Re: First DSLR shots through TEC 140


May 11, 2013

 


----------------------------

#23790 May 11, 2013

Hi Group,

I have been a longtime CCD imager, and initially got my 60Da for nightscapes while traveling to national parks. I have recently begun using it on my TEC140, and am quite impressed with what can be obtained in under 90 minutes. I was pleased to find that my Maxim DL software included DSLR control, and Focus Max worked flawlessly. I was also impressed with the round tight stars throughout the field.



Two of my first images are at

www.stardoctor.org/M101d.html

www.stardoctor.org/eagled.html

If you don't want to hear the music (at work or kids sleeping) make sure to mute your computer sound first.



Comments are welcome and encouraged.



Ruben

www.stardoctor.org



----------------------------

#23791 May 12, 2013

Ruben,



These are beautiful images indeed, especially with so short integrations!



Do you use a Field flattener?



Daniel

>Hi Group,

>I have been a longtime CCD imager, and initially got my 60Da for

>nightscapes while traveling to national parks. I have recently

>begun using it on my TEC140, and am quite impressed with what can be

>obtained in under 90 minutes. I was pleased to find that my Maxim DL

>software included DSLR control, and Focus Max worked flawlessly. I

>was also impressed with the round tight stars throughout the field.

>

>Two of my first images are at

>www.stardoctor.org/M101d.html

>www.stardoctor.org/eagled.html

>If you don't want to hear the music (at work or kids sleeping) make

>sure to mute your computer sound first.

>

>Comments are welcome and encouraged.

>

>Ruben

>www.stardoctor.org



--

Daniel Borcard

Observatoire du Geai Bleu

Recent images: biol09.biol.umontreal.ca/borcardd/astro/imagesastro/?M=D

Web site (in urgent need of update):

biol09.biol.umontreal.ca/borcardd/astro/astro.html

Clear Sky Chart: cleardarksky.com/c/ObGBlQCkey.html?1

---------------



----------------------------

#23792 May 12, 2013

- very nice, Ruben.

Does the 60Da makes imaging much easier?

Yuri

--- In tec-scopes@yahoogroups.com, "Ruben" stardoctor5@...> wrote:

>

> Hi Group,

> I have been a longtime CCD imager, and initially got my 60Da for nightscapes while traveling to national parks. I have recently begun using it on my TEC140, and am quite impressed with what can be obtained in under 90 minutes. I was pleased to find that my Maxim DL software included DSLR control, and Focus Max worked flawlessly. I was also impressed with the round tight stars throughout the field.

>

> Two of my first images are at

> www.stardoctor.org/M101d.html

> www.stardoctor.org/eagled.html

> If you don't want to hear the music (at work or kids sleeping) make sure to mute your computer sound first.

>

> Comments are welcome and encouraged.

>

> Ruben

> www.stardoctor.org

>



----------------------------

#23793 May 12, 2013

Daniel,

I do not use a field flattener. However, the chip on my Canon 60Da is APS-C, only a tiny bit larger than my QSI-583. The edges of my current image, at full resolution, are beginning to show a bit of oval stars at the very edge. If I were to use a full field chip (like on the Canon 5D or 6D), then I would likely want a field flattener.



Ruben

www.stardoctor.org

--- In tec-scopes@yahoogroups.com, Daniel Borcard daniel.borcard@...> wrote:

>

> Ruben,

>

> These are beautiful images indeed, especially with so short integrations!

>

> Do you use a Field flattener?

>

> Daniel

>

> >Hi Group,

> >I have been a longtime CCD imager, and initially got my 60Da for

> >nightscapes while traveling to national parks. I have recently

> >begun using it on my TEC140, and am quite impressed with what can be

> >obtained in under 90 minutes. I was pleased to find that my Maxim DL

> >software included DSLR control, and Focus Max worked flawlessly. I

> >was also impressed with the round tight stars throughout the field.

> >

> >Two of my first images are at

> >www.stardoctor.org/M101d.html

> >www.stardoctor.org/eagled.html

> >If you don't want to hear the music (at work or kids sleeping) make

> >sure to mute your computer sound first.

> >

> >Comments are welcome and encouraged.

> >

> >Ruben

> >www.stardoctor.org

>

> --

> Daniel Borcard

> Observatoire du Geai Bleu

> Recent images: biol09.biol.umontreal.ca/borcardd/astro/imagesastro/?M=D

> Web site (in urgent need of update):

> biol09.biol.umontreal.ca/borcardd/astro/astro.html

> Clear Sky Chart: cleardarksky.com/c/ObGBlQCkey.html?1

---------------

>



----------------------------

#23794 May 12, 2013

Hi Yuri,

The 60Da, like any single shot color, can simplify some aspects of imaging. For example:

1. Only one set of flats is needed, instead of Red, Green, Blue, and luminance flats.

2. For getting a sigma combine, one needs at least 5 images. So if I am shooting CCD RGB, then I would need at least 15 exposures, and many times clouds come rolling in before I get the third channel. With single shot color, I can plan on 12 images of 5-10 minutes, and if the clouds come in earlier, I can still salvage an image after just 5 exposures.

3. The latest DSLR cameras are very low noise, and with darks/flast/dithering, most of the noise seems to vanish on bright deep sky objects even without cooling.



BUT,



1. DSLR is okay for bright deep sky objects, which I identify for about half of the 100 Best Targets for Astrophotography, that I detail in my book Finding a dim object, especially a dim sharpless nebula, would be almost impossible with a DSLR. With a cooled CCD (and Ha filter for dim emission nebulae), that can be set to 4x4 or 9x9 binning, finding and centering a deep sky object is much easier.

2. The Canon 60Da and modified DSLR cameras have better sensitivity for H-alpha than standard DSLR's that cut off the deep red, but that does not match the S/N of a cooled CCD with an Ha filter.

3. Really dim objects, with low S/N, would get overwhelmed by thermal signal in an uncooled DSLR. That is why some CCD cameras, that can be cooled to very low temperatures, are much better for narrow band imaging.

4. If the telescope is not a true apochromat (ie...brand x), single shot color will show color fringing and bloated stars because red, green and blue light might not come to the same focus, that would not appear in RGB imaging which can focus each color channel separately. With a true apochromat like the TEC 140, this is not a problem.

5. Near the horizon, differential diffraction (also called dispersion) of red, green, and blue will lead to color fringing on a DSLR, that would not occur with CCD RGB imaging. I discussed this in my article "Shooting Low," Sky & Telescope, July 2010, and also in my book.



Ruben

www.stardoctor.org

--- In tec-scopes@yahoogroups.com, "Yuri" tec@...> wrote:

>

>

> - very nice, Ruben.

> Does the 60Da makes imaging much easier?

> Yuri

>

> --- In tec-scopes@yahoogroups.com, "Ruben" stardoctor5@> wrote:

> >

> > Hi Group,

> > I have been a longtime CCD imager, and initially got my 60Da for nightscapes while traveling to national parks. I have recently begun using it on my TEC140, and am quite impressed with what can be obtained in under 90 minutes. I was pleased to find that my Maxim DL software included DSLR control, and Focus Max worked flawlessly. I was also impressed with the round tight stars throughout the field.

> >

> > Two of my first images are at

> > www.stardoctor.org/M101d.html

> > www.stardoctor.org/eagled.html

> > If you don't want to hear the music (at work or kids sleeping) make sure to mute your computer sound first.

> >

> > Comments are welcome and encouraged.

> >

> > Ruben

> > www.stardoctor.org

> >

>







----------------------------

#23795 May 12, 2013

Hi Ruben,

thank you for detailed answer, which I will forward to a friend, who likes to do imaging with DCLR.

Regards, Yuri

--- In tec-scopes@yahoogroups.com, "Ruben" stardoctor5@...> wrote:

>

> Hi Yuri,

> The 60Da, like any single shot color, can simplify some aspects of imaging. For example:

> 1. Only one set of flats is needed, instead of Red, Green, Blue, and luminance flats.

> 2. For getting a sigma combine, one needs at least 5 images. So if I am shooting CCD RGB, then I would need at least 15 exposures, and many times clouds come rolling in before I get the third channel. With single shot color, I can plan on 12 images of 5-10 minutes, and if the clouds come in earlier, I can still salvage an image after just 5 exposures.

> 3. The latest DSLR cameras are very low noise, and with darks/flast/dithering, most of the noise seems to vanish on bright deep sky objects even without cooling.

>

> BUT,

>

> 1. DSLR is okay for bright deep sky objects, which I identify for about half of the 100 Best Targets for Astrophotography, that I detail in my book Finding a dim object, especially a dim sharpless nebula, would be almost impossible with a DSLR. With a cooled CCD (and Ha filter for dim emission nebulae), that can be set to 4x4 or 9x9 binning, finding and centering a deep sky object is much easier.

> 2. The Canon 60Da and modified DSLR cameras have better sensitivity for H-alpha than standard DSLR's that cut off the deep red, but that does not match the S/N of a cooled CCD with an Ha filter.

> 3. Really dim objects, with low S/N, would get overwhelmed by thermal signal in an uncooled DSLR. That is why some CCD cameras, that can be cooled to very low temperatures, are much better for narrow band imaging.

> 4. If the telescope is not a true apochromat (ie...brand x), single shot color will show color fringing and bloated stars because red, green and blue light might not come to the same focus, that would not appear in RGB imaging which can focus each color channel separately. With a true apochromat like the TEC 140, this is not a problem.

> 5. Near the horizon, differential diffraction (also called dispersion) of red, green, and blue will lead to color fringing on a DSLR, that would not occur with CCD RGB imaging. I discussed this in my article "Shooting Low," Sky & Telescope, July 2010, and also in my book.

>

> Ruben

> www.stardoctor.org

>

> --- In tec-scopes@yahoogroups.com, "Yuri" tec@> wrote:

> >

> >

> > - very nice, Ruben.

> > Does the 60Da makes imaging much easier?

> > Yuri

> >

> > --- In tec-scopes@yahoogroups.com, "Ruben" stardoctor5@> wrote:

> > >

> > > Hi Group,

> > > I have been a longtime CCD imager, and initially got my 60Da for nightscapes while traveling to national parks. I have recently begun using it on my TEC140, and am quite impressed with what can be obtained in under 90 minutes. I was pleased to find that my Maxim DL software included DSLR control, and Focus Max worked flawlessly. I was also impressed with the round tight stars throughout the field.

> > >

> > > Two of my first images are at

> > > www.stardoctor.org/M101d.html

> > > www.stardoctor.org/eagled.html

> > > If you don't want to hear the music (at work or kids sleeping) make sure to mute your computer sound first.

> > >

> > > Comments are welcome and encouraged.

> > >

> > > Ruben

> > > www.stardoctor.org

> > >

> >

>



----------------------------

#23796 May 13, 2013

Ruben,I image with a modified DSLR through my TEC 140 as well, and I agree completely with what you are saying. .I have a Gary Honis modified T1i. .It's the same sensor, but your camera most probably has less noise than mine. .Orion sells a cooler for a DSLR but frankly, it's way overpriced in my opinion. .Gary Honis on his website has a DIY instruction step by step in making your own. .I just haven't bothered as yet.

But for brighter images, the system works amazingly well and quickly. .In our Virtual Star Party last night I was able to get several bright images with single shot 1-2 minute exposures only.Here is an M51 that I worked on. .

But for dimmer images, it's more of a challenge, especially in my suburban skies. .I have an Astronomik clip in CLS light pollution filter, which helps, but it's not perfect by any means. .

In terms of the field flattener question, at the very edges there is some spherical aberration, which you can see here. Frankly, though, it's not enough for me to worry about and certainly not enough to buy a field flattener. I usually crop out the edges of the picture anyway because of stacking artifact. . I find that the focal reducer, when I use it (I didn't on these shots), seems to take care of it okay anyway.

Stuart



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