Trying to associate exposure length for different limiting magnitudes

alexisgreat said:

I have a question about light pollution. My limiting magnitude is about 4, and I'm trying to figure out what the longest exposure per single frame should be before light pollution overwhelms shutter speed and I can no longer capture any dimmer stars. I'm not necessarily looking for the darkest background, but for where increasing the shutter speed no longer lets me capture fainter stars. Is there any kind of association or equation that lets me figure out what the longest exposure should be for a given limiting magnitude? In my Mag 4 skies, and to my eyes, it seems that 20 second exposures at ISO 1600 and f/3.5 seem to be it, longer exposures than that (for example 30 seconds) and the whole background seems to be as bright as the stars. I went the other way too, and found that exposures of 8 seconds at ISO 1600 and f/3.5, while giving me a nice dark background (although still not black), also showed me fewer stars. For stacking purposes is it better to make the background dark or try to squeeze as many dim stars as you can per frame and go for a longer exposure that will show dimmer stars but also make the background sky look a very annoying orange?

I'll give an example for what I'm looking for- so let's say that in my Mag 4 skies I can do 20 sec ISO 1600 exposures at f/3.5. I am within 2 hours of Mag 6.5 skies which I can drive to. Since the difference between Mag 4 and Mag 6.5 is about 10x (2.512^2.5), does that mean I can do exposures 10 times longer at the dark site before light pollution washes out the image? If so, this would mean I can do 200 second exposures at ISO 1600 and f/3.5 at the dark site before light pollution prevents me from capturing any dimmer stars at longer exposures. This is all pending trying to figure out if trying to squeeze out as many dim stars per frame is better to capturing fewer stars but retaining a dark background for stacking purposes. Thanks!

I found this, but it seems to be more applicable for film:

http://www.astropix.com/HTML/I_ASTROP/FILM/EXPOSURE.HTM

Also found this which recommends lots of stacking and very short 4 sec exposures at f/2.8 and ISO 1600.

http://www.samirkharusi.net/sub-exposures.html

http://www.starrywonders.com/snr.html

Click to expand...

RustierOne said:

alexisgreat said:

I have a question about light pollution. My limiting magnitude is about 4, and I'm trying to figure out what the longest exposure per single frame should be before light pollution overwhelms shutter speed and I can no longer capture any dimmer stars. I'm not necessarily looking for the darkest background, but for where increasing the shutter speed no longer lets me capture fainter stars. Is there any kind of association or equation that lets me figure out what the longest exposure should be for a given limiting magnitude? In my Mag 4 skies, and to my eyes, it seems that 20 second exposures at ISO 1600 and f/3.5 seem to be it, longer exposures than that (for example 30 seconds) and the whole background seems to be as bright as the stars. I went the other way too, and found that exposures of 8 seconds at ISO 1600 and f/3.5, while giving me a nice dark background (although still not black), also showed me fewer stars. For stacking purposes is it better to make the background dark or try to squeeze as many dim stars as you can per frame and go for a longer exposure that will show dimmer stars but also make the background sky look a very annoying orange?

I'll give an example for what I'm looking for- so let's say that in my Mag 4 skies I can do 20 sec ISO 1600 exposures at f/3.5. I am within 2 hours of Mag 6.5 skies which I can drive to. Since the difference between Mag 4 and Mag 6.5 is about 10x (2.512^2.5), does that mean I can do exposures 10 times longer at the dark site before light pollution washes out the image? If so, this would mean I can do 200 second exposures at ISO 1600 and f/3.5 at the dark site before light pollution prevents me from capturing any dimmer stars at longer exposures. This is all pending trying to figure out if trying to squeeze out as many dim stars per frame is better to capturing fewer stars but retaining a dark background for stacking purposes. Thanks!

I found this, but it seems to be more applicable for film:

http://www.astropix.com/HTML/I_ASTROP/FILM/EXPOSURE.HTM

Also found this which recommends lots of stacking and very short 4 sec exposures at f/2.8 and ISO 1600.

http://www.samirkharusi.net/sub-exposures.html

http://www.starrywonders.com/snr.html

Click to expand...

Click to expand...

alexisgreat said:

RustierOne said:

alexisgreat said:

I have a question about light pollution. My limiting magnitude is about 4, and I'm trying to figure out what the longest exposure per single frame should be before light pollution overwhelms shutter speed and I can no longer capture any dimmer stars. I'm not necessarily looking for the darkest background, but for where increasing the shutter speed no longer lets me capture fainter stars. Is there any kind of association or equation that lets me figure out what the longest exposure should be for a given limiting magnitude? In my Mag 4 skies, and to my eyes, it seems that 20 second exposures at ISO 1600 and f/3.5 seem to be it, longer exposures than that (for example 30 seconds) and the whole background seems to be as bright as the stars. I went the other way too, and found that exposures of 8 seconds at ISO 1600 and f/3.5, while giving me a nice dark background (although still not black), also showed me fewer stars. For stacking purposes is it better to make the background dark or try to squeeze as many dim stars as you can per frame and go for a longer exposure that will show dimmer stars but also make the background sky look a very annoying orange?

I'll give an example for what I'm looking for- so let's say that in my Mag 4 skies I can do 20 sec ISO 1600 exposures at f/3.5. I am within 2 hours of Mag 6.5 skies which I can drive to. Since the difference between Mag 4 and Mag 6.5 is about 10x (2.512^2.5), does that mean I can do exposures 10 times longer at the dark site before light pollution washes out the image? If so, this would mean I can do 200 second exposures at ISO 1600 and f/3.5 at the dark site before light pollution prevents me from capturing any dimmer stars at longer exposures. This is all pending trying to figure out if trying to squeeze out as many dim stars per frame is better to capturing fewer stars but retaining a dark background for stacking purposes. Thanks!

I found this, but it seems to be more applicable for film:

http://www.astropix.com/HTML/I_ASTROP/FILM/EXPOSURE.HTM

Also found this which recommends lots of stacking and very short 4 sec exposures at f/2.8 and ISO 1600.

http://www.samirkharusi.net/sub-exposures.html

http://www.starrywonders.com/snr.html

--
https://supermanalexthegreat.shutterfly.com/

Click to expand...

Roger Clark's page on Nightscape Photography is extensive and has some interesting tables if you scroll way down.

--
Best Regards,
Russ

Click to expand...

Thanks, Russ. I'll check that out. Question, do different types of nights have different levels of exposure that one can do before light pollution becomes too intrusive? Basically I am asking if weather also plays a role. I spent 3 hours each outside on three separate nights, all three were absolutely clear. But one night it was really windy, another night it was dead calm and the third night it was breezy. The windy night the winds were gusting to 40 mph and the breezy night they were in the 15 mph range. The calm night they were under 5 mph. On the really windy night I was able to image to 20 sec shutter speed, on the calm night it was to 15 sec shutter speed and on the breezy night I was able to go all the way to 30 seconds shutter speed! The ISO and aperture were 1600 and f/3.5 for all three. Maybe it's also a matter of luck and I just happened to catch the right moment when 30 seconds turned out to work? I made sure to wait until around midnight all three nights so the levels of light pollution were the same all three nights.

Click to expand...

rnclark said:

I did an update to the limiting magnitude section and now include equations. See Table 2 and associated discussion at:
http://www.clarkvision.com/articles/nightscapes/

Click to expand...

Trollmannx said:

rnclark said:

I did an update to the limiting magnitude section and now include equations. See Table 2 and associated discussion at:
http://www.clarkvision.com/articles/nightscapes/

Click to expand...

And taking some test images to get an idea is also great - the math will tell a lot and so will hands on experience. A fine way to learn!

Click to expand...

rnclark said:

Trollmannx said:

rnclark said:

I did an update to the limiting magnitude section and now include equations. See Table 2 and associated discussion at:
http://www.clarkvision.com/articles/nightscapes/

Click to expand...

And taking some test images to get an idea is also great - the math will tell a lot and so whands on experience. A fine way to learn!

Click to expand...

Well, of course you need test images to find the constant K in the equation that applies to your camera sensitivity and sky conditions. Once you find the constant that works best for your imaging, then you can use the equations to predict for other exposure times and apertures.

Roger

Click to expand...

rnclark said:

I did an update to the limiting magnitude section and now include equations. See Table 2 and associated discussion at:
http://www.clarkvision.com/articles/nightscapes/

Click to expand...

alexisgreat said:

I have to wonder- are cameras more important now for astronomy than telescopes are? I'm talking specifically for the amateur section (8 inches or less aperture).....it seems that cameras can now reach what an 8 inch aperture can do pretty easily with exposures of 30 seconds? AND cameras show color, which is often hard to do with even an 8 inch telescope.

--
https://supermanalexthegreat.shutterfly.com/

Click to expand...

swimswithtrout said:

alexisgreat said:

I have to wonder- are cameras more important now for astronomy than telescopes are? I'm talking specifically for the amateur section (8 inches or less aperture).....it seems that cameras can now reach what an 8 inch aperture can do pretty easily with exposures of 30 seconds? AND cameras show color, which is often hard to do with even an 8 inch telescope.

--
https://supermanalexthegreat.shutterfly.com/

Click to expand...

Please think before you post ... Without a lens, a camera is completely useless. My "lens" is an 8" f4 and no matter what camera you couple it with, it will always beat any 200-400mm f4 "camera lens" there is when used on the same camera. The rest of your post is completely nonsensical.

Click to expand...

alexisgreat said:

rnclark said:

I did an update to the limiting magnitude section and now include equations. See Table 2 and associated discussion at:
http://www.clarkvision.com/articles/nightscapes/

Click to expand...

Thanks, I find all your tables VERY useful Roger. And seeing some of the great images posted here and how low we can go in limiting magnitude, I have to wonder- are cameras more important now for astronomy than telescopes are? I'm talking specifically for the amateur section (8 inches or less aperture).....it seems that cameras can now reach what an 8 inch aperture can do pretty easily with exposures of 30 seconds? AND cameras show color, which is often hard to do with even an 8 inch telescope. I've just found images taken with cameras on here much more pleasing to my eyes than what I've seen through a telescope and wonder if a camera with a good lens will replace 8 inch and smaller telescopes. Of course for the planets and such objects that need a lot of magnification, a telescope will be best, but for wide starfields and DSO imaging of extended objects, I find camera images much more pleasing than what I see with my eyes through a telescope.

Click to expand...

• Naked eye - the premium wide-field visual instrument
• Fisheye lens - the widest lens for all-sky photography
• Wide-angle lens - good for photographing larger objects, such as Milky Way star clouds
• Telephoto lens - best for some of the larger deep-sky objects
• Small, wide-angle refractors - optimum for DSOs of lessor angular size
• Telescopes, of various apertures and focal lengths - for objects appropriate for their FOV

RustierOne said:

alexisgreat said:

rnclark said:

I did an update to the limiting magnitude section and now include equations. See Table 2 and associated discussion at:
Nightscape Photography with Digital Cameras, Clarkvision.com

Click to expand...

Thanks, I find all your tables VERY useful Roger. And seeing some of the great images posted here and how low we can go in limiting magnitude, I have to wonder- are cameras more important now for astronomy than telescopes are? I'm talking specifically for the amateur section (8 inches or less aperture).....it seems that cameras can now reach what an 8 inch aperture can do pretty easily with exposures of 30 seconds? AND cameras show color, which is often hard to do with even an 8 inch telescope. I've just found images taken with cameras on here much more pleasing to my eyes than what I've seen through a telescope and wonder if a camera with a good lens will replace 8 inch and smaller telescopes. Of course for the planets and such objects that need a lot of magnification, a telescope will be best, but for wide starfields and DSO imaging of extended objects, I find camera images much more pleasing than what I see with my eyes through a telescope.

Click to expand...

You make a some good points here, Alex. I too have noticed that a telescope/camera combination shows much more than can be seen looking through the same telescope. The eye has a very short integration time, while the camera keeps integrating. Of course when you compare limiting magnitudes of a small camera lens and 8-inch telescope, you are talking about totally different fields of view. Most telescopes are never meant to show wide angle views of Milky Way star fields that could be recorded by a camera lens. They are mostly instruments suited for much narrower FOV.

While an 8-inch telescope can visually reveal stars approaching 15th magnitude in M13 (Hercules globular cluster) the camera, with much shorter focal length, would just show M13 as a bright bloated star with maybe a few outlier cluster members on the edge.

Here's an example of a telescopic image of that cluster with a 10-inch, f/5.5 reflector:


The Great Globular Cluster in Hercules - Sony NEX-5N

Specifics: DSS stack of 24 8-minute images at ISO 800, 5 darks, 33 flats, 10 bias; 10-inch f/5.5 Deep Space Hunter Newtonian reflector with GSO coma corrector

While visually it is often difficult to see a lot of color through a telescope, photographically much color can be recorded. In the above image some of the stars show a bit of color. Probably more would have shown if the ISO had been lower.

But each type of instrument has its place:

• Naked eye - the premium wide-field visual instrument
• Fisheye lens - the widest lens for all-sky photography
• Wide-angle lens - good for photographing larger objects, such as Milky Way star clouds
• Telephoto lens - best for some of the larger deep-sky objects
• Small, wide-angle refractors - optimum for DSOs of lessor angular size
• Telescopes, of various apertures and focal lengths - for objects appropriate for their FOV

The point here, Alex, is that there is a place for all of these. Each is most suited for a particular type of object and type of observing (visual or photographic). None really replaces another. The only possible exception is that a camera with telescope shows more than the same telescope used visually. The drawback of course is that photographs take a lot longer to acquire than just looking through the telescope. The above image took over three hours plus post-processing time. I can see a lot of different globular clusters in three hours.

Enough said, Alex. I'm not suggesting that you didn't know these points. But I just wanted to state my point of view for the discussion.

--

Best Regards,
Russ

Click to expand...

alexisgreat said:

RustierOne said:

alexisgreat said:

rnclark said:

I did an update to the limiting magnitude section and now include equations. See Table 2 and associated discussion at:
http://www.clarkvision.com/articles/nightscapes/

Click to expand...

Thanks, I find all your tables VERY useful Roger. And seeing some of the great images posted here and how low we can go in limiting magnitude, I have to wonder- are cameras more important now for astronomy than telescopes are? I'm talking specifically for the amateur section (8 inches or less aperture).....it seems that cameras can now reach what an 8 inch aperture can do pretty easily with exposures of 30 seconds? AND cameras show color, which is often hard to do with even an 8 inch telescope. I've just found images taken with cameras on here much more pleasing to my eyes than what I've seen through a telescope and wonder if a camera with a good lens will replace 8 inch and smaller telescopes. Of course for the planets and such objects that need a lot of magnification, a telescope will be best, but for wide starfields and DSO imaging of extended objects, I find camera images much more pleasing than what I see with my eyes through a telescope.

Click to expand...

You make a some good points here, Alex. I too have noticed that a telescope/camera combination shows much more than can be seen looking through the same telescope. The eye has a very short integration time, while the camera keeps integrating. Of course when you compare limiting magnitudes of a small camera lens and 8-inch telescope, you are talking about totally different fields of view. Most telescopes are never meant to show wide angle views of Milky Way star fields that could be recorded by a camera lens. They are mostly instruments suited for much narrower FOV.

While an 8-inch telescope can visually reveal stars approaching 15th magnitude in M13 (Hercules globular cluster) the camera, with much shorter focal length, would just show M13 as a bright bloated star with maybe a few outlier cluster members on the edge.

Here's an example of a telescopic image of that cluster with a 10-inch, f/5.5 reflector:

View attachment 1185493
The Great Globular Cluster in Hercules - Sony NEX-5N

Specifics: DSS stack of 24 8-minute images at ISO 800, 5 darks, 33 flats, 10 bias; 10-inch f/5.5 Deep Space Hunter Newtonian reflector with GSO coma corrector

While visually it is often difficult to see a lot of color through a telescope, photographically much color can be recorded. In the above image some of the stars show a bit of color. Probably more would have shown if the ISO had been lower.

But each type of instrument has its place:

• Naked eye - the premium wide-field visual instrument
• Fisheye lens - the widest lens for all-sky photography
• Wide-angle lens - good for photographing larger objects, such as Milky Way star clouds
• Telephoto lens - best for some of the larger deep-sky objects
• Small, wide-angle refractors - optimum for DSOs of lessor angular size
• Telescopes, of various apertures and focal lengths - for objects appropriate for their FOV

The point here, Alex, is that there is a place for all of these. Each is most suited for a particular type of object and type of observing (visual or photographic). None really replaces another. The only possible exception is that a camera with telescope shows more than the same telescope used visually. The drawback of course is that photographs take a lot longer to acquire than just looking through the telescope. The above image took over three hours plus post-processing time. I can see a lot of different globular clusters in three hours.

Enough said, Alex. I'm not suggesting that you didn't know these points. But I just wanted to state my point of view for the discussion.

--

Best Regards,
Russ

Click to expand...

That is a beautiful image! The naked eye is a powerful instrument too, but very handicapped for urban dwellers. When I travel about 2 hours outside of the city, I can see the Milky Way even during twilight. I find that amazing.

I think I might need to get better eyepieces for my telescopes, the ones I use for visual observing are all standard Plossls. I never put much thought into spending money on wide field eyepieces but that might help. My vision is also around 20/60 (one eye is 20/35 the other is 20/80) so maybe that's another reason why I like what I see in photographs much better than what I can see directly through the scope with my eyes. The focal lengths of the scopes I have now are 350mm, 350mm, 500mm, 1000mm, 1250mm and 2032mm and my camera lenses are 14mm, 18mm, 40mm, 42mm, 55mm, 70mm, 150mm and 300mm.

Click to expand...

• Samyang 8mm, f/2.8
• Sigma 19mm, f/2.8
• Sony 18-55mm f/3.5 kit zoom
• Sony 35mm, f/1.8
• Olympus OM Zuiko 50mm, f/1.8
• Mama-Sekor (Coma King) 55mm, f/1.4
• Tokina 35-135mm, f/3.5 zoom
• Pentax SMC Takumar 200mm, f/4.0

• Dolland achromatic refractor (~1780-1840, "Dolland, London", brass/wood draw-tubes)
• 8-inch f/4.9 Newtonian reflector, 980mm, home-made
• Celestron-8, 1981 Super C-8+, 2032mm & 1420mm w/ focal reducer
• 10-inch Hardin Deep Space Hunter (GSO) Newtonian reflector, f/5.0, 1270mm
• Celestron-11, 2008, on Losmandy G-11 GEM, 2794mm & 1980mm w/ focal reducer

• Brandon 32mm
• Celestron 12mm, Kellner
• Edscorp 18mm, orthoscopic
• Celestron Plössl - various focal lengths from 4-32mm, my favorite being the 32mm
• Celestron 26mm, Silvertop Plössl
• University Optics 16mm, Köenig wide angle,
• Scopetronix 40mm, Maxview-40
• Telvue 11mm, Nagler T6

• Guan Sheng 40mm, Superview 68°
• Explore Scientific 22mm, 100°, nitrogen-purged

rnclark said:

I did an update to the limiting magnitude section and now include equations. See Table 2 and associated discussion at:
http://www.clarkvision.com/articles/nightscapes/

Click to expand...

hha said:

rnclark said:

I did an update to the limiting magnitude section and now include equations. See Table 2 and associated discussion at:
http://www.clarkvision.com/articles/nightscapes/

Click to expand...

Your picture 5a (50mm f/2.8 30sec) of Polaris appears to reach +12.5. This is consistent with my experience using my 50 mm f/1.8 stopped down to f/2.8 with a Nikon D3200. Optimum focus using LiveView. With the same 50mm lens at f/1.8 and optimum focus, there is no gain in the star depth over the f/2.8 shot at the center. Table 2 claims that a 50mm f/1.8 should reach +13.2. I am guessing that this is due to a image quality decrease, even at the center, or is it due to the doubling of the sky background?

Any comment?

hha

Click to expand...

RustierOne said:

alexisgreat said:

RustierOne said:

alexisgreat said:

rnclark said:

I did an update to the limiting magnitude section and now include equations. See Table 2 and associated discussion at:
http://www.clarkvision.com/articles/nightscapes/

Click to expand...

Thanks, I find all your tables VERY useful Roger. And seeing some of the great images posted here and how low we can go in limiting magnitude, I have to wonder- are cameras more important now for astronomy than telescopes are? I'm talking specifically for the amateur section (8 inches or less aperture).....it seems that cameras can now reach what an 8 inch aperture can do pretty easily with exposures of 30 seconds? AND cameras show color, which is often hard to do with even an 8 inch telescope. I've just found images taken with cameras on here much more pleasing to my eyes than what I've seen through a telescope and wonder if a camera with a good lens will replace 8 inch and smaller telescopes. Of course for the planets and such objects that need a lot of magnification, a telescope will be best, but for wide starfields and DSO imaging of extended objects, I find camera images much more pleasing than what I see with my eyes through a telescope.

Click to expand...

You make a some good points here, Alex. I too have noticed that a telescope/camera combination shows much more than can be seen looking through the same telescope. The eye has a very short integration time, while the camera keeps integrating. Of course when you compare limiting magnitudes of a small camera lens and 8-inch telescope, you are talking about totally different fields of view. Most telescopes are never meant to show wide angle views of Milky Way star fields that could be recorded by a camera lens. They are mostly instruments suited for much narrower FOV.

While an 8-inch telescope can visually reveal stars approaching 15th magnitude in M13 (Hercules globular cluster) the camera, with much shorter focal length, would just show M13 as a bright bloated star with maybe a few outlier cluster members on the edge.

Here's an example of a telescopic image of that cluster with a 10-inch, f/5.5 reflector:

View attachment 1185493
The Great Globular Cluster in Hercules - Sony NEX-5N

Specifics: DSS stack of 24 8-minute images at ISO 800, 5 darks, 33 flats, 10 bias; 10-inch f/5.5 Deep Space Hunter Newtonian reflector with GSO coma corrector

While visually it is often difficult to see a lot of color through a telescope, photographically much color can be recorded. In the above image some of the stars show a bit of color. Probably more would have shown if the ISO had been lower.

But each type of instrument has its place:

• Naked eye - the premium wide-field visual instrument
• Fisheye lens - the widest lens for all-sky photography
• Wide-angle lens - good for photographing larger objects, such as Milky Way star clouds
• Telephoto lens - best for some of the larger deep-sky objects
• Small, wide-angle refractors - optimum for DSOs of lessor angular size
• Telescopes, of various apertures and focal lengths - for objects appropriate for their FOV

The point here, Alex, is that there is a place for all of these. Each is most suited for a particular type of object and type of observing (visual or photographic). None really replaces another. The only possible exception is that a camera with telescope shows more than the same telescope used visually. The drawback of course is that photographs take a lot longer to acquire than just looking through the telescope. The above image took over three hours plus post-processing time. I can see a lot of different globular clusters in three hours.

Enough said, Alex. I'm not suggesting that you didn't know these points. But I just wanted to state my point of view for the discussion.

--

Best Regards,
Russ

Click to expand...

That is a beautiful image! The naked eye is a powerful instrument too, but very handicapped for urban dwellers. When I travel about 2 hours outside of the city, I can see the Milky Way even during twilight. I find that amazing.

I think I might need to get better eyepieces for my telescopes, the ones I use for visual observing are all standard Plossls. I never put much thought into spending money on wide field eyepieces but that might help. My vision is also around 20/60 (one eye is 20/35 the other is 20/80) so maybe that's another reason why I like what I see in photographs much better than what I can see directly through the scope with my eyes. The focal lengths of the scopes I have now are 350mm, 350mm, 500mm, 1000mm, 1250mm and 2032mm and my camera lenses are 14mm, 18mm, 40mm, 42mm, 55mm, 70mm, 150mm and 300mm.

Click to expand...

Thanks, Alex. Yes for the urban light-pollution regime, the naked eye is assaulted by all manner of obnoxious glare. Like you mentioned, the dark sky view with naked eye is amazing. That's why I enjoy meteor photography so much. With the cameras automated in capturing the hundreds of images, I can lay back, wrapped in my sleeping bag on the lounge chair, watching the show. Yes, sometimes I drift off in a bit of a nap. But the show above is still there when the eyes pop open again.

My supply of camera lenses adapted for my Sony NEX cameras (5N and 7) includes:

• Samyang 8mm, f/2.8
• Sigma 19mm, f/2.8
• Sony 18-55mm f/3.5 kit zoom
• Sony 35mm, f/1.8
• Olympus OM Zuiko 50mm, f/1.8
• Mama-Sekor (Coma King) 55mm, f/1.4
• Tokina 35-135mm, f/3.5 zoom
• Pentax SMC Takumar 200mm, f/4.0

As for telescopes I have the following:

• Dolland achromatic refractor (~1780-1840, "Dolland, London", brass/wood draw-tubes)
• 8-inch f/4.9 Newtonian reflector, 980mm, home-made
• Celestron-8, 1981 Super C-8+, 2032mm & 1420mm w/ focal reducer
• 10-inch Hardin Deep Space Hunter (GSO) Newtonian reflector, f/5.0, 1270mm
• Celestron-11, 2008, on Losmandy G-11 GEM, 2794mm & 1980mm w/ focal reducer

My eyepiece collection, acquired over the years, ranges from mediocre to premium.

1-1/4 inch:

• Brandon 32mm
• Celestron 12mm, Kellner
• Edscorp 18mm, orthoscopic
• Celestron Plössl - various focal lengths from 4-32mm, my favorite being the 32mm
• Celestron 26mm, Silvertop Plössl
• University Optics 16mm, Köenig wide angle,
• Scopetronix 40mm, Maxview-40
• Telvue 11mm, Nagler T6

2-inch:

• Guan Sheng 40mm, Superview 68°
• Explore Scientific 22mm, 100°, nitrogen-purged

The last of these I won at the Golden State Star Party in 2014. But I have way more optical equipment than I have time, energy or suitable weather to use. But it does give a lot of flexibility, depending on my current interests.

--
Best Regards,
Russ

Click to expand...

hha said:

Although the D3200 has 24 Mp, I save the images as 6 Mp normal quality JPEG (typically 1.5 MB/file). On a fixed tripod I can expose for 5 seconds in the equator (15"/sec sky rotation) and get 2 (effective) pixels of star trails. This is typically better than the optical quality of the lens (stopped down to f/2.8). You get to 30 seconds total exposure by stacking 6 images. I usually take 9 (with the built-in timer) and delete those with interfering birds or airplanes.

hha

Click to expand...

hha said:

Although the D3200 has 24 Mp, I save the images as 6 Mp normal quality JPEG (typically 1.5 MB/file). On a fixed tripod I can expose for 5 seconds in the equator (15"/sec sky rotation) and get 2 (effective) pixels of star trails. This is typically better than the optical quality of the lens (stopped down to f/2.8). You get to 30 seconds total exposure by stacking 6 images. I usually take 9 (with the built-in timer) and delete those with interfering birds or airplanes.

Click to expand...