Choosing a CCD camera

[Jammy]

I'm hoping that the sky will finally clear and reveal some stars sometime soon (fingers crossed) and I'm considering buying a long exposure CCD camera for my scope.

I was wondering if anyone could make a recommendation or three?

I have a C9.25 ota, and I'm looking at paying up to 1k, but hopefully less if I don't need spend all that!!

What things should I consider when looking for a camera?

I know that the C9.25 isn't ideal for astro being f/10, but wondered if anyone had achieved decent results.

[nmoushon]

Firstly you will need a reducer/flattener that will bring your scope down to f/6.3, i think its f6.3 maybe something else but its close. There are several out there and they aren't to expensive.

[riklaunim]

You could use Brightstar Mammut camera for 400 GBP + f/3.3 focal reducer/corrector for SCTs (this camera has small enough sensor to work with f/3.3 reducer). You would have to add guiding - like a QHY5 + finderscope or 80/400 refractor for guiding.

Other option is f/6.3 reducer corrector + big color QHY 8L (like a DSLR in size) for around 900 GBP. Plus guiding setup.

[JamesF]

Did you have any particular views on LRGB or colour imaging?

James

[Jammy]

Did you have any particular views on LRGB or colour imaging?

I don't really have any predetermined views at all. I was just looking for some ideas, then I can look into it deeper. I started with planetry astro using a webcam last winter, and I'd like to move on and try my hand at long exposure astro.

Being a bit of a geek with a lot of patients I know that I can make a go of AP

Does LRGB ultimately give better images than colour?

[riklaunim]

Does LRGB ultimately give better images than colour?

If you have a mono camera you can use some filters like narrowband for nebulae which will give much better image of them. For other DS objects you can do LRGB or RGB. The LRGB can be better than plain RGB.

[JamesF]

Does LRGB ultimately give better images than colour?

It sort of depends how you define "better"

Colour allows you to get the entire image in one hit and in that respect is less complex, though from what I've read of other comments here the processing may be more awkward than for mono.

Mono can give better resolution for the same size camera sensor as you don't have to collect all three colours at once, but you need to expose each component in turn which may take longer. It also allows you to use narrowband filters for Ha, O3 and so on. The negative side is that you need to buy filters and ideally a filter wheel too and they alone may not leave you with much change out of £300 to £400 depending on which filters and wheel you buy.

I'm not sure what all the software options are for capturing and processing colour or mono images, but you may need to factor in the cost of the software as well. Could be worth checking the imaging section to see if there's a sticky posting on that.

James

[x6gas]

If you have a DSLR I would use that and focus on getting an autoguiding set-up working. You realy need to autoguide to get the length of exposure you'l need for the faint stuff using your scope (at least without a reducer).

You've got two options - Off-axis guding (OAG) or a seperate guidescope. I was recommended to go down the OAG route which I've done and it's promising so far but I've only really used it on my 90mm 'frac - waiting for clear skies to try it on the SCT.

The thread discussing it is here: http://stargazerslounge.com/topic/120500-attaching-guidescope-to-f10-sct-advice-please/page__hl__guidescope

[Jammy]

Thanks James. It's a starting point, and something to consider.

I've got a copy of 'Making Every Photon Count' sat on the bookshelf. I've just remembered it!

I'll give that a thorough read too before I buy anything.

[Jammy]

Thanks x6gas. I don't have a DSLR, but have thought about getting one. I already have a decent bridge camera for everyday use, so if I buy a DSLR it would be for AP only. In that case I think I'm probably best getting a dedicated CCD camera.

What is Off-axis guiding and how does it differ to using a seperate guidescope?

[swag72]

Steve covers a lot of the CCD pro's and cons in his book, so well worth a read.

The main thoughts will be DSLR or CCD. If you go for CCD, mono or OSC. There are advantages and disadvantages to all of these. One thing that may be of consideration is chip size with your current scope. If you use http://www.12dstring.me.uk/fov.htm and put in your scope, then you can add any combination of barlow / reducer and camera as well. It may help you make a decision with regards to the field of view you will get with different combinations.

If I was buying a camera with no previous equipment, I would go straight for a CCD. A DSLR was good and there's some people getting cracking images with theirs. It's also very good value for money with regards to chip size. The CCD's are much more expensive.

[nmoushon]

OAG - to put it simply - steals a small portion of the light coming through your main scope and uses it to guide. So it kind of like adding binos the end of your scope where one side you attach your imaging camera and the other you attach your guiding camera. Except the light isn't split 50/50. The OAG only takes about 3-5% of the light to use for guiding. Just keep in mind that you also lose 3-5% of the light on your image so you wont get as much data as if you where to use a separate guide scope. But at the same time its only 3-5%. So not to much

[x6gas]

OAG - to put it simply - steals a small portion of the light coming through your main scope and uses it to guide. So it kind of like adding binos the end of your scope where one side you attach your imaging camera and the other you attach your guiding camera. Except the light isn't split 50/50. The OAG only takes about 3-5% of the light to use for guiding. Just keep in mind that you also lose 3-5% of the light on your image so you wont get as much data as if you where to use a separate guide scope. But at the same time its only 3-5%. So not to much

Not true on my set-up and I think with most (all?) OAGs... The pick off prism sits in the light cone but below the imaging sensor so you aren't actually losing any photons from the image itself...

[nmoushon]

Not true on my set-up and I think with most (all?) OAGs... The pick off prism sits in the light cone but below the imaging sensor so you aren't actually losing any photons from the image itself...

Really? I thought that was the main reason people dont like to use them? At least thats what I remember reading anyways. If I'm wrong I'm sorry and disregard what I wrote.

[x6gas]

Really? I thought that was the main reason people dont like to use them? At least thats what I remember reading anyways. If I'm wrong I'm sorry and disregard what I wrote.

Can only speak for my set-up... Thinking about it I guess it depends on how wide your clear aperture is and whether you have room for both the imaging sensor and the pick off prism. I have 2" filters which obviously helps...

[Jammy]

Thanks Sara. I just looked at your photos on flickr. They are fantastic! I'm definately inspired.

[Jammy]

So off-axis guiding doesn't require a separate scope. I've seen that before, but didn't know it was called that.

I'd best get reading up before the better weather comes!