The "No EQ" DSO Challenge!

[Stub Mandrel]

2 minutes ago, SilverAstro said:

interesting that you should raise that - my first polar disc mount used a strut + wheel hub off a Ford Zodiac, amongst other bits and pieces !

But cars are not usually steered with arc second accuracy

 

It's interesting to speculate what the sources of inaccuracy might be.

The quality of the bearings (i.e. how accurate they are and how well they allow small movements) is not the same as their load-bearing capacity. I doubt that even my plain bearing EQ3 mount droops measurably under the overhanging weight of the gear, certainly less than the EQ5 tripod flexes. In fact the scope tube probably flexes more than the mount as its attitude changes.

I bet periodic errors in the worm of entry-level mounts swamp everything else.

[The Admiral]

10 hours ago, SilverAstro said:

But cars are not usually steered with arc second accuracy

Speak for yourself 

Ian

[Nigel G]

Last night I had nothing to do but worry and the sky's were clear. So I  decided to try my camera and 55mm lense on the mount. Starting around 11pm I thought I'd get 2 or 3 hours subs on ngc7000 wide field. 

I aligned the mount with the scope then swapped to the camera.  The first thing I noticed was not one sub was unusable , I took a couple of quick 10s to get my bearings. Then a couple of 45s, no visible trails but quite a bit of street light pollution, not as bad as with the scope though. So I  dropped the subs to 30s. 

Every sub was good, the only trouble was they started to fade in detail after about 20 minutes? I thought it must be dew on the lense, a quick check and no dew? What the heck. 

Look up you fool it's getting cloudy ?

So this image is only a tad over 20 minutes exposure with dark and bias. DSS and StarTools. Canon 1200d 55mm lense F 5.3 1600 iso on alt-az mount.

There is bags of potential for wide field imaging. I'm hoping tonight will be better to add to the data. The forecast is good. With a couple of hours subs I think much more detail will come.

Another thing I noticed was the rotation appeared to be much less  ( impossible but )

The stars are smaller and the field bigger probably making the rotation less obvious. Normally when I scroll through the raw images there's a very apparent field rotation, with these I could see no rotation but there is only 25 minutes total imaging time.

I have cropped about 20% around the image. The second image has had a touch of noise reduction and contrast . 

Nige.

[happy-kat]

I am a fan of wide field. I use a home made dew shield made from a flocked flower pot for my lenses.

Does open the door for a nice 200mm camera lens on your mount. I only had one go with the virtuoso and a lens before becoming too late for darkness.

[happy-kat]

And you can make an aperture mask if you don't want detraction spikes. It would make a near refractor experience.

Edited July 14, 2016 by happy-kat

[Nigel G]

1 hour ago, happy-kat said:

And you can make an aperture mask if you don't want detraction spikes. It would make a near refractor experience.

Aperture mask for my scope , wouldn't that reduce the field of view? 

I just looked up aperture masks,  now would I need to make a hole as big as possible for my scope?  ie missing the secondary mirror and supports.

also the scope cover cap has a small cap on it about 2.5 " diameter would that be of any use ?

Talking of aperture what would a good setting be with camera lenses for dso's, higher or lower value. I set mine on lowest value for this image. 

I like the dew shield flowerpot ☺I had a simular idea last night with a small lightweight resin pot.

Nige.

[happy-kat]

No aprature mask for a camera lens. Only needs to be card board to create a lens stop down with no defection spikes, so as an example a 200mm lens would give a near refractor experience.

You can work out for your lens what to stop it down by, night use is more aggressive so lens soft edges will show more so stop down what ever is needed to get reasonable across frame nice star shapes which is also helped by focusing on a star at the thirds intersection, focusing on a star in the middle/centre is worst creating for soft outer stars.

This is where I find it helpful having my 7 inch tablet connected to my camera for focusing.

Edited July 14, 2016 by happy-kat

[Nigel G]

I had a chance to get about 1 hour 40 minutes of subs on the North American nebula with the 55mm lense a few nights ago, nice clear sky's but before 1am so street light pollution had to be delt with. The subs were 120 x 30s the rest 45s , plus 30 dark frames and the usual bias. Star discovery mount, Canon eos 1200d with standard lense at 55mm, iso 1600 f5.6 with a converted flowerpot dew shield  ( which worked great ) DSS and StarTools. 

I have posted 2 images, one with the stars reduced.

Taking into account the camera is the cheap end of the dslr range and you can't get much cheaper alt az goto mounts this has turned out pretty good. 

I think I need to add a half decent 200mm lense to the collection. 

When I see the size of this nebula I realise it would take around 8 to 10 images from the scope stitched together to get the whole picture. 

Nige.

 

[Stub Mandrel]

Great star colour as well.

I think I prefer the one with unreduced stars; perhaps blend the two together to get around 60:40 the first one?

[Nigel G]

28 minutes ago, Stub Mandrel said:

Great star colour as well.

I think I prefer the one with unreduced stars; perhaps blend the two together to get around 60:40 the first one?

Modern software and digital images makes editing easy these days, It's really quite difficult to get an image with its true colours and shades though ☺

[happy-kat]

Ooh that is very nice, this is what I'll be trying my virtuoso mount on when it gets earlier to do. dslr and lens imaging.

[SilverAstro]

Very good !     +1 for the first one, unreduced.

 

[wxsatuser]

10 hours ago, Nigel G said:

Modern software and digital images makes editing easy these days, It's really quite difficult to get an image with its true colours and shades though ☺

 

If your imaging low down in the sky the colours become more orange.

One thing, if you want correct colours with a dslr do not equalize the histogram and do not modify the camera.
Modifying just makes nebulae more red and tends to hide all the other colours like blue and green.
If a dslr can see 20 to 30% of Ha, thats more than enough, modifying should only be done to cameras that see next to nothing of Ha.

There is a way to better your images but it means more money, you get what you pay for.

A 6D or 7DMK2 coupled to a fast lens will allow stunning short images.

An example with an unmodded  6D at f/2.8 50mm 7 x 30sec exposures ISO 1600.
Not properly processed as it was just a test but you can see what I mean.

 

 

10 hours ago, Nigel G said:

 

 

[happy-kat]

Thank you for sharing your practical approach to the need, or not, to modifying a dslr.

[SilverAstro]

10 hours ago, wxsatuser said:

Modifying just makes nebulae more red and tends to hide all the other colours like blue and green.If a dslr can see 20 to 30% of Ha, thats more than enough, modifying should only be done to cameras that see next to nothing of Ha.

An example with an unmodded  6D at f/2.8 50mm 7 x 30sec exposures ISO 1600.
Not properly processed as it was just a test but you can see what I mean.

A very nice example, yes I see !

As I am trying to decide between a 1200d{mod or maybe not} , a 1300d{not}, or a 100d{not} but not got  a clue about their %Ha ! (and I dont think Curry's will be able to help ! ) where would be a good place to get this info ?

Apart from Nige's excellent work ,, another pic some time ago, I forget where, was of Barnard's Loop next Orion, and in mod/not mod comparison the loop was not visible at all without the mod, now I am kicking myself cos I did not note the make of that camera

 

[Stub Mandrel]

Sent a while trying to get the Veil to emerge from a stack. Thought it looked a bit short on stars.

Put the result into Astometry.net and it turns out the scope had made the goto move exactly twice - I think I know what I did wrong.

There are two tiny galaxies right on the edge, but I can barely see them.

I was tempted to start a new thread "The No DSO EQ Challenge"

[wxsatuser]

3 hours ago, SilverAstro said:

A very nice example, yes I see !

As I am trying to decide between a 1200d{mod or maybe not} , a 1300d{not}, or a 100d{not} but not got  a clue about their %Ha ! (and I dont think Curry's will be able to help ! ) where would be a good place to get this info ?

Apart from Nige's excellent work ,, another pic some time ago, I forget where, was of Barnard's Loop next Orion, and in mod/not mod comparison the loop was not visible at all without the mod, now I am kicking myself cos I did not note the make of that camera

 

I don't know of a definitive site that can tell exactly how each camera reacts to Ha.
If in doubt I would most likely take the modded approach

I can definately say the 6D and 7DMK2 see enough Ha that modding is not necessary
but it's down to personal taste in the end.

[SilverAstro]

1 hour ago, wxsatuser said:

I don't know of a definitive site that can tell exactly even approx would be a good start how each camera reacts to Ha.
If in doubt I would most likely take the modded approach

I can definately say the 6D and 7DMK2 see enough Ha that modding is not necessary
but it's down to personal taste in the end.

In the end I suppose I could buy one of each and try them ! Oh, hang on an idea is germinating, , , , "try them"  measure them !! Nige, Admiral, me and others I am sure like a good experiment soooo being as there are many owners of many models, mod and not mod, on the forum  can the collective come up with a standard model (standard target?) and standard method free of user bias to determine the %Ha  for each ?

Henceforth to be known as the loadsaHa challenge   " %Ha Challenge"

Edit PS is it a bit odd that Canon have different filters for different models ? For viz light cameras one would have thought that they would have determined an optimum cut-off and stuck to it through the range ??

EDIT 2 ) A. a reflection and emission nebula in close proximity, ie. a convenient field frame size

 B. stacking OK ? but no curves / gamma etc.

 C. ?

 

Edited July 18, 2016 by SilverAstro

[Nigel G]

2 hours ago, SilverAstro said:

In the end I suppose I could buy one of each and try them ! Oh, hang on an idea is germinating, , , , "try them"  measure them !! Nige, Admiral, me and others I am sure like a good experiment soooo being as there are many owners of many models, mod and not mod, on the forum  can the collective come up with a standard model (standard target?) and standard method free of user bias to determine the %Ha  for each ?

Henceforth to be known as the loadsaHa challenge   " %Ha Challenge"

Edit PS is it a bit odd that Canon have different filters for different models ? For viz light cameras one would have thought that they would have determined an optimum cut-off and stuck to it through the range ??

EDIT 2 ) A. a reflection and emission nebula in close proximity, ie. a convenient field frame size

 B. stacking OK ? but no curves / gamma etc.

 C. ?

 

A good idea, certainly should gather some useful information,  something like orion neb although that's a few months off yet, 

30 minutes of subs  limit  ? Although light pollution in different areas could play a part in the result. Plus aperture. 

Still a good idea and worth trying. 

Nige.

[SilverAstro]

29 minutes ago, Nigel G said:

A good idea, certainly should gather some useful information,  something like orion neb although that's a few months off yet, 

30 minutes of subs  limit  ? Although light pollution in different areas could play a part in the result. Plus aperture.

Yes, Orion in the offing that is indeed why I am contemplating a new camera, be prepared, boyscouts etc initially for wide field.

Thanks for your suggestions. My initial thoughts are for a nebula in which the two regions are reasonably distinct ( not overlaid or jumbled up ! ) such that the reflection could be used as a broad spectrum reference level and the Ha signal amplitude compared to it. So aperture should affect them both equally ?(I think ?)

Light pollution hmmm yes good thinking that could be a bit of a nuisance (!) to quantify, especially if the pollution had strong emission near Ha (??) and it would rule out pollution filters I suppose - that could be a bit of a killer of the whole idea

A limit on subs, yes another problem area, if the sensor was differentially non-linear ? are they, I am rapidly getting outa my depth here !

 

Edited July 19, 2016 by SilverAstro

[Alien 13]

My gut feeling is that Canon may have tweaked the HA response on models post 60Da my 650D certainly has no problem but the downside is getting optics lens/scope that can bring HA and RGB into focus at the same time.

Alan

[The Admiral]

11 hours ago, SilverAstro said:

In the end I suppose I could buy one of each and try them ! Oh, hang on an idea is germinating, , , , "try them"  measure them !! Nige, Admiral, me and others I am sure like a good experiment soooo being as there are many owners of many models, mod and not mod, on the forum  can the collective come up with a standard model (standard target?) and standard method free of user bias to determine the %Ha  for each ?

Henceforth to be known as the loadsaHa challenge   " %Ha Challenge"

Edit PS is it a bit odd that Canon have different filters for different models ? For viz light cameras one would have thought that they would have determined an optimum cut-off and stuck to it through the range ??

EDIT 2 ) A. a reflection and emission nebula in close proximity, ie. a convenient field frame size

 B. stacking OK ? but no curves / gamma etc.

 C. ?

 

That might provide some useful information though I think one would need to think about the strategy in order to minimize conflicting factors.

Of course, it's not just astrophotographers who are interested in the red response, there are a number of 'conventional' photographers who are involved in infra-red photography, so there ought to be quite a bit of data around about the responses of various cameras. This link (which I found on another thread here on SGL) provides some useful transmission curves for a limited number of DSLR low-pass filters. May be that doesn't take into account the intrinsic efficiency of the silicon, but at least cameras with a poor transmission in the infra-red are unlikely to be good contenders.

I use a Fuji X-T1, hardly mainstream in astrophotography, which uses the same sensor as in the X-Pro1 and is shown as having an efficiency ~40%* at 656nm.

Ian

*Edit. Perhaps I should say, the filter shows a transmission of ~ 40%

Edited July 19, 2016 by The Admiral

[Nigel G]

On Monday, July 18, 2016 at 06:38, wxsatuser said:

If your imaging low down in the sky the colours become more orange.

One thing, if you want correct colours with a dslr do not equalize the histogram and do not modify the camera.
Modifying just makes nebulae more red and tends to hide all the other colours like blue and green.
If a dslr can see 20 to 30% of Ha, thats more than enough, modifying should only be done to cameras that see next to nothing of Ha.

There is a way to better your images but it means more money, you get what you pay for.

A 6D or 7DMK2 coupled to a fast lens will allow stunning short images.

An example with an unmodded  6D at f/2.8 50mm 7 x 30sec exposures ISO 1600.
Not properly processed as it was just a test but you can see what I mean.

 

 

 

Looking at this image  and my attempt it looks like I have a shed load of noise,  what is going on,  my image shows far more apparent nebulosity which isn't on other images. Is that noise ? Have I hit a brick wall? 

I have been experimenting with M31 . I have 60 minutes of good 30s  subs and 60 minutes of mixed 45s ( some have quite heavy light pollution  some have moon light interference  some are  good) I have stacked 4 different sets of images. 

1st , 1 hour of 30s........2nd 1 hour of 30s plus 30 minutes of street light polluted 45s.........3rd 1 hour of 30s plus 30 minutes taken with full moon up........ and 4th everything stacked 2h exposure. 

I still have to process the 2 hour image but there's hardly any difference if any between the images already processed,.

Have I reached the limit of my camera or scope ?  I notice the central 30% of my images seems to be good in detail  but outside that a quick loss of detail.

Camera or scope or both ?  

At the moment I can't seem to improve my images,  have I come to the point where upgrades are needed?

I'll post the M31  images once completed. 

Nige. 

[The Admiral]

Remind us what camera you are using please Nige.

Ian

[The Admiral]

And don't forget Nige, that if you're are using your 'scope then the number of photons per pixel is going to be a lot less than wxsatuser's, because the focal length he was using is only 50mm, at least an order of magnitude less than yours. It will also depend on how good your sensor is noise-wise.

Ian

Edit. Thinks!! Actually, that may not be the case as the diameter of your 'scope is a lot bigger than the camera lens, so admits more photons in the first place. The number of photons per pixel, which is the important thing, is proportional to (D squared) ÷ (f squared), where D is the diameter of the OG and f is its focal length. A shorter focal length, for the same diameter, is always going to give you a brighter image, albeit at the expense of a wider field.

Edited July 19, 2016 by The Admiral