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01-20-2013, 11:22 PM - 1 Like   #436
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IC 443 Jellyfish Nebula

More from my aging K10D in the back yard.

We had more than a week of great, clear, cold winter weather. Night temperatures dropped below freezing which is rare for my area of California. After 6 nights of letting the camera do its thing, I stacked up the results and here they are:




This is from 162 individual frames stacked for 27 hours of integration.

I'm getting hooked on letting the camera gather data from the comfort of home. This has kept me from going out to the field where I probably would have gotten as good data in one night vs 6. Right now I have the ease of lots of time between twilights. Once summer comes I'll be dragging myself out to the dark sky sites.

01-21-2013, 01:12 AM   #437
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QuoteOriginally posted by smigol Quote
More from my aging K10D in the back yard.

We had more than a week of great, clear, cold winter weather. Night temperatures dropped below freezing which is rare for my area of California. After 6 nights of letting the camera do its thing, I stacked up the results and here they are:




This is from 162 individual frames stacked for 27 hours of integration.

I'm getting hooked on letting the camera gather data from the comfort of home. This has kept me from going out to the field where I probably would have gotten as good data in one night vs 6. Right now I have the ease of lots of time between twilights. Once summer comes I'll be dragging myself out to the dark sky sites.
Wow! That's a lot of integration time but good results. I was wondering. It's usually around -20c at night here. Would that help noise performance significantly or would it have to be a lot colder?
01-21-2013, 01:45 AM   #438
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For CMOS sensors, I believe that the rule of thumb is that you half the noise with every 8-10C drop in temperature until you start getting diminishing returns below -10C. Most astronomy cameras target -10C as the desired temperature for general use. Below that and there's a need for serious power in the field.

For what I've seen with my CCD based K10D, once it gets below 10C, there's really not much thermal noise left.

The -20C would really keep your camera cold - but the question remains, would the sensor actually be cold? What does the EXIF temperature reading say? You can access this value by loading the file in PhotoMe and looking under manufacturer notes. This is an inaccurate sensor reading, as the temperature is likely coming from some component fairly far away from the CMOS. I've found an uncooled camera will have as much as 10C over ambient when using long exposures. That's why I use a peltier cooler on my K10D. It helps to force the heat out of the camera and it stabilizes the camera temperature so that over the course of a night there's little variation.
01-21-2013, 08:56 AM   #439
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Nice job on the Jellyfish nebula. I have been wanting to get out again and have been stopped by a 2-3 week forecast of overcast and snow. Keep them coming!

01-21-2013, 06:40 PM - 1 Like   #440
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Imaging telescopes or lenses: Selfmade newtonian 180
Imaging cameras: Pentax K5
Mounts: NEQ6 PRO
Guiding telescopes or lenses: GS2C DIY 60 300
Guiding cameras: ZWO ASI120MM
Focal reducers: TeleVue ParacorrII
Software: photoshop
Filters: p2


Resolution: 1600x1600
Dates: Jan. 19, 2013
Frames: 7x260"
Integration: 0.5 hours
01-21-2013, 08:32 PM   #441
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QuoteOriginally posted by smigol Quote
For CMOS sensors, I believe that the rule of thumb is that you half the noise with every 8-10C drop in temperature until you start getting diminishing returns below -10C. Most astronomy cameras target -10C as the desired temperature for general use. Below that and there's a need for serious power in the field.

For what I've seen with my CCD based K10D, once it gets below 10C, there's really not much thermal noise left.

The -20C would really keep your camera cold - but the question remains, would the sensor actually be cold? What does the EXIF temperature reading say? You can access this value by loading the file in PhotoMe and looking under manufacturer notes. This is an inaccurate sensor reading, as the temperature is likely coming from some component fairly far away from the CMOS. I've found an uncooled camera will have as much as 10C over ambient when using long exposures. That's why I use a peltier cooler on my K10D. It helps to force the heat out of the camera and it stabilizes the camera temperature so that over the course of a night there's little variation.
Excellent ! Thanks for the answer! I'll check out the data. At -20c it sounds like I'm doing alright. Cheers !
01-21-2013, 09:51 PM   #442
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Quick, probably dumb often asked question here:

I have an old Jason refractor which I would like to mate my K-30 to once I get it. I know I need a T2 adapter, but I'm hung up on which tube I need to get to attach the adapter to (if any). I've seen references to 1.25's, .9-somethings, and 2 inch tubes and I can't seem to wrap my brain around which one I'd be needing.

I don't seem to have a photo handy of the scope (and taking one would require waking my wife up) so I'll have to post one later, but the telescope itself is a 910mm x 60mm refractor (I think).

If anyone could clue me in I'd be grateful.
01-22-2013, 12:59 AM   #443
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.965"

QuoteOriginally posted by Sagitta Quote
Quick, probably dumb often asked question here:

I have an old Jason refractor which I would like to mate my K-30 to once I get it. I know I need a T2 adapter, but I'm hung up on which tube I need to get to attach the adapter to (if any). I've seen references to 1.25's, .9-somethings, and 2 inch tubes and I can't seem to wrap my brain around which one I'd be needing.

I don't seem to have a photo handy of the scope (and taking one would require waking my wife up) so I'll have to post one later, but the telescope itself is a 910mm x 60mm refractor (I think).

If anyone could clue me in I'd be grateful.
The most common type is the 1.25" barrel however, I did some reading through other websites and forums and I believe your scope has the .965" eyepiece size. This is typical of cheaper department store telescopes. There are adapters that you can buy that will go from .965 to 1.25".

01-22-2013, 02:12 AM   #444
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QuoteOriginally posted by Sagitta Quote
Quick, probably dumb often asked question here:

I have an old Jason refractor ------

If anyone could clue me in I'd be grateful.
If GWARmacine is right and your scope has a 24.5mm / 0.965" eyepiece draw tube, the direct solution would be to get a 24.5mm nosepiece that screws directly into the T2-ring (c.f. 1 below).

However, such adapters seem to have become quite rare (as are 24.5mm eyepieces themselves) and an easier solution might be to get a 1.25"-to-T2 nosepiece (2 below) and a 24.5mm-to-1.25" eyepiece adapter (3 below). The adater shown in '2' can be found "everywhere" and he latter adapter type, '3' is still widely available.
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01-23-2013, 01:36 AM   #445
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M35 and NGC 2158

Here's another one from last week.

M35 and NGC 2158 as seen with my K10D.




This is the stack from 14 subs of 600 seconds at 400 ISO under less than perfect conditions.
Shot with the Pentax K10D on a Stellarvue SV4 with flattener and IDAS LPR V2 filter

Guided and calibrated using Maxim
Stacked and debayered using DSS
Processed with PixInsight
01-23-2013, 02:53 AM   #446
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QuoteOriginally posted by smigol Quote
Here's another one from last week.

M35 and NGC 2158 as seen with my K10D.




This is the stack from 14 subs of 600 seconds at 400 ISO under less than perfect conditions.
Shot with the Pentax K10D on a Stellarvue SV4 with flattener and IDAS LPR V2 filter

Guided and calibrated using Maxim
Stacked and debayered using DSS
Processed with PixInsight
Hello S.Migol,I know you remodel your cooling k10d And I want to copy it in my K5.Does the tec Close to the cmos sensor?How did you do?
01-23-2013, 09:25 AM   #447
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Peltier device on camera

QuoteOriginally posted by gs2c Quote
Hello S.Migol,I know you remodel your cooling k10d And I want to copy it in my K5.Does the tec Close to the cmos sensor?How did you do?
What I did with my K10D was a two-step process:

First I had it converted to full spectrum by Spencer's. At the time, they were doing a brisk business in conversions and they had an option to add a passive thermal control to it. I believe that it was some kind of heat transfer material that they put on the board or frame to help it shed heat. Comparing the local warm spots on an unconverted K10D and the modified one, I could feel that the bottom of the camera body and the LCD screen were warmer.

Second, I decided to find a way to help the camera shed heat from these warm spots. I picked up a complete peltier assembly from Tellurex that had a heatsink and peltier. Then I got a power control module with thermal probe from Oven Industries. Also, I got some thermal gel pad to help transfer heat on the uneven surface of the camera to the heatsink. I also used a bit of aluminum to wrap around the bottom of the camera to help transfer heat from that hot spot.

Here you can see the peltier device on the back of the camera:



And when it's off the camera, you can see the metal I've wrapped around the base:



Note in this second shot there are shims crammed into the edge of the mount. This is because with the weight of the heatsink device, there is sagging as the telescope moves.

When I first put the kit together, I didn't do anything special about the edge where the heatsink and the camera meet. During the summer as I used it, I noticed a lot of rime ice forming at this location. This is wasted energy, so I used an old wool sock to wrap around this gap. The sock helps insulate the gap and keeps the rime ice from forming. I do have to make sure that the sock doesn't create a gap between the heat sink and the camera. If there is a gap, then the peltier will not work and may fail.

In looking at the service manual for the K10D, I can see the reason for the hot spots I've noted. The LCD is pressed against several components on a circuit board. The frame that holds the CCD is connected to the frame that is also connected to the tripod socket. Thus, with heat transfer on these two spots, the setup does a pretty good job of removing heat from the camera. I am not sure if these are the same in a K5. For someone that has a K5, you'd need to run it for a while and feel the outside of the body to determine if a similar setup would work.

Note that I do not use a battery inside the camera. I always use an external power supply. Batteries generate heat and they don't work very well at low temperatures.

Eventually, I'll retire this K10D and just use it for IR pictures or widefield piggyback shots. I will likely replace it with the QHY10 astronomy camera because it uses the same Sony CCD. The advantage there will be no amp glow and more efficient peltier cooling.

If I were to recreate this cooling, I'd want to work closely with the people doing the IR conversion. I'd want to see if there would be a way to get better thermal transfer pad added to the frame of the camera. I'm not convinced that a cold finger to the CCD would make a difference on the K10D because of the bad amp glow. I've put the camera in the freezer and let it get down to -10C and there is still amp glow. Also, adding a cold finger to the sensor would break the weather sealing. During a session, the K10D will become covered in dew and thus I'd prefer to not have a risk of water intrusion. Another thing that I would do would be to assemble my own heat sink device (I may do this someday). I'd want to have the option to use a lightweight video-card style cooler. I'd also like to investigate how small a device I could use to better manage the power budget. The existing setup will pull 3 amps all the time. This requires a lot of battery power over the course of a night - my power budget for all the gear is about 50 amp hours.

Lastly, there are complete cooling boxes that can be purchased or if you are crafty you can make your own. I decided to go with a direct-contact approach rather than trying to cool the air around the camera in the hopes it would cool the components. I'd already tried this approach by using the camera without a cooler in the cold of winter and could see that temperatures were not stable and the camera would still become rather warm at least 10C over ambient. With the device in place, the EXIF temperatures are stable over the course of a night - varying just a few degrees - and are usually at or very near ambient.
01-23-2013, 09:33 AM   #448
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Wow, crazy devices you guys use!

A cross post from the Q section. I filmed the moon with loads of turbulence in the air with my Pentax Q and Da* 300mm F4 coupled to a Kenko 1.5x PzAF TC.
01-23-2013, 06:24 PM   #449
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QuoteOriginally posted by smigol Quote
What I did with my K10D was a two-step process:

First I had it converted to full spectrum by Spencer's. At the time, they were doing a brisk business in conversions and they had an option to add a passive thermal control to it. I believe that it was some kind of heat transfer material that they put on the board or frame to help it shed heat. Comparing the local warm spots on an unconverted K10D and the modified one, I could feel that the bottom of the camera body and the LCD screen were warmer.

Second, I decided to find a way to help the camera shed heat from these warm spots. I picked up a complete peltier assembly from Tellurex that had a heatsink and peltier. Then I got a power control module with thermal probe from Oven Industries. Also, I got some thermal gel pad to help transfer heat on the uneven surface of the camera to the heatsink. I also used a bit of aluminum to wrap around the bottom of the camera to help transfer heat from that hot spot.

Here you can see the peltier device on the back of the camera:



And when it's off the camera, you can see the metal I've wrapped around the base:



Note in this second shot there are shims crammed into the edge of the mount. This is because with the weight of the heatsink device, there is sagging as the telescope moves.

When I first put the kit together, I didn't do anything special about the edge where the heatsink and the camera meet. During the summer as I used it, I noticed a lot of rime ice forming at this location. This is wasted energy, so I used an old wool sock to wrap around this gap. The sock helps insulate the gap and keeps the rime ice from forming. I do have to make sure that the sock doesn't create a gap between the heat sink and the camera. If there is a gap, then the peltier will not work and may fail.

In looking at the service manual for the K10D, I can see the reason for the hot spots I've noted. The LCD is pressed against several components on a circuit board. The frame that holds the CCD is connected to the frame that is also connected to the tripod socket. Thus, with heat transfer on these two spots, the setup does a pretty good job of removing heat from the camera. I am not sure if these are the same in a K5. For someone that has a K5, you'd need to run it for a while and feel the outside of the body to determine if a similar setup would work.

Note that I do not use a battery inside the camera. I always use an external power supply. Batteries generate heat and they don't work very well at low temperatures.

Eventually, I'll retire this K10D and just use it for IR pictures or widefield piggyback shots. I will likely replace it with the QHY10 astronomy camera because it uses the same Sony CCD. The advantage there will be no amp glow and more efficient peltier cooling.

If I were to recreate this cooling, I'd want to work closely with the people doing the IR conversion. I'd want to see if there would be a way to get better thermal transfer pad added to the frame of the camera. I'm not convinced that a cold finger to the CCD would make a difference on the K10D because of the bad amp glow. I've put the camera in the freezer and let it get down to -10C and there is still amp glow. Also, adding a cold finger to the sensor would break the weather sealing. During a session, the K10D will become covered in dew and thus I'd prefer to not have a risk of water intrusion. Another thing that I would do would be to assemble my own heat sink device (I may do this someday). I'd want to have the option to use a lightweight video-card style cooler. I'd also like to investigate how small a device I could use to better manage the power budget. The existing setup will pull 3 amps all the time. This requires a lot of battery power over the course of a night - my power budget for all the gear is about 50 amp hours.

Lastly, there are complete cooling boxes that can be purchased or if you are crafty you can make your own. I decided to go with a direct-contact approach rather than trying to cool the air around the camera in the hopes it would cool the components. I'd already tried this approach by using the camera without a cooler in the cold of winter and could see that temperatures were not stable and the camera would still become rather warm at least 10C over ambient. With the device in place, the EXIF temperatures are stable over the course of a night - varying just a few degrees - and are usually at or very near ambient.
Do you mean even if the installation of active cooling can only drops 10C?The same as air temperature?
Inside your camera does not do too much transformation.Just take advantage of the camera keel to transfer heat.

Last edited by gs2c; 01-23-2013 at 06:33 PM.
01-23-2013, 11:26 PM   #450
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QuoteOriginally posted by gs2c Quote
Do you mean even if the installation of active cooling can only drops 10C?The same as air temperature?
Inside your camera does not do too much transformation.Just take advantage of the camera keel to transfer heat.
Here's what I have seen:

Before using cooling (and after the conversion which added the passive thermal additions inside the camera), I would routinely see EXIF temperatures at least 10C above ambient. For example, I remember one evening in the field where the local temperature was dropping to about 10C. During the session, the camera started warming up and finally reported temperatures of 25C. When I touched the outside of the camera with my cold fingers, I could feel warm spots. These are the spots I targeted for putting the cooler.

After using this cooling, I have noted that the camera will track much closer to ambient. I've not seen it drop below ambient. Another thing that happens is that thermal equilibrium is reached faster and stays steady. Having the steady cooling seems to help with the noise profile and I am getting much smoother results.

Could it be possible to increase the effective cooling? Maybe. I'll play with wrapping the camera body with more insulation to better use the energy. This will be an ongoing exercise into the summer.
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