Astrophotography and what you should know

[drsureshmohan]

Friends,
Im going to share with you my experience in astrophotography with a series of discussions and essays which i hope will be helpful for the beginner.
What is so difficult about it(deep sky astrophotography)?The answer is you need to take a long exposure photo of a moving object with no shake in your camera !All stars ,nebulae, galaxies,planets and Sun rise in the east and set in the west bcos we are rotating from west to east hence we need an instrument to hold the camera with a telephoto lens or telescope to view the moving star (from east to west) fixed on your photographic chip to get a picture without a blur.We call this instrument a motorised mount because it has a stepper motor to counter earth s movement,there is also what is known a barn door mount which can be made at home and will work upto 200mm lenses. It is not enough to counter earth s rotation but also be placed parallel to earths rotational axis ; the process we call polar alignment which is beyond the scope of this discussion.
Do you need telescope for astro photography? yes and no depending on what level u want go . For a start a telephoto lens would do but a 3 inch apo refractor is ideal.
To summarise we need a mount ; the most critical component, a good telephoto lens and DSLR with long exposure capability .
The most important hassle one has to overcome with astrophotos is NOISE.
Lets quickly for the benefit of newcomers run thro the basics. First rule to know is that light itself is noisy !!?? yes that is the truth .Light reaches your photographic chip in packets in a random manner ie not all together. It is akin to a machine gun firing erratically which means the bullets will reach the target but randomly. This randomness of arrival of light packets causes noise in your picture .Put in another way it is due to the uncertain arrival times of light quanta which causes the noise .Noise in other words is the random variation of brightness levels -graininess in the darker part of your image where it is more obvious.
Why is the grain seen more in the darker or dimmer part of your picture? Because the brighter areas in a picture have more signal and hence a better signal to noise ratio. Dim areas have low signal relative to the noise hence a lower SN value. What i am trying to convey is that noise there throughout the picture but obvious in dim areas due to poor Signal to noise ratio.
To sum up we need a photograph which has an excellent S/N ratio to overcome noise.
In the next discussion id like to talk about the types of noise and how we overcome those.
Pls let me know your thoughts
Suresh

[KrishnenduKes]

Amazing Discussion Approved

Thanks Doctor! Please go on.

[rio008]

thanks doctor. hope this thread will help us learning basic Astrophotography.

i am having few doubts.

1. what is Autostar hand controller ? does every computrized telescope comws that ?
2. Is it possible to attach a DSLR with a computrized telescope ? or a computrized telescope can take pictures ?

[drsureshmohan]

thanks doctor. hope this thread will help us learning basic Astrophotography.

i am having few doubts.

1. what is Autostar hand controller ? does every computrized telescope comws that ?


Autostar hand controller just means that there ia mini computer in the hand controller having the coordinates of all the stars and galaxies ( major ones upto 65000 in my case).Once u feed the time and location it will ask you to point to 2 or 3 bright stars in the sky and the rest will be shown by the scope.
2. Is it possible to attach a DSLR with a computrized telescope ? or a computrized telescope can take pictures ?
Autostar hand controller just means that there ia mini computer in the hand controller having the coordinates of all the stars and galaxies ( major ones upto 65000 in my case).Once u feed the time and location it will ask you to point to 2 or 3 bright stars in the sky and the rest will be shown by the scope

All computerised telescopes can be mated with DSLR s once you remove your lens and u buy a special nosepiece ; this is inserted into the eye piece socket.Now the telescope becomes your telephoto lens.Kindly note the scope you saw in the market has an F ratio of 18 which is useless for deepsky astrophotography but useful for planetary pics using a webcamera.Here is a pic of saturn i took using a webcamera and used a process called stacking http://tinyurl.com/l64o42
I will explain all i know about stacking soon
Suresh

[drsureshmohan]

Hello my connection is back so im now going to say what little i know about the types of noise which u will have to deal with during astrophotography .You need to know about dealing with noise because it will become apparent in image processing which i shall go to that; each region has different noise levels and each region of the picture has to be processed differently!Gurus kindly note i have the beginner in mind

Before i start a quick recollection of facts will help(me) to explain.First is that your CCD or CMOS chip actually contains millions of light collecting buckets(pixel).The component of light ie when photon is collected in these buckets they are converted to electrons.Supposw u have uhiform white wall and an exposure is taken, the value of each pixel should be uniformly 100(theoritically) but the values will be 99,98,91,95,94,89. The variation is random. This is due to the fact that while counting electrons in the pixel there maybe small errors,some electrons stick to the pixel etc leading to a noise callled READ NOISE which is also temperature dependant hence most astronomical CCD s are cooled.
The next noise we encounter is SHOT noise or photon noise, recall that light packets arrive is random BUT follows a simple rule that noise is the square root of the signal,meaning if the brightness level(signal) is 100 then shot noise will be 10.
The brightness of the sky determines plays a large role in SHOT noise ,hence bright background(lt pollution) means shorter exposures ie multiple short exposures to overcome the shot noise , here is an example of a picture taken from my heavily light polluted balcony http://tinyurl.com/kohvan
The duration of exposure of this pictures is 7 hours. Each exposure lasting only 2 minutes and about 400 of them and some had to be discarded.
The third type of noise is thermal noise or CCD noise which can be dark subtracted ie taking a exposure with the lens cap ON, the duration of the exposure being the same as the one used for taking the galaxy, then we digitally subtract and remove the noise.
Hope it was useful and sorry if it was a bit boring
Suresh

[surya@64]

Doc, Great thread and info....It has rekindled my interest in Astrophotography....which I have been doing...( rather trying) for many years...I have restricted to Piggy back on an 8 inch Newtonian or tripod mounted wide field pic.....both having their limitations....

Non affordability of proper drives and design constraints has slowed my intrest in this field....

With you around Doc, I should be ready burn the midnight oil this observation season from Nov. December....!!

Ur pic. of Horse-head, trified, Andromeda, Orion, ring Nebula, Omega Centauri...are simply brilliant...those are dream shots for me.

Thanks Doc...LET THE GYAN FLOW.....!!!!!

[rio008]

thanks for answering my questions doctor. look like my mind is leaning towards Astrophotography :D
One more question.
What should i keep in mind while buying a telescope ? what will be good and what would not be good ?

Autostar hand controller just means that there ia mini computer in the hand controller having the coordinates of all the stars and galaxies ( major ones upto 65000 in my case).Once u feed the time and location it will ask you to point to 2 or 3 bright stars in the sky and the rest will be shown by the scope

All computerised telescopes can be mated with DSLR s once you remove your lens and u buy a special nosepiece ; this is inserted into the eye piece socket.Now the telescope becomes your telephoto lens.Kindly note the scope you saw in the market has an F ratio of 18 which is useless for deepsky astrophotography but useful for planetary pics using a webcamera.

So this capturing process will take days ? more images means more details ?
sorry if i sounds like a fool :eek:

The duration of exposure of this pictures is 7 hours. Each exposure lasting only 2 minutes and about 400 of them and some had to be discarded.

[drsureshmohan]

thanks for answering my questions doctor. look like my mind is leaning towards Astrophotography :D
One more question.
What should i keep in mind while buying a telescope ? what will be good and what would not be good ?



So this capturing process will take days ? more images means more details ?
sorry if i sounds like a fool :eek:
WHile Purchasing a telescope u need to consider whether it is for photography or visual
. If for visual u need to find the one with the biggest aperture u can afford, if it is photography all u need is a 80 mm apochromatic refractor http://www.amazon.com/Orion-80mm-Apochromatic-Refractor-Telescope/dp/B0000XMTCY


Most of my pics are from this scope and the cheapest good mount is 1500USD ,so for under 1.5 lacs u are almost there.
Capturing process if from a light polluted(noisy) background means multiple short exposures; anything beyond 2 minutes will get u a washed out white frame! So we take multiple short exposures and stack them that leads us to the question what is stacking ? and how it helps .Yes i did take the galaxy pi over three nights in a row .
First we take multiple exposures of the same image
secondly we must align these images so that each star in the image appears in the same place to the pixel level
thirdly they are arranged vertically and mathematically combined to form a single image.
since galaxies and nebulae remain unchanged in every image but the random noise changes. So we are actually summing up the signal ie for every two pictures the signal is doubled but the noise increases by the square root ie 1.4 times.put in another way stacking improves the S/N ratio by the square root of the frames stacked. a 9 frame stack would give 3x improvement of SN ratio and a 100 frame would give a 10 x improvement in S/N ratio.
I used to wonder what if i took a single picture and stack the same picture ?
I knew the answer much later ie if i stacked the same pic noise is no more random,i will simply be adding the same noise !
Hope this helps
Suresh
For stacking there is a free software called registax.

[drsureshmohan]

Hi,
im now quickly going to explain what i do in a night of photography.By now i assume all of those who read my thread surely know that adding data ie increasing the duration increases the photons striking the chip will thereby increase the signal to noise ratio. Each exposure of 3 to 10 minutes is called a sub where the data of the galaxy or nebula is stored. To clear the thermal noise attained by the hardware one has to cover the telescope in the front and take exposures of the same duration as the subs- these are called the darks ; either at the onset of the session or at the end of the session at dawn one has to take flats. What is a flat? flats are meant to remove the vignetting effect of the imaging train that would form a circle on your image. At ISO 100 WITHOUT CHANGING THE ORIENTATION of the camera one has to take several exposures till your optimum is reached .What is the optimun ? on your lcd screen the histogram should read from to 2/3rd; that would be optimun and finally bias frames are taken.After this i run the images in a software called images pluls where all the images are combined to form the RAW image. I save this in TIFF format and open it photoshop;
--- to be continued
Suresh

[shutterbug]

Doc, thanks for this informative discussion. Just started reading!

BTW, just read that today is the day Perseids meteor shower is most visible. But guess it doesnt apply for us in India.

[KrishnenduKes]

Phew! Holy heavens! This goes far and dark and deep!

[drsureshmohan]

Doc, thanks for this informative discussion. Just started reading!

BTW, just read that today is the day Perseids meteor shower is most visible. But guess it doesnt apply for us in India.

hi it was visible in delhi on Aug 11, some of my astronomy frindsin Delhi went observing. In my next write up im going to explain how i convert the Raw image into the final image in a series of steps, would like to know if you would like to join ie i can post the Raw image and apply the same steps to the image as i do?
Thanks for your inputs
Suresh

[v_310]

hi it was visible in delhi on Aug 11, some of my astronomy frindsin Delhi went observing. In my next write up im going to explain how i convert the Raw image into the final image in a series of steps, would like to know if you would like to join ie i can post the Raw image and apply the same steps to the image as i do?
Thanks for your inputs
Suresh

Sure suresh - If you could first describe what kind of exposures we should make, that would be great. I mean, if you were going to stack multiple exposures, what settings ( and how many) exposures should I start with..?

.. long weekend, I'm going to give this a shot!

[shutterbug]

Yes, yes, yes! I would like to! What software do we need?

[drsureshmohan]

Sure suresh - If you could first describe what kind of exposures we should make, that would be great. I mean, if you were going to stack multiple exposures, what settings ( and how many) exposures should I start with..?

.. long weekend, I'm going to give this a shot!
Hi,
Im assuming you dont have a equatorial mount,hence at 50 mm you could expose for 20 secs at ISO 1600, take mutliple exposures of the same area of the sky and keep one particular star as a reference as there will be a drift and try to to keep the axis of the tripod as as close to north/ south as possible. Take about 10 exposures and download a software called Registax. There is a tutorial on how to stack(all free).
Suresh

[drsureshmohan]

Yes, yes, yes! I would like to! What software do we need?

All you need is photoshop and i will upload a stacked Raw image and we shall start from there. My net is down and should be up by tomorrow

In case u want to read some stuff i will mostly be applying levels and curves, followed by correcting colour bias followed by colour balance, of course i will make extensive use of the histogram. I shall go from very very beginner level just the way i learnt( it seemed like a daunting impossible task for a rather slow learner like me, in fact all my astronomy freinds know im very slow)
Suresh
So Sunday lets do it !

[v_310]

Hi,
Im assuming you dont have a equatorial mount,hence at 50 mm you could expose for 20 secs at ISO 1600, take mutliple exposures of the same area of the sky and keep one particular star as a reference as there will be a drift and try to to keep the axis of the tripod as as close to north/ south as possible. Take about 10 exposures and download a software called Registax. There is a tutorial on how to stack(all free).
Suresh

Will take some tonight... It's totally cloudy today. hopefully it will clear up a little later.

[drsureshmohan]

Soory friends im having a bad issue with my broadband connection,would be up again from this weekend .
Suresh

[drsureshmohan]

Im really sorry for the long break, my net was down and restored only 3 days back. Ok im posting two images(link) and just going to process step by step along with you.The image on the left is just the stacked image and the one on the right is the stretched before cosmetic corrections. For these i only used levels,curves, colour bias and colour balance correction in photoshop. Will be back tonight.oops here is the link http://tinyurl.com/m74bng
Suresh

[Xavier]

Really appreciate the efford, Doctor.
I don't know much about this field, but damn, that looks amazing!

[powerslave]

I'm looking to pick up the SV70. http://www.stellarvue.com/sv70ed.html

I've just moved to a remote town in North Carolina and the skies here are brilliant on non-cloudy nights.

[Deltaone]

@powerslave: That is a very nice choice. However, do take a look in the cloudynights classifieds section as well as astromart before you buy. Both of those usually have some very good deals on used equipment. Since you are in the US, you have access to some very good scopes at some very good prices.

[powerslave]

Yup, I'm just getting my feet wet. I always wanted to own a real telescope since childhood, but ended up getting some cheap russian pocket scope instead (owing to the cost).

I might buy used, I'm really loving the sv80s triplet. From cameras and lenses, I've learned, buying used is the way to go.

I registered on cloudynights and am going through it. I can see this is going to get real expensive real fast. I thought photography was expensive.

I'm currently trying to ascertain if I can use these as a telephoto as well. I know they will have terrible bokeh and very slow apertures making them only usable in bright daylight. Something like the mirror lenses.

Lot of reading to do.

[Deltaone]

SV does make some very good ones. Getting a nice triplet would be nice. I've seen some great deals on the EON series as well. That is a very good scope to go with as well. You can usually find the 100 EON for around 400 or so.

And the short widefield ones like the SV or the AT 66 ED or the WO 72 etc have been used as teles, however they arent really corrected for terrestrial use. Focusing isnt exactly going to be fun. That said, most of the short widefield ones are usually under f6 so it is usable.

Oh, and yes, this is very very xpensive :D. Once you start getting into it, there is no end to it :D. If you are interested more on the visual aspect, might be better to get a reflector or a catadioptric as they will give you a whole lot more aperture for very little money. If you are interested in getting into the photography end, do invest in a good mount :D. And a short widefield one is very nice for getting started.

[powerslave]

If I understand correctly, the reflector ones are not good for photog right? Cos from basic optics and childhood knowledge I recall that the more the number of reflections, the more light is lost.

I don't want to jump into it like this. I want to know what I'm doing inside out. I'm VERY fascinated by the night sky since forever.

Gonna hold out a bit.

[surya@64]

Hi Guys,

This is the Pic. of Orion Constellation and its surrounding area...showing constellation lepus, Canis major...and the bright star Sirus...

Exposure of 30sec. on 18mm lens...

I have been an Amateur astronomer since last 30yrs...and Build telescope of the Reflector type.

http://farm4.static.flickr.com/3568/3855061046_8eaeb6ef13_o.jpg

Thanks for watching...

[Deltaone]

If I understand correctly, the reflector ones are not good for photog right? Cos from basic optics and childhood knowledge I recall that the more the number of reflections, the more light is lost.

I don't want to jump into it like this. I want to know what I'm doing inside out. I'm VERY fascinated by the night sky since forever.

Gonna hold out a bit.

The problem with using reflectors for astrophotography is that there just isn't really enough travel usually at the eyepeice, so bringing it into prime focus isnt usually possible. That said, if you intend to use CCD imaging, orion has a some very cheap reflector imaging packages.

http://www.telescope.com/control/product/~category_id=optical_tube/~pcategory=optical_tube/~product_id=09786

That one for example is a 6 inch reflector for just 400 USD. Reflectors give you maximum aperture per buck. They also have the advantage of not having to deal with chromatic aberration. You get coma instead.

That said, the cats are usually a good compromise. Larger reflectors are very hard to carry around. An 8 inch SCT however is usually quite portable. And the newer ones with the Hyperstar setup which can convert them up to an f2 lens iirc. Problems with both SCT and the reflectors are longer cooldown times and frequent collimation for the reflectors. However, on the flip side, even when you are not doing photography, the large apertures will give you some stunning views. So thats a bonus.

Each has its pros and cons. Usually a short wide field refractor is considered good for starting out in the photography section, but it is rather limited when it comes to actually seeing anything in it. And good apos are ridiculously expensive for anything over 100 mm in diameter. So it is your call either way.

The orion imaging setups with a CCD might be a good way to begin. The CCD eliminates a lot of the hassles of DSLR astro and it is far lighter and hence easier to balance.

But again, the most important part of your setup is not the telescope. Invest in a decent mount, something like the LDX55 or EQ6 or its variants. Forget autoguiding for now, get a decent EQ mount with an autoguider option, you can invest in that later.

Again, the main advantage you've got right now is astromart and cloudynights. You can find some very good stuff there for some very cheap prices. I know of a lot of people in singapore who actually buy from astromart and get it shipped in because it turns out still cheaper than buying from here.

Again, decide what your primary aim is gonna be. If it is visual, reflector/SCT gives you most bang for the buck. Photography, there are three camps, and yes a refractor is the easiest and most portable but also most expensive option out there. A very good idea would be to participate in some local astro gettogethers, im sure theres a society/club in your area, go to one of their night gatherings, have a look through their scopes, you will get a far better idea of the whole thing. Nothing substitutes for first hand trying out :D.

[powerslave]

BRB, LOL.

Yeah, I'm waiting for this weekend to read up some on the various ones. Nice summary.

I'll keep you updated.

[drsureshmohan]

Hi Guys,

This is the Pic. of Orion Constellation and its surrounding area...showing constellation lepus, Canis major...and the bright star Sirus...

Exposure of 30sec. on 18mm lens...

I have been an Amateur astronomer since last 30yrs...and Build telescope of the Reflector type.

http://farm4.static.flickr.com/3568/3855061046_8eaeb6ef13_o.jpg

Thanks for watching...
Beautiful, i presume u took this pic in the month of may because i see a setting orion with trees in the background.
Suresh

[drsureshmohan]

The problem with using reflectors for astrophotography is that there just isn't really enough travel usually at the eyepeice, so bringing it into prime focus isnt usually possible. That said, if you intend to use CCD imaging, orion has a some very cheap reflector imaging packages.

http://www.telescope.com/control/product/~category_id=optical_tube/~pcategory=optical_tube/~product_id=09786

That one for example is a 6 inch reflector for just 400 USD. Reflectors give you maximum aperture per buck. They also have the advantage of not having to deal with chromatic aberration. You get coma instead.

That said, the cats are usually a good compromise. Larger reflectors are very hard to carry around. An 8 inch SCT however is usually quite portable. And the newer ones with the Hyperstar setup which can convert them up to an f2 lens iirc. Problems with both SCT and the reflectors are longer cooldown times and frequent collimation for the reflectors. However, on the flip side, even when you are not doing photography, the large apertures will give you some stunning views. So thats a bonus.

Each has its pros and cons. Usually a short wide field refractor is considered good for starting out in the photography section, but it is rather limited when it comes to actually seeing anything in it. And good apos are ridiculously expensive for anything over 100 mm in diameter. So it is your call either way.

The orion imaging setups with a CCD might be a good way to begin. The CCD eliminates a lot of the hassles of DSLR astro and it is far lighter and hence easier to balance.

But again, the most important part of your setup is not the telescope. Invest in a decent mount, something like the LDX55 or EQ6 or its variants. Forget autoguiding for now, get a decent EQ mount with an autoguider option, you can invest in that later.

Again, the main advantage you've got right now is astromart and cloudynights. You can find some very good stuff there for some very cheap prices. I know of a lot of people in singapore who actually buy from astromart and get it shipped in because it turns out still cheaper than buying from here.

Again, decide what your primary aim is gonna be. If it is visual, reflector/SCT gives you most bang for the buck. Photography, there are three camps, and yes a refractor is the easiest and most portable but also most expensive option out there. A very good idea would be to participate in some local astro gettogethers, im sure theres a society/club in your area, go to one of their night gatherings, have a look through their scopes, you will get a far better idea of the whole thing. Nothing substitutes for first hand trying out :D.

I would like to add here as i would like to make a few small corrections, though u rightly said some dont prefer reflectors , it is more due to coma error inherent in reflectors (overcome with MPCC coma corrector)and harder to balance due to the lenght of the OTA. Eyepiece travel is a issue even with refractors which i found while using my ccd for the orion 80 ED , i had to buy a nose piece extender.Reflectors (newtonians are a good starting point as the cost is lower,but fraught with maintenance problems ir requires collimation once a while) I think the rest of the discussion is very exhaustive and self explanatory.
Suresh

[surya@64]

Beautiful, i presume u took this pic in the month of may because i see a setting orion with trees in the background.
Suresh[/QUOTE]

Thanks Doc...The pic. was taken on the rise of Orion...towards East....

Due to paucity of Driveable T'scope My astrophotography has taken a back seat...May be in future with a Mead or Celestron 8 inch...

Your pic. are simply outstanding....and I personifies the patience involved in generating those pic. with little star light we get...

Brilliant doc...keep it going....A lot to learn from you.

[drsureshmohan]

Ramancherry is where we went last night, it was very cloudy except near the
zenith where it was very clear. Here is my best Jupiter for the year
.Thanks for looking.

http://tinyurl.com/ydgutbs

http://lh5.ggpht.com/_WvNkIVDpCNo/Sr8rqjq_SuI/AAAAAAAADjg/nXYyXKzzzj0/jupiter-27th-sept.jpg

Suresh Mohan &

Renganathan

Orion EQ6

LX 200 10 inch f 6.3 with 2x barlow+ mirror diagonal

Philips toucam with lps filter 1023 frames/ selected 884 frames
aligned and stacked

Registax 4/Photoshop

79.49 E

13.12 N

[surya@64]

Beautiful....!! Doc....nice details of the surface...with...turbulance and GRS...

[KrishnenduKes]

@Dr: Thanks for sharing. I edited your post for the photograph to show directly on your post. Hope you do not mind.

[rio008]

@Dr. suresh, thats really a jewel. thanks for sharing.
it was just one shot or a combination of many ?

[Xavier]

Wowness! :eek:

[drsureshmohan]

Hi it is a stack of best 884 frames from a total of 1000 odd frames which the software will do; u can increase or decrease the stack number, after u run thro registax u will get the final image which u carry over to Photoshop where in unsharp masking u do a fine adjustment, go over to colour balance and add a little blue to enhance the cloud belts
Suresh

[drsureshmohan]

Hi,
Ive seen nothing but clouds over the last couple of months so I re did my California nebula and thanks for looking http://tinyurl.com/yjenvd3


Suresh Mohan
Orion EQ6
Orion 80ED
Canon 350D mod
ISO1600x 6 min x 12 subs/9 darks
Images Plus
Photoshop
13:12N
79:46E

[inder.cool]

@ Dr: Awesome photo..thanks for sharing..

[Xavier]

Here's my first (pathetic) attempt at star trails.
16 Raw shots @ 30s stacked in an application known as Startrails.

http://www.thephotographer.in/darkroom/attachment.php?attachmentid=567&stc=1&d=1255901566

[drsureshmohan]

Here's my first (pathetic) attempt at star trails.
16 Raw shots @ 30s stacked in an application known as Startrails.

http://www.thephotographer.in/darkroom/attachment.php?attachmentid=567&stc=1&d=1255901566
Ive never shot star trails and i think it is very good, and pls take a look at andromeda i took last week
http://tinyurl.com/y8k5mt7

[Xavier]

Thanks doc. :)

BTW, the Andromeda picture is wow! Seriously, its as good as the ones I've seen on APOD. Which is the little galaxy at the bottom of Andromeda?

Here's my 2nd attempt at Star trails

http://farm4.static.flickr.com/3515/4081933390_a8d0c9051d_b.jpg

[drsureshmohan]

Hey thats a beauty with the lanscape and pls take a pic of full moon rising from the same landscape and u will have a serious contender for APOD, thanks for your kind words

[anirban]

I would like to know if it is possible to try astrophotography with a P&S camera. I got my first digital camera two days back. It has a long shutter mode allowing shutter speeds of 15 secs at max, to be set. I took the attached shot yesterday at max ISO (1600). My hand shook, so obviously the star got blurred.

I had an idea, I don't know if its practical. If I buy a pair of binoculars and hold them to the front of the lens, can I couple it with maximum optical zoom to get a good moon shot? Also, for moon shots, should I use spot metering and exposure compensation? If so, how much?

Is it actually worth trying with what I have?

[ashishtamhane]

It has a long shutter mode allowing shutter speeds of 15 secs at max, to be set.

My hand shook, so obviously the star got blurred.

If I buy a pair of binoculars and hold them to the front of the lens, can I couple it with maximum optical zoom to get a good moon shot? Also, for moon shots, should I use spot metering and exposure compensation? If so, how much?

Is it actually worth trying with what I have?

For the stars:

Your main limiting factor would be the maximum shutter speed. You will need more then 15 seconds of shutter speed. Also you will get a high amount of Noise because Compact Camera sensors are not developed for low light shooting as much as DSLRs are.

You will also need a tripod.

For the Moon:

In short: It will work!

I have tried photographing the moon with my 6MP 3x Optical Zoom camera hand-held to a binocular and it actually works!

But I suggest you not to buy a binocular just to shoot the Moon because that will not be worth it. Good quality binoculars are expensive (atleast 6k). I got bored in a minute trying to shoot the moon with the binocular. :D

For photographing the moon, use Spot Metering along with ISO 200 or 400. Don't use higher ISOs because you don't need to. The moon is lit by the Sun in the same way that on a day the Earth is lit. You may actually have to under-expose the photo to get some good details in the moon.

Why ISO 200 to 400 and Spot Metering:

When you are shooting the Moon the camera's Metering System (on Matrix and Center Weighted) detects that the overall scene is dark and hence it over-exposes the photo. This results in the Moon becoming just a white featureless blob. When you select Spot Metering, the system meters just the Moon, which is nicely lit up and hence exposes the scene correctly.

By selecting Spot Metering, you are telling the camera to just meter a part of the scene and not the whole scene. Thus the camera does not know if it is night or day in this situation.

[anirban]

Firstly, thanks for taking so much trouble to answer my queries!

Star shots do have a lot of noise, as I found out while trying today, so I'll be shooting them just for fun now.

For moon shots, I was playing around with exposure compensation and metering set to spot, which is when I got a decent shot. So decided to go further.
I won't be buying a expensive binocular, just a toy one which will give a little more magnification. A purely recreational attempt as of now.

Thanks again! If, by some stroke of luck, I am able to get decent shots, I'll surely post them.