Another imaging beginner

[sedm1809]

Hello everyone - I have never taken any astro images but it's been something I've been thinking of more and more when I'm out observing. I'm not aiming to win any competitions, but I would like to be able to keep a record of what I've observed and hopefully capture a bit more detail compared to what can be seen at the eyepiece. Mostly I like open clusters/globulars and the brighter galaxies and nebulae. Also double stars and planets but I'd say this was secondary.

I'm in suburban Bristol so light pollution is an issue but not as bad as some - no direct lights in back garden. I have an EQ5 mount and (will have, when I upgrade from my current tube) a 150mm Newtonian reflector.

So I'd be grateful if anyone could give me an idea of the issues I need to think about at this stage. I have a few questions which I will only be able to get away with as a complete novice:

1) What is autoguiding and how does it work? I had assumed that it would be sufficient for my purposes to have a polar aligned scope with a clock drive?

2) I'm not interested in 'terrestrial' photography so would it be better (£ for £) to have a dedicated astro (CCD?) camera rather than a DSLR?

3) How do you go about locating a target with a camera attached to the eyepiece? What I want to do is to enjoy my observing as usual, starhop to a target I like, then pop in a camera and take a few exposures which I can manipulate with software later to build an image. Is this viable or does the camera require lots of set-up/calibration?

4) How powerful a computer is necessary for the editing process?

5) Are there any other major considerations I need to worry about?

Many thanks for your help - sorry if this all sounds hopelessly naïve!

[nephilim]

Hi,

OK there's alot of questions there which is good, unfortunately I don't have time to go into them at the moment but I will say (as will 99% of group members) is buy this book, it'll give you the answers to any/all questions you have.

https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

[happy-kat]

Hi

I would not hit the buy button on your upgrade from current tube comment until you have chosen based on what you will learn when reading the book suggested above or more reading around on here and seeing what you like to achieve and what would be needed for that.

4) I started with my win XP 32 bit PC, I then bought an additional disc and run Windows 10 64 bit 6 GB ram on that and I found that a big improvement. It is a 6+ year old box with W10 64 bits and does what I need at the level I am dabbling at. I didn't buy a new PC, but if you needed too then the above is old spec now and I would go much higher if buying new.

[almcl]

Hi (too)

(1) Auto guiding often uses a separate (smaller) scope and camera mounted on the main imaging scope and coupled to a computer of some sort which sends commands to the mount to keep a star in exactly the same spot.  

It is not essential.  I started imaging without guiding but fairly quickly moved on to using a cheap (£14) web cam and an old finder scope to guide using the free software PHD.  It did improve the length of exposures and thus allow fainter objects to be imaged.  Without guiding, star trailing and/or 'egging' can be a problem unless you have a really good mount and an accurate polar alignment.  

 

 

[wimvb]

2. Astro ccd or cmos. The ability to cool the camera is a big +. With a mono (astro) camera you can image rgb colour and narrowband.

3. Either use an eyepiece to locate the target, then switch to camera, or use live view on the camera. You can also take an image and upload to astrometry.net for platesolving. Camera/mount control software can use platesolving to locate an object.

5. Money. AP is a bottomless moneypit. Some of us just pour faster than others. 

[Pete Presland]

19 hours ago, sedm1809 said:

Hello everyone - I have never taken any astro images but it's been something I've been thinking of more and more when I'm out observing. I'm not aiming to win any competitions, but I would like to be able to keep a record of what I've observed and hopefully capture a bit more detail compared to what can be seen at the eyepiece. Mostly I like open clusters/globulars and the brighter galaxies and nebulae. Also double stars and planets but I'd say this was secondary.

I'm in suburban Bristol so light pollution is an issue but not as bad as some - no direct lights in back garden. I have an EQ5 mount and (will have, when I upgrade from my current tube) a 150mm Newtonian reflector.

So I'd be grateful if anyone could give me an idea of the issues I need to think about at this stage. I have a few questions which I will only be able to get away with as a complete novice:

1) What is autoguiding and how does it work? I had assumed that it would be sufficient for my purposes to have a polar aligned scope with a clock drive?

2) I'm not interested in 'terrestrial' photography so would it be better (£ for £) to have a dedicated astro (CCD?) camera rather than a DSLR?

3) How do you go about locating a target with a camera attached to the eyepiece? What I want to do is to enjoy my observing as usual, starhop to a target I like, then pop in a camera and take a few exposures which I can manipulate with software later to build an image. Is this viable or does the camera require lots of set-up/calibration?

4) How powerful a computer is necessary for the editing process?

5) Are there any other major considerations I need to worry about?

Many thanks for your help - sorry if this all sounds hopelessly naïve!

Its all about levels of astrophotography, if its just a quick snap you are looking for then it can be done relatively cheaply.

You don't need to guide your scope to take images, if it is well Polar aligned you might get up to 60 second exposure. Depending on the mount quality, they do vary, the position of the target in the sky etc.....

A 2nd hand DSLR would be a good entry in to astrophotography, I have seen the old Canon 350's for less £100. You will need a couple of adapters to fix the camera to the scope.

Location can be as simple as you suggest with an eye piece.

Not sure if you would need a particularly powerful computer for editing, I guess it does depend on the size of your image/stack file. 

I have used/use a Canon 350 and 450 and the raw files they both produce have to be converted into DNG files before my old version of Photoshop will recognise them. There is plenty of free software to help you capture, stacking and processing though.

As for "Are there any other major considerations I need to worry about?" Yes lots, more than can be covered in a short answer to be honest. Get plenty of opinions, take a bit time during this poor weather to think about exactly what you will happy to achieve. 

 

[happy-kat]

I use a camera flash hot shoe mounted red dot finder.

[ollypenrice]

23 hours ago, sedm1809 said:

 

2) I'm not interested in 'terrestrial' photography so would it be better (£ for £) to have a dedicated astro (CCD?) camera rather than a DSLR?

3) How do you go about locating a target with a camera attached to the eyepiece? What I want to do is to enjoy my observing as usual, starhop to a target I like, then pop in a camera and take a few exposures which I can manipulate with software later to build an image. Is this viable or does the camera require lots of set-up/calibration?

 

Starting with '3,' the images you'll see in the deep sky imaging section on here, or published in the magazines, have not been taken in the manner you describe. They are the result of long periods of time being devoted to the capture, sometimes over multiple nights. There isn't much 'popping in' of cameras, really, given the time it takes to set up, focus and frame the target. And for a good result you need to stack multiple exposures to get a good signal to noise ratio.

However, that's not to say that imaging as you envisage it cannot be done. It would be best done with a dedicated camera, probably CMOS rather than CCD, but you'd need a computer since there is no other way to see what the camera is capturing. The trouble is that for such casual imaging the price of a dedicated camera might be disproportionate. The computer can be any old thing. I use a tiny XP machine, ten years old, on one of our setups.

From what you say of your intentions, though, how about video astronomy? This might fit the bill. I know little about it but there's a dedicated section for it here on SGL. I'd check it out.

Olly

 

[carastro]

I agree with Olly regarding the popping in the camera bit, imaging is not something that can be done casually.  The point of focus will change from the eyepiece, and that means you probably need to find a major star to focus on and then go back to said target.  You could use FWHM (full width half maximum) if your conditions will allow, but I find it doesn't work very well from where I live as the numbers are jumping around too much.  Also cables and dew heaters need to be attached, and cooling time reached, though the latter won't take much time.  

If you want to do visual as well as imaging I think you'd be better off having a piggy backed or side by side scope, one for visual and one for imaging.  

Also deep sky stuff doesn't really work with a short exposure, you really need longer exposures to get anything decent, and this requires guiding.  I think the new CMOS cameras can do shorter images, depending on the speed of your optics.

Does your EQ5 have a guide port?  I think some models do and some don't.  If so I would suggest using the 9 x 50 Skywatcher finderscope as a guidescope.

Finally, "seeing the image" on live view is pretty nigh impossible with a DSLR or OSC camera, but if you get a mono camera and do x 3 binned looping whilst framing, it is quite easy to see the target.  However a mono camera also requires a filterwheel and filters, which adds to the expense, and the non practicalities of trying to image "popping in the camera". 

I am using a pretty clapped out Vista laptop for imaging, but for processing it is better to have a better laptop/PC as you need better speed than an old laptop will provide. 

HTH

Carole 

[sedm1809]

Hi - thanks everyone for your help. It's made me aware of a few things I hadn't thought of. For a start, how DO you focus a camera, if you are not using eyepiece projection?

What sort of results can be achieved without guiding? I think having two scopes on the mount I've got would really be pushing it in terms of weight limit (not to mention expense!). Also it sounds like you would need a mount that can be computer controlled - mine isn't. Is it worth bothering if I've only got a polar aligned mount and a clock drive? Like I say, I'm not trying to win any competitions. 

I wasn't aware of the difference between CCD and CMOS. Just browsing round the internet this looks like it wouldn't break the bank: www.rothervalleyoptics.co.uk/zwo-asi120mc-colour-13-cmos-usb-20-camera.html. Does anyone have any experience of this piece of kit, or can they say if it might be suitable for my purposes? I will probably be wanting to photograph things that are bright enough to see in the eyepiece.

[AKB]

3 hours ago, sedm1809 said:

wasn't aware of the difference between CCD and CMOS. Just browsing round the internet this looks like it wouldn't break the bank: www.rothervalleyoptics.co.uk/zwo-asi120mc-colour-13-cmos-usb-20-camera.html. Does anyone have any experience of this piece of kit, or can they say if it might be suitable for my purposes? I will probably be wanting to photograph things that are bright enough to see in the eyepiece.

That’s a possible starter camera.  It’s not cooled, of course, but it’s widely used in guiding and as a starter planetary camera.  It’s almost definitely more sensitive than the Mk. I eyeball.  For flipping between camera and eyepiece, I’d certainly suggest... a flip-mirror!  This lets you have both attached at the same time. 

Definitely take a look at the Video section here.

 

[wimvb]

5 hours ago, sedm1809 said:

I wasn't aware of the difference between CCD and CMOS. Just browsing round the internet this looks like it wouldn't break the bank: www.rothervalleyoptics.co.uk/zwo-asi120mc-colour-13-cmos-usb-20-camera.html. Does anyone have any experience of this piece of kit, or can they say if it might be suitable for my purposes? I will probably be wanting to photograph things that are bright enough to see in the eyepiece.

That is a really small camera (chip). You'll have a hard time centering a target on the chip, if you don't use platesolving.

Have a look here for the expected field of view with a 150 mm f/5 Newtonian:

http://astronomy.tools/calculators/field_of_view/

The camera is probably good enough for planetary imaging, but Deep Sky Objects will be too severely cropped, in my opinion.

https://astronomy-imaging-camera.com/gallery/ (scroll down to ASI120)

Cmos cameras have a variable gain (comparable to ISO on a DSLR). This means that you can use longer exposures at lower gain, or shorter exposures at higher gain. Short exposures don't need guiding. Here are a couple of unguided images taken with the (larger) ASI174MM-Cool and a 150 mm Newtonian:

Here's the fov of the ASI120 compared to the ASI174

[sedm1809]

Thanks, that's really helpful. That calculator seens suggests that even really expensive CMOS/CCD camera cannot get the whole of M31 in the FOV at once with that focal length - does that sound right?  I think I would want to take wider views, so would a DSLR (with more pixels) perhaps be a better bet? Or do I just need a smaller scope!? Thanks again.

[wimvb]

40 minutes ago, sedm1809 said:

Thanks, that's really helpful. That calculator seens suggests that even really expensive CMOS/CCD camera cannot get the whole of M31 in the FOV at once with that focal length - does that sound right?  I think I would want to take wider views, so would a DSLR (with more pixels) perhaps be a better bet? Or do I just need a smaller scope!? Thanks again.

As in daytime photography, you really need different focal lengths for different targets. There's no single camera/scope combo that does it all.

For any camera, the pixel size in combination with focal length, determines resolution (arcseconds of sky per pixel), while the sensor's dimensions in combination with focal length determines field of view. Theoretically, a small sensor with small pixels and a short focal length can give you the same resolution and field of view as a larger sensor with larger pixels and a longer focal length. But if things were so easy, NASA/ESO and many others wouldn't invest in ever larger telescopes.

If you already have a dslr, I would suggest using the FOV calculator with different scopes to get an idea of what combination works best for you. M31 is an extreme example as it is one of the larger objects in the night sky. You need a focal lenght of about 300 mm to fit it on the sensor of a dslr. But with such a setup, many other galaxies will get lost in the starfield.

If you are interested in wider views, you can either use a lens with a dslr, or invest in a short focal length scope, such as an ED80 (Skywatcher Evostar or similar). Shorter focal length scopes are more forgiving than longer fl in terms of polar alignment, balancing and guiding.

Have a look around in the imaging sections, and on astrobin.com, to see what other people are using. Then decide where to put your money. The scope and camera that you buy will most likely not be your final investment. (As I wrote before, AP is a money pit)

[TareqPhoto]

You have the mount, buy the mono astronomy camera second or even OSC, ignore DSLR, scopes come later.

I am in process to buy a new scope soon once I receive the budget, but last year I had fun testing and practicing with my mono astro cooled camera, it opened doors for me, even with a guide scope and achro one I was able to get something, so I was right to buy the mount first then the camera, now this year I will focus on scopes.

Good luck!