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Hilmi
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Re: Understanding STF-8300M & STT-8300M new [Re: jerryyyyy]
      #5738969 - 03/17/13 03:51 PM

So far I have gone down to -30°C without noticing any RBI problems on my 20 min exposures in Ha . So I have not had the need to use this feature. The only time I have had this problem was with realy bright Stars

To my understanding the only way to activate the feature is through the SBIG supplied software or Via ethernet interface


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bilgebayModerator
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Re: Understanding STF-8300M & STT-8300M new [Re: Hilmi]
      #5739031 - 03/17/13 04:23 PM

Hi Hilmi,

If you really want to see RBI, shoot moon first, then shoot a dark or some other objects. If you don't see moon replicated then you are in goos shape. This test will give you an idea about your camera.

Warning: Maybe it is a good idea not to do this test and keep using your camera happily


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jerryyyyy
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Reged: 10/06/11

Loc: Stanford, California
Re: Understanding STF-8300M & STT-8300M new [Re: bilgebay]
      #5739938 - 03/18/13 01:02 AM

If it is not broken, do not fix it....

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Hilmi
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Re: Understanding STF-8300M & STT-8300M new [Re: jerryyyyy]
      #5739960 - 03/18/13 01:29 AM

Sedat if you really want to see RBI try the St402me. Mine used to leave ghosts in the frame at -10° C when imaging m81 at f10.

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mmalik
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Re: Understanding STF-8300M & STT-8300M new [Re: MattThomas]
      #5740037 - 03/18/13 03:09 AM

Quote:

A window heater is used to keep the window above the dew point so there is no condensation on the exterior of the window.

Desiccant is used to keep the inside of the CCD chamber dry, so that when you cool the CCD below the dew point you do not get condensation or frost on the CCD.

Both are very active solutions to prevent different problems.

...

The STT camera system uses sapphire windows. These do not need heating, nor do they need to be thick.




Bear with me; following is a 'mix and match of camera system features vs. chip offerings' question...


STT seems to have pretty elaborate moisture control measures which obviously contribute to the premium pricing of these units. On a flip side, SBIG doesn't offer a chip that some may consider the latest in CCD, e.g., ICX694.


Given all the interest in ICX694, I would like to discuss where such (non-SBIG) camera systems stand when it comes to moisture control features (heaters, desiccants, etc.) and if this could be a potential problem regardless of those systems' latest and greatest chip offerings. Here are few questions/considerations:


•Alta F694/Ascent A694 mention 'moisture free chambers', what does it mean in comparison to STT moisture control measures?

•What is major difference between Alta F694 & Ascent A694? What are Alta F694 & Ascent A694 prices?

•There seems to be a disparity of cooling levels offered among ICX694 systems; how would it affect condensation and preventive measures offered or lack thereof?

•Do Atik460EX/QHY22/SXVR-H694 offer any moisture control measures? If no, shouldn't that be a concern?

•How would you rate/rank these ICX694 camera systems overall; good, bad, ugly?

•Is following chart accurate representation of all things ICX694?


Please elaborate your answers for learning sake.


Note: SBIG/FLI/QSI do not offer ICX694 systems (correction welcome).


ICX694 Specs:
Type:.....................Interline
Diagonal (mm):......15.99
Pixels (HxV):..........2750x2200
Pixel Size (um):......4.54
Pixels (Total):.........6.31M
Readout Noise:.......5e-
QE (400nm):..........62%
Peak QE (500nm):...77%





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jerryyyyy
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Reged: 10/06/11

Loc: Stanford, California
Re: Understanding STF-8300M & STT-8300M new [Re: mmalik]
      #5740602 - 03/18/13 12:21 PM

Guys,

Any experiences with SBIG Adaptive Optics? Pricy but they have a system for the STT8300M:

https://www.sbig.com/products/adaptive-optics/ao-8t/

Has been suggested to me as a way of significantly improving guiding. My skys are basically lousy and I can just watch the guide star scintillate in the image, even with 3x3 binning.

Given what I paid for this camera, this is a 10-5% add on.


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AstroGabe
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Reged: 01/10/10

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Re: Understanding STF-8300M & STT-8300M new [Re: jerryyyyy]
      #5740618 - 03/18/13 12:29 PM

I'm considering this addition too, but mainly to improve guiding on my ATLAS mount. I have yet to experiment w/ the ccd on my 9.25 Edge, but think the 2350mm fl and weight might be too much for the mount to take for good guiding. So I'm interested also in what other people have to say about the AO-8 and STT combination.

Gabe


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pfile
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Reged: 06/14/09

Re: Understanding STF-8300M & STT-8300M new [Re: AstroGabe]
      #5741077 - 03/18/13 04:27 PM

jerryyyyy, i have the STT-8300M, FW8-STT and AO-8. i bought the AO-8 in an attempt to compensate for the performance of my G11 but as you can see from my .sig i am now using a mach1gto.

i'm sure this is user error, but i've found that no matter how good my polar alignment is, the AO is reaching it's tilt/tip limits in 4-6 minutes. this means that the guiding software has to 'bump' the star back with the mount's guiding controls.

if your subexposure length is longer than the AO's period, then all your subs will have streaked star lines on them. with a narrowband filter this was not as big of a problem for me (though in the integrated result below you can see the stars have weird shapes). with LRGB filters it's definitely a spoiled sub.

one piece of advice i got was to really crank up the mount's guide rate so that the time to bump back is minimized. i have not tried that yet - the mach1gto tracks so smoothly that i've just turned off the AO-8 and am autoguiding the traditional way for the time being.

here's a horsehead taken with an AT10RC, STT-8300M + 5nm astrodon, and the AO-8. you can see the artifacts on the bright stars.



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jerryyyyy
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Reged: 10/06/11

Loc: Stanford, California
Re: Understanding STF-8300M & STT-8300M new [Re: AstroGabe]
      #5741379 - 03/18/13 06:38 PM

Quote:

I'm considering this addition too, but mainly to improve guiding on my ATLAS mount. I have yet to experiment w/ the ccd on my 9.25 Edge, but think the 2350mm fl and weight might be too much for the mount to take for good guiding. So I'm interested also in what other people have to say about the AO-8 and STT combination.

Gabe




Nothing is easy.

Interested to hear about the weight worry. I think you may be OK. I just added my Nikon D800 to my set-up to get some wide angle shots and it guides no worse. This must add 5 lbs, but I can still ballance it well.

I am using the Celestron FR to get my 2032 down to 1360, but you get a lot of distortions in the periphery and need to crop them out. Also there is an unpleasant "horseshoe" that appears around bright stars in the periphery... often cannot crop it out.

Between a rock and a hard place. I think I have tweaked my Atlas with the help of a friend to get the work gear working well... this is easier than it sounds as the adjustment is kinda hidden unless you have someone draw you a map.

BTW I was thinking about getting something bigger than the C8.. maybe will not help much in my efforts.


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jerryyyyy
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Reged: 10/06/11

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Re: Understanding STF-8300M & STT-8300M new [Re: pfile]
      #5741390 - 03/18/13 06:41 PM

Quote:

jerryyyyy, i have the STT-8300M, FW8-STT and AO-8. i bought the AO-8 in an attempt to compensate for the performance of my G11 but as you can see from my .sig i am now using a mach1gto.

i'm sure this is user error, but i've found that no matter how good my polar alignment is, the AO is reaching it's tilt/tip limits in 4-6 minutes. this means that the guiding software has to 'bump' the star back with the mount's guiding controls.

if your subexposure length is longer than the AO's period, then all your subs will have streaked star lines on them. with a narrowband filter this was not as big of a problem for me (though in the integrated result below you can see the stars have weird shapes). with LRGB filters it's definitely a spoiled sub.

one piece of advice i got was to really crank up the mount's guide rate so that the time to bump back is minimized. i have not tried that yet - the mach1gto tracks so smoothly that i've just turned off the AO-8 and am autoguiding the traditional way for the time being.

here's a horsehead taken with an AT10RC, STT-8300M + 5nm astrodon, and the AO-8. you can see the artifacts on the bright stars.






Have you asked the guys at SBIG about how to get around this. They think about this a lot. Maybe they have better ideas. Guess this will not help....


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Hilmi
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Re: Understanding STF-8300M & STT-8300M new [Re: jerryyyyy]
      #5742204 - 03/19/13 02:33 AM

It could be an issue of focal length too high for the G11 to cope with.

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pfile
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Reged: 06/14/09

Re: Understanding STF-8300M & STT-8300M new [Re: Hilmi]
      #5742209 - 03/19/13 02:36 AM

the image above was taken with the mach1gto. the issue is that the polar alignment is not good enough, and the AO-8 reaches it's limits too fast. this would happen with any mount. my point though is that my polar alignment was pretty good by my standards (20 min+ drift alignment) and yet it's not good enough for the AO-8 and long exposures.


my particular G11 is not compatible with long focal lengths, that is for sure. with some work i'm sure it could work okay but i didn't really want to become a G11 mechanic. i just want to image.


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Hilmi
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Re: Understanding STF-8300M & STT-8300M new [Re: pfile]
      #5742215 - 03/19/13 02:41 AM

As an experiment try drift wligning using pempro then imaging with the AO unit. I am curious how that would work. Should that fail, drop me a message if you want to sell your AO8 T

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pfile
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Reged: 06/14/09

Re: Understanding STF-8300M & STT-8300M new [Re: Hilmi]
      #5742233 - 03/19/13 03:09 AM

i've already done that experiment. same issue, and this is on a target with a reasonably high declination.

i think my problem is i have the older mach1gto and when you loosen the azimuth plate in order to adjust it, the altitude gets messed up. so i can only get my PA so close. i should probably upgrade the AZ plate to the new one which solves this problem.

i had the idea to try guiding the mount with my external guidescope, and then also guide with the AO. the theory being that the guidescope would keep the mount pointed in the right place. but due to differential flexure, eventually the two guiders would drift apart, the AO would lose the star, and then it would all be over. i can't tell PhD to bump the mount.

i guess i will still try this to see if we're talking about hours worth of imaging or just minutes.


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MattThomas
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Reged: 07/28/06

Re: Understanding STF-8300M & STT-8300M new [Re: pfile]
      #5742747 - 03/19/13 11:44 AM

Requiring the guiding to bump the mount during an AO exposure should not normally cause the defect in your image.

The mount bump is really no different than a normal guide correction. Usually the AO is able to guide away any variations in star position even during the mount bump.

What may have happened in your image is that you let the AO get to its maximum travel before the mount bump occurred. Instead, you should limit the AO to 50% or less of its maximum travel to let the mount bumps happen more often. This will allow the AO to continue to correct through the mount movement and should give you much better results.

You never want to rely on the AO only to do your corrections unless you have a near perfect alignment (as you've experienced). You really need to optimize your system so everything is working together as intended.

I hope this helps.


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pfile
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Reged: 06/14/09

Re: Understanding STF-8300M & STT-8300M new [Re: MattThomas]
      #5742798 - 03/19/13 12:08 PM

matt even at 50% (which is the default) the amount of travel back to 0% is very noticeable at 2000mm.

if the guide star is dim and the guide exposure is long, it can take several seconds for the AO to return the guidestar to the center of the guide crosshairs. that's ample time for a double image, or for a streak to be noticable, etc. depending on the filter in use and how bright the stars are in the FOV.

again, i never cranked up my mount guide rate. but still with long guide exposures i'm not sure how this can be avoided.


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MattThomas
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Reged: 07/28/06

Re: Understanding STF-8300M & STT-8300M new [Re: pfile]
      #5743129 - 03/19/13 02:46 PM

It doesn't need to bring the AO back to center in order to get a good star image. As long as the AO is running fast enough to track the star (whatever the deflection) you will get a good image.

If the tracker exposure is slow - which would cause the AO to run slow and you have a fast perturbation that the AO cannot track out, then you are going to have an issue.

What I usually experience is that the AO will track the star, slowly deflecting off center (remember that even though the AO is off center, the stars are still kept on the same location on the CCD). When it reaches the limit, the mount is bumped which causes the AO to come back near center - but usually not exactly center, especially if the mount bump aggressiveness is set low. During the mount move, the AO is still tracking the star keeping it centered on the CCD - which continues until the mount needs to bump again.

Hope this helps.


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Mike7Mak
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Reged: 12/07/11

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Re: Understanding STF-8300M & STT-8300M new [Re: pfile]
      #5743172 - 03/19/13 03:04 PM

Quote:

if the guide star is dim and the guide exposure is long, it can take several seconds for the AO to return the guidestar to the center of the guide crosshairs. that's ample time for a double image, or for a streak to be noticable, etc. depending on the filter in use and how bright the stars are in the FOV.




Don't long guide exposures defeat the purpose of AO? I thought the point was sub-second exposures for rapid tip-tilt corrections. It seems to me if you drive the AO with long exposures it can't possibly provide any better guiding than a regular guide camera. It's gonna reveal the error that accumulates during the exposure, just without the added lag time of moving the mount. Hence the double exposure effect instead of egg-shaped stars.


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pfile
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Reged: 06/14/09

Re: Understanding STF-8300M & STT-8300M new [Re: Mike7Mak]
      #5743445 - 03/19/13 04:57 PM

this may just be a peculiarity of equinox image. it's bumping back to 0% and i'm not sure that's configurable. also, it's not making small bumps and letting the AO correct. it makes one huge bump and then the AO has to catch up. maxim could be different; i've never tried it.

> Don't long guide exposures defeat the purpose of AO?

yes and no, if you are hoping to make up for atmospheric effects then yes i suppose. but in the end, in theory, you should get superior guiding from the AO since the mass it has to move is much, much less than the entire OTA. because of this it's probably a lot less likely to under- and over- shoot.

my good images with the AO are definitely better than without.


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korborh
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Reged: 01/29/11

Re: Understanding STF-8300M & STT-8300M [Re: pfile]
      #5744049 - 03/19/13 09:36 PM

Quote:

my good images with the AO are definitely better than without.




Were the ones without AO taken using OAG? With a mount like Mach1 you really should not need AO for that OTA to get tight round stars. Unless the OAG/calibration has some issue.


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