New camera
New camera
Since it's cloudy should I be building a library of darks? Or is it easier to just make them as I need them...
Bruce D
Re: New camera
Bruce
I suggest building a dark library ASAP.
The good thing about your camera is you can control the temp. So set the temp to -10C, set the exposure to 1 minute (or 2 or 4 ...) and take a bunch of images. Just make sure you have determined which gain to use (and you keep the lens cap on). I currently use Unity Gain but I have darks for both Unity Gain and High Dynamic Range. You can do this during the day time and just keep an eye on the progress.
This also is a good time to see how your camera functions while taking a series of exposures.
My dark Library looks like this.
Unity Gian
0 dec C 30 sec
0 Dec C 1 minute
0 deg C 2 minutes
0 Deg C 4 minutes
0 deg C 5 minutes.
same set for -10C and -20C.
I take at least 50 exposures of each (100 is better).
I then use Images Plus to generate a master for each set so that when I do image processing I only have to select the master.
Doing this eliminates the need for even thinking about darks while you are imaging.
You can do the same for bias frames (just set the exposure to 0.001 sec). So you can have a 0 C, -10C, and -20C set of biases...this does not take long since very short exposure.
Roger
I suggest building a dark library ASAP.
The good thing about your camera is you can control the temp. So set the temp to -10C, set the exposure to 1 minute (or 2 or 4 ...) and take a bunch of images. Just make sure you have determined which gain to use (and you keep the lens cap on). I currently use Unity Gain but I have darks for both Unity Gain and High Dynamic Range. You can do this during the day time and just keep an eye on the progress.
This also is a good time to see how your camera functions while taking a series of exposures.
My dark Library looks like this.
Unity Gian
0 dec C 30 sec
0 Dec C 1 minute
0 deg C 2 minutes
0 Deg C 4 minutes
0 deg C 5 minutes.
same set for -10C and -20C.
I take at least 50 exposures of each (100 is better).
I then use Images Plus to generate a master for each set so that when I do image processing I only have to select the master.
Doing this eliminates the need for even thinking about darks while you are imaging.
You can do the same for bias frames (just set the exposure to 0.001 sec). So you can have a 0 C, -10C, and -20C set of biases...this does not take long since very short exposure.
Roger
Roger M.
Celestron CPC1100 EDGE, Stellarvue 130T refractor dual mounted on iOptron CEM120 on permanent pier mounted in Observatory. Imaging camera ZWO ASI2600 OSC, guide camera Lodestar or ZWO ASI290MM.
Celestron CPC1100 EDGE, Stellarvue 130T refractor dual mounted on iOptron CEM120 on permanent pier mounted in Observatory. Imaging camera ZWO ASI2600 OSC, guide camera Lodestar or ZWO ASI290MM.
Re: New camera
Hi Bruce,
Been wondering when we were going to hear about that new camera. And maybe get an idea as to what your setup's going to be.
Your first images are experimental and will be poor. Darks, bias, flats and dark flats are sort of secondary considerations at this point.
Because dark frames should be run at the same temperature, exposure length, gain, and pixel array size as the lights, there are an intimidating number of combinations.
At ambient temperature, contrary to what you read, I've found the ASI2600MC-P to be very noisy. Since cooler weather standardized cooling at -20°C (which is only about 55% of the dual stage Peltie rcooling capacity.)
I've also standardized using the full size array. After all, that's what I paid for.
As for gain, I've been setting it at 200. But as discussed elsewhere in recent board postings, increasing gain doesn't actually increase sensitivity. ZWO says "When the gain value is 100, the magical HCG high gain mode is turned on, the readout noise is greatly reduced, and the dynamic range is basically unchanged. It is recommended to set the gain to 0 or gain 100 in deep space." So for my next set of darks I'm going to emulate Roger M and leave a little bit of leeway, running gain at 116 (or perhaps a nice round 120.
That said, for your initial setup I recommend a gain of 200. You're learning the camera and the brighter image display will better allow you to make the many on-the-fly adjustments associated with a new setup.
That covers temperature, array and gain.
Last time out I'd been running the Hyperstar at less than full frame size, and just run that set of darks for 1, 2 ,3 & 5 minutes. That's a good starting point. My more complete sets of darks run 15s, 30s, 1m, 90s, 2m, 3m, 4m, 5m and 8m. With CCDs 15 frames was almost overkill. But as Mark M pointed out elsewhere on this board you may want between 30 and 80 frames to smooth out CMOS. So it can get very time consuming.
Setting up a dark library can be creative. It won't hurt to create darks at this stage.
How are you planning on setting up? What scope?
____________________________________________
Just caught Roger's posting as I write.
Different software uses different approaches. With SharpCap the software automatically creates master darks and just saves the master. And it incorporates bias corrections into the flat frames. Robin disregards taking separate dark frames to correct the flat frames, claiming that with CMOS it's unnecessary.
Even though Softcap develops real time images, and you can stretch the image as you're seeing it build, the saved stack is not stretched. And darks and flats haven't been added to the individual frames that are saved with the stacked frame. So post processing is necessary.
Been wondering when we were going to hear about that new camera. And maybe get an idea as to what your setup's going to be.
Your first images are experimental and will be poor. Darks, bias, flats and dark flats are sort of secondary considerations at this point.
Because dark frames should be run at the same temperature, exposure length, gain, and pixel array size as the lights, there are an intimidating number of combinations.
At ambient temperature, contrary to what you read, I've found the ASI2600MC-P to be very noisy. Since cooler weather standardized cooling at -20°C (which is only about 55% of the dual stage Peltie rcooling capacity.)
I've also standardized using the full size array. After all, that's what I paid for.
As for gain, I've been setting it at 200. But as discussed elsewhere in recent board postings, increasing gain doesn't actually increase sensitivity. ZWO says "When the gain value is 100, the magical HCG high gain mode is turned on, the readout noise is greatly reduced, and the dynamic range is basically unchanged. It is recommended to set the gain to 0 or gain 100 in deep space." So for my next set of darks I'm going to emulate Roger M and leave a little bit of leeway, running gain at 116 (or perhaps a nice round 120.
That said, for your initial setup I recommend a gain of 200. You're learning the camera and the brighter image display will better allow you to make the many on-the-fly adjustments associated with a new setup.
That covers temperature, array and gain.
Last time out I'd been running the Hyperstar at less than full frame size, and just run that set of darks for 1, 2 ,3 & 5 minutes. That's a good starting point. My more complete sets of darks run 15s, 30s, 1m, 90s, 2m, 3m, 4m, 5m and 8m. With CCDs 15 frames was almost overkill. But as Mark M pointed out elsewhere on this board you may want between 30 and 80 frames to smooth out CMOS. So it can get very time consuming.
Setting up a dark library can be creative. It won't hurt to create darks at this stage.
How are you planning on setting up? What scope?
____________________________________________
Just caught Roger's posting as I write.
Different software uses different approaches. With SharpCap the software automatically creates master darks and just saves the master. And it incorporates bias corrections into the flat frames. Robin disregards taking separate dark frames to correct the flat frames, claiming that with CMOS it's unnecessary.
Even though Softcap develops real time images, and you can stretch the image as you're seeing it build, the saved stack is not stretched. And darks and flats haven't been added to the individual frames that are saved with the stacked frame. So post processing is necessary.
Pete P.
Re: New camera
Thanks guys, these things will make more sense to me when I'm actually using them.
Unfortunately the rare clear nights have occured either when I've had a very long day, or I have family things to do but I'll get out there eventually. I plan to start out with the 10" SCT if for no other reason than it being the scope I am most familiar with. I have some question as to whether it is too heavy for the CGEM, I'll find out. I have an ASI 1224 planetary camera I plan to use on a small refractor as a guide setup, though I'm curious if using sharpcap to get a very accurate polar alignment will allow unguided subs and if so, for how long. The f10 SCT will have a pretty narrow fov and it won't take much error for stars to streak so it might not work at all. I have a 0.5 focal reducer kicking around somewhere I am considering it might be good to start off with that, perhaps it will make for a somewhat more forgiving setup.
Unfortunately the rare clear nights have occured either when I've had a very long day, or I have family things to do but I'll get out there eventually. I plan to start out with the 10" SCT if for no other reason than it being the scope I am most familiar with. I have some question as to whether it is too heavy for the CGEM, I'll find out. I have an ASI 1224 planetary camera I plan to use on a small refractor as a guide setup, though I'm curious if using sharpcap to get a very accurate polar alignment will allow unguided subs and if so, for how long. The f10 SCT will have a pretty narrow fov and it won't take much error for stars to streak so it might not work at all. I have a 0.5 focal reducer kicking around somewhere I am considering it might be good to start off with that, perhaps it will make for a somewhat more forgiving setup.
Bruce D
Re: New camera
Bruce, forget the f/5 focal reducer. Focal reducers are actually image size reducers for use when image size at the focal plane exceeds the boundaries of a small imaging chip. Your C sized chip does that without the focal reducer, and to introduce the focal reducer only creates vignetting. Even with the slight f8.6 reduction I'd tried the vignetting was so severe that flats were unworkable.
My first "getting to know your" work with the ASI2600 was to image through the guide scope and guide thru the main scope. There are so many issues with imaging at long focal lengths that it was easier to just deal with one problem at a time.
My first "getting to know your" work with the ASI2600 was to image through the guide scope and guide thru the main scope. There are so many issues with imaging at long focal lengths that it was easier to just deal with one problem at a time.
Pete P.
Re: New camera
Pete unfortunately i don't have a decent mid size scope for imaging. I have the 5" ETX which is a fine little scope but it's not a short fl instrument either, and it cannot accept a 2" ep holder. My 66mm ED refractor doesn't have enough focuser in-travel to bring these cameras to focus so that's out. For a guide scope I'm planning to use a nice little refractor, about 50mm aperture, I'm guessing between 300 - 400 mm fl. No color that I can see, and a very nice indexed helical focuser. I got the scope from Commander Cosmos at the Stellafane swaps. A larger guide scope would be better, but another scope isn't in my near future and I don't know that the mount will handle the additional weight of an 80mm scope. The other option would.be to make use of a turret gizmo that has an OAG port but I envision catching a decent guide star on the little prism could be difficult with the small fov of the schmidt. I can try imaging through the guide scope I have and see what happens, i was very pleasantly surprised with what i captured with a zoom lens on my DSLR wkth a single 30 second exposure, and the aperture of the zoom wasn't substantially more than my guide scope. Well, lots to experiment with!
Bruce D
Re: New camera
Hi Bruce,
The ASI2600 uses a female 42mm T-thread for mounting. And the 28mm diagonal of your chip will not experience vignetting from a 42mm T-thread. Nor will it have problems with a 1.25" tube to male T-thread adapter as that's 31.75" wide. And it's how I mount the 2600 to the little piggybacked 80mm Orion.
Some/most refractors require the use of T-thread extension tubes to back the camera out far enough to achieve focus. Expect that like all of us you've got a T-thread adapter collection, and if it'll help I've an extra 1.25" tube to male T-thread adapter.
We're looking ahead at a week of overcast. Mount the camera on a small scope and get to play with it a bit. Give you a jump start, eh?
The ASI2600 uses a female 42mm T-thread for mounting. And the 28mm diagonal of your chip will not experience vignetting from a 42mm T-thread. Nor will it have problems with a 1.25" tube to male T-thread adapter as that's 31.75" wide. And it's how I mount the 2600 to the little piggybacked 80mm Orion.
Some/most refractors require the use of T-thread extension tubes to back the camera out far enough to achieve focus. Expect that like all of us you've got a T-thread adapter collection, and if it'll help I've an extra 1.25" tube to male T-thread adapter.
We're looking ahead at a week of overcast. Mount the camera on a small scope and get to play with it a bit. Give you a jump start, eh?
Pete P.
Re: New camera
Hey Bruce, did you get out last night? With the remounting of the Hyperstar achieving/finding focus was my goal. Lots of cloud but caught a brief enough break to focus and then snap a quickie of Luna.
The moon is the most wonderful object for catching an alignment on a long focal length scope. Here ‘tis.
Subsequent calculations derived from frame measurements determined that there’s a 1°47’ X 1°11’ FOV. (2.13° diagonal) And the scope’s running at an equivalent FL of 760mm (f/2.14) Never before had anything approaching this. Like another new telescope even..
Vignetting was unworkable with the previous Hyperstar mount setup. It may be a bit better now:
Next step is catching a new flat field. The flame/horsehead separation is only about 40’ and I’m looking forward to that image.
The moon is the most wonderful object for catching an alignment on a long focal length scope. Here ‘tis.
- FOV perspective ps.jpg (43.5 KiB) Viewed 1780 times
Vignetting was unworkable with the previous Hyperstar mount setup. It may be a bit better now:
- vignetting situation ps.jpg (207.92 KiB) Viewed 1780 times
Next step is catching a new flat field. The flame/horsehead separation is only about 40’ and I’m looking forward to that image.
Pete P.
Re: New camera
Nice Pete! Not having a permanent setup I can't really do spur of the moment stuff here, I did look out a number of times and most times I couldn't even see a bright spot in the clouds where the moon was, I have to be pretty sure of several hours of clear sky to make it worth lugging everything out, polar align, star align... winter- ugh!
Bruce D