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Can't decide whether to change from CCd to CMOS


steviemac500
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I need some advice.....I currently have a Moravian G2-8300 on my ED80 which is a great camera. However, I don't like the fact that my internal FW only holds 5 filters so when I want to do colour NB I have to change out something. I am also quite liking mosaics at the moment but it takes such a long time to construct them that I am thinking of something faster. My idea was to take the jump into the land of CMOS, possibly an ASI1600 MC and buy a larger FW, funded by the sale of the Moravian but I cant decide if I am being daft or not? I'd like some honest impartial advice please!!

Thanks,

Steve

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1 hour ago, steviemac500 said:

I am also quite liking mosaics at the moment but it takes such a long time to construct them that I am thinking of something faster.

You need faster optics for this or a larger sensor. Apart from being able to switch more filters without opening the FW, not much will change by moving to an ASI1600 and a larger FW.

I suppose you mean ASI1600 MMC.

 

Edited by moise212
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Mmmm, tricky! I really rate the Moravian G2-8300 as a mono camera, but if that was my main camera I would find the 5 position internal filter wheel a killer and so I'd change that for their larger external wheel. The actual sensor size of the CMOS 1600 isn't largely different to the KAF8300, so you'd still be in mosaic territory... perhaps you'd consider one of the larger CCD sensors to over come that.

I guess that you feel that the CMOS will be quicker in mosaics because you will be able to take shorter exposures and obtain the same quality in a shorter time?

It's a tough question.... I'm sticking with CCD for now, I have a fair few £k invested in them! If I was looking at only changing one camera would I go for a CMOS? I'm not totally sure as I know I'd end up having to change my PC as the files are so much bigger so both storage and processing. I *think* I'd get the large external filter wheel and put all filters into use on the CCD....... But on the other hand...... :) 

Not helping much am I? I guess that shows what a tricky decision it is and how there's not much that is cut and dry between the CCD and CMOS as time marches on.

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I have no experience with the Moravian G2-8300 or CMOS cameras, but I will say that I would find only 5 filter positions very limiting.  

I am going to make a daft suggestion which might be impossible because of spacing, but just might be a light bulb moment.  What would happen if you had one of those filter positions empty and added a 2nd slim line filterwheel for say narrowband again leaving a space blank on that for your Broadband filters to "see through". 

I bet the spacing will be an issue, but just thought I'd chuck it into the pot.

Carole 

Edited by carastro
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1 minute ago, carastro said:

I have no experience with the Moravian G2-8300 or CMOS cameras, but I will say that I would find only 5 filter positions very limiting.  

I am going to make a daft suggestion which might be impossible because of spacing, but just might be a light bulb moment.  What would happen if you had one of those filter positions empty and added a 2nd slim line filterwheel for say narrowband again leaving a space blank on that for your Broadband filters.

I bet the spacing will be an issue, but just thought I'd chuck it into the pot.

Carole 

That’s an idea. Has anyone tried this?

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23 minutes ago, moise212 said:

You need faster optics for this or a larger sensor. Apart from being able to switch more filters without opening the FW, not much will change by moving to an ASI1600 and a larger FW.

If I read again, you plan to move to an OSC? By no means it will be faster this way, especially with narrowband.

No not OSC and by faster I mean the exposure lengths. I do minimum of 20mins in HA which means on a bitty night it can be difficult to get even one exposure (winter in Cyprus). 

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4 hours ago, swag72 said:

I'm not totally sure as I know I'd end up having to change my PC as the files are so much bigger so both storage and processing.

Question from a CCD guy, why are CMOS files larger? Not just the added pixels?

/Jesper

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1 hour ago, kens said:

Given that you already have a focal reducer, it sounds like you may be better off getting a good 135mm or 200mm lens for a wider FOV.

Hi, it’s not really the FOV that bothers me,if I’m being honest it’s the hassle of changing filters out!!

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You can't get more signal by using CMOS.  It still depends on total imaging time.  With CMOS you can take shorter exposures but you need more of them.  There are some advantages of the shorter exposures with CMOS - you may be able to make better use of gaps in the clouds on what would otherwise be an unusable night sky.  Also, with a wide field and fast scope (or lens) you may be able to get away without guiding.  With the ASI1600MM-C you can use the larger ZWO filter wheel with 7 or 8 filter spaces and still get the back focus required for field flatteners or SLR lenses.  But the same results in a shorter time - definitely not. 

I usually take several hundred subs in each wavelength for NB imaging with my ASI1600MM-C and they are 32MB each - that's a lot of data.  I bought a high speed games machine and added SSD drives to get enough speed for data processing to take a reasonable time.

Edited by Gina
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To be honest, and given the advice by Moravian, I think if I was in your shoes I would be swapping my camera for one I can have all 7 filters on.  (Unless you can borrow a filterwheel to see if my original suggestion would work). 

Atik have brought out a 7 position 2" filterwheel if you want to stick with the large format chip which means if you have 2" mounted filters you won't have to change them.  Or the AtikEFW2 takes 7 35mm unmounted filters depending on what you currently have.  

Carole 

 

 

 

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I think that's the crux of the matter Carole - the size of filter.  Buying a new set of filters is a very expensive business.  That's why I decided to go no bigger than 4/3" size of sensor and the ZWO EFW - I can use the 1.25" filters I already have without significant vignetting.  Astrodon 3nm NB filter are expensive, particularly in the larger sizes!

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16 hours ago, Jessun said:

Question from a CCD guy, why are CMOS files larger? Not just the added pixels?

/Jesper

Yes. The sensor is 16MP, data is converted in 12bits which are actually stored in a .fit file on 16bits - 2Bytes. That means ~16M pixels x2 = ~32MBytes.

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Quote

I think that's the crux of the matter Carole - the size of filter.  Buying a new set of filters is a very expensive business.

Tell me abut it.  

I didn't tell the whole story of my filters.  I had two manual filter wheels when I first started each with 2" filters each with 4 filter positions.  I used one for LRGB and the other for Narrowband.  

Eventually I decided I was fed up with doing it manually and having to change the filter wheel when I wanted to swap from BB to NB, or even add Ha, and got myself a 7 position EFW2 which would not take 2" filters, but took 35mm unmounted, (I had an Atik383L) at the time, so I sold all my 2" filters and bought a new set of 35mm mounted, as well as the EFW.  That was expensive!!

About a year later I decided to dispense with my Atik383L for various reasons and bought the smaller Atik460EX instead, so didn't actually need the 35mm filters any more, but decided I would stick with it as I couldn't stand having to change them all over again, so I have 35mm unmounted filters with cameras that don't really need them so large. 

Carole  

Edited by carastro
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On 06/12/2017 at 12:03, carastro said:

To be honest, and given the advice by Moravian, I think if I was in your shoes I would be swapping my camera for one I can have all 7 filters on.  (Unless you can borrow a filterwheel to see if my original suggestion would work). 

Atik have brought out a 7 position 2" filterwheel if you want to stick with the large format chip which means if you have 2" mounted filters you won't have to change them.  Or the AtikEFW2 takes 7 35mm unmounted filters depending on what you currently have.  

Carole 

 

 

 

I use 1.25” filters, changing them isn’t really an option just now. 

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56 minutes ago, steviemac500 said:

I use 1.25” filters, changing them isn’t really an option just now. 

The ASI1600 seems to be the only viable option with their 20mm wide FW. The other cameras using the same sensor have a longer backfocus and using 1.25" filters in a FW will lead to vignetting.

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I have the G2 8300 and yes, the 5 filter wheel is a pain for obvious reasons.

Where I am, my light pollution isn't the worst, but I clearly get better results with the NB filters as I climb the imaging learning ladder.

If I want to use LRGB then as you, I don't want to keep opening the camera, so I figured a dual set up would be the best option as I already have 2 of the same scope, I just need a 2nd camera.

NB in one plus a BB colour, then LRGB in the other plus, I dunno, Ha.

I guess what I'm trying to say is, if you decide to sell the Moravian on, please let me know!

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13 hours ago, Jonk said:

I have the G2 8300 and yes, the 5 filter wheel is a pain for obvious reasons.

Where I am, my light pollution isn't the worst, but I clearly get better results with the NB filters as I climb the imaging learning ladder.

If I want to use LRGB then as you, I don't want to keep opening the camera, so I figured a dual set up would be the best option as I already have 2 of the same scope, I just need a 2nd camera.

NB in one plus a BB colour, then LRGB in the other plus, I dunno, Ha.

I guess what I'm trying to say is, if you decide to sell the Moravian on, please let me know!

Two set ups......now thats a great idea.....said my wife never!!!!!!

I am thinking about selling the rig to get a new one with external wheel but not really prepared to buy a whole new filter set (just upgraded the marine fish tank).I do love my Moravian though.

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On 06/12/2017 at 14:09, moise212 said:

Yes. The sensor is 16MP, data is converted in 12bits which are actually stored in a .fit file on 16bits - 2Bytes. That means ~16M pixels x2 = ~32MBytes.

I think the real issue is the number of files if you do long integration in short subs. AstroArt is a remarkably fast stacking and calibration programme and might be a help to CMOS users.

Olly

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33 minutes ago, ollypenrice said:

I think the real issue is the number of files if you do long integration in short subs. AstroArt is a remarkably fast stacking and calibration programme and might be a help to CMOS users.

Olly

Olly, any thoughts on the 8 pos fw and possible vignetting?

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1 hour ago, steviemac500 said:

Olly, any thoughts on the 8 pos fw and possible vignetting?

Unless someone has actually tried it the best you can do, I think, would be find out the limit at which similar chip sizes vignette with 1.25 filters. Close to the limit is the Atik 383 with Atik FW. The back focus of the camera is 17.5mm and the FW is 19mm thick. By chance I happen to have one right now on my desk here and, though it's awkward to measure, I'd say that the front of the filter would be about 9mm from the front of the camera. That suggests that you should be able to get away with the front of the filter placed about 26.5 mm forward of the chip, or less.  If it were more than that I think it would be getting dangerously close to the limits of what flats can correct. This estimate does not come with a guarantee!

Olly

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