sheila took. I have taken to using my little st80 of late. It is 400mm in F/L and F5 so not that far off some of the lenses you can get relatively cheaply. It is possible to make a very cheap mount for a DSLR called a barn door tracker. I haven't made one nor used one, but they can deliver suprisingly good results I believe. A google search on that might give you some ideas. Really though you do need an equatorial mount of some description with some sort of motorised drive in RA. Be very carefull, the darkside is very addictive, you could soon find yourself getting way further into it than you intend, I certainly know all about that! Most of what you find written in these forums in relation to methods etc will still be most applicable when shooting with your camera and lens. The usual applies, focus focus focus and data data data. Link to comment Share on other sites More sharing options...
dawson Posted November 9, 2012 Author Share Posted November 9, 2012 (edited) The mount Tony recommended is £840! />http://www.firstlightoptics.com/vixen-mounts/vixen-gpd2-gem-mount.html By "not terribly expensive" I thought he was talking of £300 or so! Even the simplistic looking Astrotrac is over £400: />http://www.firstlightoptics.com/astrotrac/astrotrac-tt320x-ag.html Would it be relatively easy to attach the DLSR (Canon 600D) to the Skywatcher HEQ5 PRO Synscan mount, which could then also be used for mounting the scope? />http://www.firstlightoptics.com/skywatcher-mounts/skywatcher-heq5-pro-synscan.html This is all very theoretical at the moment. James Edited November 9, 2012 by dawson Link to comment Share on other sites More sharing options...
Brantuk Posted November 9, 2012 Share Posted November 9, 2012 For dso imaging James an alt/az mount can't be polar aligned and will induce star trailing because of the Earths spin and the need for it to to track in two planes - it's not really appropriate at all. An EQ mount once polar aligned will be able to track in a single plane counteracting the spin of Earth and providing the pixel perfect accuracy that the camera requires. Pretty mandatory really. The HEQ5 Synscan pro is a fine mount with everything you need for photography in terms of accuracy and tracking. And for the size of ota's you are considering (ED80 or GT81) you can't really go wrong with it. A good example in perfect condition under two years old generally goes for around £500 s/h. I got one recently and it's fabulous. The money saved can go into the ota or accessories. There are plenty of options for mounting a camera independent of scope. SW do an "L" shaped dovetail camera bracket and you can also get a level mounting camera dovetail from Modern Astronomy to go straight on the mount clamp. Hth Link to comment Share on other sites More sharing options...
Perkil8r Posted November 9, 2012 Share Posted November 9, 2012 It all depends where you see things going in the future and how much money you have of course. The general concensus is that a HEQ5 is the least mount you need for astro photography with a scope, that said a good few have managed some very acceptable results with the eq5 or the celestron version, the cg5. I use an eq5 and I'm happy enough with the results I am getting so far. As for mounting the camera it's relatively easy. Probably the easiest way would be to use a vixen type dovetail bar with a 1/4 UNC bolt through it into the tripod mounting screw hole in the bottom of the camera body. If you stick to short exposures of say 10 secs or less You should just about get away with a sturdy standard camera tripod. Take lots of exposures and stack them together in a suitable program such as Deep Sky Stacker. It's a freeware program so no cost there. You should be able to take some very nice widefield shots of the brightest objects. Orion would make a good target for this as the constelation is nice and has a lot of stuff going on tht even at short exposures should start to pop out. You will of course have to gently nudge the camera around a little from time to time to keep it in the field of view, but the stacking program will deal with a lot of the rotational difference as long as the subject is still in the frame. Another good one would be around Cassiopeia there is a lot going off up there too. Don't forget to have a look at the idea of a barn door tracker though, it's a cheap way to get started and is a method even NASA use! See here for some great insights http://gizmodo.com/5958413/watch-a-nasa-astronaut-describe-the-complexities-of-photography-in-space?fb_action_ids=10100770076494309&fb_action_types=og.likes&fb_source=aggregation&fb_aggregation_id=288381481237582 Link to comment Share on other sites More sharing options...
dawson Posted November 9, 2012 Author Share Posted November 9, 2012 This is really showing my ignorance, so go easy on me With a equatorial mount, is aligning it similar to aligning my alt-az mount and telescope, using two stars? How does polar alignment differ from other alignment with an equatorial mount? Do both motorised and non-morotised equatorial mounts "know" how much the telescope is pointing away from the pole star and adjust the speed of rotation accordingly to keep the object in view? James Link to comment Share on other sites More sharing options...
Perkil8r Posted November 9, 2012 Share Posted November 9, 2012 Oooooh can of worms...... I'll do my best, although I should point out I am new to this myself so don't take my word as gospel. An equatorial mount, often reffered to as German Equatorial Mount (I will call it a GEM for the purposes of this post) is relatively simple in design. With a GEM the basic principal is to align the Rotational Axis (RA) with the rotational axis of the earth, motors if fitted then counter act the rotation of the earth which should keep the target in the field of view. In most GEM's there is a polar scope that runs directly through the RA of the GEM. To align the mount with the RA of the earth we need to find a fixed point in the sky to align with. Polaris is known as a pole star because although it does still move slightly, it is as close to static as any star that we can easily find in the night sky being almost exactly over the RA of the earth. Once the RA is aligned with polaris the GEM will rotate pretty much exactly on the RA of the earth which is the important part for astro photography. Goto mounts and the such do still often have 2 or 3 star alignment processes that basically improve upon the polar alignment. There are a lot deeper theories and practices beyond this of course. There is guiding and alsorts of stuff, but for starters Polar Alignment is the single most important thing to get right with a GEM. It is awkward to get right at first, but with time it gets easier. I wrote a quick guide on polar alignment a while back now here: http://www.eastmidlandsstargazers.co.uk/topic/1965-polar-alignment-made-easy-ish/page__hl__%2Bpolar+%2Balignment__fromsearch__1 Whilst not all that applicable to you just yet, it should explain a little more maybe. Link to comment Share on other sites More sharing options...
Brantuk Posted November 9, 2012 Share Posted November 9, 2012 Not a prob James Polar alignment has to be done first - after that comes star alignment like on your alt/az handset. To polar align, the mount has to be aligned with the north celestial pole (NCP). The more accurate this is the better for your images. Start by setting the mount up pointing as north as possible. Using a polar scope (wich is usually inside the mount head) and the alt/az bolts, it can be fine adjusted closer to align with NCP. The mount must also be at the correct altitude for your latitude on Earth. There are latitude bolts to refine this as well - again using the polar scope. And that's roughly it. Now using the right ascension (RA) and declination (Dec) clutches - the scope can be aimed at any object and (if it has a tracking motor) will track your dso in RA only. This is just a brief explanation wich can be refined somewhat - but that all comes in the manual. It's really not as difficult as it sounds and can be done in a few mins once well practised. Link to comment Share on other sites More sharing options...
Perkil8r Posted November 9, 2012 Share Posted November 9, 2012 Just to clarify, I was reffering to rotational axis as RA, I may have chosen badly there and caused some confusion, although right ascension is in effect the same thing... sort of. But what I said still stands, you're looking to counter the rotation of the earth. Link to comment Share on other sites More sharing options...
dawson Posted November 9, 2012 Author Share Posted November 9, 2012 Struth! I thought aligning my alt-az mounted scope was tedious! Thanks for that reply and link, very comprehensive, but yet more incentive for me to win the lotter and buy a house in somewhere really dark where I can have an observatory! James Link to comment Share on other sites More sharing options...
Brantuk Posted November 9, 2012 Share Posted November 9, 2012 Lol James - yep - you still have star alignment to do after the polar alignment. I won't go into wedge aligning an alt/az mount at this stage - I remember how it fried my brain first time around. Link to comment Share on other sites More sharing options...
catman161 Posted November 9, 2012 Share Posted November 9, 2012 (edited) Hi James, I cant seem to find the thread but Mick (Doc) made a fantastic barn door tracker very cheaply if I recall. So if you want to go down that route he is the guy to speak to. Edited November 9, 2012 by catman161 Link to comment Share on other sites More sharing options...
dawson Posted November 9, 2012 Author Share Posted November 9, 2012 To be honest, I'm not really good with intricate things with my hands [i shouldn't say that because of my work!], and I don't really have the interest / drive to make that sort of thing. I think if I wanted to go down the equatorial mount route, I'd just save up and buy one. Lazy I know.... James Link to comment Share on other sites More sharing options...
catman161 Posted November 9, 2012 Share Posted November 9, 2012 No problem, I am not majorly into DIY either but gave modding my dob a go and its worked out ok if not as aesthetically pleasing as I would have liked . What do you do for work James? Link to comment Share on other sites More sharing options...
dawson Posted November 10, 2012 Author Share Posted November 10, 2012 Was wide awake at 5am, clear sky in north wales (only time this week!) So set up one camera to attempt a star trail, and with my other had a play with Orion. At 70mm with the telephoto lens the nebulae is minute in the final image, so won't be a great deal bigger at 200mm, so how on earth is it possible to get images as good as the ones advertised? Does the stacking software allow a minute area of the frame to be selected and it blow the resultant image back up to an acceptible size? Cloud appeared out of no where within minutes, then my glasses steam up! Yet another unsucessful astrophotography exercise I'm sure it's all good experience really. James Link to comment Share on other sites More sharing options...
Brantuk Posted November 10, 2012 Share Posted November 10, 2012 Post it up James - someone may be able to improve it a little for you. Make sure you include wich camera and model was used, how long the exposure was, specification of the telephoto lens, and how the camera was mounted. I'm no imager but I do know that most good beginner shots of the Orion nebula come from cameras mounted on the back of a scope at prime focus taken with long exposures (typically 2+ mins) on a driven EQ mount. Orion has a lot of hydrogen alpha (Ha) dust cloud and to capture the colour the camera often has the "red eye" filter removed to allow that wavelength through. Once you have a series of frames they can then be stacked and aligned using Deep Sky Stacker (free to download) and processed in Photoshop or similar to tweak it up a bit. Gimp is a good processing package (also free to download). You're now looking at the black hole that is "astro photography" and you've taken a step closer (up to near the moon) and you're soon to be sucked in at light speed. Welcome to the dark side. lol Link to comment Share on other sites More sharing options...
dawson Posted November 10, 2012 Author Share Posted November 10, 2012 Ok, I'll post it later; I've just arrived back in nottingham and treating myself to a fat boys breakfast before I unpack the car James Link to comment Share on other sites More sharing options...
dawson Posted November 11, 2012 Author Share Posted November 11, 2012 What I'll do is to take an image of M42 with the lens set to 200mm to make it more representative of the issue in hand. The one I've got is only set to 70mm; 2 second exposure on a rigid camera mount, f/4.0, ISO 6400 (yes I know it's high). The website won't let me upload the image at present, but it is similar to this, but not as good (fewer background stars), but as you can seem M42 forms only a very minor part of the frame: />http://www.pentaxforums.com/gallery/images/5744/large/1_Orions-Belt-135mm_filtered.jpg I'll try and get a better image myself. James Link to comment Share on other sites More sharing options...
Brantuk Posted November 11, 2012 Share Posted November 11, 2012 In that shot James you can also see the effect of a rigid mount - some of the stars around M42 appear oblong shaped which is caused by star trailing. With a polar aligned EQ tracking mount the stars will come out perfectly round if set up right - and longer exposures will be possible. Link to comment Share on other sites More sharing options...
dawson Posted November 11, 2012 Author Share Posted November 11, 2012 Yes, I get the star trailing, I'm sold on an equatorial mount (if I had the cash flow to get one), but I'm just confused how such impressive images can be achieve when M42 is so small! Admitedly my image was shot at 70mm focal length and the experts are promoting 200mm. This website is useful, seems he is suggesting at 200mm with a fixed mount, the longest exposure time is 1/3 second! Blimey, that is short: />http://www.bobatkins.com/photography/tutorials/astrophotography.html James Link to comment Share on other sites More sharing options...
Brantuk Posted November 11, 2012 Share Posted November 11, 2012 That's a cracking link James thanks - added to favourites. It'll help a lot of newbie imagers. Link to comment Share on other sites More sharing options...
dawson Posted November 11, 2012 Author Share Posted November 11, 2012 I'm so envious of even this image: />http://www.bobatkins.com/photography/tutorials/astrophotography/jupiter_2010.jpg From: />http://www.bobatkins.com/photography/tutorials/astrophotography2.html James Link to comment Share on other sites More sharing options...
Brantuk Posted November 11, 2012 Share Posted November 11, 2012 Have a look at Celeste's Jupiter in the imaging section - done with a bulk standard webcam - no mods and on a dodgey mount. Link to comment Share on other sites More sharing options...
dawson Posted November 11, 2012 Author Share Posted November 11, 2012 Lovely image! Link to comment Share on other sites More sharing options...
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