Ideas for a CCD on a SW Evostar 120ED

[swag72]

Hi All,

Well it looks like hubby is resigned to the fact that a CCD will be a purchase for me at some stage. So, I wanted to put it to you good folks out here what you think would be a good option for me with my SW Evostar 120ED scope.

I have decided that I'd like a mono as I want to do some narrowband imaging. I have spent a lot of time looking at the FOV calculators with the different cameras and I can't help thinking that the 120 at 900mm is just a bit long, even with the 0.85 reducer fitted (Takes it down to 765mm). If I had an 80ED, the Atik 314L would be the camera for me, but with my FL it seems just a little too ......... small a FOV.

I would welcome some thoughts and ideas on this (rather nice) dilemma I find myself in!! Especially those using a similar FL, what camera do you have?

Budget approx £1500 to include filters and filter wheel.

[ollypenrice]

I used the Atik 16HR( earlier 314L) in the similar Meade 127. You are right, it is a bit cramped.

Maybe an 8300 camera would be a better bet. If you have good Spanish skies then mosaics are good fun and not impossibly complicated, but run beofre you can walk is always good advice.

Olly

[swag72]

Cramped Olly, that was exactly the word I was looking for!!

Are the 8300 camera's within budget though? I suppose I could always use the Canon lens's with the CCD though to get a little more breathing room.

[Merlin66]

The chip size is always an issue!

Check also the arc sec/ pixel - this needs to be matched to the focal length...Harry Nyquist and his sampling theory has a lot to answer for!

[martin_h]

Take a look at Modern Astronomy - QHY9 + motorised filter wheel + 2" LRGB filters.

A tad over your budget at £1759 but worth a look.

[Deneb]

Or an Atik 383L+ you can get away with using 1.25" filters with it, it does cause some vignetting but taking some flats will sort that out...

Nadeem.

[ollypenrice]

I think the Atik 8300 is within budget. You will certainly need flats, though. You always do if you want a good result but with the 8300/small filters it is essential.

Camera lenses with CCD are great, I use them a lot, but there is an issue. You can't easily change filters so what I do is use our OSC Atik and then add an Ha layer with the mono equivalent. In a mono camera Ha or Ha/O111/O111 would be okay though. One camera or filter change is fine but four...??? With my setup (a Geoptik adapter) the lens or camera has to come off and changing filter is a daylight job for sure.

While Ken is right about sampling rates I can't buy a new camera for each FL so use the 4000s anywhere from 85mm FL to a metre and beyond. The results work out okay.

Olly

[swag72]

I have spent some time looking at the QHY9 and the FOV with the 120ED, I can't decide whether I like it, it's certainly less cramped than with the 314L. Unfortunately the Atik 383 is well over budget once you factor in filter wheel and filters.

What filters will the 314L need? 2" or 1.25"?

So what would I need exactly to make this transition? I read about the spacing being critical for focus - If I had a camera and it's own make filter wheel, I guess that would be the distance sorted? I don't want to be fannying around with spacers and the like, I just want to plug and play so to speak.

[martin_h]

If you are using the reducer you need 55mm from the edge of the reducer to the chip face.....if not using the reducer it doesn't realy matter - within reason

I use the QHY9 and a filter wheel (not the QHY one) and reducer and it all fits - just

[swag72]

I take it that's from the back of the reducer? Are filter wheels produced in different depths to accomodate this sort of issue? Is that 55mm exactly or maximum? If exact, how on earth does anyone get that?

[martin_h]

When using the reducer/flattener with a CCD you are not going to get plug and play....The reducer was designed for a DSLR so...slap on the T mount and the camera and the spacing is correct.

CCD's all have different face to chip distance, no two makes of filter wheel are the same thickness.

If you are going to use the reducer you will need a M48 to T thread adaptor

TS Adapter vom M48 (2' Filtergewinde) auf T2 - kurzbauend

[swag72]

Is there any advantage over using a reducer with a CCD? I ask as I have been putting the 0.85 reducer into the FOV calculator. If I don't need to use it, then I could consider something other than the Atik.

Do you need reducers for flattening the field with a CCD camera then? Or would I be using my native 900mm?

Interesting though, the QHY9 would give me very little more size on the frame than my 1000D. I want bigger!!!

[martin_h]

Yes you need a flat field - no matter what you use... Also the bigger the chip the flatter you need to be.

If you want bigger than a DSLR chip....be prepaired to re-mortgage the house

[swag72]

So is there a specific field flattener to use with a CCD?

[martin_h]

The one you have will do

This is my setup on a ED100 - the same on the ED80 as well

[swag72]

Oh my goodness!!! Hardly neat looking is it?!!! Thanks for that picture, shows it really well what you need.

When I look at the FLO site for filter wheels, what measurement is the width? How would I work out which one is best?

[Deneb]

What filters will the 314L need? 2" or 1.25"?

yep You can use 1.25" filters with the 314L+ & the Atik Software is quite intuitive from what I remember.

Nadeem.

[martin_h]

Oh my goodness!!! Hardly neat looking is it?!!! Thanks for that picture, shows it really well what you need.

When I look at the FLO site for filter wheels, what measurement is the width? How would I work out which one is best?

Your best bet would be to contact them, or Bern at Modern Astronomy, tell them what you have, what you want and they should be able to sort something out for you.

My filter wheel is the True-Tech Supaslim Manual Filter Wheel, they do all sorts of adaptors to fit most scopes/CCDs

[ollypenrice]

With a small chip like the Sony 285 (Atik 314L) you would not need the flattening aspect of the reducer but speeding up the f ratio is a plus. It is a minor hassle but the dealers will sort you out with the spacers etc. If they don't, don't buy! And when it is done it is done. Both my wheels are 19mm thick. The chip distance on the camera is given by the maker. So then you just need spacers, eg Baader from Telescope Service or lots of other places.

In choosing your camera, be aware that with an Atik 314L you have a small chip but on that chip you can take world class pictures. Check out RobH's work.

I don't use the term world class lightly.

You can't have everything. For a wider field get a shorter focal length and guide with the big boy! The power of modern amateur imaging comes from the camera. It is the cameras that allow clowns like me to take better M42s than David Malin (a genius) on film with three hundred tons of telescope beneath him only a few years ago.

Olly

[swag72]

Thanks folks, guess it will be the Atik then and hopefully fairly soon!! Great info from you all.