New CCD setup help !

[halli]

Hi Everyone

Almost ready to go with pushing the button on jumping from DSLR to CCD.  

I've looked at a number of threads and have contemplated whether to maximise FOV with  a large sensor using a KAF8300 (Atik 383l+) or go for a more modern but perhaps less noisy Sony chip (perhaps this thought is heresey).  The debates on this seem endless but I guess at the end of the day it ultimately boils down to FOV !  

I've decided (currently !)  to go for the large FOV sensor as I feel it offers the most flexible approach.  I do want to image large nebula as well as small galaxies and I have a 130pds for the former and GSO RC8 for the latter.  

I feel the RC8 plus KAF8300 without FR will give me enough zoom in potential for small galaxies and also the 8300 offers considerable advantage for large FOV shots with the 130pds (or perhaps later with a small widefield refractor).  Cant really see any other logic wrt CCD selection if you want to go widefield  and close up with these scopes.  

There doesn't appear to be any significant  advantage in using a smaller sensor (as long as the KAF8300 doesn't have any real performance downside)  or am I missing something ??  Comments welcome ! 

Mono seems to be the obvious preferred choice, but imaging time with the UK weather concerns me !  

Then there are the filters and filter wheel to get.   Its at this point you start thinking about the cost eg is it 5 or 7 position, manual or a USB.  As I appear to need 36mm filters for the 383l+, the choice of filter wheel is more limited and the ATIK EFW looks quite expensive but has the advantage of being controlled by the Atik software !  I am tempted by the Starlight express one which is cheaper but am not sure how I can control the camera and wheel with the same software.  I think Sequence generator pro may be a possibility ?  I would welcome comments on this as I am unsure of which way to go at this point !  

I  am hoping that Baader or Optolong filters will be sufficiently parfocal so I can go to bed at some point and allow automatic filter changing to take place without refocusing !   If this is not possible then a manual wheel seems a better bet as there is no software control headache and I dont see the advantage of the USB wheel apart from being able to sequence filter changes, but if you need to go outside to refocus then whats the point ?? In  LRGB imaging, if the luminance is accurately focused -  is the focus of the colours as critical if they end up combined ?

To summarise I am looking at an Atik 383l+ with starlight express usb 7 position 36mm wheel or a manual one (depending on whether automation will allow me to go to bed !)  with a set of LRGB Baader or Optolong filters - preference is the latter as they are cheaper and seem to be equivalent in quality to the Baader   As this will be pushing £2k  just to replace my DSLR,   comments  on my deliberations and choices would be very welcome before I spend he money -  and apologies for the brain dump all in one post !

Thanks in anticipation for any guidance

Ian

[swag72]

I think that your sensor choice is sound. Too many people (myself included) are seduced by the claims of the Sony sensors that darks aren't needed for example and that the QE is really good. Well I can say that with my Sony chip, my noise was helped by adding darks, so zero advantage there then. Regarding sensitivity - Again I think that they claims are heavily outweighed by the increased FOV and dynamic range of the Kodak sensor.

A good choice!

Personally, I know it's more expensive, but I really rate the all in one approach that QSI offer of integrated filter wheel and OAG - Will be beneficial to your 8" for sure. Also with the QSI you can use 1.25" filters as they are close enough to the sensor to work fine. I've used them at f3.9 with no issues. 

[halli]

Thanks Sara.

Its difficult for me to justify the extra cost of the QSI 683 as I am already pushing it and there appears to be always something with some advantage at an additional price !

Probably the most important decision left then is whether its worth spending the money on a USB filter wheel given that I may need to adjust the focus at each filter change anyway.

I think from some of your previous posts you have an automatic focusing system Sara - so I guess this takes care of any manual focus intervention issues.

I would appreciate views of people with manual focus who have USB filter wheels as to whether they adjust focus between filters even though they may have sequenced the filter change or is  the USB wheel justified on the basis of simply the smoother change it delivers anyway as apposed to a manual change.  I guess if you do one filter's worth of data per night it doesn't matter anyway !  However this risks running out of clear nights in the UK.  I guess using one filter change per night sounds reasonable and that still means some sleep is possible.

Although even this may be potentially frustrating in waiting for another clear night to complete the data capture.

Any views please?

Ian

[perfrej]

Generally speaking, don't bet on parfocality being anything but a myth. None of my three sets of parfocal filters have been even close to the claim. These come from Baader an Astrodon, so no cheapo stuff.

/per

[swag72]

I did have a manual filter wheel for some time Ian and my filters weren't parfocal. To that end I used to do one filter per night. But .................. with temperature changes affecting focus too, I was having to refocus anyway perhaps 2x a night and still by the end of the run my subs were often so far out of focus to be unusable.

With a USB wheel I set the software to focus every 1 degree temperature drop. So I get all usable subs. With your UK weather as it is, you don't want to be wasting exposures because they are out of focus, you need to maximise your imaging time for sure.

Auto focusers are brilliant ......... that's all I can say on that matter! And if you want to plan and maximise your time, I believe that they are a must. For example, you could do a run in the night of L,R,G,B,L,R,G,B .............. so that you would be getting the complete data set through the night instead of doing all red one night and all blue on another. You can also ensure that you capture data at the best time, so that you can programme your blue to be taken around the zenith as that will help to ensure that you don't get blue halos (as it's the colour most affected by the atmospherics)........ Just a couple of ideas!

[halli]

Ok Sara,  I guess thats a resounding vote for also spending money on automated focus - sounds brilliant -   and then I dont need to worry about not going to bed or falling asleep on the setee whilst looking at a team viewer screen ! !    

Only problem is i'm not very good at smuggling all these goodies into the house..................  I guess I will need to formulate a plan of drip feeding my hard earned cash into an evolving strategy - although even then the number of goodies will become apparent over a longer time span !  

And thanks Pefrej for your comment - so I cant rely on parfocality ( probably not a word !) to save me from sleepless nights.........

[ollypenrice]

Whether or not your filters are parfocal does not just depend on your filters, it depends on your optics and your pixel scale. At the pixel scales I use (3.5"PP in the Taks and 1.8"PP in the TEC140) I can regard them as pafocal. Certainly the colours, anyway, since any tiny variance will be invisible in the final result. In single filter runs (most obviously Ha and Luminance) this doesn't apply because I do these runs in one continuous sequence and an hourly focus check seems to work.

Sara has an autofocus system which works. You cannot take it for granted that yours will just work!  If you have one which does, then you'll be a happy bunny. They can be a royal pain, though, when they don't.

Olly

[ollypenrice]

PS...

'Mono seems to be the obvious preferred choice, but imaging time with the UK weather concerns me !  '

We are all short of time, wherever we live, but mono is the fastest imaging system available to us. OSC may, possibly, be less frustrating but it is most certainly significantly slower. It is doomed to take colour all the time - and take it in the wrong proportions for AP since we have no need of twice as much green as red and blue. When we shoot luminance we are working at treble speed (actually better than that) because we are catching all colours at once. And we can bin colour 2X2 if we wish. And shoot Ha in the moonlight. The fastest system is mono.

Olly

[halli]

Thanks for your comments Olly.

Yes its strange how the human mind works with the automatic certain assumption that mono needs more time than OSC.    I guess its related to the thought of needing to use 4 phases of filters serially whereas with OSC everything occurs in parrallel.    The thought process however neglects the fact that only part of the chip estate is used for each colour which effectively slows it down.    Its still the sleepless nights with serial activities that worry me !

My mind is starting to gel on Atik 383l+, 36mm Baader LRGB filters and Starlight express USB 7 position filter wheel.  Perhaps smuggling some narrowband filters in at a later date.........

I will keep my fingers crossed wrt parfocality to help with the lost sleep and hope I can simply automate the filter change with SGP.  

I've just realised I need to use a light pollution filter - how would I implement this with this setup ?  Answers welcome !!

Thanks

Ian

[swag72]

I use my LP filter in place of my luminance filter - I don't use it for the other filters. Some do though and will get a 2" fllter that screws into the imaging train after the filter wheel

[halli]

Ah thanks Sara -  ive already got a 2" lpf so I guess I can simply use this as i would normally do to start with and hope there is somewhere to screw it in !

[swag72]

Depends on how your imaging train connects to the focuser - If it's a 2" pushfit then you will often have internal screws in that connector

[ollypenrice]

Thanks for your comments Olly.

Yes its strange how the human mind works with the automatic certain assumption that mono needs more time than OSC.    I guess its related to the thought of needing to use 4 phases of filters serially whereas with OSC everything occurs in parrallel.    The thought process however neglects the fact that only part of the chip estate is used for each colour which effectively slows it down.    Its still the sleepless nights with serial activities that worry me !

My mind is starting to gel on Atik 383l+, 36mm Baader LRGB filters and Starlight express USB 7 position filter wheel.  Perhaps smuggling some narrowband filters in at a later date.........

I will keep my fingers crossed wrt parfocality to help with the lost sleep and hope I can simply automate the filter change with SGP.  

I've just realised I need to use a light pollution filter - how would I implement this with this setup ?  Answers welcome !!

Thanks

Ian

I think it's partly linguistic. As I've said before, the term 'One shot colour' is misleading since it is really 'Half a shot green, quarter of a shot blue, quarter of a shot red' which doesn't sound quite so good... though it means the same thing.

Olly

[opticalpath]

+1 for the QSI camera if you can stretch to it.  Very convenient and compact with the integrated filter wheel and OAG. 

Adrian

[Horwig]

I can vouch for the QSI as well, really nice construction, very well thought out unit. I have the 6120 wsg-8 model, so not the 8300 sensor, but identical mechanics. Used 583s do come up occasionally, might be worth keeping an eye out if you are not in a hurry.

The only thing against it if that if it has to go back to the manufacturer for any reason, then it's back to the States, Atik and Starlight are Uk based.

Moravian instrument seem to be getting good results, their 8300 based G2 camera's price is close to the Atik, and a lot cheaper than QSI, and the OAG can be added later if costs are tight.

Sorry for the ramble

Huw

[Horwig]

And there again, there's this 383 on ABS:

http://www.astrobuysell.com/uk/propview.php?view=106137

For the price you can't go wrong.

Huw

[halli]

Thanks Huw and Adrian.  i think the QSI is just too expensive - perhaps I need to look at the Moravian but I have seen quite a few threads about the 383 and probably feel more comfortable with it.

I had seen the ABS ad Huw  but thanks for pointing it out - its a coincidence that it has come up now !  It is tempting and I am looking into it - the camera is late 2011 ie about 4 years old.  Its a bit older than I wanted but obviously cheaper.  Is there anything that should  concern me  re the age do you think ?

Ian

[wigggyy]

I use the Atik 383l mono with the Atik usb filter wheel  5 position with astronomik 2" filters it is a nice setup the whell is very smooth which are meant to be parfocal but as others have commented always best to check between filters

[halli]

Thanks for your comment wigggyy.

just looked at Moravian instruments and  they have quite a number of config options for the 8300 chip !  Including an integral filter wheel.  

http://www.365astronomy.com/Moravian-Instruments-G2-8300-Monochrome-CCD-Camera-with-KAF-8300-CCD-and-5-pos-Filter-Wheel.html

I believe this wheel can take 1.25" mounted or 31mm unmounted. Its a shame to go to the non standard 31mm .  1.25" appears to be 31.75mm which is larger !   I see little difference unless its something to do with the thickness of the mounting  - am I missing sometthing here ?  Why should the 31mm cause less vignetting ?  

I presume the filters are close to the chip anyway as they are integral.  Also the 31mm filters are unmounted and therefore if I want to use a set of narrowband fiters it will be fiddly to change them.

Has anyone used 1.25" mounted filters in the Moravian with integral filter wheel ?  

Ta

Ian

[opticalpath]

1.25" is the outer thread size of the filter mounting, not the clear aperture of the filter .... which is quite a bit smaller.   31mm filters are unmounted so the diameter of the glass is the full 31mm and the clear aperture is determined by the size of apertures of the filter wheel into which the 31mm filters drop. In practice, the clear aperture of 31mm filters is a few mm more than 1.25" threaded ones and therefore they permit a slightly wider un-vignetted field of view, which could make a difference at very fast focal ratios.

Adrian

[Physopto]

If you buy the Atik you will need a separate filter wheel and larger 36 mm filters. That is an extra cost for the wheel and larger filters on top of the camera. If you get the QSI 583/683wsg the filter wheel is in the body of the camera and you can fit either the 1.25" or better still the 31mm filters. 31mm filters allow more light through and so less vignetting. I had a 583 for several years and now have a 683. They are worth the extra, but of course that is just my opinion. The Morovian may be a good choice but never had one.

Derek

[swag72]

A friend of mine has the Moravian and you can use the 1.25" filters. I use the 1.25" in my QSI and any vignetting is sorted with flats. It's really no big deal.

[halli]

Thanks everyone - I now have a clear picture of the 1.25 and 31mm differences - it seems like splitting hairs to me and the 31mm route is certainly not preferred as it seems there are limited choice and unmounted are fiddly to change which leads to a weel with at least 7 positions.  

I think if I hadn't seen the ad in ABS I would probably have  gone for the Moravian with 1.25 filters

As it stands I am plumping for a second hand  Atik 383l+ , EFW2 5 position wheel, a set of Baader 2" LRGB and narrowband filters Ha, Hb, OIII, and SII  as a complete package !!  

 I am picking this lot up tomorrow !!  So fingers crossed everything is ok.  I guess there may be a few more questions in the setting up phase !!

Cheers

Ian

[ollypenrice]

Thanks everyone - I now have a clear picture of the 1.25 and 31mm differences - it seems like splitting hairs to me and the 31mm route is certainly not preferred as it seems there are limited choice and unmounted are fiddly to change which leads to a weel with at least 7 positions.  

I think if I hadn't seen the ad in ABS I would probably have  gone for the Moravian with 1.25 filters

As it stands I am plumping for a second hand  Atik 383l+ , EFW2 5 position wheel, a set of Baader 2" LRGB and narrowband filters Ha, Hb, OIII, and SII  as a complete package !!  

 I am picking this lot up tomorrow !!  So fingers crossed everything is ok.  I guess there may be a few more questions in the setting up phase !!

Cheers

Ian

Aha, I think one of my robotic shed clients will be disappointed. I was just on the phone to him and he rather fancied this one! Sounds fine to me.

Olly

[gnomus]

Ok Sara,  I guess thats a resounding vote for also spending money on automated focus - sounds brilliant -   and then I dont need to worry about not going to bed or falling asleep on the setee whilst looking at a team viewer screen.......

I have the 383L and EFW2 and so think you have made a good choice...

You may still not get any sleep though...... I don't want to rain on your parade, but I hope you are not going to rely on the UK weather forecast!!!! You may end up waking up with soaked equipment....