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Equipment Discussions >> Electronically Assisted Astronomy

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norden
sage


Reged: 09/08/08

Loc: Norden
Which camera?
      #5679134 - 02/14/13 10:36 AM

Hello friends,
I am an astronomy interested man who lives in Sweden, far up in cold northern Europe, I am a very happy owner of a Celestron CPC100 SCT. I love it much and I use every clear night. I devote myself exclusively to visual observations but would like to reach a little further out into the universe and catch a little more detail than what I currently are able to do with my equipment. I have long thought about a MallinCam which I think is an excellent addition to my visual observations. I have read many posts on Cloudy Nights and studied Rocks' website thoroughly and I am sure that MallinCam is an amazing nice and useful camera suitable for my purposes. I would appreciate your opinion and I would like to get some advice from you.

My SCT telescope is mounted on the original ALT / AZ mount so I think exposures of 60 seconds will be enough for my purposes due to sky rotation. Do you think HYPER PLUS is a suitable camera for me? If not, what camera do you suggest?

I'm very interested in the distant galaxy groups. Should I choose a B/W ? Of course I would like a color but can I still reach faint galaxies, like Hickson 50, around magnitude 15 within 50 seconds? My observing site is rather dark, thank god.

My telescope has F10, but think about F4 is appropriate for my purposes . I would like to keep my 2 "diagonal when using the MallinCam. What special equipment do I need to buy?

Is MallinCam HYPER PLUS in Pal format and what type of screen do I need?

Grateful for any advice and suggestions.


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mclewis1
Thread Killer
*****

Reged: 02/25/06

Loc: New Brunswick, Canada
Re: Which camera? new [Re: norden]
      #5679348 - 02/14/13 12:21 PM

Mikael,

What is your light pollution like?

I think you will be happy with 30-60s exposures with your alt az setup. You will see a little bit of field rotation in some areas of the sky, and if you stay away from them or keep your exposures down to 30-45s when in those areas then even that won't be an issue for you.

The difference between BW and color with the Mallincams is so minimal that I wouldn't suggest the BW camera, color has many advantages and really doesn't give up anything to the BW in sensitivity.

The MCHP camera has very manual exposure and cooler settings (7/14/28/56s) and on/off for the TEC. This means that you need to be accessing the camera directly on a regular basis. This is not a big problem but it means that you won't be able to automate things (like on those really cold winter nights) in the future. You can however get the MCHP upgraded at any time. Rock Mallin offers a upgrade service which takes a MCHP and turns it into an Xtreme model for what I think is a reasonable price.

F4 on a C11 is a good target for viewing small objects like galaxies. The Meade f3.3 SCT focal reducer would be a good choice. I often use one with my C11 and it's setup like this ... C11 > f3.3 reducer > Meade T adapter with 10mm spacer (these comes with the reducer) > metal T to C mount adapter > Mallincam. In this configuration I am at about f4 (the spacing is a little shorter than what Meade specifies). Another option would be the Mallincam MFR-5 reducer which won't require any adapters (it fits into any place where a 1.25" eyepiece is used) ... it's more flexible than the Meade reducer but also more expensive.

You can get any Mallincam in PAL video format, it's just an ordering option. I would also order the ExView HAD sensor upgrade at the same time. The extra sensitivity of this sensor would help to keep your exposure as short as possible which would help with tracking and field rotation issues with your alt az mount.

You have two display options -
1) Direct to a video monitor. This is the simplest setup but you will need to find a good quality PAL video monitor with a composite (or better an S-Video) input. Ideally a good quality CRT type of monitor will give the best images but good LCD/LED monitors can be very effective as well. If it's just you viewing the images (not a group of people on a regular basis) avoid going too big, an 8-12" model would be fine and will work better than a larger display (assuming both are of the same quality).

2) Using a PC/laptop. This requires a USB frame grabber in between. These units usually handle both PAL and NTSC video automatically (so you don't have to go looking specifically for a PAL version) and start off in the $20-40 range. Mallincam also offers a couple of very nice units, the basic one is $80 USD and the more interesting + model is $150 USD. This + model offers the ability to adjust the black levels which makes viewing fine faint details (like faint galactic arms and dust lanes) much easier.

Edited by mclewis1 (02/14/13 12:25 PM)


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rmollise
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Reged: 07/06/07

Re: Which camera? new [Re: mclewis1]
      #5679494 - 02/14/13 01:33 PM

Everyone of us has differnt tastes, and for some objects color doesn't make too much difference. For me? I used a black and white Stellacam for years, and after a color Xtreme, I will never go back. Just being able to pick out little galaxies due to the golden color is incredible!

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norden
sage


Reged: 09/08/08

Loc: Norden
Re: Which camera? new [Re: rmollise]
      #5679707 - 02/14/13 03:08 PM

Thank you for your encouraging response! I live about 200 miles east of Copenhagen in a light blue to blue area where I have a relatively dark sky. The visual limiting magnitude is approximately 6. Unfortunately, the western part of the sky is always destroyed by the light from Copenhagen. Despite the cold weather, I like being close to my telescope and sky and nature and all the sounds in the darkness. So observations from the inside of my house is not for me. So with a Mallincam MFR-5 reducer can I still use my diagonal? Which do you recommend video monitor or a laptop in terms of best and clearest images? I understand that a laptop is great because the camera then you can more easily controlled. Please explain to me why the difference between B / W and color is only marginal.

Edited by norden (02/14/13 03:11 PM)


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GlennLeDrew
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Which camera? new [Re: norden]
      #5679792 - 02/14/13 03:58 PM

Because field rotation is worst at the zenith, you will not be pointing your scope straight up and might be able to dispense with a diagonal. Especially if the mount's controller allows you to set a maximum altitude limit.

The advantage of leaving the diagonal out of the picture is that you will be working at a somewhat smaller focal length. (When moving the focus farther back on SCTs, the focal length and f/ratio increase somewhat.) and if you obtain a Meade f/3.3 focal reducer (recommended by me), you will not be able to use a diagonal anyway.

Regarding field rotation limits to exposure duration. This depends to a great degree on the detector's pixel count. Video cameras, having only about 330,000 pixels, are fairly 'forgiving' in this respect. And your northerly latitude helps, by allowing a full minute over most of your sky, and even up to two minutes over fair portion toward the east and west.

You may wish to consider a camera which offers longer integrations than 56 seconds. Particularly because your sky is dark, where longer exposure times will be required to bring out fainter nebulosities. And if down the road you obtain a polar aligned mount, field rotation will not be a limiter.


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norden
sage


Reged: 09/08/08

Loc: Norden
Re: Which camera? new [Re: GlennLeDrew]
      #5679817 - 02/14/13 04:17 PM

Hi Glenn,

Maybe you are right. Maybe better leaving out the diagonal. Perhaps one VSS+? I have to think about it. What is the maximum angle I can use the camera without hitting the base (including Meade f/3.3 focal reducer) ?

Edited by norden (02/14/13 04:18 PM)


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GlennLeDrew
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Which camera? new [Re: norden]
      #5679966 - 02/14/13 06:00 PM

I would think you should be able to get to within about 20 degrees of the zenith, certainly 25. This is based on an estimate made from examining a photo on Celestron's web site. In the product specifications there is no indication of the clearance between the rear baffle opening and the base when the OTA is vertical (which there should be.)

Can you measure this distance? I'll compare it to the length of my VSS+ and Meade f/3.3 reducer combo.


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nytecam
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Reged: 08/20/05

Loc: London UK
Re: Which camera? new [Re: norden]
      #5680703 - 02/15/13 05:46 AM Attachment (19 downloads)

Quote:

Hello friends..... I devote myself exclusively to visual observations but would like to reach a little further out into the universe and catch a little more detail than what I currently are able to do with my equipment. I have long thought about a MallinCam.... I'm very interested in the distant galaxy groups....but can I still reach faint galaxies, like Hickson 50, around magnitude 15 within 50 seconds? My observing site is rather dark, thank god. My telescope has F10, but think about F4....Grateful for any advice and suggestions.


You're on the slippery slope once you use some form of electronic imaging and much like aperture fever there's no way back On the rare occasions I attend a visual ob club meeting I groan under my breath at what is barely detectable whilst from my severely LP backyard at home remote gxys pop into view in colour if I wish

Your reference to Hickson 50 had me searching my images like below in 4m stack so could be difficult in only 60s exp which just recorded gxys A and B. My DSO gallery here but as you'll see, I use a regular CCD cam and not video cam - stellar penetration is similar and I get to see the images downloaded in realtime in brief exposures, but I have more control of finished results


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: Which camera? new [Re: GlennLeDrew]
      #5680860 - 02/15/13 08:41 AM

Quote:


Regarding field rotation limits to exposure duration. This depends to a great degree on the detector's pixel count. Video cameras, having only about 330,000 pixels, are fairly 'forgiving' in this respect. And your northerly latitude helps, by allowing a full minute over most of your sky, and even up to two minutes over fair portion toward the east and west.





Actually it depends more on the sensor size than pixel count. When displayed at 640x480 or less on a monitor a .3 megapixel 1/2" sensor will show the field rotation much more than an ASP-C sensor even with 24 megapixels. Field of view matters most here and the smaller chip will yield the smallest field of view if they are both used on the exact same scope. That will make the field rotation very apparent with the smaller chip sensor.

The nice thing is that the smaller chip can use a focal reducer to get the focal ratio down drastically. That will decrease exposure times and widen the field of view. If you already have a fast inexpensive scope like a Newtonian then the larger chip is much more forgiving. If you have a long focal length scope like an SCT then the smaller chip is definitely a better option if you also get the focal reducer.

Basically the focal reducer is an absolute must with a small chip camera and a longer focal length scope like the SCTs regardless of the resolution of the camera.

Edited by mpgxsvcd (02/15/13 03:02 PM)


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norden
sage


Reged: 09/08/08

Loc: Norden
Re: Which camera? new [Re: mpgxsvcd]
      #5681335 - 02/15/13 12:23 PM

Quote:

Quote:


Regarding field rotation limits to exposure duration. This depends to a great degree on the detector's pixel count. Video cameras, having only about 330,000 pixels, are fairly 'forgiving' in this respect. And your northerly latitude helps, by allowing a full minute over most of your sky, and even up to two minutes over fair portion toward the east and west.





Actually it depends more on the sensor size than pixel count. When displayed at 640x480 or less on a monitor a .3 megapixel 1/2" sensor will show the field rotation much more than an ASP-C sensor even with 24 megapixels. Field of view matters most here and the smaller chip will yield the smallest field of view if they are both used on the exact same scope. That will make the field rotation very apparent with the smaller chip sensor.

The nice thing is that the smaller chip can use a focal reducer to get the focal ratio down drastically. That will decrease expsure times and widen the field of view. If you already have a fast inexpensive scope like a Newtonian then the larger chip is much more forgiving. If you have a long focal length scope like an SCT then the smaller chip is definitely a better option if you also get the focal reducer.

Basically the focal reducer is an absolute must with a small chip camera and a longer focal length scope like the SCTs regardless of the resolution of the camera.




I guess I need a focal reducer


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norden
sage


Reged: 09/08/08

Loc: Norden
Re: Which camera? new [Re: nytecam]
      #5681339 - 02/15/13 12:25 PM

Quote:

Quote:

Hello friends..... I devote myself exclusively to visual observations but would like to reach a little further out into the universe and catch a little more detail than what I currently are able to do with my equipment. I have long thought about a MallinCam.... I'm very interested in the distant galaxy groups....but can I still reach faint galaxies, like Hickson 50, around magnitude 15 within 50 seconds? My observing site is rather dark, thank god. My telescope has F10, but think about F4....Grateful for any advice and suggestions.


You're on the slippery slope once you use some form of electronic imaging and much like aperture fever there's no way back On the rare occasions I attend a visual ob club meeting I groan under my breath at what is barely detectable whilst from my severely LP backyard at home remote gxys pop into view in colour if I wish

Your reference to Hickson 50 had me searching my images like below in 4m stack so could be difficult in only 60s exp which just recorded gxys A and B. My DSO gallery here but as you'll see, I use a regular CCD cam and not video cam - stellar penetration is similar and I get to see the images downloaded in realtime in brief exposures, but I have more control of finished results




I would be very happy if I could get a similar picture in 60 seconds with a MallinCam. Is that possible?


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rmollise
Postmaster
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Reged: 07/06/07

Re: Which camera? new [Re: norden]
      #5681488 - 02/15/13 01:24 PM

Yes. The Hicksons are easy with a Mallincam. And no computer frippery is required if you don't want it.

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norden
sage


Reged: 09/08/08

Loc: Norden
Re: Which camera? new [Re: rmollise]
      #5681539 - 02/15/13 01:43 PM

Quote:

Yes. The Hicksons are easy with a Mallincam. And no computer frippery is required if you don't want it.




Thats great news! Thanks Rod! Soon time to order I think


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jambi99
sage


Reged: 08/14/10

Loc: Québec, Canada
Re: Which camera? new [Re: rmollise]
      #5681742 - 02/15/13 03:08 PM

Whats wrong with the netbook\laptop? A 7" netbook has the same size and the display quality is better than any portable lcd screen. As i said in an other post, you can add a privacy filter to overcome the laptop brightness. This will also improve the contrast:

Link

Personnaly, the ccd camera\netbook combo is a cheaper(much more) and a more versatile option. Any ccd camera with the 1/2" Exview color sensor would be as good\sensitive as the mallincan, but more than half the price.

The main advantage of using a laptop\netbook is that you can stack images(using DSS) to reduce the noise. So while, your are observing, the next exposure will automatically stack the image so at the end your keep getting a better view. Its like a two stages live view imaging process.

Plus,you can use the ccd as a regular ccd or guiding.

Following ccd model would work really well for live view:

Starlight Xpress LodeStar-c ~650$
Brightstar Mammut ~650$
Meade DSI II ~250$ used(discontinued)
Orion Start Shoot II ~250$ used (discontinued)

Edited by jambi99 (02/15/13 03:38 PM)


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jambi99
sage


Reged: 08/14/10

Loc: Québec, Canada
Re: Which camera? new [Re: jambi99]
      #5681757 - 02/15/13 03:15 PM

I forgot to add that for camera control(for remote observation), you can use VNC by connecting the camera to the netbook and controlling it with another lapotp/pc or even a smartphone\tablet(using vnc client).

You can not only control the camera, but the telescope also.

All that is free if you consider that most people already have a laptop or smartphone\tablet. No 250$ remote control + ~100$ video transmitter.

Edited by jambi99 (02/15/13 03:17 PM)


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norden
sage


Reged: 09/08/08

Loc: Norden
Re: Which camera? new [Re: jambi99]
      #5681897 - 02/15/13 04:25 PM

Quote:

Whats wrong with the netbook\laptop? A 7" netbook has the same size and the display quality is better than any portable lcd screen. As i said in an other post, you can add a privacy filter to overcome the laptop brightness. This will also improve the contrast:

Link

Personnaly, the ccd camera\netbook combo is a cheaper(much more) and a more versatile option. Any ccd camera with the 1/2" Exview color sensor would be as good\sensitive as the mallincan, but more than half the price.

The main advantage of using a laptop\netbook is that you can stack images(using DSS) to reduce the noise. So while, your are observing, the next exposure will automatically stack the image so at the end your keep getting a better view. Its like a two stages live view imaging process.

Plus,you can use the ccd as a regular ccd or guiding.

Following ccd model would work really well for live view:

Starlight Xpress LodeStar-c ~650$
Brightstar Mammut ~650$
Meade DSI II ~250$ used(discontinued)
Orion Start Shoot II ~250$ used (discontinued)




Some special 1/2" Exview color sensor camera you recommend?


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jambi99
sage


Reged: 08/14/10

Loc: Québec, Canada
Re: Which camera? new [Re: norden]
      #5681931 - 02/15/13 04:44 PM

Thats the thing , there is nothing special about the Exview sensor. I mean, at the end it will always be the same sensor whatever the camera. It will be the same QE. There is no such thing as special sensor. All the camera i enumerated above will have the same sensor(ICX428/429) as the mallincam. Therefore, about the same sensitivity.

Edited by jambi99 (02/15/13 04:55 PM)


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GlennLeDrew
Postmaster
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Which camera? new [Re: jambi99]
      #5681966 - 02/15/13 04:58 PM

Travis,
Working it out using the math, you'll see that the pixel array count alone is an excellent indicator of field rotation tolerance.

Consider two chips having the same pixel count, but one has larger pixels (and hence a larger size.) The field rotation tolerance is identical. Why? Because the ratio of corner pixel size to distance from center is identical.

How about difference in field of view for a given chip? There in difference in field rotation tolerance, for the rotation is an angular rate. Whether zoomed in to a few arcminutes or zoomed out to many degrees, at a corner pixel the same rate of rotation exists.

Fundamentally, the only factor is this. What is the angle subtended by a corner pixel as 'seen' from the center pixel? And how does this angle compare to the angular rate of field rotation?

(To be sure there is no confusion on this matter if pixel angular size, imagine you have been shrunk down the size of a pixel and are standing on the center pixel. A cube exactly as large as a pixel has been placed on top of a corner pixel. You wish to know the angle this cube subtends as seen from your location at the chip's center.)

A low pixel count chip by definition has a corner pixel which subtends a large angle as 'seen' from the center. As pixel count goes up, the angular extent of a corner pixel must only decrease.

Example 1. Consider two chips, each having 10 micron (0.01mm) pixels. Their arrays are 640X480 and 3000X2000. Their sizes (assuming no interstitial space between pixels, for simplicity) are 6.4X4.8mm and 30X20mm, respectively.

The smaller chip has a corner pixel which subtends an angle
ARCTAN(0.01 / (SQRT(3.2^2 + 2.4^2))) = 0.143 degree

The larger chip has a corner pixel which subtends an angle
ARCTAN(0.01 / (SQRT(15^2 + 10^2))) = 0.032 degree.

The high pixel count chip is 4.5 times more sensitive to field rotation. This makes sense, for the distance from the center to corner (18mm) is 4.5X the center-to-corner distance (4mm) on the lower pixel count chip.


Example 2. We now have two chips of the same size, they being 15X10mm. One has 10 micron (0.01mm) pixels and the other 5 micron (0.005mm) pixels. Their array sizes are thus 750X500 and 1500X1000 pixels, respectively.

The big-pixel chip has a corner pixel which subtends an angle
ARCTAN(0.01 / (SQRT(7.5^2 + 5^2))) = 0.064 degree.

The small-pixel chip has a corner pixel which subtends an angle
ARCTAN(0.005 / (SQRT(7.5^2 + 5^2))) = 0.032 degree.

The small-pixel chip is twice as sensitive to field rotation, which makes sense for its pixels are half as large.


To sum up. Field rotation tolerance depends only on the corner pixel size with respect to its distance from the chip's center. And this scales as the pixel array count.


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Dwight J
scholastic sledgehammer
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Reged: 05/14/09

Loc: Lethbridge, Alberta, Canada
Re: Which camera? new [Re: jambi99]
      #5682007 - 02/15/13 05:23 PM

Just one problem with that list of cameras, despite all having the same sensor, is that none of them are cooled and on a warm night (or day) excessive noise noise will be evident. Some of the heat from the camera can be removed by a fan blowing on it or placing a cold pack on the camera. Cooling the camera will cost extra. The new Orion G3 camera has TEC cooling and is now on sale for $399 in either mono or color and would be a steal. I would add this camera to your list of possiblilites.

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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: Which camera? new [Re: jambi99]
      #5682198 - 02/15/13 07:22 PM

Quote:

Thats the thing , there is nothing special about the Exview sensor. I mean, at the end it will always be the same sensor whatever the camera. It will be the same QE. There is no such thing as special sensor. All the camera i enumerated above will have the same sensor(ICX428/429) as the mallincam. Therefore, about the same sensitivity.



IT's true that the Exview sensor is the same in all cams.
It is however not true that this means all cameras are the same if they use the same sensor.
After the sensor comes the analog front end, which among other things does a black level clamp , an optional amplifier stage, then another optional amplifier stage , a sample and hold and an A/D converter. The AFE chips used in cameras , either video cams , mallincams, samsung, lntech, stellacam, or digital usb/firewire/IP , vary wildly.
There are AFE chips with barely 18dB of gain and lots of noise while there are others with up to 46dB of gain and less noise .
A 20dB gain difference means a 10 fold difference in sensitivity . That's 10 times shorter exposure with the same exact ccd .
For some cameas, there's too little gain or too much noise in the AFE. For others, there's too much gain that can't be manually set to the optimal value and all the image highlights are blown , image is washed out with no color. Same ccd just different AGC .
Then there are various A/D converters with various resolutions ranging from 8 bits to 16 bits. The 16 bit is ihnerently 256 times LESS noisy than the 8 bit as far as quantization noise . That means you can strech that histogram and bring detail out of the dark levels while introducing 256 times less noise if you use a 16 bit AD vs a lowly 8 bit.
But quantization noise is not the only noise or error stemming from the A/D .
Some of these chips have useless specs , for example a 12 bit AD that has the lowest 3 bits buried in the noise floor . Its internal noise is larger than the 3 LSB , making it effectively a 9 bit AD (except if a large number of samples is taken and stacked, when autocorrelation takes care of the bits buried in the noise ).
Then there are various ways of driving the ccds for the long exposures and various ways to eliminate amp glow . Depending on the camera hardware, these different methods yield different amounts of noise and amp glow .
Some cameras exhibit digital noise that's radiated or conducted by its own digital or power circuits into the analog low level signal circuits. Power supply rejection and common mode rejection varies by tens of dB between various circuits. Then you find out one cam has much more digital fixed pattern or interference noise than another at high gain or long integration.
Then there are a variety of different DSP's used to process the image . Different speeds, different bit depths , different firmware algorithms all yield vastly different results especially when it comes to noise performance . Huge difference between some Chinese 12 bit old DSP , an Analog Devices Blackfin , or an ARM based 32 bit DSP .
For example performing an image calculation and truncating the result to 1 LSB vs. calculating it to the same 1LSB but without truncating might result in 40% more noise .
Then all this wildly different hardware generates very different power consumption levels, which all generate in turn various level of internal heating . A 6 deg of temperature difference doubles the noise . Some cameras will be more than 6 deg hotter than others (ccd temp).
Then there are various ways to cool the cameras and reduce thermal noise. Peltier , or just fans, or just a big chunk of heatsink . IF there's a Peltier, then it depends how deep can it cool the ccd, what's the thermal temporal profile , all influence noise and therefore the gain that could be applied. Is it set point or ...
So you get the idea, even though the ccd might be the same, the cameras end up vastly different in performance , and not by a small amount like a difference in QE of 20% but by orders of magnitude .


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rmollise
Postmaster
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Reged: 07/06/07

Re: Which camera? new [Re: jambi99]
      #5682320 - 02/15/13 08:47 PM

Quote:

Whats wrong with the netbook\laptop?




Not everybody wants to bring a computer in the field, and the Xtreme is simply _more sensitive_. Have you used a Mallincam?


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jambi99
sage


Reged: 08/14/10

Loc: Québec, Canada
Re: Which camera? new [Re: Dwight J]
      #5682522 - 02/15/13 10:52 PM

I just bought a used StarShoot II for 250$. The camera is cooled(-20 C) and has the ICX428 color sensor. The mammut is also cooled(-20 C). The Lodestar-c and the DSI are not, however stacking would solve that problem. Judging by Nytecame images(he has the Lodestar-C, noise it doesn't to be problem.I think cooling is a plus, but for exposure around 60s its mostly trivial...

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jambi99
sage


Reged: 08/14/10

Loc: Québec, Canada
Re: Which camera? new [Re: rmollise]
      #5682562 - 02/15/13 11:13 PM

Why the mallincam would be more sensitive ? What are the arguments about such statement? The mallincam use the same ccd. This mean that it has the same QE. QE is the bottle neck of any ccd camera. You can't produce photon that are not detected by the senor. Of course you can raise the gain, but that will never make your camera more sensitive. It will only make your camera look like it is more sensitive.You can also raise the gain up to saturation on these cameras.

I'm not bashing the Mallincam. I think they are really good camera. However, this is a forum and people come here for advices. I don't think that it is really fair give them the impression that there is only one option. There is other product that are more than capable of providing live view. This, at a much lower cost.


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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: Which camera? new [Re: jambi99]
      #5682674 - 02/16/13 12:41 AM

Quote:

Why the mallincam would be more sensitive ? What are the arguments about such statement? The mallincam use the same ccd. This mean that it has the same QE. QE is the bottle neck of any ccd camera. You can't produce photon that are not detected by the senor. Of course you can raise the gain, but that will never make your camera more sensitive. It will only make your camera look like it is more sensitive.You can also raise the gain up to saturation on these cameras.

I'm not bashing the Mallincam. I think they are really good camera. However, this is a forum and people come here for advices. I don't think that it is really fair give them the impression that there is only one option. There is other product that are more than capable of providing live view. This, at a much lower cost.



That is correct, can't produce signal without photons .
However, different cams implement different design compromises .
Let's say you wanted the shortest integration time and were willing to sacrifice some othe aspects in order to get it.
Add a 10dB gain stage before the camera's normal AFE. Price you pay for this is lower dynamic range, lower singal to noise .
What you gain is 3 times higher "perceived sensitivity" . Can an imager live with the lower signal to noise ? PRobably not .
Can a video observer live with it ?
Yes, if the advantage is you only have to wait for 20 seconds for an image instead of 1 min (and the advantage gets multiplied by the fact that you may use a dob, that could track for 20 sec but not for a while whopping minute , or an altaz mount which would show too much field rotation in 1 min , or an eq mount with bad tracking or alignment ).
Add to this the horrendous pixel scale of 6-7 arcsec/pixel that most of these perceived very sensitive cams are using .
Can an imager live with such gross undersampling? Probably not . Imagers fret over 1.7FWHM seeing or mount tracking , use AO and guiding , etc. They don't want to use 7 arcsec/pixel.
Video astronomers like it to see stars the size of golfballs . This buys them shorter focal lengths and faster f ratios , which means a lot shorter exposures. Same camera, same gain, same S/N but double the pixel scale and you get 4 times the exposure .
Couple the 4 fold gained due to the pixel scale with the 3 times gained with the lower signal to noise due to higher gain and you have a camera that now can see in 30 seconds what it takes "less sensitive" imagers 6 minutes.
In theory all cameras with the same sensor model could have the same min/max gain adjustment (manual of course) and the same best signal to noise but due to many other issues, they don't. Up to this point it appears that very few have actually pushed for the shortest integration times even with degraded image quality . And the ones which are doing it use tricks such black clipping , look at the histograms of most of these great short exposure images . The black levels are clipped like with a chainsaw . Imagers don't do that unless they want to, but video gives no such choice . If you want to see it quick, you must live with the issues.


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mclewis1
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Re: Which camera? new [Re: jambi99]
      #5682755 - 02/16/13 02:13 AM

Quote:

I just bought a used StarShoot II for 250$. The camera is cooled(-20 C) and has the ICX428 color sensor. The mammut is also cooled(-20 C). The Lodestar-c and the DSI are not, however stacking would solve that problem. Judging by Nytecame images(he has the Lodestar-C, noise it doesn't to be problem.I think cooling is a plus, but for exposure around 60s its mostly trivial...



I would be very careful suggesting that noise isn't a problem from Nytecam's image. Take a close look at what he said about the Hickson 50 image ...
Quote:

Your reference to Hickson 50 had me searching my images like below in 4m stack so could be difficult in only 60s exp which just recorded gxys A and B. My DSO gallery here but as you'll see, I use a regular CCD cam and not video cam - stellar penetration is similar and I get to see the images downloaded in realtime in brief exposures, but I have more control of finished results



It's a single stacked image from numerous subs, and stacking is a popular method of lower noise. The image is also somewhat processed ... the capture software is performing some video processing on the images (stretching and applying various filters). So to be clear that image is NOT representative of what you'll see as a "live view" from that camera.

Maurice gets some absolutely amazing images off of that camera/software combination (the best I've ever seen) but that little un cooled camera isn't quite in the same league as the cooled models or the video based Mallincams, particularly when using longer exposures (as he clearly states).

Cooling does start to benefit images at well under 60s exposures. It certainly helps those longer exposures but it's one of the main requirements for a continuous read video setup like in the Mallincams (who's sensor generates tons more heat at any exposure than the single exposure imaging cameras).


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nytecam
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Re: Which camera? new [Re: rmollise]
      #5682810 - 02/16/13 04:13 AM

Quote:

Yes. The Hicksons are easy with a Mallincam. And no computer frippery is required if you don't want it.


Rod - precious few examples [=images] of what the Mallincam can do on faint stuff on this forum beyond hearsay me thinks

Quote:

Maurice gets some absolutely amazing images off of that camera/software combination (the best I've ever seen) but that little un cooled camera isn't quite in the same league as the cooled models or the video based Mallincams, particularly when using longer exposures (as he clearly states).

Cooling does start to benefit images at well under 60s exposures. It certainly helps those longer exposures but it's one of the main requirements for a continuous read video setup like in the Mallincams (who's sensor generates tons more heat at any exposure than the single exposure imaging cameras). Mark


Mark - not convinced cooling is essential [for my 'cool' running Lodestar] at <60s exp [get saturation in <2m @ f/3.6] but removing my severe orange LP via software does take a hit on data. LP filters before cam [which I've tried] needs increased exposure so a no-win option.

What we need is a Mallincam v Lodestar/others unbiased head-to-head on same DSO, same exposure and similar scope but don't think, on this forum, unbiased is going to happen


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norden
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Re: Which camera? new [Re: nytecam]
      #5682869 - 02/16/13 06:19 AM

Thanks for all the thoughtful responses! But remember I am a simple visual amateur without much knowledge of CCD cameras. I must say that I am interested in Orion G3. but can i use this camera with my CPC1100 telescope without a wedge? Can I take pictures of maximum 30-50 seconds without any problems? These are important questions for me. So should I buy a Mallincam VVS+ or Orion Star Shoot II. That is the question.

Edited by norden (02/16/13 07:15 AM)


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jgraham
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Re: Which camera? new [Re: norden]
      #5682939 - 02/16/13 08:14 AM

The challenge with your telescope is that it has a very long focal length and most inexpensive cameras have a small chip giving a very small field of view. The G3 uses a Type 1/2 chip which is pretty small. A really neat option would be to mount the G3 on a small telescope riding piggyback on your CPC. I once built such a system with a little camera that used a Type 1/3 chip and a 35mm f/4 lens from a binoccular. This gave a field of view similar to the 6" f/5 Newtonian that I mounted it on. Another interesting option if you really wanted to mount a camera on your CPC would be a Canon DSLR and Backyard EOS. I wasn't a huge fan of using DSLRs for real-time observing, but things have greatly improved significantly after Canon released the XSi (450D) and Backyard EOS became available. The live view mode works well with bright objects like the moon and planets while the still frame mode gives you many options for deep sky. The large APS-C chip, high gain, and in-camera noise reduction would work well with you scope. I've been using a Canon T2i (550D) for over a year for both imaging and observing and I've really enjoyed it. The camera body only was $495 (I didn't need any lenses) which made it very economical as compared to some other options.

Food for thought...


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rmollise
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Re: Which camera? new [Re: nytecam]
      #5682945 - 02/16/13 08:20 AM Attachment (22 downloads)

Quote:

Rod - precious few examples [=images] of what the Mallincam can do on faint stuff on this forum beyond hearsay me thinks




OK, if you don't feel inclined to take my word for it, or are worried I might be joshing or even fibbing, for god's sake, here's an image for you.

This was done with a Stellacam II at 10-seconds, and my Xtreme can easily best this. I just haven't been back to the Hickons.

Edited by rmollise (02/16/13 08:21 AM)


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mclewis1
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Re: Which camera? new [Re: nytecam]
      #5682956 - 02/16/13 08:32 AM

Quote:

Mark - not convinced cooling is essential [for my 'cool' running Lodestar] at <60s exp [get saturation in <2m @ f/3.6] but removing my severe orange LP via software does take a hit on data. LP filters before cam [which I've tried] needs increased exposure so a no-win option.

What we need is a Mallincam v Lodestar/others unbiased head-to-head on same DSO, same exposure and similar scope but don't think, on this forum, unbiased is going to happen



Maurice,

I agree, not essential but the cooling does make life a lot easier noise wise. Your work clearly shows the benefits of one alternative approach (stacking) to reducing image noise.

The physical filter issue is just one of the many realities of imaging. It's interesting that a number of Mallincam owners are pushing the exposure capabilities to enable some form of viewing under severely light polluted skies. Instead of 15-60s exposures they are going with multiple minutes. The filters are not the general LP type but rather very restrictive narrow band models. They of course now need good accurate tracking from their mounts but the results have been very surprising. The cameras are being worked very hard (and in a manner that Rock never originally designed them for but he has been gradually increasing this capability with each new model). In order to handle this more demanding type of viewing/imaging the cooling capabilities have been further improved (with the X2 model with it's improved cold finger and upgraded cooling control).

This is of course all very similar to the multiple filter narrow band imaging many folks with traditional imaging cameras are doing.

Yeah I'd also love to see some good well managed head to head comparisons.


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A. Viegas
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Re: Which camera? new [Re: mclewis1]
      #5683006 - 02/16/13 09:13 AM

Hickson 50 - on the Mallincam Website: Hickson 50

as the caption describes, SCT 10" 15 seconds. no processing whatsoever.

And here is another image, from this forum using 10" Newtonian and 56sec exposure, but under a full moon: Hickson50 under full moon

So... lets see the lodestar with same factors, 15 seconds and 56 seconds, no processing or tweaking.



Al


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ccs_hello
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Re: Which camera? new [Re: Dwight J]
      #5683055 - 02/16/13 09:37 AM

Quote:

... The new Orion G3 camera ...



Please note that G3 when it first showed up in the market, the software isn't mature enough and got a few negative feedbacks. I think for "imaging", the situation has improved. For LiveView (it's part of the product description), there is no user feedback up to this day. So the result can go one way or the other.

Clear Skies!

ccs_hello


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ccs_hello
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Re: Which camera? new [Re: A. Viegas]
      #5683088 - 02/16/13 09:56 AM

I do not recommend any head-to-head comparison that one side is a picture published in a website while the original picture publisher has not given the chance to defend himself, nor all info are disclosed.

We need scientifically provable/repeatable apple-to-apple comparison.
- under the same observation condition (LP and temperature)
- if using a filter, both have to use the same filter
- using the same OTA and same aux optics (e.g., focal reducer set at the same reduction ratio),
- document all camera parameters set (gain, exp time, gamma, etc.),
- present the data as original as possible. I.e. do not scale, do not process <-- if possible (some devices cannot defeat such settings), do as little compression as possible. Use astrobin or other sites to publish the data.

I.e., no details, no need to say mine is better than yours or even someone else' is better than another person's.
Adding non-scientifically quantified/qualified terms certainly is not helping. E.g., "million" times better. <-- is it an adjective or really means 10^6 (translated to 20 stops) better capability to gather photon flux .


P.S. Actually, in my own 0.02 view, I don't need any convincing. An extremely-high gain image system will definitely "see" more, so long as I can live with the noise level and spatial resolution.
Everything in life is a tradeoff.

P.S. the art of how to optimize these design parameters is well known (a few strategies and can be used in combination.) It's a matter that the astro-imaging/viewing market is so small that there aren't many players here. In that small market, majority of mfgs are concentrated in astro-imaging market and little on near-realtime view market. The situation changes a bit in recent days. Some began to re-purpose the imaging devices designed for one sector to the other (jack up the system gain and willing to tolerate low S/N), while the other side is building devices which can be dual-purposed (let smart brain - the computer software to do a better job, even possible in near-realtime.)
The world is turning and so should we.


Clear Skies!

ccs_hello


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jujumaster
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Re: Which camera? new [Re: mattflastro]
      #5683100 - 02/16/13 10:00 AM

Norden,
There is nifty little thing called a field de-rotator you can use for Alt-Az mounts. It looks a bit like a filter wheel and is a bit pricy, but it allows you to go beyond 60s. Rock Mallin uses it on his Alt-Az setup with great success.

Thanks,
Ian


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rmollise
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Re: Which camera? new [Re: ccs_hello]
      #5683105 - 02/16/13 10:03 AM

Quote:

I do not recommend any head-to-head comparison that one side is a picture published in a website.

We need scientifically provable/repeatable apple-to-apple comparison.




I ask again...have you actually USED a Mallincam or Stellacam? For one thing, while the video cameras can produce decent stills, their true forte is video images in near real time. If you don't like that, or think your DSI is better hooked to a computer, have fun.


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nytecam
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Re: Which camera? new [Re: ccs_hello]
      #5684645 - 02/17/13 05:19 AM Attachment (14 downloads)

Quote:

I do not recommend any head-to-head comparison that one side is a picture published in a website while the original picture publisher has not given the chance to defend himself, nor all info are disclosed. Clear Skies! ccs_hello


Exactly but unless one person/group uses the various camera[s] on same night and same equipment etc etc it ain't going to happen.

Below is my 0.02 with Hickson 50 in UMa from last night in 60s exp [sorry don't do video 56s!] via 12"SCT + SX Lodestar-C and ALL 5 gxys A-E recorded and annotated inset - not too bad for my LP London skies


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Stew57
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Re: Which camera? new [Re: nytecam]
      #5684836 - 02/17/13 09:31 AM

How do you get such dark looking sky at 60seconds? Both of my mallincams give a bright sky at anything over 40 seconds. Is there a filter for galaxies or some processing?

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Dwight J
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Re: Which camera? new [Re: Stew57]
      #5685260 - 02/17/13 01:47 PM

It's called post processing.

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GlennLeDrew
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Re: Which camera? new [Re: Stew57]
      #5685277 - 02/17/13 01:52 PM

Maurice's dark skies result from the use of a software 'filter' to cut out sky glow. I believe he doesn't use a physical filter, either!

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Dwight J
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Re: Which camera? new [Re: GlennLeDrew]
      #5685490 - 02/17/13 04:33 PM

Must be quite the filter. This would be a revolution in astroimaging. Must be similar to the filter that adds color to the final raw image output of the Lodestar C camera. "This means that your ‘raw’ images are initially
black and white, with a ‘tiled’ look, owing to the filter grid. Conversion into colour is usually handled
by processing the raw images on the following day, when you can take time to optimise the colour
balance, saturation etc." is a quote from the manual for the camera so any images that are in color have been post-processed. Various "challenges" by Nytcam to the output of a Mallincam would be bogus as the Mallincam does not require any post processing to get a color image. The real challenge would be to see the various cameras in action on NSN but I won't hold my breath.


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Stew57
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Re: Which camera? new [Re: Dwight J]
      #5685693 - 02/17/13 06:25 PM

He gets a lot out of his setup but with my lack of processing skill (read none) and my lack of time (you could insert laziness also) I will have to stick with my mallincams. I willhave to admitt that mpgxsvcd has me looking real hard at a GH3 later this year.

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norden
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Re: Which camera? new [Re: Dwight J]
      #5687068 - 02/18/13 02:49 PM

Thanks friends for all your answers and thoughts! I've come a long way in my decision. It will be a Mallincam VSS. I think more exposure range is an advantage against hyper plus. The question now is which sensor to select? Exview HAD CCD sensor seems to be a sensor for me. Short exposures with my ALT/AZ mount. Are there any of you who use this sensor and have experience with it. Please let me know.

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GlennLeDrew
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Re: Which camera? new [Re: norden]
      #5687279 - 02/18/13 04:37 PM

Norden,
My camera has the EXview HAD sensor, or some variant; I can't remember the details. To see what it can do with 30-56 second exposures on a C8 with f/3.3 focal reducer, go to page 86 of the image gallery at the top of this forum.

You should contact Rock Mallin for advice on the best CCD to have installed.


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Stew57
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Re: Which camera? new [Re: norden]
      #5687298 - 02/18/13 04:52 PM

I would opt for the class 0 chip whichever flavor I chose. I am not wanting to start a war but the class 0 chip (however Rock measures it) does have less hot pixels that the standard chip. I have one of each and the "star" fields of the closs 0 chip is much closer to reality. When doing 50 seconds at half gain the standard chip I have shows about 25 or so nice round tight stars more than the class 0 chip. For a lot (most) objects it won't make a difference but it just bugs me for some reason

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GlennLeDrew
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Re: Which camera? new [Re: Stew57]
      #5687688 - 02/18/13 08:08 PM

My chip is a class 0, and has one hot, three moderately hot, and about three dozen warm pixels.

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Stew57
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Re: Which camera? new [Re: GlennLeDrew]
      #5687950 - 02/18/13 10:21 PM

How long an integration do you have to do at middle gain setting for the warm pixels show?

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GlennLeDrew
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Re: Which camera? new [Re: Stew57]
      #5687990 - 02/18/13 10:43 PM

I can't recall to any exactitude, as I didn't test for this, but it requires something like 10(?) seconds at mid-gain for those warm pixels to show up. I'll have to look into this...

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Stew57
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Re: Which camera? new [Re: GlennLeDrew]
      #5688037 - 02/18/13 11:10 PM

My VSS class 1 has a constellation of stars I can count on at 20 seconds with low gain, no matter where I point the scope.

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Re: Which camera? new [Re: Stew57]
      #5688099 - 02/18/13 11:59 PM

Quote:

My VSS class 1 has a constellation of stars I can count on at 20 seconds with low gain, no matter where I point the scope.



is it changing with ambient temperature ?


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GlennLeDrew
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Re: Which camera? new [Re: mattflastro]
      #5688260 - 02/19/13 03:05 AM

As to any change in the warm/hot pixels with ambient temperature, I haven't looked for such a relationship.

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Stew57
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Re: Which camera? new [Re: GlennLeDrew]
      #5688400 - 02/19/13 07:29 AM

My temps are fairly stable through the night normally. They are usually a little on the warmside however. I never tried to test the difference. I really notice the sudden appearence of the particular constellation my class 1 vss shows when the integration is increased past about 12 seconds.

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ccs_hello
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Re: Which camera? new [Re: Stew57]
      #5688449 - 02/19/13 08:16 AM

RE: class 0, 1, 2 CCD sensor "binning" (means grade selection)

1. it is sensor technology dependent
2. there is no common industry-wide standard, different image sensor mfgs play their own. Some are consistent being applied over the years, and some ...
3. some imaging device vendors do a fairly good job on classifying "their own" made, but their is no industry-wide standard
4. Also note that with imaging device in the loop, the observed picture/pixel defects may not reflect the actual sensor quality (e.g., by dead pixel masking),
5. about individual feedback: take it as a grain or salt, since the test/observation is not under a normalized/standard test condition

some info:
- it is image sensor temperature dependent (also active and passive cooling)
- it is time dependent (more than just the temperature factor)
- it is image system gain, post-processing "dosage" dependent
- it needs to be qualified by a scientific method (one man's "hot" may mean another's "warm" pixel

Users of course can state their own observations (more info would be even nicer), I am just stating the caveats.

Now back to our regular scheduled program...


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mpgxsvcd
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Re: Which camera? new [Re: Stew57]
      #5688592 - 02/19/13 10:03 AM

Quote:

He gets a lot out of his setup but with my lack of processing skill (read none) and my lack of time (you could insert laziness also) I will have to stick with my mallincams. I will have to admit that mpgxsvcd has me looking real hard at a GH3 later this year.




My intent is not to sway anyone towards any one camera. They all have their strengths and weaknesses. I am in fact very interested in finding out more about the Mallincam. I think it is a great device. However, I am also skeptical about these Hickson 50 pictures with the Mallincam.

I am not skeptical that they are able to see that object with the Mallincam. I believe them that it can be done. However, I don't believe it is solely because the Mallincam is more sensitive.

The fact still remains that at some point adding more sensitivity will just make the light pollution and sky glow dominate the image. The Mallincam or the users are doing something with software or hardware that eliminates the sky glow effect. There simply is no way around it. You can't see a Mag 20 object in Mag 3 skies without removing the sky glow.

Now the real question is what are they doing? I tried to get the Hickson 50 the other night. However, the sky conditions were not good as we had clouds rolling in. I tried to take images in-between clouds and I could see all of the brighter stars around that area but not the Hickson group.

I was blowing out the sky in 23 seconds with my F4.0 scope and the strongest Light Pollution filter I could find. However, that was while taking RAW images. I tried taking an HDR image and I was able to extend the exposure time to 60 seconds at the same ISO value(ISO 6400) without blowing out the sky.

Basically with HDR I am using a 20 second base exposure and then combining it with a 60 second exposure for the really dark areas and using a 5 second exposure to keep the bright stars under control. I also fine tune the contrast so that it clips the light pollution but not the signal.

Basically when you stack images if you can get the sky glow to be under the lowest black point then summing or averaging zero plus zero will still be zero. As long as the signal you want registers more than zero then it will increase its exposure as you stack more and more images and the sky glow will still be at zero if it is clipped.

The big issue is getting the signal you want to be above the sky glow in very light polluted areas. I am able to reduce the sky glow by 1-2 stops with the light pollution filter and get another 1-2 stops with the HDR and contrast techniques. However, that is no where near enough to get from Mag 3 to Mag 20.

I really want to test out the Mallincam again now that we figured out the settings. I would like to see what it does on the exact same scope as another camera. Changing anything in the optical chain is not a fair comparison. Even my 3rd grade son knows that from doing science projects.

They have been testing the micro four thirds sensors lately at DXO mark. Now these tests are not the end all be all of testing because they only test the sensors themselves and they also neglect some things that I think are necessary. However, it is still interesting to note that All of the newest m4/3s cameras score higher than ALL of the Canon APS-C cameras including the T2i and the 7D. M4/3s still trails the Sony cameras and Nikon D7000 but it definitely shows that Canon APS-C cameras should not be used as the benchmark anymore.

http://www.dxomark.com/index.php/en%C3%83%C2%AF%C3%85%E2%80%B9%C3%A2%E2%82%AC...

If you want to try out m4/3s but you don't want to fork out $1300 for the GH3 then the new Olympus EPM-2 is an outstanding deal at $499 for the body only. This camera has the same sensor as the more expensive cameras and it also retains the live bulb mode feature that mimics the sense-up screen refresh of the Mallincam. It also goes for at least 8 minutes in bulb mode which should be plenty for near real time live viewing.


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mpgxsvcd
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Re: Which camera? new [Re: A. Viegas]
      #5688621 - 02/19/13 10:31 AM

Quote:

Hickson 50 - on the Mallincam Website: Hickson 50

as the caption describes, SCT 10" 15 seconds. no processing whatsoever.

And here is another image, from this forum using 10" Newtonian and 56sec exposure, but under a full moon: Hickson50 under full moon

So... lets see the lodestar with same factors, 15 seconds and 56 seconds, no processing or tweaking.



Al




I doubt that post processing would help enough to get that image. The only thing that could help is doing something in camera. What that is I don't know. However, I don't believe that simply getting a more sensitive camera will allow you to see a Mag 20 object under a full moon. There is something being done to remove the sky glow.


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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

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Re: Which camera? new [Re: mpgxsvcd]
      #5688694 - 02/19/13 11:22 AM

Quote:

Quote:

Hickson 50 - on the Mallincam Website: Hickson 50

as the caption describes, SCT 10" 15 seconds. no processing whatsoever.

And here is another image, from this forum using 10" Newtonian and 56sec exposure, but under a full moon: Hickson50 under full moon

So... lets see the lodestar with same factors, 15 seconds and 56 seconds, no processing or tweaking.



Al




I doubt that post processing would help enough to get that image. The only thing that could help is doing something in camera. What that is I don't know. However, I don't believe that simply getting a more sensitive camera will allow you to see a Mag 20 object under a full moon. There is something being done to remove the sky glow.



Have you taken any darks (of equal duration with the exposure you tried) with your camera? Just to make sure what stops you is really _sky_ glow and not amp glow or some in-camera noise reduction that can't be switched off even if you switched off noise reduction ? I have one of my cameras totally unusable for astro due to such a feature, noise reduction off is not actually off .


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Stew57
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Re: Which camera? new [Re: mattflastro]
      #5688732 - 02/19/13 11:49 AM

My comparison on hot pixels is between my class 1 vss and class0 xtreme used at the same time and settings. I do not know if the peltier cooling gives the same chip temps or not though. The vss shows a significantly larger amount of hot pixels. They are my best look8ng stars even at long integrations unguided.

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mpgxsvcd
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Re: Which camera? new [Re: mattflastro]
      #5688790 - 02/19/13 12:19 PM

Quote:


Have you taken any darks (of equal duration with the exposure you tried) with your camera? Just to make sure what stops you is really _sky_ glow and not amp glow or some in-camera noise reduction that can't be switched off even if you switched off noise reduction ? I have one of my cameras totally unusable for astro due to such a feature, noise reduction off is not actually off .




That is a good point. Yes I have taken the darks and they don't show any unusual signs of amp glow. However, I am not entirely sure what amp glow looks like? Can you demonstrate it or define it?


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Dwight J
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Re: Which camera? new [Re: mpgxsvcd]
      #5688891 - 02/19/13 01:07 PM

Travis: part or perhaps most of the reason you are reaching the sky fog limit sooner than a Mallincam is due to the actual size of the sensor. The same effect is seen when comparing low magnification to high, fast focal length to slow. When you "see" more sky you lose contrast. Your camera has a chip several times the size of the Mallincam so you "see" more sky. Just outside of the city (pop 90,000) I saw light pollutiion in a 20 sec exp using a normal lens and iso 6400. At the same site I saw sky fog affecting a 3 min exp @ F5 and iso 800. A deepsky filter was used for the last two. In my backyard within the city I can go 112 sec with my VSS and deepsky filter and have plenty of room for adjustment. Keep in mind that brightness and contrast can be adjusted on the fly, something nonvideo cameras can't do.

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nytecam
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Re: Which camera? new [Re: mpgxsvcd]
      #5688894 - 02/19/13 01:08 PM Attachment (10 downloads)

No bostin' but another routine and deeper Hickson 50 Lodestar shot from the other night with gxys between mag 15.95[A] to mag 18.45[E] according to Sloan DSS. A short dozen of other field gxys of similar mags marked with horizontal ticks, again identified via Sloan DSS - I'm very happy so enjoy

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mpgxsvcd
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Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: Which camera? new [Re: Dwight J]
      #5688998 - 02/19/13 02:25 PM

Quote:

Travis: part or perhaps most of the reason you are reaching the sky fog limit sooner than a Mallincam is due to the actual size of the sensor. The same effect is seen when comparing low magnification to high, fast focal length to slow. When you "see" more sky you lose contrast. Your camera has a chip several times the size of the Mallincam so you "see" more sky. Just outside of the city (pop 90,000) I saw light pollutiion in a 20 sec exp using a normal lens and iso 6400. At the same site I saw sky fog affecting a 3 min exp @ F5 and iso 800. A deepsky filter was used for the last two. In my backyard within the city I can go 112 sec with my VSS and deepsky filter and have plenty of room for adjustment. Keep in mind that brightness and contrast can be adjusted on the fly, something nonvideo cameras can't do.




A couple of things. I see what you are saying about focal length. I hope to test Tony's Mallincam and my GH3 on his 14" SCT when he gets it this week. At 2800+mm that should be a long enough focal length.

A couple of things you said are incorrect though. My camera has a cropped sensor mode. It can literally use the the center 1920x1080 pixels which gives it almost the exact same sensor size with a Different aspect ratio as the Mallincam's sensor. That does not eliminate sky glow though.


In addition the GH3 and Olympus cameras allow contrast and individual white balance adjustments and exposure adjustments on the fly while using the live view. I fail to see the difference between this and what the Mallincam can do.


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Chris A
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Reged: 02/03/07

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Re: Which camera? new [Re: nytecam]
      #5689116 - 02/19/13 03:38 PM Attachment (7 downloads)

Nice capture Maurice! Here is a live capture from NSN when I was showing my audience that a Mallincam is capable of capturing the Hickson 50 from a large city under mag 4 skies.

The image captured was a single 90 sec exposure using my MX and C9.25 @ f5.8 and no filters. Image was capture off the screen using Screen Shot Pilot and was only labelled with no post processing.

http://www.flickr.com/photos/47296963@N08/7061889393/in/photostream

Chris A
Astrogate


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Dwight J
scholastic sledgehammer
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Reged: 05/14/09

Loc: Lethbridge, Alberta, Canada
Re: Which camera? new [Re: mpgxsvcd]
      #5689209 - 02/19/13 04:22 PM

Hmmm. Interesting problem. Have you tried reducing ISO and if so, does it reduce or eliminate the sky glow? I believe ISO and gain are similar and if I have my gain at 4 or higher with the VSS I certainly encounter LP fog sooner. My DSLR images at lower ISO show less. Your local light pollution could be much worse than most too and trying to filter it out can interfere with exp times as you would have to expose longer and with more subs. I can do 5 min subs from my yard @ ISO 800 but 1600 is a washout. That is using a Lumicon Deepsky filter. I notice that the new street lamps we have here are white so it is hard to filter them out.

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mpgxsvcd
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Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: Which camera? new [Re: Dwight J]
      #5689235 - 02/19/13 04:35 PM

I am not sure if my light pollution is better or worse than anywhere else. I haven't really tested it at another light polluted place.

Again the only way to judge this is to stick these cameras on the same scope with the same sky and use the same filters and reducers. Simply put. The camera that displays the object best in the least amount of time is the winner. I think that camera will be the Mallincam but perhaps not by the margin some would expect.

Edited by mpgxsvcd (02/19/13 04:38 PM)


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Stew57
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Re: Which camera? new [Re: mpgxsvcd]
      #5689293 - 02/19/13 05:07 PM

The reason I am conntemplating picking up a GH3 to compliment the mallincams if for the FOV. I would like to see a Universe compared to the GH3.

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mclewis1
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Re: Which camera? new [Re: mpgxsvcd]
      #5689328 - 02/19/13 05:24 PM

Quote:

However, I am not entirely sure what amp glow looks like? Can you demonstrate it or define it?



Travis,

Have a look at Chris's great Hickson 50 image, amp glow is slightly visible in the upper left corner.


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GlennLeDrew
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Re: Which camera? new [Re: mpgxsvcd]
      #5689329 - 02/19/13 05:24 PM

Chip size has absolutely nothing to do with recorded sky glow. Just because a chip is large and therefore takes in more sky does not mean the surface brightness increases. No matter the chip size, the surface brightness per unit area is identical.

If size had an impact on sky glow, then when looking up at the night sky one could visually darken skyglow by merely peering through a toilet paper tube. A smaller portion of your retina is now being illuminated by the sky. But does this darken the sky (and, by inference, allow fainter stars to be seen)? Only insofar as it might eliminate other annoying light sources. But fundamentally, there will be no change. And so it it with detectors.

---

The detection of compact sources such as the galaxies in Hickson 50 is affected to some degree by the same factors impacting on point sources. These galaxies have reasonably high central surface brightness, for which sky glow must be quite bad to completely dominate.

Many galaxies have a peak core brightness of at least 18 magnitudes per square arcsecond, and often enough brighter still. And some even a quite bad sky such as the 18 MPSAS found at full Moon, or over a large metropolis, will have an 18 MPSAS object appearing twice as bright as the sky (object and sky brightness add together). All that's requires is sufficient *focal length* to allow the tiny galaxy to at least fill one bunch of the 4 pixels making up the Bayer group, or one pixel on a monochrome camera. Of course, a larger image filling more pixels results in something resembling more than a point-like, dim star. Once the focal length requirement is met, more aperture so as to result in a faster f/ratio and hence higher surface brightness affords a shorter exposure duration.

There is no sky glow reduction occurring in the Mallincam, or any such device. The laws of optics and the normal acquisition of photons is all that's required to obtain images of faint galaxies under even notable sky glow (provided object surface brightness is high enough to result in sufficient contrast.)


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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: Which camera? new [Re: mpgxsvcd]
      #5689361 - 02/19/13 05:42 PM

Quote:

I am not sure if my light pollution is better or worse than anywhere else. I haven't really tested it at another light polluted place.

Again the only way to judge this is to stick these cameras on the same scope with the same sky and use the same filters and reducers. Simply put. The camera that displays the object best in the least amount of time is the winner. I think that camera will be the Mallincam but perhaps not by the margin some would expect.



Let's assume a simple hypothetical experiment to figure out what's going on.
- assume we have 2 identical cameras. Same sensitivity, same camera noise, same well depth , etc.
- use one and the same telescope with each cam to image one and the same faint target. We select the target to be at the threshold of detectability for the given scope and cameras. Let's say a signal to noise of 3 . Obviously both cams will see the target equally well (poorly but detectable).
- now we change the conditions when camera #1 is used, we use a x2 barlow . Let's think what happens to the signal, noise and signal to noise . Without the barlow, there was a certain number of photons illuminating one pixel of the camera. When the barlow is inserted, the same number fo photons is spread over 4 times the area. That means 4 pixels are receiving in total the number of photons that a single pixel was receiving without the barlow.
Each pixel receives 4 times fewer photons when using the barlow.
But because the signal to noise was 3 , now it is 3/4 .
The reality is that such a signal can NOT be seen or detected in a single frame, whereas without the barlow, it could be seen (albeit poorly).
- Question: because the camera is used at the wrong image scale, which results in the target signal being lowered below the noise floor and the target being no longer detectable , is the camera suddenly BAD ? Or just used poorly?
- now let' use the other camera and insert a .5x focal reducer . Suddenly the camera will see a 4x increase in the signal to noise . Image will be much cleaner than without the reducer.
- looking at both cameras, is one worse than the other ? Or is just the optical system not configured to use the camera(s) properly ?
Judging by the results, the same camera with a barlow has 16 times worse signal to noise and can only detect targets that are 16 times brighter than the same camera with the .5x reducer.
-now let's say we didn't use barlows and reducers with 2 identical cameras.
Let's say we had cameras with identical performance but different size pixels.
The effect is exactly the same .
Conclusion is the same , you need to match the pixel scale , as in having both cameras see the same number of sky arcsec/pixel. Otherwise, the camera with the fewer arcsec/pixel will see a lower signal thru the same scope from the same target. This will reduce the signal to possibly under the noise floor.
If you're comparing 2 cameras one with 14 square micron pixels and another with 85 square micron pixels , you need to give the pixels the same signal .
That means each camera needs to see the same image scale (arcsec/pixel) .
Since the 2 camera pixels are vastly different in size, you need to adapt each to the optical system by using adequate reducers or barlows to achieve the same pixel scale .
The above applies if you want to compare camera performance with respect to signal to noise and detectability threshold .
The requirement to use the same scope is fair.
Having the same filters is possibly/maybe fair , depending on the cameras spectal response differences .
The requirement to not adapt the cameras to the scope is not .


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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: Which camera? new [Re: mattflastro]
      #5689443 - 02/19/13 06:30 PM

In all the above images, the Hicksons were at the threshold of detectability . Just for fun I measured the max brightness in each photo compared to the surrounding background and the ratio is less than 2 to 1 (with the exception of a referenced image taken with a 25' dob and a Canon, which was 3:1) .
So if you do the slightest thing to reduce signal to noise a mere 30% further they simply vanish under the noise floor. No matter how long you integrate you will only see more and more skyglow and noise.
In your shooting conditions, with a pixel scale that yields pixel illumination reduced to 10%, there's no way to see them , unless you stack about 100 frames with your current setup and exposure time, or you use a .33 reducer.


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Dwight J
scholastic sledgehammer
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Reged: 05/14/09

Loc: Lethbridge, Alberta, Canada
Re: Which camera? new [Re: GlennLeDrew]
      #5689454 - 02/19/13 06:37 PM

Well Glen, my eyes must be deceiving me. I see objects with better contrast by increasing magnification, effectively seeing less sky. A smaller chip works the same way - the light is spread out so each pixel receives less. If I imaged a section of sky at F5 and then at F10 with the same exposure, the sky in the F5 image will be brighter.

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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: Which camera? new [Re: Dwight J]
      #5689515 - 02/19/13 07:09 PM

Quote:

Well Glen, my eyes must be deceiving me. I see objects with better contrast by increasing magnification, effectively seeing less sky. A smaller chip works the same way - the light is spread out so each pixel receives less. If I imaged a section of sky at F5 and then at F10 with the same exposure, the sky in the F5 image will be brighter.



The sky will be brighter in the F5 per unit of area. However, noise and signal to noise are per pixel, and if pixel sizes are different....


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GlennLeDrew
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Re: Which camera? new [Re: mattflastro]
      #5689888 - 02/19/13 10:39 PM

Dwight,
You're conflating what you observe in the visual, afocal configuration with what happens when placing a sensor at the focus.

At the eyepiece, increasing magnification shrinks the exit pupil, which darkens the sky glow, and any other extended objects. For stars, the contrast is definitely improved, for a point source--unless so magnified that it is seen as the Airy disk--retains brightness while the sky dims. Extended targets like galaxies *seem* to improve in contrast only because they are now seen as larger, allowing more detail to be seen.

In short, the eyepiece view of the sky is dimmed because of the reduced exit pupil, *not* the reduced area of sky seen. A small scope at a given exit pupil will show a larger piece of sky than a big scope at the same exit pupil. Yet the sky in both cases has identical brightness.

And what occurs at the eyepiece is not directly applicable to imaging.


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