Matching a CCD to your scope

[Billy- the -Badger]

Ok folks.

I have just been told that I have to Mach the CCD camera to the focal length of my scope.

So here goes.

I have a Meade LX90 12"

with a focal length of 3048mm.

Suggestions are welcome and cameras that cost less than my car are very welcome.

[JamesF]

There's no law that you have to One might I guess say that you might get better results if the camera is chosen with the scope in mind, but equally it has to suit your pocket and there may be other factors too.

I take it this is for DSO imaging?

James

[Billy- the -Badger]

Yes james.

Im using a Sony NPC 900 and getting pretty decent results.

I'm just wondering if the massive hike in price is gonna be reflected in the images

[JamesF]

The SPC900 is an exceptional camera for what some of us paid for it. Given a scope of 3m focal length it's never going to make a DSO camera however.

To be honest, perhaps the scope is where you should start. I've no experience of your scope, but 3m is a huge focal length to be using for DSO imaging. At random I've picked the Rosette Nebula for an example. It's 1.3 degrees across. To fit that on a camera with your scope you'd need at least a four-panel mosiac even with a full-frame sensor. And exposure times will be massive. Not to mention the difficulty of guiding at that focal length. Even with a reducer it's going to be very tricky, I reckon.

Perhaps it would be sensible to consider a different scope for DSO imaging first?

James

[r3i]

There's a great piece of software called CCDCalc which allows you to see how well known DSOs will appear in the FOV of a particular scope/camera combination. It's available for download here: http://www.newastro.com/book_new/camera_app.php

[Billy- the -Badger]

Cheers peeps.

[Earl]

Imaging with a long focal length will be very challenging, I would do some serious research into it before considering pressing the buy button.

[ollypenrice]

Yes, I woud never entertain trying to use a Meade mount for DS imaging, espeicially the 12 inch with its immense focal length. I tried going into DS imaging with a 10 inch LX200. I spent quite a bit and got nowhere at all. I would strongly advise a rethink.

If you aim for about 2 arcseconds per pixel you'll be in the sweet spot but, to be honest, I've used all sorts of sampling rates and you can get good results when way off the ideal. If you have a very long FL and small pixels you just bin them 2x2 to gain speed withut losing real resolution.

Olly

http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/22435624_WLMPTM#!i=2277139556&k=FGgG233

[Billy- the -Badger]

Time to stick the meade on eBay

[swag72]

If you are looking at imaging DSO's you can do much worse than spending £20 in the book section of the FLO website and getting a copy of 'Making Every Photon Count' - A brilliant read and will help you no end.

If you want to make it as easy as possible, you'll be looking at a short focal length refractor, such as an ED80. Many people use this size scope to good effect.

[dph1nm]

You want a chip with big pixels, but these are very expensive. So get a smaller pixel chip you can bin up 3x3 - this will work great on a 12" Meade. Effectively you will then be working at 1000mm not 3000mm.

NigelM

[lensman57]

Ok folks.

I have just been told that I have to Mach the CCD camera to the focal length of my scope.

So here goes.

I have a Meade LX90 12"

with a focal length of 3048mm.

Suggestions are welcome and cameras that cost less than my car are very welcome.

Hi,

I don't know how good, accurate your mount tracks but you have at least two massive problems to overcome. For DSO you need long exposures, fast focal length and very accurate guiding. With 3000mm focal length you'd be looking for a miracle to guide this scope with reasonable amateur equipment. I am sure that it is a brilliant planetary scope but for DSO imaging even 1000 mm is too long. So perhaps you'd need to look at this again from a different angle.

regards,

A.G

[dph1nm]

For DSO you need long exposures, fast focal length and very accurate guiding. With 3000mm focal length you'd be looking for a miracle to guide this scope with reasonable amateur equipment

What matters, both for exposure times and guiding, is the pixel scale at the camera, not the focal length of the scope (although the two are related). So you need to choose a chip which gives you a reasonable pixel scale, of, say, 1 arcsec/pixel (as I said above, this might mean binning). If you can manage that within your budget then you will be amazed what you can do with a 12" scope with 30sec exposures.

NigelM

[Davey-T]

I use 10" Meade SCT but image with 6.3f/reducer which makes the focal lenghth about 1500mm.

You can use the Celestron one as it's identical, usually a few going secondhand.

I would agree with Olly as you'd be making a rod for your back loosing more subs than saved , also I never had any luck when mounted on a tripod .

As said you'd be better of selling the scope and putting it down to experience and buying a short f/l refractor .

Dave

[Billy- the -Badger]

Tried running the sale of the Meade to buy another scope by the wife.

The good news is I will be out of intensive care soon.

Now I am open to suggestions on a decent scope for dso photography

my budget will be up to about £2000.

[nmoushon]

Your mount makes a big deference to. I don't recall reading what your mount is. Also I would suggest switching from the SPC900 webcam to at least a DSLR, especially for DSO, unless you have a seperate budget for a CCD camera.

[lensman57]

Tried running the sale of the Meade to buy another scope by the wife.

The good news is I will be out of intensive care soon.

Now I am open to suggestions on a decent scope for dso photography

my budget will be up to about £2000.

Hi,

You'd need to put at least half your budget away for a mount of some description, HEQ5-EQ6? And some money for guidescope and guide camera and bits and pieces. You will probably have enough left for an 80mm triplet apo of about f6. If alresady have a tracking mount then have a look at SW 100mm ED Espirit pro 5 elements. It is purpose made for astroimaging. You should also not dismiss fast newtonians such the Skywatcher 200 F4 quatro, at just over £400.00 is a steal if you can put up with collimation every session.

With this one you really do need an EQ6 mount.

Regards,

A.G

[r3i]

Tried running the sale of the Meade to buy another scope by the wife.

The good news is I will be out of intensive care soon.

Wishing you a speedy recovery . Having previously owned an 8" LX90, I would concur that if you want to get into DSO imaging, the LX90 mount isn't the weapon of choice. A nice visual platform for sure but a GEM is the way to go for imaging. If you can fit an NEQ6 into your budget you won't be sorry and it should last you years.

[Billy- the -Badger]

I must admit. I am tempted by the Skywatcher Esprit ED 100 PRO 5-element.

[nmoushon]

Its a good scope. But make sure you have the appropriate mount.

[Billy- the -Badger]

1368648083[/url'>' post='1935719']

Its a good scope. But make sure you have the appropriate mount.

Would have to be a NEQ6

[x6gas]

You want a chip with big pixels, but these are very expensive. So get a smaller pixel chip you can bin up 3x3 - this will work great on a 12" Meade. Effectively you will then be working at 1000mm not 3000mm.

NigelM

Huh? How does that work? Binning alters the resolution and the effective sensitivity of the chip but it doesn't change the focal length which is determinant of native magnification... does it?

[JamesF]

I think what Nigel meant was that the apparent image size will be smaller because where you might have originally have had three pixels you'll only now have one in the final rendered image, which is effectively what you'd have if you'd used the shorter focal length to start with.

I'm really not sure you can get away from needing a big sensor regardless of pixel size however. And they don't seem to come cheap whichever way you cut it.

James

[x6gas]

I think what Nigel meant was that the apparent image size will be smaller because where you might have originally have had three pixels you'll only now have one in the final rendered image, which is effectively what you'd have if you'd used the shorter focal length to start with.

I'm really not sure you can get away from needing a big sensor regardless of pixel size however. And they don't seem to come cheap whichever way you cut it.

James

Ah I see - so you'd have higher resolution so could crop and have the same number of pixels in the end. OK, get it now!

[dph1nm]

Yes, that is probably what I meant! You do have to sacrifice something with a long FL scope, and that is usually field of view. So whilst binning recovers the speed of a smaller FL scope, and makes the tracking easier, you do end up with a smaller patch of sky in your image. The only way round that is a bigger chip, or to mosaic several chips together (which is what professional scopes do these days). I wonder if we will ever see amateur mosaiced ccds?

NigelM