Full frame advantage

[Robindonne]

Ok a seperate thread for a small question with a simple answer i hope. Im thinking out loud because i really dont have an answer!!  If glow is really problamatic for lets say the outer 33% of an image, full frame and cropped, and uncooled. Will one benefit from imaging with a full frame sensor and crop images afterwards to remove much of the glow?

(I know go cooled and astro-dedicated is the right answer😅😅.)  

Based on the fov examples given with each camera, it looks like sensor size and maybe increase of pixel density with larger sensors effect the fov, it looks like your target object fill a smaller part of the image when using larger sensors. 
 

So basically my question is: 

Does it help to get cleaner results when using a full frame sensor, wider fov, and increased pixel density to afterwards remove most of the unused area?

[ollypenrice]

19 minutes ago, Robindonne said:

Ok a seperate thread for a small question with a simple answer i hope. Im thinking out loud because i really dont have an answer!!  If glow is really problamatic for lets say the outer 33% of an image, full frame and cropped, and uncooled. Will one benefit from imaging with a full frame sensor and crop images afterwards to remove much of the glow?

(I know go cooled and astro-dedicated is the right answer😅😅.)  

Based on the fov examples given with each camera, it looks like sensor size and maybe increase of pixel density with larger sensors effect the fov, it looks like your target object fill a smaller part of the image when using larger sensors. 
 

So basically my question is: 

Does it help to get cleaner results when using a full frame sensor, wider fov, and increased pixel density to afterwards remove most of the unused area?

Firstly is glow problematic for the outer 33% of the chip? Plenty of people use full frame sensors, including uncooled ones, with good results. The real problem is almost the inverse: relatively few telescopes will fully illuminate a full frame sensor. Flat fielding is essential to correct the vignetting produced by many of those which will. My own Tak FSQ106N covers full frame but with a 22% drop off in brightness from centre to corners. Flats correct it.

Secondly the question of pixel size should only be considered in terms of the sampling rate it will give you in a particular telescope. It will be difficult to turn details captured below about 0.9 arcseconds per pixel into real details in the final image. Choose the pixel size which suits your intentions. They should be as large as possible consistent with your intentions because over-sampling costs time and brings no benefit. Many people settle for 2 arcsecs per pixel as a sweet spot. In short pixel size matters, for sure, but matters only in connection with focal length.

Olly

[Star101]

What Olly says

[Robindonne]

1 hour ago, ollypenrice said:

Firstly is glow problematic for the outer 33% of the chip? Plenty of people use full frame sensors, including uncooled ones, with good results. The real problem is almost the inverse: relatively few telescopes will fully illuminate a full frame sensor. Flat fielding is essential to correct the vignetting produced by many of those which will. My own Tak FSQ106N covers full frame but with a 22% drop off in brightness from centre to corners. Flats correct it.

Secondly the question of pixel size should only be considered in terms of the sampling rate it will give you in a particular telescope. It will be difficult to turn details captured below about 0.9 arcseconds per pixel into real details in the final image. Choose the pixel size which suits your intentions. They should be as large as possible consistent with your intentions because over-sampling costs time and brings no benefit. Many people settle for 2 arcsecs per pixel as a sweet spot. In short pixel size matters, for sure, but matters only in connection with focal length.

Olly

Oke. Sounds very usefull.  I do have zero photography background due to just not being interested in it.  Astrophotography though interests me because of the beautiful and otherwise unseen objects out there.  
 

Most of the “fill in” parts in the formula to determine what camera-specs will work for me cant be filled in by me at the moment.  

I started with buying a 8” quattro with zero accessoires Then a heq5 mount for it.  When searching a used sct I found a retired seller who sold me his ap set.  C8 on an eq5pro with a guidescope and mono camera, an asi178, polemaster etc.  Lots of good stuff i think but i sold the cameras and now need to find out what to look for.  To get a proofed working setup i could easily buy all the sold items to return to that setup.  Or look for identical specs cameras.  But without soaking up all the info with questioning the issues im facing right now.  

If i use my c8, it came incl focalreducer, and planning to do ap mostly on nebulae and galaxys, is it then important to select a cam based on these plans?  You mentioned focal length is related to pixel size. What should be a good camera (eos 5/6/60:80) for f/6.3 with a c8 and possible using a f/4 newton now and then?

Edited May 2, 2020 by Robindonne

[Robindonne]

Found this.  It might answer some of my questions

[Robindonne]

So for 800 mm (quattro 8”)- 1280 mm (c8) focal length, the best option is 7 um?

[ollypenrice]

10 minutes ago, Robindonne said:

 

Neither of these scopes, to the best of my knowledge, will cover full frame cameras. Scope manufacturers should quote an 'image circle' in mm. This must be at least as large as the diagonal measurement of the chip. So a 33mm corrected circle will cover a chip with a 33mm diagonal.

I've always used this calculator to derive the sampling rate in arcsecs per pixel for given combinations of scopes/reducers/cameras.  http://www.12dstring.me.uk/fovcalc.php  The Atik graph will do the same job and I'm a very happy user of several Atik cameras. Your scopes have very different focal lengths but if you operate a mono camera in 2X2 binning you make its pixels effectively 4x larger so you can have, in effect, two cameras in one.

A word of caution over the phrase 'nebulae and galaxies.' There are a few large galaxies (not many) and quite a few small nebulae but in the majority of cases nebulae need a large field of view (short focal length) and galaxies need a high resolution (longer focal length.)

Olly

 

[Robindonne]

30 minutes ago, ollypenrice said:

camera in 2X2 binning

my phrase started with nebulaS.  Its edited, sorry.  
Ok.  Could that be done with a dslr? Its like atik a cmos.  Or is binning just like setting a lower resolution on your camera? Then a dslr sure can do that job?   The 60d has a pixelsize of 4,3   Does 2x2 binning mean pixelsize change from 4,3 to 8,6 um?

If so then the 60d for example would be a perfect choise, concerning pixel size, for occasionally use with small refractors and mainly use with the c8 when set to 2x2 binning?

Or go for a 6d with an “unfilled” full frame sensor with 6,5 um pixelsize and never use the 2x2 binning?

Will, like my initial question (unused glow affected parts of the image when using a full frame), i benefit from choosing a larger sensor and remove most outer part of the final image? Or will the overall quality of the image go down when my scope cant deliver enough light for the full frame? Or does it just deliver enough light on a part of the sensor and the other part wont receive any light? So that possible glow will not affect the main object.

 

ive bookmarked the 12dstring calculator  thx

Edited May 2, 2020 by Robindonne

[Robindonne]

I hope im not the only with these questions and therefore this thread might be helpful for more rookies😬

[ollypenrice]

35 minutes ago, Robindonne said:

So for 800 mm (quattro 8”)- 1280 mm (c8) focal length, the best option is 7 um?

The 16200 (a great camera) would probably be a tad oversampled in the C8 but, if you can get the guiding good and have stable seeing, it would give you a galaxy imaging scale similar to mine. (Caution, here. High resolution imaging means you have to get the tracking and focus spot on and you need a night of good seeing. That means of high stability, not just high transparency.

In the Quattro it would give you a very nice 1.7"PP.

The camera has a large chip. You'd need to check your manufacturers' published image circles.

Proper hardware binning is confined to mono CCD cameras. You can't do this with OSC cameras because you'd lose the colour information which is single pixel by single pixel. But, yes, a 4x4 micron pixel, binned, becomes a more sensitive 8x8 micron pixel. You'd need to ask a CMOS expert about binning those cameras. It's complicated. 

The Atik 4000 would also be a good match for your focal lengths. Note that the optimal sampling rate is also target dependent, in the real world. For small targets like galaxies you want detail, so ideally about 1"PP. For wide field nebulae you can have a coarser sampling rate and gain speed. The Atik chart suggests that their 11000 camera would be grossly under sampled at 530mm. But this is what you get from it:

0.9"PP looks like this (1000mm Atik 460)

Do be careful to check the chip size. Some of the cameras on the list have very small chips.

Persoanlly I would nt buy a DSLR for deep sky imaging. I'd go for a cooled CMOS if CCDs are most costly than you'd like.

I know it's a lot to take in!!!

Olly

 

 

Edited May 2, 2020 by ollypenrice

[Robindonne]

31 minutes ago, ollypenrice said:

I know it's a lot to take in!!!

No its very useful!! Thx a lot.  Im stunned by these images🤩.  And probably a million miles away from reaching it.  But i do have my reasons, against all advices, to start with a dslr.  And one of them is just not willing to spend on an inbetween dedicated camera.

So my stubborn schedule is, the best possible dslr in a pricerange 0-600,-  a dedicated camera for guiding ánd occasionally use on small apo’s without guiding (ánd i want to dive in with, and drag, my daughter into this hobby by giving a classic c5 and one of the mentioned cameras when im stepping up, turning 18 and trying to let her use her camera time for diagonal use instead of horizontal insta/tiktok etc use)

I made an unthought? choise by buying an asiar so im stucked with either zwo or canon/nikon dslr.  It will be a canon.   
I do however see the benefits of stepping away at one point to something like stellarmate and have free choises in equipment-brands.  For the moment its asiair.  But cant wait to let that asiair/dslr period behind me and follow all your and others advices in equipment. 
 

Edited May 2, 2020 by Robindonne

[ollypenrice]

9 minutes ago, Robindonne said:

No its very useful!! Thx a lot.  Im stunned by these images🤩.  And probably a million miles away from reaching it.  But i do have my reasons, against all advices, to start with a dslr.  And one of them is just not willing to spend on an inbetween dedicated camera.

So my stubborn schedule is, the best possible dslr in a pricerange 0-600,-  a dedicated camera for guiding ánd occasionally use on small apo’s without guiding (ánd i want to dive in with, and drag, my daughter into this hobby by giving a classic c5 and one of the mentioned cameras when im stepping up, turning 18 and trying to let her use her camera time for diagonal use instead of horizontal insta/tiktok etc use)

I made an unthought? choise by buying an asiar so im stucked with either zwo or canon/nikon dslr.  It will be a canon.   
I do however see the benefits of stepping away at one point to something like stellarmate and have free choises in equipment-brands.  For the moment its asiair.  But cant wait to let that asiair/dslr period behind me and follow all your and others advices in equipment. 
 

It might also be worth considering the Sony A7 but I have no astrophotography experience outside CCD. Best of luck!

Olly

[Robindonne]

I

2 minutes ago, ollypenrice said:

It might also be worth considering the Sony A7 but I have no astrophotography experience outside CCD. Best of luck!

Olly

Thanks a lot.  Very very helpful talk this last hour.  
 

its this list that’s provided with asiair.  Maybe one day they support more dslr, im afraid they’ll never accept other astro camera brands.  Thx again