CCD for F5 and F8 use

[halli]

Hi All

I have a 130pds and also a RC8 operating at F5 and F8 respectively and am looking to get a mono CCD for use with both scopes.

I am contemplating an ATIK 314L+ or ATIK 414 ex.   

I think both theses have the same chip and pixel size but the 414 is more sensitive and therefore could be more suitable for a longer focal length.  

However because these are rather expensive items I wanted to seek views on these choices for the scopes in question - just in case I have missed something and make a horrible mistake !

Thanks for any input and advice particularly wrt the pixel size and scopes I want to use

Thanks in anticipation

Ian

[perfrej]

Ian,

I would start by checking how large an imaging circle they can produce, and then figuring on the desired imaging scale. The cameras you mention have small sensors, and you really should look at something that fills your circle as much as possible.

/per

[swag72]

Take a look at the field of view calculator  putting in the various combos and look for a couple of things.....

1) Image scale or resolution (generally given in arc seconds per pixel)

2) Field of view for each scope

This is a really good tool for gauging how you would feel about either of these camera's. They are small sensors and you may find that when you put in your favourite nebula's you may actually want something bigger.

[halli]

Thanks for the advice Pefrej and Sara.  

I have played around with the FOV calculator which is a really good tool for bringing most of the info together.  

I guess it probably all boils down to what I want to image with the CCD !

I bought the RC8  to give me access to imaging small galaxies so the smalll chip size on the 314l+ is not an issue and the resolution is around 0.8"/pixel which appears ok from what I have read.  

The difficulty comes for the larger galaxies like M31 or M33 where even with the 130PDS th FOV is too small and certainly objects like NGC7000 etc are not possible.

However I guess to buy a lager chip would be expensive and these objects might still not be possible  - I am not adverse to still using the DSLR.

There is also the alternative to using something like a camera lens which would probably be less expensive than the extra money on a large CCD chip.

Seems to me like the framework is DSLR with 130pds or short focus refractor for very large objects,   Small refractor or camera lens for the large objects with smaller chip CCD,  130pds with smaller chip CCD for medium size and RC8 with smaller chip CCD for small objects.  

To achieve the above I may need to get hold of a short focus refractor or camera lens  at some point to make the most out of the smaller chip CCD - but then that will be more cost effective than buying a large chip CCD !

Its true to say that the resolution goes down when you have a larger field of view but not sure how much of an issue that is !  

I think, therefore  for what I want to do the smaller chip ATIKs combined with the use of a DSLR and then potentially including a short focus refractor in my armory at some point  seems like it might be a cost effective way forward to cover most things !

Im sure I have over simplified this - but would welcome any further comment as this discussion might also  help  others in the same plight as me in jumping to a CCD and trying to think through the consequences both in terms of cost, performance and versatility ! 

Thanks again and best wishes

Ian

[ollypenrice]

Very few setups can image M31 in one go. Even with a focal length of 530mm and a full frame Kodak chip I needed two panels.

Olly

[pete_l]

The difficulty comes for the larger galaxies like M31 or M33 where even with the 130PDS th FOV is too small and certainly objects like NGC7000 etc are not possible.

I wouldn't get too hung up on large DSOs -- there are very few of them. Since you say you are interested in small objects then a small sensor size is just fine. It's like if you buy a small car for city driving, it doesn't matter that you can't get 6 passengers in. It wouldn't make sense spending two or three times the money just for the few times you'd want that capability.

[halli]

Thanks Olly and Pete - I think you have confirmed my views as well !

So probably look at an Atik 414ex which has a greater sensitivity than the 314L+ and isn't that much more expensive.  

All the advice points to a mono CCD although I am worried about the UK weather and taking LRGB subs !

Also a manual filter wheel will mean staying up in the night and motorised ones are expensive - I guess I will need to bite the dollar bullet !  

However also I may need to refocus between filters ?   Can I avoid this ?  So if I want to go to bed I need to get an auto focusing system !  I guess I also need some sequencing software as well as the filters themselves  - it Seems like a complete new world ! 

Perhaps I can start with narrowband to get me going !?

Cheers

Ian