endless-sky

I have done plate-solving with my Nikon D5300 and any combination of the focal lengths I have available: from 18mm to 2032mm. As long as you install the required indexes - and specify what focal length you are using, in the telescope tab of EKOS - plate-solving works fine, even with a DSLR. The exposure just needs to be long enough to show a few stars - usually anywhere between 1s-10s.

If you have cameras, you can take advantage of plate-solving. To me, after I discovered it, there's nothing better and I have never done star alignment ever since. Also, does the KStars/EKOS suite work on OS X? If you want to abandon Windows - which I don't blame you for - consider using KStars and EKOS. It's a spectacular package. KStars is a planetarium and works pretty much the same as Cartes du Ciel. EKOS is a controller for every and any piece of gear astrophotography related that you can think of or own.

I guess that the more points you take - and the more spread apart they are - the better your mount modelling of the sky would be. From some videos I saw about the subject, it seems that if you align with 3 stars, every slew inside the "triangle" made by putting those stars at the vertices should be pretty much spot on. Outside the "triangle", things start to be more off the further you go. Another pointer I could give you is to try with the hand-controller alone, just to see if the behavior is similar: this would rule out any software related problems.

Tried for the first time last night, with my old Celestron C8, at 200x. I could clearly see both splits, it was really awesome! I didn't think about going lower in magnification, but I will for sure next time I take out my rig.

The color cast can be corrected in post-processing. You could also just put back into place one of the two low-pass filters (I don't remember which one, but one of the two will only filter UV and IR). This should make things a little better, but you'll still probably have some color cast that needs to be corrected in post-processing. That said, the main reason for not going completely full spectrum is that, when using lenses, or refractors, not all light wavelengths focus on the same focal plane. This effect is more evident the further into the red (IR and past) and into the blue (UV and before) you go, resulting in bloated stars or purple/magenta halos around them. That's why you want to put back the UV/IR cut low-pass filter or another type of UV/IR cut filter. This, however, shouldn't matter if you only have mirrors in your imaging train (but will as soon as you add a lens - coma corrector, for example, if you use one).

Hi, I used "All sky plate solver" index installation wizard to calculate the indexes you need. Plugging in your sensor pixel size (6.5 microns) and number of pixels (5505 x 3670), the wizard advices to install these indexes: for the 50mm: index-4216, index-4217, index-4218, index-4219, index-4100 for the 200mm: index-4212, index-4213, index-4214, index-4215, index-4216 Hope this helps!

Definitely turn off any "in-camera" noise reduction. If you want to calibrate the images, taking proper darks works better: just take 20-25 dark frames at the same exposure time that you took the lights and integrate them into a master-dark, which then will be subtracted from the lights during the calibration phase. Long exposure noise reduction does this after each light, but only takes one dark and subtracts it: an average of 20-25 darks works much better. With that said, I believe taking darks with a thermally uncontrolled DSLR could actually do more harm than good. Noise is very sensitive with temperature and if the temperature of the sensor/camera while taking the lights is not the same while taking the darks, the noise of the darks won't match the one in the lights, resulting in more noise actually being injected in the calibrated frame. This is another aspect where dedicated and cooled astrocameras shine with respect to regular DSLRs: the ability to control the temperature with very good accuracy and repeatability. To control the sequence of exposures, consider investing in an intervalometer. They are relatively cheap (less than 20 Euros) and you can program the entire sequence: exposure length, number of exposures, delay between shots. Amazon has many examples, just make sure you buy one that is compatible with your camera. Another tip is to turn on the in-camera setting called delay exposure: this is useful because the camera will start recording the picture about 1 second after the mirror has been lifted up (this reduces the possibility of vibrations ruining the long exposure). Just take into account that the 1 second is part of the total exposure time you chose (so, if you want a 5 second exposure, with the delay exposure setting on, you'll have to program a 6 second exposure, instead).

If you open one single RAW file with Camera Raw or some other compatible file reader, it should tell you the exposure settings (ISO, shutter speed, f/, etc.). You can check there if it was 2s or 1/2s. If it is 1/2s, then the difference is quite significant: 600*2=1200s=20min total integration, 600*(1/2)=300s=5min.

That was probably me, as I posted something similar in another thread. The way I understand ISO-less is like this: if you are correctly exposed at 200 ISO, say with 10 second exposure - and by correctly I mean the histogram is detached from the left by a good margin and you are not clipping any data - doing 10 seconds at 400 ISO won't give you any extra details: it will simply shift the histogram further right, but not collect more light, so it just boosts the signal that was already there at 200 ISO - sort of like a stretch. This is something that you can and will do in post-processing, anyway. So, by raising the ISO you actually don't gain anything in terms of light collected, but you lose in terms of more noise and lower dynamic range. This reasoning only works if you compare a correctly exposed photo taken at 200 ISO with a correctly exposed photo taken at 400 ISO. But if your exposure time is limited by having to take the photo without tracking, from a static tripod, and the highest time that you can use before you get star trails is not enough to expose correctly, without clipping data (histogram not detached from the left), then you have to compromise and trade off some dynamic range for a higher ISO, just so that you can expose correctly with that chosen exposure time. This is how I understand it, I don't know if what I said is completely correct, but if someone knows more about how it works, please feel free to comment.

I would keep the current setup, maybe move it to the place where you are for the longest stretches of time, so you can get more use out of it. Or, if you have the means, build some sort of shed/observatory by your father's house and control everything remotely, could be an idea as well. Another thing you could do is buying a smaller telescope - or even some good lenses for the D5300 (I have seen plenty of beautiful pictures with the Samyang 135mm f/2 or the Rokinon 135mm f/2) and a star tracker (Sky-Watcher Star Adventurer Pro, for example), a small guide scope and guide camera (you could even "steal" the same ones you already have from your current setup). What I wouldn't do is sell that telescope. I think it's been in my "dream list" since I have seen the pictures people take with it. Definitely a life-time keeper. EDIT: also, keep the camera, at least to start with. I have been using my modified D5300 for the past six months and - horrible kit zoom lenses aside - I absolutely love the results.

Hi, the images you linked are most likely taken with an equatorial mount or a star tracker. Most nebulae are really faint and most DSLR are really blind to one of the most important part of the light spectrum (H-alpha). I use a D5300 as well, for astrophotography. But, before astromodifying it to make it more sensitive to H-alpha, I was struggling to get any significant signal even with 1 or 2 hours of total integration time (I do, however, use an equatorial mount - Sky-Watcher NEQ6 Pro - so I usually expose for at least 60-120s, depending on the focal length I use). Without a tracker and without modifying your camera, there's a couple of things that you can still do to get better results: - raise the exposure time: with 50mm you should be able to go around 5-8 seconds, depending on where in the sky you are shooting, before stars start to trail. Experiment with this and keep raising the exposure by 1 second increments, until you start seeing star trails, then go to the previous exposure setting that didn't show trails and use that for the rest of the session - raise the ISO. You should try to get the histogram shown by the screen of the camera, after you took the picture, to have a gap between the far left of the histogram (where 0 is) and where the foot of the curve of the data collected begin to show. If the curve starts "already high" at 0, then you are clipping (not collecting) data. If the exposure is not enough to show a clearly detached curve, raise the ISO in full increments (200, 400, 800, etc.), until you find a combination of exposure time and ISO that is good (goal is: no star trails and curve detached from the far left of the histogram). Practice with these and see if your results improve. Eventually, if you like the hobby, consider buying a star tracker or an equatorial mount, depending on what load you plan on putting on it and eventual future upgrades.

I modified my D5300 myself, as well. Before removing the screws, I marked them and I also counted the turns I needed to unscrew each one of them. I, too, counted 5 turns. I did replace the stock filter with a UV/IR cut filter, as I didn't want a full spectrum camera and I read pretty much everywhere that without UV and IR cut, you get bloated stars, with purple halos, if using lenses - and I am using lenses. The biggest problem I encountered was finding a suitable UV/IR cut filter. I couldn't find pre-cut, rectangular filters that would even come close to the correct dimensions. So, at the end, I had to buy a 2", round, UV/IR cut filter and cut it myself with a glass cutter - hardest thing ever. I completely broke the first one, even if I had 4 tries (4 complete rectangular filters would fit inside the 2"). I bought another one and finally manage to get 2 good samples. I mounted one and kept the other one as a spare. I didn't care much about autofocus, but I tried my best to achieve it anyway. Main problem was that the new filter was a lot thicker than the original one and I tried some formula to determine by how much to correct the original distance. By the math, it seemed I had to do 4 turns and 3/4, instead of 5. But I had to stop at 4.5, because the screws were becoming really hard to turn (I suspect the extra thickness of the new filter made the sensor/filter/enclosure reach some mechanical stopping point before the 4 and 3/4 turns), so I didn't force it and stopped at 4.5. Screwing all 3 screws at 4.5 seems enough to keep the sensor planar (I have bad tilting on the lens I use, but the stars have exactly the same shape in the framing before and after the modification). When I get my imaging refractor next month I will do eventual adjustments, if needed. I couldn't, however, retain autofocus. It's not a big deal, as I don't use the camera for everyday use and I use either live-view or the laptop screen for focusing, with a Bahtinov mask - didn't have any problems with that.

Hi, I have been using a D5300 for astrophotography, for the past 6 months. Before that, I used for a brief period a D90, just because I had it since many years before, for daytime photography. I did a lot of researching before purchasing a - used - new DSLR, in what is available in the APS-C sensor format, both from Canon and from Nikon. At the end, I went with the D5300, because I already had some Nikon lenses that I was using with the D90 (18-105mm, 70-300mm and a 50mm prime lens). But that was not the only reason. More reasons behind the choice were that the D5300 is one of the best suited cameras for astrophotography, in the APS-C format: it has very low noise, high dynamic range, it is ISO-less, it has an adjustable screen, it's very light. Most people used the Canon 60D or 600D, but the sensor of the D5300 is much better, even when compared to newer Canon models. I have been very happy with my D5300. But I also had to "astromodify" it. No DSLR is very much sensitive - natively - to the H-alpha line of the spectrum (one of the most important from nebulae photography), unless it is produced that way (some niche Canon models). So, I had to remove the stock filter and replace it with a UV/IR cut filter, to take advantage of all the sensor sensitivity, even in the H-alpha part of the spectrum.

Well, I suppose it depends on the fact if data is getting clipped (not recorded) or not. For example, if I can expose 20 seconds at ISO 200 without getting clipped (the histogram is detached by a good margin from the left, where 0 would be complete black), there would be no point in doing 20 seconds at ISO 400 (as this would only shift the histogram further right, without recording any more data). It would be equivalent of shooting 10 seconds at ISO 400 (or pretty close), but then you would be losing dynamic range. This works perfectly fine if I have a tracking device that can expose for 20 seconds, at a given focal length, without star trails. In the case of static shooting, you actually have to find a combination that works good enough: short enough that you don't get star trails, long enough that the histogram is detached from the left (otherwise clipping). If this exposure time is not enough to detach the histogram at 200 ISO, then you will inevitably have to compromise a little on the dynamic range and try 400 or even 800 ISO. The generic "rule" to calculate static exposure is 500 / focal length = maximum number of seconds in order to not get star trails. I tried this, but it is not entirely true. I found that I need to further shorten the time. For a 50mm I found that I could go up to 8 seconds, for example, when I shot the comet from a dark place and I couldn't bring my mount with me. But it also depends by how much away from the North Celestial Pole you are shooting (the closer you are to it, the less stars move for a given time, while the further away, the more they move), so you'll have to adjust the exposure even more. I guess all I can tell you is to experiment and check the screen on the back of the camera until you find a combination that work.

I don't have much experience with filters, because so far I only have one for light pollution (Optolong L-Pro). So I don't know if the amount of vignetting different filters produce is the same (and only depends on the rest of the imaging train) or if it is filter specific. I guess all I could think of is for you to try calibrating some lights you have already taken (so you don't potentially "ruin" your next imaging session by not taking flats that might be needed) with the flats of just one filter and see if the results are comparable to calibrating each light with the corresponding filter flat. If the results do not change by an appreciable amount, then you should be fine doing flats only with one filter. If that's the case, maybe do the flats with the filter that has a "middle" focus position between the filter that needs the "further in" focus position and the one that needs the "further out" focus position. This way you mediate the effects that a change in focusing might have in the resulting flat calibration.

If you only have vignetting problems, you might get away with doing flats with only one filter (as stated above), or with just one focus position. However, when trying to get rid of dust spots, if each filter has different spots, then you'll have to take flats for each filter. I also found that focusing was important (I haven't tried with a telescope, yet, but with my DSLR lenses, difference in focus between lights and flats meant that the correction spots of the flats would be either bigger or smaller than the ones in the lights, basically leaving a ring around where the spots used to be). Shortcuts are fine, when you can take them. But when skipping 5 minutes might ruin 4-5 hours of imaging, I learnt the hard way that extra work always pays off at the end.

You got a really good camera for astrophotography. The Nikon D5300 is one of the best APS-C DSLRs for the job. Yes, I am biased, as I have one as well. But I have also been using it for astrophotography for the past 6 months and I really like the results: low noise, high dynamic range, light body. You can definitely start doing some static astrophotography with the lenses you have: the shorter the focal length you will use, the longer the exposure can be, before stars start to trail. Definitely do not use any filters that block light and try to unscrew the polarised filter - all these are not needed for astrophotography and might make things worse. The D5300 is ISO-less, that means it doesn't matter at what ISO you shoot, so you should use the ISO that gives you the highest dynamic range: 200 ISO. Everything else past that just increases noise and diminishes dynamic range. Take a lot of short exposures (short enough that you don't get star trails, with the given lens/focal length) and stack them with some free stacking program (DeepSkyStacker, for example). The more you stack, the better the result will be (up to a diminishing return limit). Next upgrade, if you like the hobby and want better results, would be to buy a star tracker (for example, the Sky-Watcher Star Adventurer Pro): with that, you can raise your exposures and gather more data.

That. Plus think what £3,400 could get you. Surely, an HEQ5 Pro, a fast 80mm apo triplet and even a dedicated astrocamera. Maybe even guide-scope and guide-camera.

Tesla is an actual upgrade over a regular combustion engine vehicle. 0-100 Kph in about the same time as most Ferrari/Lamborghini/Porsche for 1/10th the price? Yes, thank you! That thing instead? That's paying more to have way less.

No, star alignment doesn't correct polar alignment. Think about it like this: polar alignment is needed so that the axis of rotation of the mount can be parallel to the Earth's axis. This is needed so that when the mount tracks in AR, it can describe an arc in the sky that follows the apparent motion of the stars. If polar alignment was perfect, in theory you wouldn't even need to ever touch the declination axis during tracking/guiding. On the other hand, star alignment is needed so that the mount can "know" where it is pointing. Each night, for a given time, the positions of the objects in the sky change with respect to the night before, at the same time. Giving the mount the location and time should be enough for the mount to "roughly" know where everything is. This, however, is not entirely true, because there can be many compounded errors (longitude, latitude, date, time, polar alignment, tripod levelling, etc.). So, you give a few "points" to the mount to better determine where everything is. If you plan to do visual observation, the more points you give, the more accurate the model becomes and the more likely it will be that the next object you tell the mount to go to will be inside the field of view of the eye-piece. For astrophotography all this precision in pointing is not needed, as the field of view of a camera is - usually - bigger than the one offered by the eye-piece. Furthermore, you can use a technique, called plate-solving, which consists in taking a picture of where the mount and camera are currently pointing, comparing it to online (or offline, if you download them for later use) maps (using the calculated field of view of your camera and lens combination). The software then tells the mount / planetarium software exactly where it is pointing and the mount can do the appropriate corrections to center the object (if it isn't already in the center) that you asked it to slew to, before the plate-solving.

For astrophotography, the only required thing is a correct polar alignment. You don't need any star alignments, they don't have any influence in the tracking/guiding capability of your mount. What I usually do is this: - polar align with the polar scope, using an app on my phone, to roughly eyeball the position of Polaris in the polar scope (I found this is plenty good enough for my 1-2 minutes exposures, at 300mm focal length) - slew to a bright star to focus, plate-solve if it is not in the frame of the camera, until the mount pretty much centers it (I also sync the mount to the star position, once centered - so this technically counts also as a 1-star alignment) - slew to the object I am interested in capturing and plate-solve until it is framed exactly as I want (I also rotate the camera, in this step, to frame the object to my liking) - start my imaging sequence No star alignment required, only plate-solving for focusing and for framing.

The advantage of doing it with a Canon is that some models actually have two stock filters: one that blocks UV/IR (good) and one that blocks most of the red, including H-alpha (bad). If you remove only the second one, you are good to go and you don't need to add anything else (unless you want to keep autofocus, which doesn't work and is basically useless for astrophotography - you'll have to focus using live-view or your laptop screen, anyway, which is exactly what the sensor sees). If you remove the stock filter(s) completely, you'll have to add a UV/IR cut filter somewhere in the imaging train (closest to the sensor is better). This is because lenses do not focus all the light spectrum in the same focal plane. UV is on the far blue end of the spectrum, IR is on the far red. Without a filter, these "unfocused" parts of the light will create bloating in your stars and purple/magenta halos - same as if you would use an achromat instead of an apochromat refractor. So, my advice is: modify the camera, but leave in the UV/IR cut stock filter (if the camera has one) or add one (if it doesn't).

This definitely is a winner: https://www.rothervalleyoptics.co.uk/rvo-horizon-72-ed-doublet-refractor-ota.html Since it is supposed to be a real telescope. Can we throw some more colors on it?!

If you already have a Nikon and some lenses for it that you could use to get started in astrophotography, I would consider getting another Nikon. When I started back astrophotography with a digital camera, in January of this year, I was in the same boat: I already had a D90, which I didn't want to modify, because I wanted to keep using it also for daytime photography. It's also a very old camera, so not worth modifying it, in my opinion. I started using it for a couple of months and was never satisfied with the results: very noisy, no H-alpha or very little being captured. I felt like I was wasting my time out there for hours and not capture any significant data. So I started reasearching what to replace it with. My research wasn't limited just to Nikon, I looked into Canon as well. At the end, I chose to buy a used Nikon D5300 (the price was very nice and it only had 2000 shots taken, so basically new). From all the graphs I have seen, the dynamic range, noise levels and overall quality, the D5300 was a lot better than the 60D or the 600D or the other Canon choices that popped up in the forums. So I bought it, used it for a couple of sessions stock: the noise was very little, compared to the D90, the colors popped up more, and being "ISO-less", I could shoot at 200 ISO instead of 800 ISO with the D90. After a couple of sessions, I opened it up, removed the stock filter and replaced it with a UV/IR cut filter that I bought in a 2", round variant and I cut it myself to the exact dimensions of the one I removed (I couldn't find any pre-cut filter that suited the dimensions I needed). Opening the camera and removing the stock filter was very easy. Cutting the other filter was the hardest part, for me. If I could go back, I would probably send it to a professional store that would modify it for me. Anyway, the modification turned out great and the camera is now very sensitive to the H-alpha emission line and I can capture a lot of nebulosity even in a Bortle 5 zone, with 2-3 hours worth of integration time. I plan to go a lot longer once the nights start getting colder and longer, in a couple of months. Another thing that I read over and over is how Canon is more supported by the many astrophotography softwares (expecially the free ones). This might have been true in the past, for the older Nikon models, but the D5300 works perfectly fine with AstroPhotography Tool, EKOS and N.I.N.A.

When I use my camera/lens combination, I usually bolt a ball-head on a Vixen or Losmandy dovetail and then I clamp the dovetail on the mount saddle. There are a lot of different adapters that can do the job. Other people even put locking rings around the lens, and bolt the rings on a dovetail.