[newman]

If you can get to a dark site (unfortunately, with you being in the UK (?), dark-ish is the best you'll get without heading to rural Wales or Scotland),

I live in Croatia, unfortunately in one of the areas with the heaviest light pollution which is the reason I haven't purchased a scope so far; recently acquired a retreat in an area that has clear starry nights and minimal light pollution, which is why my desire to purchase a telescope has reemerged. Since the house there isn't 100% complete with still missing essentials a pricey telescope isn't on the top of my list though; there'll still be work being done there and that sort of an environment isn't conducive to proper storage and maintenance of fine optics. I'll probably get a real newtonian next year, but for now I'm considering getting a high powered binoculars to get re-acquainted with the sky; looking at 20x80 and 25x100 options - already have a camera tripod they're supposedly compatible with so that'd work out great.

You do make a good point about portability, however; newman, I'd advise going to see one of these scopes in person before getting one.  It can be surprising how big they are, but 8 to 10 inches is eminently manageable for just about everyone in my experience (I started with an 8, and now have a 10-inch Orion dob).

Newman, I also would not store your scope outside.  To protect it from the elements, especially rain, wind, and snow, it needs to be in an enclosure of some kind, even just an unheated garage.  You'll need to take it out every time you want to observe, but a Dob makes it so your setup time is two or three trips and about five to ten minutes, even in the dark.

The house where I plan to use my scope has a nicely sized terrace so I can definitely fit a 300mm dob there. To avoid constant dismantlings I was considering building an enclosing for the scope to keep on the terrace - which would protect it against the elements during my vacation weeks when I'm there. When it's time to go home I'd disassemble the scope and take it inside. A quality enclosing with some nylon insulation should protect the scope fine for a few weeks, no? It has the added benefit of not having to wait hours for the optics to cool down to ambient temperature
I'll take a look at those 10" ones though - in the end a larger telescope isn't too useful if it's too much of a pain to set up every time so you end up using it like once a year. Thanks a lot for the information, though - once I get to a point of actually buying a scope I might bother you with some PMs containing specific newbie questions

[Astronomiya]

I live in Croatia, unfortunately in one of the areas with the heaviest light pollution which is the reason I haven't purchased a scope so far; recently acquired a retreat in an area that has clear starry nights and minimal light pollution, which is why my desire to purchase a telescope has reemerged. Since the house there isn't 100% complete with still missing essentials a pricey telescope isn't on the top of my list though; there'll still be work being done there and that sort of an environment isn't conducive to proper storage and maintenance of fine optics. I'll probably get a real newtonian next year, but for now I'm considering getting a high powered binoculars to get re-acquainted with the sky; looking at 20x80 and 25x100 options - already have a camera tripod they're supposedly compatible with so that'd work out great.

Well, the southern part of Croatia is actually pretty dark, based off this map.  So you should be able to get to some excellent skies.  I would skip the giant binos for now; get a good pair of 7 or 10x50's for about $250 US equivalent, and use them instead.  They won't show you quite as much, but their ability to be hand-held and their wider field of view will serve you well as a beginner, I think.

The house where I plan to use my scope has a nicely sized terrace so I can definitely fit a 300mm dob there. To avoid constant dismantlings I was considering building an enclosing for the scope to keep on the terrace - which would protect it against the elements during my vacation weeks when I'm there. When it's time to go home I'd disassemble the scope and take it inside. A quality enclosing with some nylon insulation should protect the scope fine for a few weeks, no? It has the added benefit of not having to wait hours for the optics to cool down to ambient temperature
I'll take a look at those 10" ones though - in the end a larger telescope isn't too useful if it's too much of a pain to set up every time so you end up using it like once a year. Thanks a lot for the information, though - once I get to a point of actually buying a scope I might bother you with some PMs containing specific newbie questions

The enclosure wouldn't need to be insulated; in fact, you want as little as possible.  However, it must be completely water- and windproof when closed.  You might want to go looking around at plans for roll-off roof observatories and such, although that may be a little overkill for your purposes.

And feel free to send me some PMs when you get around to buying the scope; I'm always glad to help.

[Snail]

In London I'm lucky to see any stars at all.

[newman]

Well, the southern part of Croatia is actually pretty dark, based off this map.  So you should be able to get to some excellent skies. 

Thanks for the map, I've actually been trying to find a good light pollution map of Croatia, and this has shortened my search According to that map the place I intend to do my stargazing has virtually no light pollution, so yea it should work out great. I did always notice stunning clear skies when over there, the only place where I ever saw a clearer sky was from a sailboat in the middle of the Adriatic, at a point where you can't see either shore.

And feel free to send me some PMs when you get around to buying the scope; I'm always glad to help.

Thanks man, I'll probably take you up on that next year

[Herra Tohtori]

Heh, here are some shots I took years ago.

These were taken with Minolta DiMage G400, 4 Megapixels,


Ursa Major / Big Dipper. My favourite shot of these, actually, despite the high level of noise...




Some unspecified area of sky - can't remember what constellation I was aiming at; post-processing includes noise subtraction and level adjustment. Original JPEG linked.

EDIT: Ha, recognized it. It's the zenith at the time and place (in Stellarium, you'll get close enough when you search for Kemi, Finland as location and set time to 2004/10/9 21:12. The irregular rectangle at upper left corner is the head of Draco, and you can see Ursa Minor (or small dipper) right on the centre of the image. Polaris is the brightest, somewhat stretched star in the upper right quadrant of the image.


(Original JPEG)


Cassiopeia and Perseus. Sadly, the camera wasn't really capable of capturing the details of milky way and star clusters in Perseus, but hey, it does incredibly awesomely considering its specifications. Again, noise layer subtraction and level edits done to the image, original JPEG linked.

(Original JPEG)


Now this one is interesting; if you know what to look for, it seems I actually managed to capture few stray photons from the M31 Andromeda galaxy with this tiny little camera, although it might be just my imagination. I have included guide on finding the spot that the galaxy occupies; make your own mind whether the little dot of light is actually the galaxy or a random concentrated noise, but nevertheless interesting. The image shows the constellations of Cassiopeia and Andromeda, as well as parts of Pegasus. Original JPEG linked for closer inspection.



(Original JPEG)


The noise layer I used for noise subtraction is taken with the camera, but by the unfortunate fact of not outputting RAW files, that means the noise layer is JPEG compressed, and thus it isn't exactly the noise output from the CCD itself. Better than nothing, though.

I don't remember the exact optical specs of the objective on this Minolta, but all shots were taken using 15 second exposure with no tracking at all (hence the slight streakyness of the stars).

[watsisname]

That's in exactly the right place, plus there's no stars brighter than about magnitude 7 in that location, so I do think you got some photons from M31 there.  Awesome!
Also in your third shot it looks like you caught a bit of the double cluster in Perseus (Caldwell 14).

[Mongoose]

Man, these pictures are making me want to actually take out my 114mm reflector at some point.  I've never done much with it since it doesn't have any star-finding/tracking capabilities, and the equatorial mount it's on is kind of goofy.

[Herra Tohtori]

That's in exactly the right place, plus there's no stars brighter than about magnitude 7 in that location, so I do think you got some photons from M31 there.  Awesome!

Ridiculously so, considering my equipment was this:

Also in your third shot it looks like you caught a bit of the double cluster in Perseus (Caldwell 14).

So it would seem. I have a zoomed-in image of that area as well:


(Original JPEG)

Doesn't show any dimmer detail, though, which is not surprising because zooming in increases the F number of the already small objective so even less light actually ends up on the CCD during exposure. It does have a bit more angular separation, though - on the T-shaped pattern in the middle, the low left and low middle elements are the centres of the two mentioned star clusters. The one in the middle even shows up as two separate dots.

Considering the limitations of the hardware, I'm surprised I was able to salvage even this much information out of the JPEG's.

[Nemesis6]

Necroing this thread for something that resembles great justice:

- The galaxy M31.

- NGC 869, a dual star cluster.

- the Pleiades. Note the blue in the picture is a nebula that is lit up by the stars.

There are a couple of problems with these images that I will be working on fixing, mainly collimation and some issues with noise removal; I am not yet fully aware of how the Canon 1000D handles noise removal. It has two types: One for high ISO settings, and one for long exposures. All I know is that if enabled for long exposures, they camera will spend just as much time working on the image that it does to actually take it, hence the camera being "busy" for 30 seconds after a shot with long exposure noise-removal being enabled. I'd love to be able to use the ISO noise removal setting because I can't shoot at anything over 200 without introducing crazy color noise.

[Mika]

Hello Nemesis,

Nice photos you have there. I recommend not using any high ISO noise removal algorithms when exposing the sky. What you could try is setting ISO to 200 and taking a photo with and without long exposure noise removal to see it for yourself. There seems to be some amount of banding in the last photo (periodic undulation of brighter and dimmer regions in the last picture), though I'm not sure if this is because of downscaling of the image in the forum or because of the camera. I don't know how to improve the banding effect, but you could ask for a firmware update in the Canon shop. This is a known defect even in 5DmkII, and was partially addressed with a firmware update. I guess the same thing applies for 1000D too.

1000D is probably limited to ISO200 due to low-ISO noise, there seems to be some in the more modern Canon hulls. For the color noise in higher ISOs, you could try if a firmware update has any effect, and if not, consider it a limit of the camera.

This made me actually think if the ISO100 or ISO50 is the best setting for astrophotography in the first place. If the sensors collect dark noise during the longer exposure, and higher ISOs make a grainier image, is there a best ISO to use that is not the lowest ISO available? I suspect the dark noise levels are lower than high ISO shot noise, but has any of our astrophotographers already tested this so that I wouldn't have to? Granted, I haven''t taken photos of stars myself, but work otherwise in low light environments.

[Herra Tohtori]

Black frame reduction works pretty well for noise reduction from uncompressed images (whichever RAW format your camera supports). Basically, while you're still in same observation conditions (mainly the camera temperature, ISO sensitivity and same exposure time as your actual exposure of the sky) you cover the lens and take a few images of darkness. Ideally, these images would be totally black, but they won't be that - instead, they will contain the noise produced by the electronics of the camera.

Truly random noise (such as, say, stray X-Ray or gamma photons hitting the CCD grid) can never be fully eradicated, but this method is a good way of negating dead (white) pixels, banding, striping and any other systematic noise anomalies that result from the camera hardware itself.

With any decent image editing software, it's trivial to stack the black frame over your exposures to subtract the noise. This often drastically improves image quality.

In general, I prefer to take RAW's produced by the camera and do all the corrections manually. This will give you the maximal amount of data to work with - especially as many cameras can give you RAW files with 10-bit or even 12-bit precision, rather than the 8-bit per channel images that most cameras produce.

I really need to do some astrophotography with my own little Canon as the nights grow darker...


As to reducing noise - yeah it's usually best to take shots with smallest ISO sensitivity to reduce the noise, but without good tracking hardware, your exposure time is severely limited. With tracking, it's better to take a lot of short exposures, handle them with black frame reduction, then stack them to increase the luminance of targets in the image(s). Long exposures are more vulnerable to atmospheric conditions, bumps on the tracking device, small vibrations and tremors - and they take a lot of time. The downside is that lots of short exposures eat memory card space fast compared to single long exposure...

[Mika]

Oh, I indeed forgot to ask if the photos were RAW or JPEG.

If astrophotography is the main thing to do, in this case RAW would likely be the better option. However, in normal photography, I don't see much difference between RAW vs. JPEG, so I use JPEG. Astrophotography would be the only exception where I would likely use RAW, for the reasons mentioned by Herra.

As a general comment, I personally don't like the idea of fine tuning everything with Photoshop, as it will start to feel more like scientific work rather than art. I only recently was able to take continuously photos that I didn't need to adjust in Photoshop at all, and I then realized how much time I spent using Photoshop. Now if I just remembered to check if the front glass was free of dust before taking a photo...

[Herra Tohtori]

Merry Christmas to everyone!

Caught this today:



Object reference:



Equipment: Canon PowerShot SX130IS, tripod


I also captured these shots.

[Hellstryker]

This is awesome. More please. 

[watsisname]

You captured the moons of Jupiter with a camera and tripod?  Wow! 

I just went through my collection of old planet shots and found a couple of Jupiter and Saturn that I felt worth sharing.  Taken using a Meade 8" SCT with Lunar/Planetary Imaging camera (basically just a glorified webcam that screws into the eye-piece.)

Jupiter on June 10, 2008



This is actually nearly a hundred individual frames stacked together using Registax, to improve clarity and reduce noise.  The Great Red Spot can be seen rotating into view on the left side.  (Edit:  Wait, no, that's going out of view, the planet is upside down!) =o
Jupiter's distance at the time:  ~4.29AU.  Apparent Diameter:  46"

Saturn on the same night:


I was very surprised that the relative bluish color of the northern hemisphere came out in the image, also the shadow of the planet on the rings on the left side.  Cassini Division is barely visible, too.
Celestia screenshot for comparison: 

Looking ahead, Mars is coming up for closest approach early March 2012.  I'd never tried photographing the Red Planet, so I'll do some practice on it in the coming months as it gets closer. 

[Herra Tohtori]

This is awesome. More please. 

Well, this is probably the best of the rest of the images:



Skies are overcast today, so I probably  can't take any more pictures, and weather forecast is quite bad for the couple days on, too.

EDIT: There was also this five second exposure of Pleiades, with slight trailing on the stars already showing:

[Mongoose]

Wow.  I can't even manage to get my telescope pointed at anything interesting, much less take a picture of it.

[watsisname]

What kind of scope have you got, Mongoose?  Perhaps somebody here can give you some tips.

[Mongoose]

It's a Meade 114 EQ-AS reflector.  It has an analog equatorial mount, so the times I've taken it out, the biggest challenge has been managing to get something in view, let alone spending time looking at it.  It doesn't help that this area isn't exactly the darkest at night, so I've never done much in the way of long-term stargazing, though I'd like to try.

[Astronomiya]

Well, it'll be a little more difficult than the ideal beginner's scope (a 6-8 inch Dobsonian), but far from impossible.  First thing first is to polar align the mount.  Since it's an EQ mount, this'll have to be done every time you take it out.  Rotate the tripod head in azimuth until the telescope counterweight faces north with the tube parallel to the mount head (you can use a compass to get it close, but you'll want to check a magnetic declination map first to get the correct offset from magnetic north).  Use the latitude adjustment to set the telescope to the correct latitude, and then set the telescope to 90 degrees declination.  More than likely the scope came with a declination setting circle which is mostly useless but helpful here.  Once you've done this, you should see Polaris in the eyepiece field.  If you don't, adjust the mount head azimuth or the latitude until you do.  Congratulations, your mount is now (roughly) polar aligned.

Now that you've done this, you'll need to use the method of right angle sweep to find targets starting from bright stars.  Since you can't just push the telescope where you want it to go like an alt-az system, you need to move in one axis, then the other.   Figure out how large in degrees the field of the finder or your low power eyepiece is, then consult your star charts (you do have good charts, right?).  Measure how far in angle you have to go in each axis, then divide that into field-widths you need to move.  Then move the right number of field widths for each axis, and you should hit the target.  For the next couple of months, a good target to practice on since it'll be real damn obvious when you hit it is the Orion Nebula.  Try getting there from Orion's Belt, Rigel, and Betelgeuse.  Other good winter targets are the Double Cluster, Jupiter, M35, the Pleiades, the Beehive (M44), M36,  M37, M38, M81 and M82, M31, M32, M110, M33, M15, NGC 7331, and so on.

One other benefit of having the mount polar aligned is that once you have a target in view, you only need to move in the right ascension axis (R.A., the E-W axis) to keep it there.  Without polar alignment, this becomes a rather tricky process.  This is in fact why EQ mounts are desirable in the first place.

One more thing:  if my instructions seem unclear, or you have no idea what I'm talking about, you can google both polar alignment and right angle sweep.  Last time I did that, I recall finding pretty good info sources in the first few hits.