Fish Head Nebula

[Rodd]

I thought this was deserving of its own post.  This image is a crop of a much larger region--the Heart Nebula-which was originally shot at a focal length of 318mm (FSQ 106 with .6x reducer ) and a small pixel camera (ASI 1600-3.8um pixels), giving a resolution of 2.46 arcsec/pixel, which is not super high, but fairly high for the FOV.  This crop is a very small region of the original image, so a considerable zoom.   I got the FSQ and ASI 1600 and the .6x reducer specifically to bring down the focal ratio to F3, which, in theory, should have reduced my needed exposure times and total integration time.  I went through allot of research, and questioned many folks regarding the best way to accomplish the goal of reduced exposure times and total integration times (or, conversely going deep). I finally settled on this setup.  It was an expensive experiment that I must say utterly failed to do what I intended---my individual sub durations are less due to the ASI 1600, but my total integration times are no different--again, typical with the ASI1600.  I see no difference in exposure times between this system (F3) and F5.38 and F4.3 (TOA and Televue reduced) They are actually worse, for more, shorter subs means more dither delays, which add about an hour for each 4 hours of imaging.  I guess the experiment did have an upside--if anyone else finds themselves trying to decide upon the best way of accomplishing these goals, the choice of the OS200 or Epsilon would probably be better (maybe even the RASA or hyperstar--the stars couldn't be any worse than these!).  I hope these results benefit others who are faced with this same decision.

But--I must say I am really exited about the combination of large(ish) FOV and high(ish) resolution.  A very fun combination to play with.  The stars are not particularly nice--I have come to realize that it probably is not spacing.  the spot size associated with the .6x reducer is the cause I think.  I am learning to live with them.  Of this I am not 100% convinced, though, so any ideas are welcome.

 

[Rodd]

Just for kicks-here is the entire image.  Another reprocess, though I was not dissatisfied with the original.  But I do think the reprocess is better.

 

[Demonperformer]

People who are willing to blaze a trail into uncharted territory are sometimes going to find themselves in a dead-end. I applaud you for the attempt - definitely better to be a rhinoceros than a cow [ISBN-13: 978-0937382004]!

And I do like images of nebulae where you can actually see how they got their name without having to work too hard.

[fireballxl5]

Thanks for the feedback on your experience as I've often thought to do something along the same lines. I'll stick with my f7.3 refractor and CCD ?

Great images, love the colours!

Andy

 

[Rodd]

7 hours ago, Demonperformer said:

People who are willing to blaze a trail into uncharted territory are sometimes going to find themselves in a dead-end. I applaud you for the attempt - definitely better to be a rhinoceros than a cow [ISBN-13: 978-0937382004]!

And I do like images of nebulae where you can actually see how they got their name without having to work too hard.

I am glad you included the ISBN number--I had never heard of the book, and I thought it was a strange comparison.  Had me scratching my head with a crinkled brow.  

Rodd

[Rodd]

4 hours ago, fireballxl5 said:

Thanks for the feedback on your experience as I've often thought to do something along the same lines. I'll stick with my f7.3 refractor and CCD ?

Great images, love the colours!

Andy

 

I probably should have gone with a CCD instead of the ASI1600--but 2 things made that difficult 1) the cost of CCDs compared to the ASI 1600 and 2) the FOV of the sensor.  There isn't a CCD with small pixels that has a similar sensor size.  Don't get me wrong--I love the FSQ 106.  Maybe as much as the TOA 130.  I'm just not sure it was necessary.  I suppose a 17" rifast scope would be the way to go.

Rodd

[don4l]

Brilliant image.

 

I'm currently imaging with a similar(F3.65) set-up, but with an aged STL6303 (9 micron pixels).  I've recently realised that my pixels are far too big.  As you have pointed out, there are not any suitable CCD based cameras out there.  Currently, I am leaning towards a 16200 based camera, which would still be a compromise.

I've recently imaged the "Heart" and I compared my fish head with yours.  You have more stars, and your stars are pinpoints by comparison.  Is this purely down to image scale, or do you have a magic technique for reducing stars?

Your comments about exposure times are very interesting.   While trying to understand the importance of  image scale I compared a pair of stars in M31 that I have imaged at F3.6, F5, F8 and F10.

The stars in the F10 image were much sharper, as well as brighter [EDIT... they wern't brighter at all.  They were dimmer, but better defined].  The sharpness didn't surprise me, but I wasn't expecting them to be brighter.

Looking at your image, there are another 3 or more parts that could be presented as images in their own right.  Maybe the exposure time to collect all that data, at that resolution, would have been longer at F5???

 

 

 

 

 

 

[souls33k3r]

Mate i'm not sure what you're after but i'll take this image any day of the week/year/millennia. I know what you're saying but the results you're able to achieve with this are just spectacular. The sharpness in the nebula and the clarity is beyond belief. I agree the stars are a bit odd looking but my mind went straight on to the nebula structures and the details within it.

If only i had 1% of your brain, i'm sure i can get better. Hope to see more of your images very soon mate. Chin up and march forward

[david_taurus83]

The full image looks fantastic! Wish I could pull something like this out of the hat!

[Rodd]

2 hours ago, don4l said:

Looking at your image, there are another 3 or more parts that could be presented as images in their own right.  Maybe the exposure time to collect all that data, at that resolution, would have been longer at F5???

 

Its hard to say.  I tend to collect a lot of data regardless.  But I got the FSQ 106, .6x reducer and asi1600 to be able to shoot at f3 so I could finish an image in 1 night--like the epsilon users.  It did not work out that way!

Regarding my stars--I typically do not use mush star control.  Decent guiding, good focus and quality optics should give small stars--providing teh atmosphere is not pea soup. 

With respect to stars at varying focal ratios--I though that aperture was more critical to star sizes.  A 10" scope will reveal more stars and they will be brighter than a 4" scope all other things being equal.  Were your exposure times the same at teh various focal lengths?  did you use the same scope and camera?

Rodd

[Rodd]

1 hour ago, souls33k3r said:

Mate i'm not sure what you're after

Thanks Souls!. I was after speed--this image contains over 8 hours of data, and over 11 hours of imaging time. I was hoping to produce similar results with just 3-4 hours.  

Rodd

[Rodd]

1 hour ago, david_taurus83 said:

The full image looks fantastic! Wish I could pull something like this out of the hat!

Thanks David.  keep at it.   I am sure you can.

Rodd

[souls33k3r]

1 minute ago, Rodd said:

Thanks Souls!. I was after speed--this image contains over 8 hours of data, and over 11 hours of imaging time. I was hoping to produce similar results with just 3-4 hours.  

Rodd

I totally get that and i would expect the same too ... i mean after all the money we spend on getting a faster scopes is then of no use if we end up having the same amount of integration time to bring out the similar result. I think i might be missing something here but you're the man with a faster scope and someone with your level of experience if says something like that then there's a definite weight to it. 

[Rodd]

23 minutes ago, souls33k3r said:

I totally get that and i would expect the same too ... i mean after all the money we spend on getting a faster scopes is then of no use if we end up having the same amount of integration time to bring out the similar result. I think i might be missing something here but you're the man with a faster scope and someone with your level of experience if says something like that then there's a definite weight to it. 

Maybe things would be different at a dark sky site.  I don't know.  I am happy with the setup except for the time--but it is certainly no worse than my other setups--probably better--just not as much better as I hoped.  The star shapes do bother me a bit.  But getting to the bottom of that will require a lot of effort.  I will do it though once I get a stretch of clear nights.  If its spacing its only a mm or 2 (but I think it might be the reducer itself.  Its not teh diamond shaped ones that are at issue--its the ones in teh individual subs in the corners.  Once integrated they pretty much fix themselves.  I think teh diamond sized ones are due to teh spot size and shape of the spots as depected in eth literature for the .6x reducer.  They are only diamond shape when zoomed pretty far in--kind of like being square when undersampled.   Rodd

 

EDIT: I take that back--at full resolution in the full image they look diamondy too.  I guess that's zoomed though.  Not sure.  I can live with it for now.  

[david_taurus83]

26 minutes ago, Rodd said:

Thanks David.  keep at it.   I am sure you can.

Rodd

I have made the leap into the (financial) abyss and ordered the very same camera so we will see. There's not a hope in hell I could get a silky smooth image like that with my Canon!

[Guest]

Best examples of these objects I've seen - outstanding!

David

[Rodd]

46 minutes ago, david_taurus83 said:

I have made the leap into the (financial) abyss and ordered the very same camera so we will see. There's not a hope in hell I could get a silky smooth image like that with my Canon!

there are some amazing results out there obtained from DSLRs--modified and unmodified.  But it is allot harder.  

Rodd

[Rodd]

5 minutes ago, David_L said:

Best examples of these objects I've seen - outstanding!

David

Thanks David, much appreciated

Rodd

[souls33k3r]

3 hours ago, Rodd said:

 

Its hard to say.  I tend to collect a lot of data regardless.  But I got the FSQ 106, .6x reducer and asi1600 to be able to shoot at f3 so I could finish an image in 1 night--like the epsilon users.  It did not work out that way!

Regarding my stars--I typically do not use mush star control.  Decent guiding, good focus and quality optics should give small stars--providing teh atmosphere is not pea soup. 

With respect to stars at varying focal ratios--I though that aperture was more critical to star sizes.  A 10" scope will reveal more stars and they will be brighter than a 4" scope all other things being equal.  Were your exposure times the same at teh various focal lengths?  did you use the same scope and camera?

Rodd

I'm most definitely not a maths guy but at F3 I should expect this setup to be at least twice as fast as an F6 scope.

I sincerely do hope you get to the bottom of these diamond shape stars soon mate and without wasting any of the imaging time.

[don4l]

2 hours ago, Rodd said:

 

Its hard to say.  I tend to collect a lot of data regardless.  But I got the FSQ 106, .6x reducer and asi1600 to be able to shoot at f3 so I could finish an image in 1 night--like the epsilon users.  It did not work out that way!

Regarding my stars--I typically do not use mush star control.  Decent guiding, good focus and quality optics should give small stars--providing teh atmosphere is not pea soup. 

With respect to stars at varying focal ratios--I though that aperture was more critical to star sizes.  A 10" scope will reveal more stars and they will be brighter than a 4" scope all other things being equal.  Were your exposure times the same at teh various focal lengths?  did you use the same scope and camera?

Rodd

 

I've gone back and looked at the subs.  They were taken in 2009, 2010, and 2018, so They are not all taken under the same conditions.  The F10 image was taken on a Tal200 8" reflector, and the others were taken on an FSQ106ED.

 

I was wrong earlier about the brightness.  Things are as one would expect.  As you go up in F number, the stars have better definition, but the signal goes down, and the nebulosity disappears into the noise.  I'll go back and edit my earlier post with a note.

IMHO, you should be quite pleased with your setup.  To be able to publish a brilliant image that looks like it was taken at a much longer focal length with only 8 hours of data is quite something.

 

Thanks for posting the image, and your thoughts, because it has helped me see the issues in camera selection more clearly.

 

 

[Rodd]

13 minutes ago, don4l said:

I've gone back and looked at the subs.  They were taken in 2009, 2010, and 2018, so They are not all taken under the same conditions.  The F10 image was taken on a Tal200 8" reflector, and the others were taken on an FSQ106ED.

 

I was wrong earlier about the brightness.  Things are as one would expect.  As you go up in F number, the stars have better definition, but the signal goes down, and the nebulosity disappears into the noise.  I'll go back and edit my earlier post with a note.

IMHO, you should be quite pleased with your setup.  To be able to publish a brilliant image that looks like it was taken at a much longer focal length with only 8 hours of data is quite something.

 

Thanks for posting the image, and your thoughts, because it has helped me see the issues in camera selection more clearly.

I would definitely expect the stars in an 8" scope to be smaller than the stars in the FSQ 106 (once the images are scaled that is).  Yes--camera selection is big.  There is actually a rhyme and reason to all this...little did I know!  Looking forward to the continued adventure

Rodd

[HunterHarling]

Excellent image, Rodd! What process/script do you use to get that great color with SHO?? I usually get green and aqua.

Also, your stars are incredible compared to mine with Hyperstar.

[Demonperformer]

3 hours ago, souls33k3r said:

at F3 I should expect this setup to be at least twice as fast as an F6 scope.

I'm going to put what I understand to be @ollypenrice 's approach (tagging him so that he can correct me if I am misrepresenting him - apologies if that's the case).

A faster f ratio does not produce more photons, it just increases the area from which you are getting them. So, if I have two scopes of the same aperture, one f6 and one f3, then the f3 scope will get 4x the number of photons, but from 4x the area of sky. The number of photons that arrive from the bit of sky in which I am interested (in this case the fish-head nebula) in a given time remains the same (that's just aperture-dependant). You are just squeezing those photons onto a smaller number of pixels.

[Rodd]

3 hours ago, HunterHarling said:

Excellent image, Rodd! What process/script do you use to get that great color with SHO?? I usually get green and aqua.

Also, your stars are incredible compared to mine with Hyperstar.

Thanks Hunter.  I usually use a straight channel combination with S to red and H tyo green and O to blue.  But I do backgrounmd neutralization and color calibration and after the first stretch I use SVNR green set at average neutral.  Removes the green in a way using the histogram can't

Rodd

[Rodd]

2 hours ago, Demonperformer said:

I'm going to put what I understand to be @ollypenrice 's approach (tagging him so that he can correct me if I am misrepresenting him - apologies if that's the case).

A faster f ratio does not produce more photons, it just increases the area from which you are getting them. So, if I have two scopes of the same aperture, one f6 and one f3, then the f3 scope will get 4x the number of photons, but from 4x the area of sky. The number of photons that arrive from the bit of sky in which I am interested (in this case the fish-head nebula) in a given time remains the same (that's just aperture-dependant). You are just squeezing those photons onto a smaller number of pixels.

True, but I asked Olly if reducers reduce exposure times for extended objects and he said they did.  If you use a 6" scope at F7 and the same 6" scope at F3--the integration times needed to produce an image at F3 will be less.  This is due in part yo a reduced resolution--so less information--but a bigger FOV.  But accortding to Olly--reducers DO REDUCE EXPOSURE TIMES

Rodd